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 International Journal of Material FormingJournal Prestige (SJR): 0.536 Citation Impact (citeScore): 2Number of Followers: 1      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1960-6214 - ISSN (Online) 1960-6206 Published by Springer-Verlag  [2469 journals]
• Correction to: Strain path dependency in incremental sheet-bulk metal
forming

PubDate: 2022-06-22

• Correction to: Calibration of the residual stresses with an active die
during the ejection phase of cold extrusion

PubDate: 2022-06-21

• Research on hydroforming through combination of internal and external
pressures for manufacturing the structure of double-layer tube with gap

Abstract: Abstract According to the current development of commercial vehicles, a novel structure of the double-layer exhaust pipe with gap was designed. Hydroforming through the combination of internal and external pressures (HIEP) was proposed to form the complex structure of the new exhaust pipe. The double-layer tube without gap was used as the initial tube blank. High-pressure liquid was introduced into the inner tube and between the two tubes. The outer tube would bulge outward and fit the die cavity as its inner surface was subjected to hydraulic pressure. Meanwhile, the inner tube would not deform due to both the inner and outer surfaces were subjected to hydraulic pressure. In addition, before the HIEP, it is necessary to pre-bend the double-layer tube. The feasibility of the process was analyzed by numerical simulation. The process parameters were optimized by response surface methodology (RSM). The objective functions such as the maximum thinning rate, unevenness of wall thickness and gap dispersion were established in RSM models, whose accuracy was verified by a statistical method of analysis of variance. Subsequently, the die of HIEP was designed and developed. The verification experiments were carried out and the double-layer exhaust pipe with gap was successfully manufactured.
PubDate: 2022-06-19

• Failure behaviour of various pre-formed steel sheets with respect to the
mechanical grain boundary properties

Abstract: Abstract The forming history influences the mechanical properties and the formability of sheet metals. Numerous models and approaches have been published to implement this influence into FE-tools, based on isotropic damage or failure criterions. In this paper, the influence of a uniaxial pre-forming and a change in loading direction on the material parameters is investigated for two different steel grades in tensile tests. It was found, that a change in loading direction significantly affects the mechanical properties of the material. The force–displacement curves obtained from nanoindentation experiments were utilized to determine the flow curves for single grains as well as grain boundaries of the pre-formed materials. This was done by inverse parameter identification using finite element analysis.
PubDate: 2022-06-15

• Formulation, identification and validation of a stochastic internal
variables model describing the evolution of metallic materials
microstructure during hot forming

Abstract: Abstract Construction metallic materials combine strength with formability. These features are obtained for heterogeneous microstructures with hard constituents dispersed in a soft matrix. On the other hand, sharp gradients of properties between phases cause a local fracture. Advanced models are needed to design microstructures with smoother gradients of their features. Models based on stochastic internal variables meet this requirement. Our objective was to account for the random character of the recrystallization and to transfer this randomness to equations describing the evolution of dislocations and grain size. The idea of the internal variable model with dislocation density and grain size being stochastic variables is described in the paper. Experiments composed of uniaxial compression tests were performed to supply data for the identification and verification of the model. The loads as a function of time during compression and histograms of the grain size after deformation were measured in each test. Identification and validation of the model were performed. Finally, the developed model was applied to simulate selected industrial hot forming processes.
PubDate: 2022-06-09

• Analysis of springback of aluminum and high-strength steels through a new
large strain anisotropic elastoplastic formulation based on elastic
corrector rates

Abstract: Abstract Aluminum and high-strength steels (HSS) are increasingly being employed in the sheet metal forming in the automotive, aeronautical, and household appliances industries. These metals are characterized by substantially larger strength-to-moduli ratios than classical steels, and result in much more important elastