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  Subjects -> ENGINEERING (Total: 2282 journals)
    - CHEMICAL ENGINEERING (192 journals)
    - CIVIL ENGINEERING (186 journals)
    - ELECTRICAL ENGINEERING (102 journals)
    - ENGINEERING (1204 journals)
    - ENGINEERING MECHANICS AND MATERIALS (385 journals)
    - HYDRAULIC ENGINEERING (55 journals)
    - INDUSTRIAL ENGINEERING (68 journals)
    - MECHANICAL ENGINEERING (90 journals)

CIVIL ENGINEERING (186 journals)                     

Showing 1 - 186 of 186 Journals sorted alphabetically
ACI Structural Journal     Full-text available via subscription   (Followers: 17)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 2)
Acta Structilia : Journal for the Physical and Development Sciences     Open Access   (Followers: 2)
Advances in Civil Engineering     Open Access   (Followers: 34)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 27)
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 30)
Architectural Engineering     Open Access   (Followers: 4)
Archives of Civil and Mechanical Engineering     Full-text available via subscription   (Followers: 1)
Archives of Civil Engineering     Open Access   (Followers: 10)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access   (Followers: 1)
ATBU Journal of Environmental Technology     Open Access   (Followers: 3)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 6)
Baltic Journal of Road and Bridge Engineering     Full-text available via subscription   (Followers: 1)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 9)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 4)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 4)
Berkeley Planning Journal     Open Access   (Followers: 7)
Bioinspired Materials     Open Access   (Followers: 5)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 15)
Building and Environment     Hybrid Journal   (Followers: 15)
Building Women     Full-text available via subscription  
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 15)
Bulletin of Pridniprovsk State Academy of Civil Engineering and Architecture     Open Access   (Followers: 6)
Canadian Journal of Civil Engineering     Hybrid Journal   (Followers: 11)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Nondestructive Testing and Evaluation     Open Access   (Followers: 10)
Case Studies in Structural Engineering     Open Access   (Followers: 9)
Cement and Concrete Composites     Hybrid Journal   (Followers: 17)
Challenge Journal of Concrete Research Letters     Open Access   (Followers: 2)
Challenge Journal of Structural Mechanics     Open Access   (Followers: 5)
Change Over Time     Full-text available via subscription   (Followers: 2)
Civil and Environmental Engineering     Open Access   (Followers: 7)
Civil And Environmental Engineering Reports     Open Access   (Followers: 5)
Civil and Environmental Research     Open Access   (Followers: 19)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 4)
Civil Engineering and Architecture     Open Access   (Followers: 17)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 3)
Civil Engineering and Technology     Open Access   (Followers: 9)
Civil Engineering Dimension     Open Access   (Followers: 8)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 258)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 10)
Computers & Structures     Hybrid Journal   (Followers: 36)
Concrete Research Letters     Open Access   (Followers: 6)
Construction Economics and Building     Open Access   (Followers: 2)
Construction Engineering     Open Access   (Followers: 8)
Construction Management and Economics     Hybrid Journal   (Followers: 21)
Construction Science     Open Access   (Followers: 4)
Constructive Approximation     Hybrid Journal  
Curved and Layered Structures     Open Access   (Followers: 2)
DFI Journal : The Journal of the Deep Foundations Institute     Hybrid Journal   (Followers: 1)
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 16)
Enfoque UTE     Open Access   (Followers: 4)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 7)
Engineering Structures     Hybrid Journal   (Followers: 13)
Engineering Structures and Technologies     Hybrid Journal   (Followers: 2)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 14)
Environmental Geotechnics     Hybrid Journal   (Followers: 5)
European Journal of Environmental and Civil Engineering     Hybrid Journal   (Followers: 8)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 16)
Frattura ed Integrità Strutturale : Fracture and Structural Integrity     Open Access  
Frontiers in Built Environment     Open Access  
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 6)
Geomaterials     Open Access   (Followers: 4)
Geosystem Engineering     Hybrid Journal   (Followers: 1)
Geotechnik     Hybrid Journal   (Followers: 3)
Géotechnique Letters     Hybrid Journal   (Followers: 6)
HBRC Journal     Open Access   (Followers: 2)
Hormigón y Acero     Full-text available via subscription  
HVAC&R Research     Hybrid Journal  
Indoor and Built Environment     Hybrid Journal   (Followers: 2)
Infrastructure Asset Management     Hybrid Journal   (Followers: 2)
Infrastructures     Open Access  
Ingenio Magno     Open Access   (Followers: 1)
Insight - Non-Destructive Testing and Condition Monitoring     Full-text available via subscription   (Followers: 22)
International Journal for Service Learning in Engineering     Open Access  
International Journal of 3-D Information Modeling     Full-text available via subscription   (Followers: 3)
International Journal of Advanced Structural Engineering     Open Access   (Followers: 16)
International Journal of Civil, Mechanical and Energy Science     Open Access   (Followers: 1)
International Journal of Concrete Structures and Materials     Open Access   (Followers: 13)
International Journal of Condition Monitoring     Full-text available via subscription   (Followers: 2)
International Journal of Construction Engineering and Management     Open Access   (Followers: 8)
International Journal of Geo-Engineering     Open Access   (Followers: 3)
International Journal of Geosynthetics and Ground Engineering     Full-text available via subscription   (Followers: 4)
International Journal of Masonry Research and Innovation     Hybrid Journal   (Followers: 1)
International Journal of Pavement Research and Technology     Open Access   (Followers: 4)
International Journal of Protective Structures     Hybrid Journal   (Followers: 6)
International Journal of Steel Structures     Hybrid Journal   (Followers: 2)
International Journal of Structural Engineering     Hybrid Journal   (Followers: 10)
International Journal of Structural Integrity     Hybrid Journal   (Followers: 2)
International Journal of Structural Stability and Dynamics     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Built Environment     Open Access   (Followers: 4)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 8)
International Journal on Pavement Engineering & Asphalt Technology     Open Access   (Followers: 6)
International Journal Sustainable Construction & Design     Open Access  
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 15)
Journal of Building Engineering     Hybrid Journal   (Followers: 1)
Journal of Building Materials and Structures     Open Access   (Followers: 2)
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 6)
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 11)
Journal of Civil Engineering and Management     Hybrid Journal   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 7)
Journal of Civil Engineering Research     Open Access   (Followers: 6)
Journal of Civil Society     Hybrid Journal   (Followers: 3)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 4)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 13)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 24)
Journal of Construction Engineering     Open Access   (Followers: 7)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 19)
Journal of Construction Engineering, Technology & Management     Full-text available via subscription   (Followers: 4)
Journal of Constructional Steel Research     Hybrid Journal   (Followers: 8)
Journal of Earth Sciences and Geotechnical Engineering     Open Access   (Followers: 4)
Journal of Fluids and Structures     Hybrid Journal   (Followers: 6)
Journal of Frontiers in Construction Engineering     Open Access   (Followers: 2)
Journal of Green Building     Full-text available via subscription   (Followers: 11)
Journal of Highway and Transportation Research and Development (English Edition)     Full-text available via subscription   (Followers: 12)
Journal of Infrastructure Systems     Full-text available via subscription   (Followers: 21)
Journal of Legal Affairs and Dispute Resolution in Engineering and Construction     Full-text available via subscription   (Followers: 5)
Journal of Marine Science and Engineering     Open Access   (Followers: 1)
Journal of Materials and Engineering Structures     Open Access   (Followers: 4)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 10)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 11)
Journal of Offshore Structure and Technology     Full-text available via subscription  
Journal of Performance of Constructed Facilities     Full-text available via subscription   (Followers: 4)
Journal of Pipeline Systems Engineering and Practice     Full-text available via subscription   (Followers: 7)
Journal of Rehabilitation in Civil Engineering     Open Access   (Followers: 3)
Journal of Solid Waste Technology and Management     Full-text available via subscription   (Followers: 1)
Journal of Structural Engineering     Full-text available via subscription   (Followers: 39)
Journal of Structural Fire Engineering     Full-text available via subscription   (Followers: 6)
Journal of Sustainable Architecture and Civil Engineering     Open Access   (Followers: 3)
Journal of Sustainable Design and Applied Research in Innovative Engineering of the Built Environment     Open Access   (Followers: 1)
Journal of the South African Institution of Civil Engineering     Open Access   (Followers: 4)
Jurnal Spektran     Open Access   (Followers: 1)
Jurnal Teknik Sipil dan Perencanaan     Open Access  
Konstruksia     Open Access  
KSCE Journal of Civil Engineering     Hybrid Journal   (Followers: 2)
Latin American Journal of Solids and Structures     Open Access   (Followers: 4)
Materiales de Construcción     Open Access  
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 3)
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 17)
Obras y Proyectos     Open Access   (Followers: 1)
Open Journal of Civil Engineering     Open Access   (Followers: 6)
Photonics and Nanostructures - Fundamentals and Applications     Hybrid Journal   (Followers: 2)
Practice Periodical on Structural Design and Construction     Full-text available via subscription   (Followers: 4)
Proceedings of the Institution of Civil Engineers - Bridge Engineering     Hybrid Journal   (Followers: 7)
Proceedings of the Institution of Civil Engineers - Civil Engineering     Hybrid Journal   (Followers: 11)
Proceedings of the Institution of Civil Engineers - Management, Procurement and Law     Hybrid Journal   (Followers: 8)
Proceedings of the Institution of Civil Engineers - Municipal Engineer     Hybrid Journal   (Followers: 3)
Proceedings of the Institution of Civil Engineers - Structures and Buildings     Hybrid Journal   (Followers: 4)
Random Structures and Algorithms     Hybrid Journal   (Followers: 5)
Recent Trends In Civil Engineering & Technology     Full-text available via subscription   (Followers: 4)
Research in Nondestructive Evaluation     Hybrid Journal   (Followers: 7)
Revista IBRACON de Estruturas e Materiais     Open Access   (Followers: 1)
Road Materials and Pavement Design     Hybrid Journal   (Followers: 9)
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 6)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 61)
Selected Scientific Papers - Journal of Civil Engineering     Open Access   (Followers: 3)
Slovak Journal of Civil Engineering     Open Access   (Followers: 2)
Soils and foundations     Full-text available via subscription   (Followers: 4)
Steel Construction - Design and Research     Hybrid Journal   (Followers: 3)
Structural and Multidisciplinary Optimization     Hybrid Journal   (Followers: 9)
Structural Concrete     Hybrid Journal   (Followers: 11)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 9)
Structural Engineering International     Full-text available via subscription   (Followers: 11)
Structural Safety     Hybrid Journal   (Followers: 7)
Structural Survey     Hybrid Journal  
Structure     Full-text available via subscription   (Followers: 23)
Structure and Infrastructure Engineering: Maintenance, Management, Life-Cycle Design and Performance     Hybrid Journal   (Followers: 12)
Structures     Hybrid Journal   (Followers: 1)
Study of Civil Engineering and Architecture     Open Access   (Followers: 8)
Superlattices and Microstructures     Hybrid Journal   (Followers: 2)
Surface Innovations     Hybrid Journal  
Technical Report Civil and Architectural Engineering     Open Access  
Teknik     Open Access  
The IES Journal Part A: Civil & Structural Engineering     Hybrid Journal   (Followers: 6)
The Structural Design of Tall and Special Buildings     Hybrid Journal   (Followers: 6)
Thin Films and Nanostructures     Full-text available via subscription   (Followers: 2)
Thin-Walled Structures     Hybrid Journal   (Followers: 4)
Transactions of the VŠB - Technical University of Ostrava. Construction Series     Open Access   (Followers: 1)
Transportation Geotechnics     Full-text available via subscription   (Followers: 1)
Transportation Infrastructure Geotechnology     Hybrid Journal   (Followers: 8)
Underground Space     Open Access  
Water Science & Technology     Partially Free   (Followers: 25)
Water Science and Technology : Water Supply     Partially Free   (Followers: 22)

           

Journal Cover Fatigue & Fracture of Engineering Materials and Structures
  [SJR: 1.185]   [H-I: 60]   [16 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 8756-758X - ISSN (Online) 1460-2695
   Published by John Wiley and Sons Homepage  [1577 journals]
  • Investigation of thickness effects on the bending singularities of a
           notched plate
    • Authors: C.-D. Chen
      Abstract: In this paper, the bending singularities of a notched plate are investigated through the finite element method. The computed singular parameters, including the singularity orders and associated corner functions, are compared with those of classical plate theory and first-order shear deformation plate theory (FSDPT); the comparisons demonstrate the inaccuracy of the boundary conditions in classical plate theory. The thickness effects are then investigated through the finite element method. The results show that although the singularity parameters computed by finite element agree with those of the FSDPT in the interior of the plate, the FSDPT is not applicable at the notch tip on the top or bottom surface because of substantial free surface effects. For a very thin plate, the inconsistence in the comparison slightly increases because of the free surface effects.
      PubDate: 2017-09-21T01:40:38.066451-05:
      DOI: 10.1111/ffe.12719
       
  • Estimation of P-S-N curves in very-high-cycle fatigue: Statistical
           procedure based on a general crack growth rate model
    • Authors: D.S. Paolino; A. Tridello, G. Chiandussi, M. Rossetto
      Abstract: Extensive experimental investigations show that internal defects play a key role in the very-high-cycle fatigue (VHCF) response of metallic materials and that crack growth from internal defects can take place even if the stress intensity factor associated to the initial defect is below the threshold for crack growth. By introducing a reduction term in the typical formulation of the threshold for crack growth, the authors recently proposed a general phenomenological model, which can effectively describe crack growth from internal defects in VHCF. The model is able to consider the different crack growth scenarios that may arise in VHCF and is enough general to embrace the various weakening mechanisms proposed in the literature for explaining why crack can grow below the threshold.In the present paper, the model is generalized in a statistical framework. The statistical distributions of the crack growth threshold and of the initial defect size are put into the model. The procedure for the estimation of the Probabilistic-S-N curves and of the fatigue limit distribution is illustrated and numerically applied to an experimental dataset.
      PubDate: 2017-09-18T02:05:33.484303-05:
      DOI: 10.1111/ffe.12715
       
  • Fatigue and damage accumulation in open cell aluminium foams
    • Authors: H. Pinto; A. Amini, Á. Peña, P. Moraga, M. Valenzuela
      Abstract: Open-cell aluminium foams are a relatively new material with interesting uses in different engineering applications. This study investigates the fatigue behaviour and damage accumulation of metal foams via a fatigue analysis (Weibull E-N model), a failure criterion (the relation among the prepeak compressive and tensile slopes, the reduction in the tensile stress, or the reduction in the compressive stress), and a mathematical approach (linear, quadratic, or exponential). As a result of combining the 3 mathematical approaches and 3 failure criteria, different approaches are obtained, analysed, and validated by using experimental data. Finally, the proposed approaches can be used to directly obtain the damage accumulation level for open-cell metal foams under fully reversed cyclic loading as a function of the number of cycles applied, the total strain amplitude, and the initial damage accumulation condition.
      PubDate: 2017-09-14T02:41:50.42654-05:0
      DOI: 10.1111/ffe.12716
       
  • Effect of 475°C embrittlement on the low cycle fatigue behaviour of lean
           duplex stainless steels
    • Authors: Renata Strubbia; Mohamed Sennour, Silvina Hereñú
      Abstract: Lean duplex stainless steels (LDSSs) with lower nickel and molybdenum are less susceptible to suffer spinodal decomposition than standard duplex stainless steels. It is the purpose of this work to study the effect of thermal embrittlement on the low cycle fatigue behaviour of 2 LDSSs with different Creq and Nieq. The correlation between the fatigue behaviour and the dislocation structure is attempted. Transmission electron microscopy was used to observe the dislocation microstructure. Additionally, STEM-EDS technique in conjunction with Vickers microhardness measurements was used to characterize the amplitude of the spinodal decomposition. The results show that the LDSS with lower Creq and Nieq values exhibits improved fatigue properties in the as received and aged conditions. Furthermore, it is important to emphasize that with an adequate volume fraction of phases in LDSSs, the ageing treatment leads to an increase in strength without causing a great detriment in low cycle fatigue life.
      PubDate: 2017-09-14T02:20:23.167589-05:
      DOI: 10.1111/ffe.12714
       
  • Investigating creep rupture and damage behaviour in notched P92 steel
           specimen using a microscale modelling approach
    • Authors: L. Zhao; N. Alang, K. Nikbin
      Abstract: Idealized random grains separated by pseudo grain boundaries were generated by using Voronoi tessellation to simulate the polycrystalline microstructure. Combined with finite element analyses, this approach made it possible to addressing crack initiation and progressive failure due to crack growth in notched bar geometries of P92 steel at high temperature. The calculations provided good predictions for creep rupture lives of notched specimen with different notch radii and external stress. Simultaneously, irregular crack growth shape, intergranular crack mode, and wedge cracks at triple grain interaction were captured in the model. The crack initiation positions were found to be influenced by notch radius and applied stress causing high stress triaxiality at the subgrain level. Furthermore, the preferential crack growth directions were changed as the notch varied from sharp to blunt.
      PubDate: 2017-09-12T02:07:30.642403-05:
      DOI: 10.1111/ffe.12713
       
  • A non-probabilistic reliability-based design optimization method for
           structures based on interval models
    • Authors: M.R. Wang; J.P. Fan, J. Hu
      Abstract: A non-probabilistic reliability optimization method for structures with uncertain-but-bounded variables was presented. Based on the interval model description for the uncertain-but-bounded parameters, the non-probabilistic reliability index was used to measure the structural reliability. The optimal design was formulated as a nested two-loop optimization problem. For a nonlinear function, a number of constraints that satisfied the non-probabilistic reliability index were treated as the serial system, and the feasible region of the uncertain parameters was determined by the target non-probabilistic reliability index. The inner optimization method for solving a number of non-probabilistic reliability indices was transformed into the problem of minimizing the functions within the feasible range. For a linear function, the non-probabilistic reliability optimization problem can be transformed into a deterministic optimization problem. The high computational cost of determining the non-probabilistic reliability was greatly reduced. Three numerical examples were presented to illustrate the efficiency of the proposed method.
      PubDate: 2017-09-11T02:00:40.478518-05:
      DOI: 10.1111/ffe.12698
       
  • Influence of filler size on the mechanical properties of cement-based
           composites
    • Authors: L. Restuccia; G.A. Ferro
      Abstract: Nano inclusion of various particles in cement-based materials has been widely investigated during the last decade, as they have the capability to enhance several properties of composites. However, obtaining nano-sized particles means a high expenditure of energy, related to their functionalization and grinding process.The main theme of this research is to evaluate the mechanical properties of cement-based composites with coarse particles of pyrolyzed hazelnut shells, already investigated at the nanoscale. In this research activity, the particle size distribution used is in the range from some micron up to 140 μm. The experimental results demonstrate that it is possible to use pyrolyzed materials with coarser particle size, guaranteeing the improvement of the mechanical properties in terms of flexural and compressive strength, but not in terms of ductility, as obtained by using smaller particles.
      PubDate: 2017-09-06T21:41:16.153948-05:
      DOI: 10.1111/ffe.12694
       
  • Effect of electroslag remelting on the VHCF response of an AISI H13 steel
    • Authors: A. Tridello; D.S. Paolino, G. Chiandussi, M. Rossetto
      Abstract: Experimental results have shown that high-strength steels can fail in the Very-High-Cycle Fatigue (VHCF) regime with cracks originating from internal defects. Material cleanliness thus plays a major role in the VHCF response of high-strength steels and refinement processes (eg, electroslag remelting [ESR] and vacuum arc remelting) could significantly enhance their performance.The present paper aims at investigating the effect of the ESR process on the VHCF behavior of an AISI H13 steel by carrying out fully reversed ultrasonic tension-compression tests on hourglass specimens manufactured with and without the ESR process. Size effect is also taken into account in the paper: the effectiveness in the prediction of the VHCF response of specimens with large risk-volumes from experimental data on specimens with small risk-volumes is discussed and experimentally validated.
      PubDate: 2017-08-29T00:35:59.990544-05:
      DOI: 10.1111/ffe.12696
       
  • The effect of mean stress and stress biaxiality in high-cycle fatigue
    • Authors: Imade Koutiri; Daniel Bellett, Franck Morel
      Abstract: This article presents a review of selected multiaxial high-cycle fatigue criteria with an emphasis on their ability to take into account the mean stress effect and the effect of a biaxial stress state. It is shown that the predictions of the various criteria are very different for the case of biaxial tensile loads. This is in contrast to the case of combined tension-torsion loads, where the predictions are very similar. The second part of the article investigates which mechanical parameter (eg, the hydrostatic stress or the normal stress) is the most appropriate to take into account these cyclic stress states.
      PubDate: 2017-08-29T00:31:49.596956-05:
      DOI: 10.1111/ffe.12699
       
  • Numerical verification of stress intensity factor solution for clamped
           single edge notched tension (SENT) specimens
    • Authors: C. Bassindale; X. Wang, W.R. Tyson, S. Xu
      Abstract: Stress intensity factor solutions for clamped single edge notched tension (SENT) specimens, including a closed-form function recently proposed by Zhu along with a function by CanmetMATERIALS referenced in the British Standard BS 8571, have been assessed. Solutions for an SENT specimen with a daylight-to-width ratio of 10 have been compared with new finite element results generated in this work to assess their accuracies. The results of this study show that the polynomial proposed by Zhu differs by no more than 0.23% compared with the numerical results over the range of 0.2 ≤a/W ≤ 0.7. The CANMET function differs by no more than 0.69% over the same range.
      PubDate: 2017-08-24T02:25:36.477511-05:
      DOI: 10.1111/ffe.12700
       
  • Microscopic damage evolution during very-high-cycle fatigue (VHCF) of
           tempered martensitic steel
    • Authors: U. Krupp; A. Giertler, K. Koschella
      Abstract: Dimensioning with high-strength steels relies on the knowledge of Wöhler-type S/N data and the assumption that no failure occurs for load levels below the fatigue limit for applications where the number of load cycles exceeds 107. Very-high-cycle fatigue (VHCF) experiments applied to a 0.5C-1.0Cr-Mo tempered steel (German designation: 50CrMo4) revealed surface crack initiation at prior austenite grain boundaries in medium strength condition (37HRC) and internal crack initiation at nonmetallic inclusions at high strength condition (57HRC). Despite the formation of small cracks during cycling up to 109 cycles, it seems that these are nonpropagating cracks in the case of the medium strength condition and therefore a real fatigue limit exists. Application of automated electron back-scatter diffraction (EBSD) within the shallow-notched area of electro-polished fatigue specimens had shown that prior austenite grain boundaries act as effective obstacles to crack propagation. High-resolution thermography during cycling of the specimens allowed the identification of local plasticity, which led to crack initiation at a later stage of the fatigue life. It was found that Cr segregation rows play a decisive role in the crack initiation process. By means of high-resolution electron microscopy in combination with focused ion beam milling (FIB), evolution of cyclic plasticity and crack initiation was correlated with the material's microstructure. The results are discussed in terms of the completely different crack initiation mechanisms of medium and high strength variants of the same steel. EBSD microstructure and crack propagation data are used to adapt a numerical modeling tool to predict microcrack propagation in the VHCF regime.
      PubDate: 2017-08-23T02:11:25.684035-05:
      DOI: 10.1111/ffe.12685
       
  • Fatigue analysis of railway wheel using a multiaxial strain-based
           critical-plane index
    • Authors: M. Kiani; G.T. Fry
      Abstract: A fatigue damage model to assess the development of subsurface fatigue cracks in railway wheels is presented in this paper. A 3-dimensional finite element model (FEM) is constructed to simulate repeated cycles of contact loading between a railway wheel and a rail. The computational approach includes a hard-contact over-closure relationship and an elastoplastic material model with isotropic and kinematic hardening.Results from the simulation are used in a multiaxial critical-plane fatigue damage analysis. The employed strain-based critical-plane fatigue damage approach is based on Fatemi-Socie fatigue index that takes into account the non-proportional and out-of-phase nature of the multiaxial state of stress occurs when a railway wheel rolls on a rail. It predicts fatigue-induced micro-crack nucleation at a depth of about 3.7 mm beneath the wheel tread, as well as the crack plane growth orientation which indicates the possible failure pattern. Additionally, the influence of various factors such as contribution of normal stresses, higher wheel load, and material model have been investigated.
      PubDate: 2017-08-23T02:10:54.52398-05:0
      DOI: 10.1111/ffe.12697
       
  • Fatigue crack propagation under in-phase and out-of-phase biaxial loading
    • Authors: R.K. Neerukatti; S. Datta, A. Chattopadhyay, N. Iyyer, N. Phan
      Abstract: Fatigue damage characteristics of aluminium alloy under complex biaxial loads such as in-phase and out-of-phase loading conditions and different biaxiality ratios have been investigated. The effects of microscale phenomena on macroscale crack growth were studied to develop an in-depth understanding of crack nucleation and growth. Material characterization was conducted to study the microstructure variability. Scanning electron microscopy was used to identify the second phase particles, and energy dispersive X-ray spectroscopy was performed to analyse their phases and elements. Extensive quasi-static and fatigue tests were conducted on Al7075-T651 cruciform specimens over a wide range of load ratios and phases. Detailed fractography analysis was conducted to understand the crack growth behaviour observed during the fatigue tests. Significant differences in crack initiation and propagation behaviour were observed when a phase difference was applied. Primarily, crack retardation and splitting were observed because of the constantly varying mode mixity caused by phase difference. The crack growth behaviour and fatigue lives under out-of-phase loading were compared with those under in-phase loading to understand the effect of mixed-mode fracture.
      PubDate: 2017-08-22T05:36:27.057166-05:
      DOI: 10.1111/ffe.12690
       
  • Fatigue resistance investigation of warm-mix recycled asphalt binder,
           mastic, and fine aggregate matrix
    • Authors: Q. Li; X. Chen, G. Li, S. Zhang
      Abstract: Fatigue cracking is one of the primary distresses in warm-mix recycled asphalt pavements. This paper evaluates the fatigue resistance evolution of warm-mix recycled asphalt materials in different scales during the service period. The strain sweep test and time sweep test were performed, respectively, by dynamic shear rheometer to determine the linear viscoelastic limits and to characterize the fatigue behavior of warm-mix recycled asphalt binder, mastic, and fine aggregate matrix with different ageing levels and recycling plans. The dissipated energy method was used to define the failure criterion and to construct the fatigue model. Effects of ageing levels and recycling plans on stiffness and fatigue resistance were investigated. Performance correlations among warm-mix recycled asphalt binder, mastic, and fine aggregate matrix were developed, respectively, by the statistical method to determine the critical material scale for stiffness and fatigue resistance.
      PubDate: 2017-08-22T05:20:49.388954-05:
      DOI: 10.1111/ffe.12692
       
  • Some influencing variables on internal fatigue crack initiation in
           structural materials
    • Authors: R. Ebara
      Abstract: This paper emphasizes the important effect of Kt and corrosive environment on internal fatigue crack initiation of structural materials in very high cycle regime. The conventional and ultrasonic fatigue testing results on notched specimens with Kt of 1.5 to 2.5 for YXR3 steel with HRC 60.7 showed subsurface fatigue crack initiation on all notched specimens at Nf higher than 106. On the contrary, fatigue crack initiated at notched surface for HAP72 with HRC 67 with Kt of 2.0. The fatigue crack initiation mode in notched specimens at high cycle regime is governed by surface hardness of high strength steels. The contrasting effect of refrigeration compressor gaseous environment on fatigue crack initiation mode is also demonstrated in the plate bending fatigue testing results of 1% carbon steel.
      PubDate: 2017-08-17T00:36:42.2803-05:00
      DOI: 10.1111/ffe.12687
       
  • Guest editorial: Special issue “Internal Fatigue Crack”
    • Authors: Stefanie E. Stanzl-Tschegg; Eberhard Kerscher
      PubDate: 2017-08-11T02:10:18.138275-05:
      DOI: 10.1111/ffe.12693
       
  • Effect of environment's aggressiveness on the corrosion damage evolution
           and mechanical behavior of AA 2024-T3
    • Authors: M. C. Vasco; A. N. Chamos, Sp. G. Pantelakis
      Abstract: The aim of this work is to contribute on establishing correlations between corrosion damage from accelerated laboratory corrosion tests of varying aggressiveness; by accounting for both, the metallographic features of corrosion damage and the mechanical properties of the corroded material. The work is based on the investigation of corrosion damage caused by the exposure of 2024-T3 aluminum alloy to 3.5% NaCl solution, which is presently considered to properly represent in-service exposure. Corrosion damage evolution was quantified for periods ranging between 500 and 3000 hours by evaluating pitting density, depth, and diameter. It was compared to available results of corrosion damage of the same alloy subjected to exfoliation corrosion test. Furthermore, the tensile properties of precorroded material in each solution were evaluated. The results allow the formulation of correlation functions between corrosion damage geometrical metallographic features from low- to high-aggressiveness environment exposures. On the other hand, the degradation of tensile properties, and particularly of tensile ductility, is more pronounced in specimens exposed to higher corrosion rate environments, even when damage in both environments leads to equivalent metallographic features. This suggests significant differences in the underlying physical mechanisms of the damage accumulation process when the same material is exposed to different corrosive solutions. This work suggests the need to expand current corrosion damage interpretation, to account not only for geometrical metallographic features but also for mechanical properties of the affected material.
      PubDate: 2017-08-10T01:45:38.739992-05:
      DOI: 10.1111/ffe.12651
       
  • Designing pro-composite truss layout for load-bearing aircraft structures
    • Authors: A. Shanygin; E. Dubovikov, V. Fomin, I. Mareskin, M. Zichenkov
      Abstract: The frame (truss) layout based on the hybrid metal-composite rod elements is proposed for weight saving of the primary aircraft structures. It is proposed to provide the durability of rod elements by protection system against impacts and environment. The algorithm of designing the structure with frame layout has been developed on the basis of 2-level approach. Fast strength analysis methods based on automated numerical models have been developed. The results of comparative weight estimations of frame and conventional wing box structure of prospective civil aircraft are presented.
      PubDate: 2017-08-10T01:42:36.233486-05:
      DOI: 10.1111/ffe.12695
       
  • Nonlinear numerical study of crack initiation and propagation in a reactor
           pressure vessel under pressurized thermal shock using XFEM
    • Authors: X. Sun; G. Chai, Y. Bao
      Abstract: Under pressurized thermal shock (PTS), once crack initiation occurs in a reactor pressure vessel (RPV), the stress concentration around the crack tips may result in local instability and crack propagation. The temperature-dependent material properties are introduced into the finite element analysis model. According to the response of the transient temperature field and stress field near the crack tip region, the influence of PTS on the carrying capacity of the structure is demonstrated. Also, the process of crack initiation and propagation is simulated by using the extended finite element method (XFEM). The results show that the crack of mode I is easy to be initiated on the nozzle in the initial high temperature and high pressure working state. The effect of cladding on the RPV integrity is enhanced with the increase of crack size, and it mainly depends on the crack length. During the PTS transient, a discontinuity of stress exists near the cladding-base interface, and the cladding bears more loading than the base of the same size. As the unloading of the internal pressure, the stress does not decline due to the strong thermal shock. In the late stage of the PTS process, the internal pressure caused by repressurization poses a challenge to the strength of the structure. With the decrease of the base wall thickness, the allowable repressure value also gradually decreases. However, the increase of the base wall thickness causes the rise of thermal stress, and the allowable repressure load is not significantly improved.
      PubDate: 2017-08-10T01:42:20.416572-05:
      DOI: 10.1111/ffe.12689
       
  • Constitutive relationship of polyolefin fibre–reinforced concrete:
           Experimental and numerical approaches to tensile and flexural behaviour
    • Authors: A. Enfedaque; M.G. Alberti, J.C. Gálvez, M. Beltrán
      Abstract: Flexural tensile tests are usually used to evaluate the suitability of fibre-reinforced concrete (FRC) in structural applications. The constitutive relationships of FRC are derived from such tests by using several inverse analyses. Given that the structural design of FRC is based on the residual load-bearing capacities obtained under flexural tests, the approach to analyse fracture behaviour by means of uniaxial tensile tests would mean use of more direct and reliable constitutive curves compared with those obtained by indirect means. The significance of this paper lies in the characterisation of polyolefin fibre–reinforced concrete (PFRC) not only by using fracture flexural results tests but also by comparing such results with the direct tensile behaviour of the material obtained from uniaxial tests. This comparison would both extend the knowledge of the PFRC mechanical properties and broaden the reliability of structural design by comparing the behaviour of PFRC under flexural and tensile stresses. Moreover, the suitability of an iterative method proposed by the authors for obtaining the constitutive relations of PFRC from flexural tests has been checked by performing a series of numerical simulations of the tensile tests performed. The differences in the properties obtained in the flexural tests and the tensile tests have been assessed. The experimental results gathered from the tensile tests have been accurately reproduced by using a cohesive crack approach with trilinear softening functions by the iterative inverse analysis proposed.
      PubDate: 2017-08-10T01:35:52.51295-05:0
      DOI: 10.1111/ffe.12688
       
  • Special issue: Fatigue of aeronautical materials and structures
    • Authors: Spiros Pantelakis; Paulo Castro, Mario Guagliano, Filippo Berto
      PubDate: 2017-08-09T02:00:20.726586-05:
      DOI: 10.1111/ffe.12691
       
  • Simulation of low cycle fatigue stress-strain response in 316LN stainless
           steel using non-linear isotropic kinematic hardening model—A comparison
           of different approaches
    • Authors: Ashraf Q. J; Prasad Reddy G. V, Sandhya R, Laha K, Harmain G. A.
      Abstract: Cyclic stress-strain response of 316LN stainless steel subjected to low cycle fatigue at strain amplitude of ±0.4% and at 873 K is simulated using finite element analysis with non-linear isotropic-kinematic hardening Chaboche model. Four different approaches have been used in simulating cyclic stress response and hysteresis loops: 3 based on Chaboche model-parameters and the fourth on direct experimental data (stabilized loop and cyclic stress-strain curve [CSSC]). Among them, simulations performed with direct experimental data have not yielded expected initial cyclic response. The source of data used for evaluation of kinematic-hardening (KH) parameters determined the extent of closeness between experimental results and Chaboche-model predictions. KH parameters determined from first-cycle loop and modified-CSSC predicted the overall stress-strain response (from initial to stabilized condition) with reasonable fit, compared with other approaches. All 4 approaches though predicted stabilized response, simulations based on “KH-parameters from stabilized-cycle” accurately described stabilized response with coefficient of determination (r2) 0.995.
      PubDate: 2017-08-02T02:15:41.447973-05:
      DOI: 10.1111/ffe.12683
       
  • Ratcheting response of nylon fiber reinforced natural rubber/styrene
           butadiene rubber composites under uniaxial stress cycles: Experimental
           studies
    • Authors: A. Vahidifar; E. Esmizadeh, G. Naderi, A. Varvani-Farahani
      Abstract: The present study intends to study the ratcheting response of nylon fiber reinforced natural rubber (NR)-styrene butadiene rubber (SBR) composite samples under asymmetric stress cycles. Uniaxial tests conducted on composite samples have shown how influential the weight fraction of short nylon fibers on the stress-strain curves/loops under monotonic and cyclic loads is. NR/SBR composite samples with various fiber contents of 0, 10, 20, 30, and 40 per hundred rubber (phr) were tested under asymmetric stress cycles. In these tests, stress-strain hysteresis loops were progressively shifted over stress cycles resulting in progressive plastic strain accumulation. Over stress cycles, ratcheting strain progressed within the first few cycles with a relatively high rate, and as the number of cycles increased, this rate decayed resulting in a plateau in strain accumulation (shakedown). The ratcheting strain rate and magnitude resulting in shakedown were highly affected by the nylon fiber content. The experimental observations showed that this plateau (shakedown) occurred after a number of cycles in NR/SBR composite samples where the widths of hysteresis loops stayed unchanged. Samples with no fiber and that with 10 phr fiber content possessed high ratcheting rates leading samples to failure after a few stress cycles. Fracture surfaces in these samples were further analyzed through SEM investigation.
      PubDate: 2017-08-02T02:10:40.34133-05:0
      DOI: 10.1111/ffe.12684
       
  • A residual stress dependent multiaxial fatigue life model of welded
           structures
    • Authors: Z.C. Liu; C. Jiang, B.C. Li, X.G. Wang
      Abstract: In this paper, the influence of the residual stress on the fatigue performance of a welded structure under multiaxial loading modes is studied. First, the local stress state at weld toe is modified via introduction of the residual stress, and a new fatigue life estimation model considering the effect of the residual stress is established by modifying our recently proposed critical plane method. Second, the basic theory and procedure of the finite element simulation on the calculation of the welding residual stress are presented. Finally, a numerical simulation of an aluminum alloy flange-to-tube welding process is conducted, and the calculated residual stress is verified with X-ray diffraction measurement. Furthermore, the performance of the proposed fatigue life estimation model is verified by the experimental data obtained in the fatigue test under different loading modes. It confirms that the consideration of the residual stress is important, especially under the out-of-phase loading mode.
      PubDate: 2017-07-31T03:06:23.773517-05:
      DOI: 10.1111/ffe.12679
       
  • An extended finite element method-based representative model for primary
           water stress corrosion cracking of a control rod driving mechanism
           penetration nozzle
    • Authors: H. Lee; S.J. Kang, J.B. Choi, M.K. Kim
      Abstract: Primary water stress corrosion cracking incidents have been reported in nuclear reactors over the past several decades. Garud et al developed an empirical equation to express primary water stress corrosion cracking (PWSCC) initiation time by using experimental data. This strain rate damage model has been used in multiple simulation studies. Some of these studies used the extended finite element method (XFEM) to simulate the PWSCC propagation in Alloy 600. However, several studies showed that the accuracy of XFEM depends on the mesh quality. Different mesh qualities can change the heat flux of a welding procedure, leading to different weld residual stresses. We performed a parametric study on PWSCC initiation and propagation of a control rod driving mechanism by using different mesh qualities. The major variables explored here are number of elements per bead, number of circumferential elements, and number of weld beads. Finally, an XFEM-based representative model was suggested for PWSCC initiation and propagation simulation.
      PubDate: 2017-07-31T03:02:32.645588-05:
      DOI: 10.1111/ffe.12667
       
  • On the interaction between corrosion and fatigue which determines the
           remaining life of bridges
    • Authors: D. Peng; R. Jones, R.R.K. Singh, F. Berto, A.J. McMillan
      Abstract: This paper studies the prior effect of corrosion on fatigue on the growth of cracks that arise from natural corrosion in steel bridges. It is shown that these 2 effects need to be simultaneously analysed. If not, then the resulting life is not conservative. This paper presents a simple methodology for performing this coupled analysis.
      PubDate: 2017-07-31T03:01:32.845622-05:
      DOI: 10.1111/ffe.12680
       
  • Energy-based fatigue failure characteristics of materials under random
           bending loading in elastic-plastic range
    • Authors: Wojciech Macek; Tadeusz Łagoda, Norbert Mucha
      Abstract: This article presents selected aspects connected to the methods of identification of strain energy density that are used to calculate the fatigue strength of materials. The authors focus on selected methods for determination of energy-based (stress-strain) characteristics of the fatigue life of materials (Wa − Nf), including a new approach for the determination of strain energy density parameter Wa. The paper also contains description and evaluation of models for determining the stress amplitudes σa in the elastic-plastic range, for bending. The developed procedure should give new capabilities in fatigue life calculations.
      PubDate: 2017-07-31T03:00:48.687874-05:
      DOI: 10.1111/ffe.12677
       
  • Effects of different indentation methods on fatigue life extension of
           cracked specimens
    • Authors: S.M.J. Razavi; M.R. Ayatollahi, A. Amouzadi, F. Berto
      Abstract: In this paper, 3 different indentation methods have been investigated for crack arresting and fatigue life enhancement of cracked components. The influence of residual stresses induced by indentation on fatigue crack growth (FCG) rate was explored by experiments and numerical simulations. Fatigue tests were conducted on a group of specimens which were indented on the crack tip by various indentation load magnitudes. For another group of specimens, the double indentation and triple indentation methods were applied on the cracked specimens with the aim of obtaining proper residual stress fields that contribute to higher crack growth retardations. Both the numerical and experimental results revealed that the higher indentation loads led to larger domain of compressive residual stress around the crack tip and consequently to higher fatigue life extension. In addition, the triple indentation method resulted in more FCG retardation compared with single and double indentation methods. Furthermore, for the specimens repaired by double and triple indentation methods, indenting ahead of the crack tip led to retardation in more crack growth compared with the other horizontal positions of indentation.
      PubDate: 2017-07-27T22:21:44.001854-05:
      DOI: 10.1111/ffe.12678
       
  • Molecular dynamics simulation of crack initiation and propagation in bcc
           iron under load within spur gear tooth root
    • Authors: Z. Zhao; F. Chu
      Abstract: Spur gears are widely used in practice, and one of their typical failures is tooth breakage. In general, the tooth breakage occurs at tooth root, and the amount of crack growth during a meshing cycle is in atomistic scale. This work aims at identifying the mechanisms of crack initiation and propagation at tooth root by using molecular dynamics simulation. The results prove that there are phase transition regions and edge dislocations at crack tips. According to the distribution characteristic of the atomic potential, its concentration can be observed obviously by visualization software. In these concentration regions, microvoids come into being and expand gradually, which results in the subcrack initiation. Additionally, the microvoids and subcracks propagate along the high potential direction and then come together to accelerate the crack growth. Through carrying out a comparative simulation, the effects of heavy load at single meshing area on crack initiation and propagation are addressed.
      PubDate: 2017-07-27T00:21:17.223701-05:
      DOI: 10.1111/ffe.12681
       
  • The design of durability tests by fatigue damage spectrum approach
    • Authors: F. Cianetti; A. Alvino, A. Bolognini, M. Palmieri, C. Braccesi
      Abstract: In the present paper, a new approach to combine load conditions expressed by power spectral density functions and to synthesize them into an equivalent one was presented. This method is based on the concept of fatigue damage spectrum and on the system dynamics. It was developed to design or verify operative durability tests (i.e., tracks), able to test payloads transported by vehicles, which could be alternative to laboratory ones, defined by the norm. By analyzing the acceleration spectrum of the norm and the acceleration measurements (all expressed in terms of power spectral density functions) acquired on the designed tracks during an experimental activity conducted on a wheeled transport vehicle, it was possible to verify the goodness of the proposed approach.
      PubDate: 2017-07-27T00:20:48.209786-05:
      DOI: 10.1111/ffe.12686
       
  • A weight function method for mixed modes hole-edge cracks
    • Authors: W. Xu; X.R. Wu, Y. Yu, Z.H. Li
      Abstract: A weight function approach is proposed to calculate the stress intensity factor and crack opening displacement for cracks emanating from a circular hole in an infinite sheet subjected to mixed modes load. The weight function for a pure mode II hole-edge crack is given in this paper. The stress intensity factors for a mixed modes hole-edge crack are obtained by using the present mode II weight function and existing mode I Green (weight) function for a hole-edge crack. Without complex derivation, the weight functions for a single hole-edge crack and a centre crack in infinite sheets are used to study 2 unequal-length hole-edge cracks. The stress intensity factor and crack opening displacement obtained from the present weight function method are compared well with available results from literature and finite element analysis. Compared with the alternative methods, the present weight function approach is simple, accurate, efficient, and versatile in calculating the stress intensity factor and crack opening displacement.
      PubDate: 2017-07-26T00:45:57.209679-05:
      DOI: 10.1111/ffe.12674
       
  • Application of continuum damage mechanics to vibration fatigue life
           prediction
    • Authors: Yi Li; Bing Sun, Jie Fang, Xue-Feng Liu, Tong Liang, Guo-Biao Cai
      Abstract: It is pivotal to predict the multiaxial vibration fatigue life during mechanical structural dynamics design. An algorithm of the finite element method implementation for multiaxial high cycle fatigue life evaluation is proposed, on the basis of elastic evolution model of continuum damage mechanics. By considering structural dynamic characteristics, namely, resonant frequencies and mode shapes, this algorithm includes a modal analysis and harmonic analysis, which makes this different from existing fatigue life prediction methods. A 10% decrease in the resonant frequency is regarded as the failure criterion. A critical damage value was obtained, which indicates mesocrack initiation fulfilment. To validate the effectiveness of the algorithm, auto-phase sine resonance track-and-dwell experiments were conducted on notched cantilever beams made of Ti-6Al-4V alloy. The life predictions are conservative and in good agreements with the experimental results, which are mainly distributed within a scatter band of 2. This investigation could provide technical support for structural dynamics design and the analysis of reusable spacecraft.
      PubDate: 2017-07-26T00:45:35.697518-05:
      DOI: 10.1111/ffe.12662
       
  • Effects of side-groove depth on creep crack-tip constraint and creep crack
           growth rate in C(T) specimens
    • Authors: J.Z. He; G.Z. Wang, S.T. Tu, F.Z. Xuan
      Abstract: The effects of side-groove depth on creep crack-tip constraint and creep crack growth (CCG) rate in C(T) specimens have been quantitatively studied. The results indicate that with increasing side-groove depth, the constraint level and CCG rate increase and constraint distribution along crack front (specimen thickness) becomes more uniform. The constraint and CCG rate of thinner specimen are more sensitive to side-groove depth. Two new creep constraint parameters (namely R* and Ac) both can quantify constraint levels of the specimens with and without side-grooves, and the quantitative correlations of CCG rate with constraint have been established. The mechanism of the side-groove depth effect on the CCG rate has also been analyzed.
      PubDate: 2017-07-26T00:40:41.564254-05:
      DOI: 10.1111/ffe.12676
       
  • Threshold values for very high cycle fatigue failure of high-strength
           steels
    • Authors: D. Spriestersbach; P. Grad, E. Kerscher
      Abstract: Cracks leading to failure in very high cycle fatigue (VHCF) of high-strength steels mostly initiate at subsurface inclusions at stress intensity factors (SIF) below the classical threshold value Kth for long cracks, especially for negative stress ratios. Here, a characteristic fine granular area (FGA) can be observed at the fracture surface in the vicinity of these initiating inclusions. According to various researchers, the FGA formation might be responsible for the late initiation of a propagable long crack. This study aims to clarify the threshold values of SIF for crack initiation for VHCF failure with FGA formation at nonmetallic inclusions. For this purpose, ultrasonic fatigue tests (R = −1) with the high-strength steel 100Cr6 (SAE 52100) were carried out until an ultimate number of cycles of 109. In addition, very high cycle stress increase tests were performed. A serial grinding investigation of fatigued specimens acted as a technique to evaluate the distribution of unharmful inclusion in the tested volume. By the combination of these tests, a threshold value of the SIF for the VHCF by FGA formation at inclusions can be derived. This threshold value depends on the size of the crack initiating inclusion.
      PubDate: 2017-07-26T00:36:02.061337-05:
      DOI: 10.1111/ffe.12682
       
  • Influence of mean stress and notches on the very high cycle fatigue
           behaviour and crack initiation of a low-pressure steam turbine steel
    • Authors: F. Ritz; T. Beck
      Abstract: The aim of the present work is to investigate the influence of different stress concentration factors (1.09, 1.31, and 2.42) and several R-values on the fatigue behaviour of martensitic steel X10CrNiMoV12-2-2 up to 2 · 109 load cycles at ambient temperature. The tests were performed using an ultrasonic fatigue testing system developed at the authors' institute. The S-N curves of specimens with the lowest investigated stress concentration factor of 1.09 show for both R = −1 and R = 0.5 a flat slope with transition from surface to volume crack initiation at about 1–2 · 107 load cycles. The maximum number of load cycles where fracture occurs increases with increasing R-value. The √area approach by Murakami describes lifetime behaviour within about 4 decades of lifetime and a wide range of load ratios. In case of internal crack initiation at R = −1, the fracture surface contains a fine granular area (FGA) around the inclusion within the typical “fish-eye” fracture. With increasing notch factor, the fatigue strength up to 2 · 109 load cycles decreases and the slope of the S-N curve becomes steeper in the low cycle fatigue and high cycle fatigue regime, especially for αk = 2.42. In this case, damage at internal defects is suppressed and fatigue cracks are generally initiated at the notch root.
      PubDate: 2017-07-19T01:06:40.610421-05:
      DOI: 10.1111/ffe.12666
       
  • Development of a unified creep-fatigue equation including heat treatment
    • Authors: Dan Liu; Dirk John Pons
      Abstract: BackgroundCreep and fatigue damages in metals are known to interact and then lead to aggregated damage. While models exist for fatigue, creep and creep-fatigue, no models cover all 3 load regimes. Also, a heat treatment–related parameter is not well included in most creep-fatigue models.NeedThere is a need to develop a creep-fatigue equation, which covers the full loading regime from pure fatigue to pure creep, and creep-fatigue. Also needed is inclusion of a heat treatment–related parameter.ApproachThe unified creep-fatigue equation was started from the Coffin-Manson equation and integrated with the Manson-Haferd parameter. This equation was validated on Inconel 718.OutcomesThe method of deriving the coefficients and the formula of the creep function are demonstrated, and the resulting equation shows a good ability to describe the grain-size effect and the fully integrated characteristics.OriginalityOriginal contributions of this work are the development of a new formulation to represent creep, fatigue and creep-fatigue in metals. Also the inclusion of grain size—which is a proxy for heat treatment—in the formulation of this equation and in a proposed modified Manson-Haferd parameter.
      PubDate: 2017-07-19T01:05:57.47363-05:0
      DOI: 10.1111/ffe.12670
       
  • A method for assessing critical plane-based multiaxial fatigue damage
           models
    • Authors: S.H. Iftikhar; J. Albinmousa
      Abstract: Fatigue failure is a complex phenomenon. Therefore, development of a fatigue damage model that considers all associated complexities resulting from the application of different cyclic loading types, geometries, materials, and environmental conditions is a challenging task. Nevertheless, fatigue damage models such as critical plane-based models are popular because of their capability to estimate life mostly within ±2 and ±3 factors of life for smooth specimens. In this study, a method is proposed for assessing the fatigue life estimation capability of different critical plane-based models. In this method, a subroutine was developed and used to search for best estimated life regardless of critical plane assumption. Therefore, different fatigue damage models were evaluated at all possible planes to search for the best life. Smith-Watson-Topper (normal strain-based), Fatemi-Socie (shear strain-based), and Jahed-Varvani (total strain energy density-based) models are compared by using the proposed assessment method. The assessment is done on smooth specimen level by using the experimental multiaxial fatigue data of 3 alloys, namely, AZ31B and AZ61A extruded magnesium alloys and S460N structural steel alloy. Using the proposed assessment method, it was found that the examined models may not be able to reproduce the experimental lives even if they were evaluated at all physical planes.
      PubDate: 2017-07-19T01:02:29.791717-05:
      DOI: 10.1111/ffe.12675
       
  • An investigation of the beneficial effects of adding carbon nanotubes to
           standard injection grout
    • Authors: L. Restuccia; A. Lopez, G.A. Ferro, D. Liberatore, J.M. Tulliani
      Abstract: Mortar grouting is often used in masonry constructions to mitigate structural decay and repair damage by filling cracks and voids, resulting in an improvement in mechanical properties. This paper presents an original experimental investigation on grout with added carbon nanotubes (CNTs). The samples were prepared with different percentages of CNTs, up to 1.2 wt% with respect to the binder, and underwent three-point bending tests in crack mouth opening displacement mode and compressive tests. The results showed that very small additions (up to 0.12 wt% of CNTs) increased not only flexural and compressive strengths (+73% and 35%, respectively, in comparison with plain mortar) but also fracture energy (+80%). These results can be explained on the basis of a reduction in porosity, as evidenced by mercury intrusion porosimetry, as well as by a crack bridging mechanism and by the probable formation of nucleation sites for hydration products, as observed through scanning electron microscopy.
      PubDate: 2017-07-14T00:36:52.286845-05:
      DOI: 10.1111/ffe.12663
       
  • Fatigue crack growth of multiple interacting cracks: Analytical models and
           experimental validation
    • Authors: R. Galatolo; R. Lazzeri
      Abstract: This article deals with the fatigue propagation of multiple cracks in finite width holed panels, which are typical of aircraft structural components. Theoretical studies in the literature have been considered and critically analyzed. Some of them have been translated into analytical models and implemented in a computer code. To check the effectiveness of the used models, a fatigue testing campaign has been conducted on six different configurations of notches and cracks. The comparison between experimental results and those obtained from the implemented models has shown a good agreement.
      PubDate: 2017-07-13T00:43:40.699606-05:
      DOI: 10.1111/ffe.12671
       
  • High cycle fatigue mechanisms of aluminum self-piercing riveted joints
    • Authors: J.F.C. Moraes; H.M. Rao, J.B. Jordon, M.E. Barkey
      Abstract: A study examining the fatigue failure mechanism of self-piercing riveted (SPR) joints between aluminum alloy 6111-T4 and 5754-O is presented in this paper. In particular, the high-cycle fatigue behavior of the SPR joints in the lap-shear configuration is characterized. Experimental fatigue testing revealed that failure of SPR joints occurred because of cracks propagating through the sheet thickness at locations away from the rivet. In-depth postmortem analysis showed that significant fretting wear occurred at the location of the fatigue crack initiation. Energy dispersive X-ray of the fretting debris revealed the presence of aluminum oxide that is consistent with fretting initiated fatigue damage. High-fidelity finite element analysis of the SPR process revealed high surface contact pressure at the location of fretting-initiated fatigue determined by postmortem analysis of failed coupons. Furthermore, fatigue modeling predictions of the number of cycles to failure based on linear elastic fracture mechanics supports the conclusion that fretting-initiated fatigue occurred at regions of high surface contact pressure and not at locations of nominal high-stress concentration at the rivet.
      PubDate: 2017-07-12T00:42:12.316379-05:
      DOI: 10.1111/ffe.12648
       
  • In-phase and out-of-phase thermomechanical fatigue behavior of 4Cr5MoSiV1
           hot work die steel cycling from 400 °C to 700 °C
    • Authors: Pengpeng Zuo; Xiaochun Wu, Yan Zeng, Xijuan He
      Abstract: The hysteresis loops, stress and strain behavior, lifetime behavior and fracture characteristic of 4Cr5MoSiV1 hot work die steel at a wide range of mechanical strain amplitudes (from 0.5% to 1.3%) during the in-phase (IP) and out-of-phase (OP) thermomechanical fatigue (TMF) tests cycling from 400 °C to 700 °C under full reverse strain-controlled condition were investigated. Stress-mechanical strain hysteresis loops of 4Cr5MoSiV1 steel are asymmetric, and stress reduction appears at high-temperature half cycles owing to a decrease in strength with increasing temperature. 4Cr5MoSiV1 steel always exhibits continuous cyclic softening for both types of TMF tests, and the cyclic softening rate is larger in OP loading condition. OP TMF life of 4Cr5MoSiV1 steel is approximately 60% of IP TMF life at the same mechanical strain amplitude and maximum temperature. Lifetime determined and predicted in both types of TMF tests is adequately described by the Ostergren model. Fracture surfaces under IP TMF loading display the striation and tear ridge, showing quasi-cleavage characteristics, and the cracks are less but longer. However, fracture surfaces under OP TMF loading mainly display the striation and dimple characteristics, and the cracks are more and shorter.
      PubDate: 2017-07-12T00:36:27.927706-05:
      DOI: 10.1111/ffe.12669
       
  • Morphing structures and fatigue: The case of an unmanned aerial vehicle
           wing leading edge
    • Authors: S.J. Moreira; S.M.O. Tavares, P.M.S.T. Castro
      Abstract: With the emergence of novel aircraft structural concepts, which make use of large-scale shape deflections to achieve improved flight performance across significantly different flight regimes and missions, unusual crack paths and mixed-mode crack propagation situations may take place. Consequently, morphing concepts require a full understanding of the materials' behaviour in primary or secondary structures to reliably withstand unusual and demanding operating conditions.A case study of a morphing leading edge developed for the wings of an unmanned aerial vehicle is presented in this paper. Leading edges are subjected to damage originated by bird strike or other events, and those damages can compromise the structural integrity and stability of the flight. Due to the deflections during the morphing structure actuation, cracks will propagate eventually until critical sizes. Possible crack propagation scenarios are presented, considering the service operation of the morphing leading edge.
      PubDate: 2017-07-12T00:35:41.368151-05:
      DOI: 10.1111/ffe.12664
       
  • Experimental and numerical investigation of cracked chevron notched
           Brazilian disc specimen for fracture toughness testing of rock
    • Authors: M.D. Wei; F. Dai, N.W. Xu, T. Zhao
      Abstract: The cracked chevron notched Brazilian disc (CCNBD) specimen has been suggested by the International Society for Rock Mechanics to quantify mode I fracture toughness (KIc) of rock, and it has also been applied to mode II fracture toughness (KIIc) testing in some research on the basis of some assumptions about the crack growth process in the specimen. However, the KIc value measured using the CCNBD specimen is usually conservative, and the assumptions made in the mode II test are rarely assessed. In this study, both laboratory experiments and numerical modeling are performed to study the modes I and II CCNBD tests, and an acoustic emission technique is used to monitor the fracture processes of the specimens. A large fracture process zone and a length of subcritical crack growth are found to be key factors affecting the KIc measurement using the CCNBD specimen. For the mode II CCNBD test, the crack growth process is actually quite different from the assumptions often made for determining the fracture toughness. The experimental and numerical results call for more attention on the realistic crack growth processes in rock fracture toughness specimens.
      PubDate: 2017-07-12T00:31:35.532672-05:
      DOI: 10.1111/ffe.12672
       
  • Fatigue crack propagation behavior of RC beams strengthened with CFRP
           under cyclic bending loads
    • Authors: Dongyang Li; Peiyan Huang, Xinyan Guo, Xiaohong Zheng, Jiaxiang Lin, Zhanbiao Chen
      Abstract: A fatigue crack propagation equation of reinforced concrete (RC) beams strengthened with a new type carbon fiber reinforced polymer was proposed in this paper on the basis of experimental and numerical methods. Fatigue crack propagation tests were performed to obtain the crack propagation rate of the strengthened RC beams. Digital image correlation method was used to capture the fatigue crack pattern. Finite element model of RC beam strengthened with carbon fiber reinforced polymer was established to determinate J-integral of a main crack considering material nonlinearities and degradation of material properties under cyclic loading. Paris law with a parameter of J-integral was developed on the basis of the fatigue tests and finite element analysis. This law was preliminarily verified, which can be applied for prediction of fatigue lives of the strengthened RC beams.
      PubDate: 2017-07-12T00:26:25.558179-05:
      DOI: 10.1111/ffe.12673
       
  • Nondestructive characterization of thermal damages and its interactions in
           carbon fibre composite panels
    • Authors: A. Haridas; C. Song, K. Chan, V.M. Murukeshan
      Abstract: Driven by high strength-to-weight ratios and advanced design flexibility, the application of composite structures in the aerospace industry is growing exponentially. A low thermal conductivity and thermal expansion coefficient give an edge when it comes to applications requiring stringent thermal loads, especially in aircraft engines. It is thus necessary to characterize, qualitatively and quantitatively, the behaviour of composite structures under harsh thermal loads for their certification. In this paper, characterization of multiple heat damages on 30 × 30 cm2 composite panels (16 layers, 00 unidirectional, and carbon fibre composite panel) is carried out by using visual inspection, ultrasound (a- and c-scans), and shearography. It has been observed that shearography, being a fast and noncontact technique, offers multiple advantages for sizing thermal damages. Primarily, it could be applied as a technique for a quick and effective inspection of composites, in turn, increasing the productivity of the quality assurance cycle.
      PubDate: 2017-07-11T23:12:05.875596-05:
      DOI: 10.1111/ffe.12657
       
  • Effects of inclusions on the very high cycle fatigue behaviour of steels
    • Authors: André Pineau; Samuel Forest
      Abstract: The very high cycle fatigue of high-strength steels and many other alloys is controlled by the initiation and the propagation of cracks initiated at nonmetallic inclusions. Tiny cracks are early initiated from these inclusions. They propagate very slowly in a specific zone located close to the inclusion and called the fine-grained area (FGA) or optical dark area. This area has a size of the order of that of the inclusion. The FGA is followed by the formation of conventional crack propagation area with the presence of striations in many cases. The details of initiation of these very high cycle fatigue cracks depend on the relative elastic and thermal properties of inclusions and matrix. The specificities of the FGA zone are dependent on the hydrogen segregated at the interface of the inclusions. An elasto-plastic finite element calculation is performed to determine the residual stresses in the vicinity of the inclusions and to evaluate the effect of residual stresses.
      PubDate: 2017-07-10T00:41:23.82211-05:0
      DOI: 10.1111/ffe.12649
       
  • A new expression for crack opening stress determined based on maximum
           crack opening displacement under tension–compression cyclic loading
    • Authors: J. J. Chen; M. You, Y. Huang
      Abstract: The maximum crack opening displacement is introduced to investigate the effect of compressive loads on crack opening stress in tension–compression loading cycles. Based on elastic–plastic finite element analysis of centre cracked finite plate and accounting for the effects of crack geometry size, Young's modulus, yield stress and strain hardening, the explicit expression of crack opening stress versus maximum crack opening displacement is presented. This model considers the effect of compressive loads on crack opening stress and avoids adopting fracture parameters around crack tip. Besides, it could be applied in a wide range of materials and load conditions. Further studies show that experimental results of da/dN − ΔK curves with negative stress ratios could be condensed to a single curve using this crack opening stress model.
      PubDate: 2017-07-10T00:40:41.775171-05:
      DOI: 10.1111/ffe.12637
       
  • Tangential strain-based criteria for mixed-mode I/II fracture toughness of
           cement concrete
    • Authors: M.M. Mirsayar; A. Razmi, F. Berto
      Abstract: Experimental and theoretical works are performed on the mixed-mode I/II brittle fracture of cement concrete tested by edge cracked semicircular bend specimens. Theoretical background of the traditional fracture criteria including strain energy density, maximum tangential stress, and maximum tangential strain (MTSN) are introduced. The ability of each fracture criterion in prediction of the fracture test data is investigated. The comparison between the evaluations by the traditional criteria and the experimental data shows that none of them are capable of successfully estimating the fracture resistance of cement concrete. An enhanced version of the MTSN criterion is then employed to predict the test data. It is demonstrated that the extended MTSN criterion can successfully predict the test data in a higher accuracy than traditional criteria.
      PubDate: 2017-07-10T00:37:01.491629-05:
      DOI: 10.1111/ffe.12665
       
  • Experimental study of the effect of pre-bond contamination with de-icing
           fluid and ageing on the fracture toughness of composite bonded joints
    • Authors: E. Moutsompegka; K.I. Tserpes, P. Polydoropoulou, C. Tornow, M. Schlag, K. Brune, B. Mayer, S. Pantelakis
      Abstract: The scope of the present work is to experimentally investigate the effect of pre-bond contamination with de-icing (DI) fluid and the combined effect of DI fluid and hygrothermal ageing on the fracture toughness of carbon fibre reinforced plastic bonded joints. These scenarios could occur in the implementation of an adhesively bonded patch repair in a composite aircraft structural part. To this end, mode I and mode II fracture toughness tests were conducted on contaminated specimens and mode II fracture toughness tests on contaminated/aged specimens. Three levels of contamination with a de-icer were considered. The hygrothermal ageing conditions applied until saturation are 70°C/85% relative humidity. The experimental results reveal a detrimental effect of DI fluid on both mode I and mode II fracture toughness of the bonded joints. With increasing the contamination level, the mode I and mode II critical energy release rates decrease. Under mode I loading, the specimens failed mainly in light-fibre-tear mode, while under mode II loading, in adhesive failure mode. Hygrothermal ageing decreased further the mode II fracture toughness of the specimens and increased the adhesive failure mode. The present study reveals that the pre-bond DI contamination and after-bond ageing could critically degrade the strength of adhesively bonded patch repairs.
      PubDate: 2017-07-10T00:36:50.013427-05:
      DOI: 10.1111/ffe.12660
       
  • On the use of British standard 7910 option 1 failure assessment diagram
           to non-metallic materials
    • Authors: J.D. Fuentes; S. Cicero, F.T. Ibáñez-Gutiérrez, I. Procopio
      Abstract: This paper provides a structural integrity assessment methodology for the analysis of non-metallic materials. The approach uses the British standard 7910 option 1 failure assessment diagram, originally proposed for the fracture-plastic collapse assessment of metallic materials. The methodology has been applied to 60 fracture specimens, combining 12 different materials and covering polymers, composites, and rocks. The results obtained validate the proposed assessment methodology and demonstrate its safety for the materials analysed here.
      PubDate: 2017-07-10T00:30:29.559113-05:
      DOI: 10.1111/ffe.12668
       
  • Dual boundary element method and finite element method for mixed-mode
           crack propagation simulations in a cracked hollow shaft
    • Authors: R. Citarella; V. Giannella, M. Lepore, G. Dhondt
      Abstract: Three-dimensional mixed-mode crack propagation simulations were performed by means of the dual boundary element method code BEASY and 2 finite element method-based crack propagation codes: ZENCRACK (ZC) and CRACKTRACER3D (CT3D). The stress intensity factors (SIFs) along the front of an initial semielliptical crack, initiated from the external surface of a shaft, were calculated for 4 different load cases: bending, press fit, shear, and torsion. The methods used for the SIF assessment along the crack front were the J-integral for BEASY and ZC and the quarter point element stress method for CT3D. Subsequently, crack propagation simulations were performed, with the crack growth rate evaluated by using Paris' law, calibrated for the material at stake (American Society for Testing and Materials A469 steel). The kink angles were evaluated by using the minimum strain energy density and maximum tangential stress criteria for BEASY, the maximum energy release rate and maximum tangential stress for ZC, and the maximum principal asymptotic stress for CT3D. The results obtained in terms of SIFs and crack propagation life show very good agreement among the 3 codes. Also, the shape of the propagated crack, which is significantly out-of-plane for the shear and torsion loading, matched very well.
      PubDate: 2017-07-06T00:37:40.175181-05:
      DOI: 10.1111/ffe.12655
       
  • Reason for the transition of fatigue crack initiation site from surface to
           subsurface inclusions in high-strength steels
    • Authors: P. Grad; E. Kerscher
      Abstract: The fatigue crack initiation in high-strength steels at surface inclusions is linked to high stress amplitudes. Low stress amplitudes are associated with a crack initiation at subsurface inclusions. The aim of the paper is to gain insight regarding the factors that lead to the transition of the crack initiation site from the surface to the interior. On the basis of fatigue tests and fracture mechanics evaluation, it was determined that the transition of the crack initiation site is effected by a constant threshold value for crack initiation at the surface and different crack propagation rates at the surface as opposed to the interior. It is shown that with lower stress amplitudes no critical inclusions with stress intensity factors above this threshold value are positioned at the specimen's surface. Therefore, the cumulative number of inclusions on the surface is calculated based on the cumulative number of inclusions in a metallographic section.
      PubDate: 2017-07-06T00:35:43.525193-05:
      DOI: 10.1111/ffe.12635
       
  • Study of electromechanical impedance changes caused by modifications of
           CFRP adhesive bonds
    • Authors: Paweł H. Malinowski; Wiesław M. Ostachowicz, Kai Brune, Mareike Schlag
      Abstract: Numerous techniques of nondestructive testing and structural health monitoring of CFRP structural parts are studied. In this research, we focus on electromechanical impedance (EMI) technique. This technique is based on a piezoelectric sensor that is surface mounted on or embedded in the inspected structure. Because of direct and converse piezoelectric effects, the electrical response of the sensor is related to mechanical characteristic of the structure. In the reported research, adhesively bonded CFRP samples were investigated. The EMI characteristics of samples with modified bonds were compared with properly bonded referential samples. The following modifications were considered: prebond thermal treatment, prebond contamination with de-icing fluid, and precuring of the adhesive. The EMI spectra were investigated searching for anomalies and changes caused by modification of the adhesive bonds. Numerical indexes were used for the comparison of EMI characteristics. The sensitivity of the EMI method to modified bonds was observed.
      PubDate: 2017-06-27T21:31:18.092255-05:
      DOI: 10.1111/ffe.12661
       
  • Dynamic response and microstructure evolution of the finite steel target
           
    • Authors: J.F. Liu; Y. Long, C. Ji, M.S. Zhong
      Abstract: The dynamic deformation of the finite steel target subjected to high velocity impact of copper explosively formed projectile is investigated by optical, scanning, and transmission electron microscopy. Morphology analysis of fracture surfaces indicates that the copper remainder plated to the crater wall shows extremely plastic deformation, which consists of elongated parabolic dimples, and the mild carbon steel target exhibits excellent brittle features that material fails mainly along the cleavage facets on the rear surface of target under strong impact of explosively formed projectile. In the surface of crater, the whole part of copper remainder and partial material of steel target undergoes completely dynamic recrystallization. The layer thickness of dynamic recrystallization zone, which displays an extreme plastic flow in solid state, is about 21.3 μm in steel target, and the average size of the refined grains significantly decreases to approximately 200 nm. Theoretically calculated results indicate that the temperature increase is associated with shock wave and plastic deformation of steel target and can reach 1352 K, which is 0.75Tm (where Tm is the melting temperature of steel target). The change in microhardness from the crater wall to the matrix of target is consistent with micro-deformation of grains, and maximum microhardness is observed on the interface between dynamic recrystallization and severe plastic deformation zones of steel target.
      PubDate: 2017-06-21T02:04:45.145738-05:
      DOI: 10.1111/ffe.12640
       
  • Microstructural evolution and thermal fatigue resistance of grey cast iron
    • Authors: R. Casati; R. Faccin, M. Vedani
      Abstract: In the present work, thermal fatigue in grey cast iron has been investigated by means of a numerical and an experimental approach. Temperature gradients were generated within the material by means of a testing rig specifically designed for the experiments. The temperature gradients were responsible for the formation of severe stress fields that led to the failure of the specimens after a fairly low number of cycles. Crack growth was monitored during the tests, and the microstructure and hardness of samples were analysed after failure and compared with those of untested alloy. The repeated thermal cycles at peak temperatures of 600, 700, and 800°C led to important microstructural alterations of cast iron and to a drop in material hardness. The pearlite lamellae lost their original shape and became more fragmented. Oxygen-rich regions surrounding the graphite flakes were produced by microgalvanic corrosion mechanism.
      PubDate: 2017-06-21T01:56:53.2661-05:00
      DOI: 10.1111/ffe.12656
       
  • An approximation in closed form for the integral of Oore–Burns for
           cracks similar to a star domain
    • Authors: P. Livieri; F. Segala
      Abstract: In this paper, we give an explicit new formulation for the three-dimensional mode I weight function of Oore–Burns in the case where the crack border agrees with a star domain. Analysis in the complex field allows us to establish the asymptotic behaviour of the Riemann sums of the Oore–Burns integral in terms of the Fourier expansion of the crack border. The new approach gives remarkable accuracy in the computation of the Oore–Burns integral with the advantage of reducing the size of the mesh.Furthermore, the asymptotic behaviour of the stress intensity factor at the tip of an elliptical crack subjected to uniform tensile stress is carefully evaluated. The obtained analytical equation shows that the error of the Oore–Burns integral tends to zero when the ratio between the ellipse axes tends to zero as further confirmation of its goodness of fit.
      PubDate: 2017-06-19T02:01:44.952234-05:
      DOI: 10.1111/ffe.12629
       
  • Mixed mode fracture analysis of CCBD specimens based on the extended
           maximum tangential strain criterion
    • Authors: W. Hua; S. Dong, X. Pan, Q. Wang
      Abstract: The maximum tangential strain (MTSN) criterion has been modified to include the effects of T-stress and stress intensity factors in conditions of both plane stress and plane strain. Further, both the T-stress and Poisson's ratio affecting the crack propagation are also discussed according to the extended MTSN (EMTSN) criterion, which is a modified MTSN criterion. Finally, the generalized maximum tangential stress (GMTS) criterion and the EMTSN criterion are used to predict the test results obtained with central cracked Brazilian disc (CCBD) specimens. The results indicate that the T-stress and Poisson's ratio have a remarkable influence on the mixed mode fracture resistance based on the EMTSN criterion. Theoretical values of both the EMTSN and the GMTS criteria are in very good agreement with the test results. Moreover, the EMTSN criterion provides a better prediction for pure mode II.
      PubDate: 2017-06-15T00:45:36.420096-05:
      DOI: 10.1111/ffe.12638
       
  • Crack incubation in shot peened AA7050 and mechanism for fatigue
           enhancement
    • Authors: Daniel J. Chadwick; Siavash Ghanbari, David F. Bahr, Michael D. Sangid
      Abstract: Shot peening is a dynamic cold-working process involving the impingement of peening media onto a substrate surface. Shot peening is commonly used as a surface treatment technique within the aerospace industry during manufacturing to improve fatigue performance of structural components. The compressive residual stress induced during shot peening results in fatigue crack growth retardation, improving the performance of shot-peened components. However, shot peening is a compromise between the benefit of inducing a compressive residual stress and causing detrimental surface damage. Because of the relatively soft nature of AA7050-T7451, shot peening can result in cracking of the constituent precipitate particles, creating an initial damage state. The aim of this paper is to understand the balance and fundamentals of these competing phenomena through a comparative study throughout the fatigue lifecycle of baseline versus shot-peened AA7050-T7451. Microstructure and surface topology characterization and comparison of the baseline and shot-peened AA7050-T7451 has been performed using scanning electron microscopy, electron backscatter diffraction, energy dispersive spectroscopy, and optical profilometry techniques. A residual stress analysis through interrupted fatigue of the baseline and shot-peened AA7050-T7451 was completed using a combination of X-ray diffraction and nanoindentation. The fatigue life performance of the baseline versus shot-peened material has been evaluated, including crack initiation and propagation. Subsurface particles crack upon shot peening but did not incubate into the matrix during fatigue loading, presumably due to the compressive residual stress field. In the baseline samples, the particles were initially intact, but upon fatigue loading, crack nucleation was observed in the particles, and these cracks incubated into the matrix. In damage tolerant analysis, an initial defect size is needed for lifetime assessment, which is often difficult to determine, leading to overly conservative evaluations. This work provides a critical assessment of the mechanism for shot peening enhancement for fatigue performance and quantifies how incubation of a short crack is inhibited from an initially cracked particle into the matrix within a residual stress field.
      PubDate: 2017-06-15T00:40:43.314731-05:
      DOI: 10.1111/ffe.12652
       
  • Towards improved ODS steels: A comparative high-temperature low-cycle
           fatigue study
    • Authors: A. Chauhan; M. Walter, J. Aktaa
      Abstract: Within the frame of this work, the mechanical behaviour of a bimodal ferritic 12Cr-ODS steel as well as of a ferritic-martensitic 9Cr-ODS steel under alternating load conditions was investigated. In general, strain-controlled low-cycle fatigue tests at 550°C and 650°C revealed similar cyclic stress response. At elevated temperatures, the two steels manifest transitional stages, ie, cyclic softening and/or hardening corresponding to the small fraction of the cyclic life, which is followed by a linear cyclic softening stage that occupies the major fraction of the cyclic life until failure. However, it is clearly seen that the presence of the nano-sized oxide particles is certainly beneficial, as the degree of cyclic softening is significantly reduced compared with non-ODS steels. Besides, it is found that both applied strain amplitude and testing temperature show a strong influence on the cyclic stress response. It is observed that the degree of linear cyclic softening in both steels increases with increasing strain amplitude and decreasing test temperature. The effect of temperature on inelastic strain and hence lifetime becomes more pronounced with decreasing applied strain amplitude. When analysing the lifetime behaviour of both ODS steels in terms of inelastic strain energy calculations, it is found that comparable inelastic strain energies lead to similar lifetimes at 550°C. At 650°C, however, the higher inelastic strain energies of 12Cr-ODS steel result in significant lower lifetimes compared with those of the 9Cr-ODS steel. The strong degradation of the cyclic properties of the 12Cr-ODS steel is obviously linked to the fact that the initial hardening response appears significantly more pronounced at 650°C than at 550°C. Finally, the obtained results depict that the 9Cr-ODS steel offers higher number of cycles to failure at 650°C, compared with other novel ODS steels described in literature.
      PubDate: 2017-06-15T00:40:32.64969-05:0
      DOI: 10.1111/ffe.12639
       
  • Methodology for assessing embryonic cracks development in structures under
           high-cycle multiaxial random vibrations
    • Authors: S. Vantadori; R. Haynes, G. Fortese, E. Habtour, C. Ronchei, D. Scorza, A. Zanichelli
      Abstract: The myriad applicability of the frequency-domain critical plane criterion is outlined in order to evaluate and track the progression of fatigue damage in metallic structures subjected to high-cycle multiaxial random vibrations. The fatigue assessment using the given criterion is performed according to the following stages: (i) critical plane definition, (ii) power spectral density evaluation of an equivalent normal stress and (iii) computation of the damage precursor and fatigue life.The frequency-domain critical plane criterion is validated using experimental results related to (a) AISI 1095 steel cantilever beams under nonlinear base vibration, (b) 18G2A steel and (c) 10HNAP steel round specimens under random non-proportional combined flexural and torsional loads.
      PubDate: 2017-06-15T00:25:30.631426-05:
      DOI: 10.1111/ffe.12634
       
  • Extension of the modified Bai-Wierzbicki model for predicting ductile
           fracture under complex loading conditions
    • Authors: B. Wu; X. Li, Y. Di, V. Brinnel, J. Lian, S. Münstermann
      Abstract: The ductile fracture behaviour of metallic materials is strongly dependent on the material's stress state and loading history. This paper presents a concept of damage initiation and failure indicators and corresponding evolution laws to enhance the modified Bai-Wierzbicki model for predicting ductile damage under complex loading conditions. The proposed model considers the influence of stress triaxiality and the Lode angle parameter on both damage initiation and the subsequent damage propagation. The model parameters are calibrated for C45E + N steel using a series of mechanical tests and numerical simulations. The enhanced approach is applied to the modelling of various mechanical tests under proportional and non-proportional loading conditions and successfully predicts the ductile damage behaviour in these tests.
      PubDate: 2017-06-13T00:50:57.66685-05:0
      DOI: 10.1111/ffe.12645
       
  • Numerical and experimental study of ratcheting in cold expanded plate of
           Al-alloy 2024-T3 in double shear lap joints
    • Authors: E. Abdollahi; T. N. Chakherlou
      Abstract: In this paper strain ratcheting in cold expanded flat plate of Al-alloy 2024-T3 in double shear lap joints was studied both experimentally and numerically. In the experimental part, two types of symmetric strain-controlled and asymmetric stress-controlled cyclic tests were performed. Also, the cold expanded double shear lap joints subjected to cyclic stress-controlled tests. The required parameters for simulating the cyclic plastic behaviour of Al-alloy 2024-T3 were obtained on the basis of the experimental responses. In the numerical part, a combination of nonlinear isotropic and nonlinear kinematic hardening model (Chaboche) was implemented in the commercial finite element code of ABAQUS, using the subroutine UMAT written in FORTRAN. The results of simulations give an accurate prediction of ratcheting for all types of loading. The obtained results show that increasing the mean stress increases the strain ratcheting. It is clearly shown that the cold expansion process decreases the magnitude of strain ratcheting remarkably compared with “as drilled” specimens and the decrease is bigger for larger cold expansion sizes. Also, it is shown that the middle plane has the highest amount of ratcheting compared to the pin entrance plane and exit plane of the plate hole.
      PubDate: 2017-06-13T00:50:45.822104-05:
      DOI: 10.1111/ffe.12643
       
  • Fracture mechanics-based progressive damage modelling of adhesively bonded
           fibre-reinforced polymer joints
    • Authors: Aida Cameselle-Molares; Roohollah Sarfaraz, Moslem Shahverdi, Thomas Keller, Anastasios P. Vassilopoulos
      Abstract: A quasi-static progressive damage model for prediction of the fracture behaviour and strength of adhesively bonded fibre-reinforced polymer joints is introduced in this paper. The model is based on the development of a mixed-mode failure criterion as a function of a master R-curve derived from the experimental results obtained from standard fracture mechanics joints. Consequently, the developed failure criterion is crack-length and mode-mixity dependent, and it takes into account the contribution of the fibre-bridging effect. Energy release rate values for adhesively bonded double-lap joints are obtained by using the virtual crack closure technique method in a finite element model, and the numerically obtained strain energy release rate is compared to the critical strain energy release rate given by the mixed-mode failure criterion. The entire procedure is implemented in a numerical algorithm, which was successfully used for predicting the strength and R-curve response of adhesively bonded double-lap structural joints made of pultruded glass fibre-reinforced polymers and epoxy adhesives.
      PubDate: 2017-06-13T00:45:51.016737-05:
      DOI: 10.1111/ffe.12647
       
  • Quantification of different effects occurring during fatigue tests on
           bituminous mixtures
    • Authors: Cong Viet Phan; Hervé Di Benedetto, Cédric Sauzéat, Josselin Dayde, Simon Pouget
      Abstract: Quantification of different effects (nonlinearity, heating, thixotropy, and fatigue) occurring during fatigue tests on bituminous mixtures is presented in this paper. A focus is given on the nonlinearity phenomenon.Continuous fatigue tests and a test with specific protocol (called fatigue tests to estimate biasing effects) were performed in tension/compression mode on cylindrical samples of the same material. The analysis of results reveals that reversible effects (nonlinearity, heating, and thixotropy) are important (more than 90% decrease at 100,000 cycles for a strain amplitude of 100 μm/m at 10 Hz) and cannot be ignored when interpreting classical fatigue tests. The nonlinearity effects respect the time-temperature superposition principle, and they are more pronounced at “high” temperature (at the same frequency). Direction of nonlinearity curve in the Cole-Cole axes is shown to be independent of temperature and frequency for the considered range.
      PubDate: 2017-06-13T00:45:31.976252-05:
      DOI: 10.1111/ffe.12646
       
  • Investigation of bird strike events on composite wing panels
    • Authors: I. Diamantakos; K. Fotopoulos, M. Jamin, A. Eberhardt, G. Lampeas
      Abstract: One of the most important events during an aircraft's service life is the impact of a bird (ie, bird strike), which could possibly lead to catastrophic failure. According to airworthiness authorities, compliance of an aircraft structure to bird-strike certification specifications can potentially be proved by simulation. In the present work, combined experimental and numerical investigations are performed, aiming to provide a validated numerical simulation tool for the certification of a composite leading edge structure. To increase the numerical simulation efficiency, the stacked shell approach in the frame of the finite element method is adopted. Comparison of numerical and experimental results shows that the proposed methodology is very promising for the simulation of impact events on complex composite structures. The proposed methodology has been applied for the development of a numerical tool for the simulation of bird strike on a composite leading edge structure.
      PubDate: 2017-06-13T00:40:46.897022-05:
      DOI: 10.1111/ffe.12644
       
  • Influence of strain range on fatigue life reduction of stainless steel in
           PWR primary water
    • Authors: Masayuki Kamaya
      Abstract: The environmental effect in the pressurized water reactor (PWR) water was investigated for various applied strain range using a type 316 stainless steel. The tests were conducted using cylindrical hollow specimens at 325°C. It was shown that the ratio of the fatigue life in the PWR water environment to that in air was about 0.3 to 0.4 regardless of the strain range when the applied strain ranges were 0.8% or more. Crack growth rates identified from spacing of striations observed on fractured surfaces were used to demonstrate that the fatigue life reduction in the PWR water environment could be attributed to the crack growth acceleration. The fractured surface observations revealed that crack initiation was enhanced by the PWR water environment. On the other hand, the reduction in the fatigue life was not significant when the strain ranges were 0.5% and 0.44%, and the specimens did not fail when the strain ranges were 0.38% or less. It was deduced that the crack initiation was not enhanced for the relatively small strain range, and the crack growth was not accelerated. Since the fatigue limit of the test material was 0.4% in the strain range in air, it was concluded that the fatigue limit was not reduced in the PWR water environment.
      PubDate: 2017-06-13T00:40:31.519368-05:
      DOI: 10.1111/ffe.12650
       
  • Non-oscillatory and non-singular asymptotic solutions to stress fields at
           interface cracks
    • Authors: W.-S. Lei
      Abstract: This work concerns the complex oscillatory singularities revealed in Williams's asymptotic solutions to stress fields around arbitrary interface cracks, which are the foundation of phenomenological interface fracture mechanics. First, we highlight the fatal discrepancy between the asymptotic stress fields for cracks in a homogeneous material obtained by assigning an identical material on both regions embracing an interface crack, and the solutions directly derived from cracks in a single material. Next, following a brief introduction to Williams's formulation process, we adopt the method of repeatedly eliminating variables instead of solving the determinant equation for the coefficient matrix to reformulate the asymptotic analysis of stress fields at arbitrary interface cracks. The resultant stresses get rid of oscillatory character. Further, under two specific loading conditions, namely, remotely uniaxial tension or shear, non-oscillatory and non-singular asymptotic solutions to stress fields around interface cracks are obtained.
      PubDate: 2017-06-09T02:30:38.800731-05:
      DOI: 10.1111/ffe.12624
       
  • Probabilistic assessment of VHCF data as pertaining to concurrent
           populations using a Weibull regression model
    • Authors: M. Muniz-Calvente; A. Fernández-Canteli, B. Pyttel, E. Castillo
      Abstract: The Weibull regression model proposed by Castillo and Canteli to evaluate fatigue results represents a possible and adequate option to be used for the assessment and prediction of very high cycle fatigue (VHCF) lifetimes. Among others, this model provides a probabilistic definition of the S-N field for determining failure mechanisms, ie, internal and surface ones, based on extreme value distributions of the Weibull family for minima, as well as the existence of an asymptotic fatigue limit and the capability to reduce the S-N field to a single cumulative distribution function by considering the normalized variable V = (log N-B) (log Δσ). In this way, both dual fracture mechanisms characterizing the VHCF data can be adequately interpreted and handled as independent distributions in such a particular and complex case of concurrent populations, known statistically as a confounded data problem. Once the model parameters of both normalized cumulative distribution functions are estimated, the probability of failure for any of both failure mechanisms at whatever stress range can be determined by applying a back normalization to the original Wöhler field. Two examples of application are presented, the first one to introduce the proposed methodology by means of an example with simulated data to show the reliability of the proposed approach to fit correctly the model parameters assumed for the simulation, and the second one, using real results from a former external experimental VHCF program. Finally, a test strategy, which optimizes the planning of the fatigue program, is suggested.
      PubDate: 2017-06-06T02:30:30.098966-05:
      DOI: 10.1111/ffe.12641
       
  • Issue Information
    • Pages: 1507 - 1508
      Abstract: No abstract is available for this article.
      PubDate: 2017-09-04T01:37:44.222256-05:
      DOI: 10.1111/ffe.12528
       
  • An overview of fatigue in aircraft structures
    • Authors: S. M. O. Tavares; P. M. S. T. Castro
      Pages: 1510 - 1529
      Abstract: From safe-life to fail-safe and damage-tolerance approaches, the last one emerged as the main design philosophy for aerostructures, allowing weight savings and at the same time increasing reliability and structural integrity in the presence of damages which may have occurred during the manufacturing process or during service. The application of damage-tolerance philosophy requires extensive know-how of the fatigue and fracture properties, corrosion strength, potential failure modes and non-destructive inspection techniques, particularly minimum detectable defect and inspection intervals.To face scatter in material properties, conservative approaches considering the worst scenario or statistical methods dealing with the variability of material have been employed in the fatigue assessment of structures. The fatigue life estimation can display substantial variability, illustrating the need for a probabilistic assessment in practical applications. As an example, the variation in the fatigue life for the common scenario of a through crack in an Al alloy plate was evaluated taking into account scatter of properties.The 2010 FAA rule establishing a limit of validity (LOV) puts a bound in the indefinite operational life allowed for by earlier regulations. This requirement, together with the diminishing role of aluminium in airframes, will certainly shape the directions of fatigue, fracture and damage mechanics research in years to come, expanding the knowledge base upon which substantiation of LOV values is made, and ensuring safety under sustainable conditions.
      PubDate: 2017-05-17T02:41:44.535663-05:
      DOI: 10.1111/ffe.12631
       
  • Fatigue behaviour of innovative multifunctional epoxy resins
    • Authors: Sp. G. Pantelakis; P. V. Polydoropoulou, Ch. V. Katsiropoulos
      Pages: 1530 - 1537
      Abstract: Multi walled carbon nanotubes (MWCNTs) and glycidyl polyhedral oligomeric silsesquioxanes (GPOSS) are common additives to enhance electrical conductivity and flame resistance of polymer resins, respectively. Yet, these additions may appreciably influence the mechanical behaviour of the polymers. In this work, the synergistic effect of MWCNTs and GPOSS on the fatigue behaviour of the polymer RTM6-2 was investigated. The results were discussed supported by scanning electron microscopy and energy dispersive spectroscopy analyses. By enhancing the polymer with MWCNTs, a slight decrease in the fatigue life is observed in the range of the low stress levels; however, it tends to coincide with the reference material at fatigue limit. The incorporation of the flame retardant GPOSS into the polymer enhanced with MWCNTs seems to have a significant deteriorating effect on the fatigue life. Scanning electron microscopy and energy dispersive spectroscopy investigation revealed MWCNTs and GPOSS agglomerations; they seem to act as defects leading to a degradation of the fatigue resistance.
      PubDate: 2017-04-20T00:11:45.297102-05:
      DOI: 10.1111/ffe.12604
       
  • An η-compliance method to estimate the J-Δa curve for pipes with a
           circumferential surface crack
    • Authors: N. Parool; X. Qian, C. G. Koh
      Pages: 1624 - 1639
      Abstract: This paper presents an η-compliance method to measure the J-Δa curve for pipes with a circumferential surface crack, using the experimentally recorded load versus the crack mouth opening displacement (CMOD) relationship. This study modifies the η method commonly practiced for standard through-thickness fracture specimens to measure the energy release rate, J, from P-CMOD curve for pipes with a circumferential surface crack. The non-dimensional parameter η for the surface-cracked pipes derives from elastic–plastic finite element analyses. The relationship between the crack size and the CMOD-based compliance, coupled with crack profiles interpolated linearly between the fatigue crack profile and the crack profile after ductile tearing, allows determining the crack depth corresponding to the measured CMOD compliance. The measured location-specific J-Δa curves indicate consistency with the fracture resistance curve measured from through-thickness fracture specimens at small crack extension levels. The difference between the fracture resistances becomes significantly larger as the crack extends beyond 0.5 mm.
      PubDate: 2017-02-10T01:00:51.028887-05:
      DOI: 10.1111/ffe.12592
       
  • High-temperature LCF life estimation based on stress gradient effect of
           notched GH4169 alloy specimens
    • Authors: J. L. Wang; D. S. Wei, Y. R. Wang, B. Zhong
      Pages: 1640 - 1651
      Abstract: Based on the Neuber's rule and Walker equation, a new measurement method considering the influence of mean stress and stress gradient is proposed. A stress gradient factor is defined to correct the traditional Walker equation; thus, it is easy to estimate the life of the structural components only based on the purely elastic finite element analysis. The low-cycle fatigue experiment was carried out by using the direct aging GH4169 notched specimen with different stress concentration factors under evaluated temperature. The fracture morphology of specimens was analyzed to determine the crack initiation position and the damage mechanism. The data points of the experiment life and the estimation life are correlated well within a three times scatter band. It indicates that the Walker equation corrected by introducing a new kind of measurement of stress gradient is reliable to estimate the notched specimen fatigue life.
      PubDate: 2017-02-21T03:05:50.243582-05:
      DOI: 10.1111/ffe.12594
       
  • Correction of plastic zone estimates from linear elastic stress field: a
           qualitative analysis
    • Authors: R. A. Sousa; F. P. Figueiredo
      Pages: 1652 - 1663
      Abstract: This paper shows the usual inconsistency made in the linear elastic fracture mechanic, which is to estimate plastic zones (pz) from a linear elastic (LE) analysis with correction of the pz size based on assumptions of equilibrium. The corrected LE pz is compared with the pz obtained from elastic–plastic analyses. For this purpose, the finite element method is used. Moreover, the load histories in points along the domains of the corrected LE pz and elastic–plastic pz are computed and analysed. This paper, showing that LE pz, corrected or not, has only a qualitative interpretation.
      PubDate: 2017-02-10T00:55:44.932287-05:
      DOI: 10.1111/ffe.12596
       
  • Crack growth at fastener holes containing intergranular cracking
    • Authors: M. Lo; R. Jones, A. Bowler, M. Dorman, D. Edwards
      Pages: 1664 - 1675
      Abstract: This paper examines the growth of cracks at a fastener hole containing intergranular cracking with a focus on ‘dome nut hole’ coupons that are representative of a critical location in the Royal Australian Air Force AP-3C Orion wing. It is shown that crack growth under operational flight loads can be captured using the NASGRO formulation and that the scatter in these various tests can also be captured by allowing for small variations in the value of the cyclic stress intensity fatigue threshold. In this context, it is shown that crack growth can be captured using both a cycle-by-cycle analysis and also a United States Air Force ‘characteristic K’ approach. We also see that, for the operational load spectra considered, the crack growth history is approximately exponential so that the United States Air Force risk assessment computer program (PRobability Of Fracture) can be used to assess the risk of failure by fracture. The results of this study also suggest that, provided that intergranular cracking does not turn and break through to a free surface, it should have little effect on crack growth at a fastener hole.
      PubDate: 2017-02-27T03:05:41.585972-05:
      DOI: 10.1111/ffe.12597
       
  • VHCF response of Gaussian specimens made of high-strength steels:
           comparison between unrefined and refined AISI H13
    • Authors: A. Tridello
      Pages: 1676 - 1689
      Abstract: It is well-known in the literature that the characteristic defect size of high-strength steels strongly influences their Very-High-Cycle Fatigue (VHCF) response. Currently, several refining processes permit to reduce the characteristic defect size and permit to remove large defects in high-strength steels, thus inducing a possible significant enhancement of the VHCF response.The present paper investigates the effects of a specific refinement process, the Electro-Slag Remelting (ESR), on the VHCF response of an AISI H13 steel. Ultrasonic VHCF tests are carried out on large Gaussian specimens made of unrefined and refined AISI H13 steels. Fracture surfaces are investigated to compare inclusion populations before and after the ESR process. Finally, the fatigue limit and the design S-N curves are statistically estimated to quantify the beneficial effects induced by the ESR process.
      PubDate: 2017-04-12T03:11:33.728667-05:
      DOI: 10.1111/ffe.12610
       
 
 
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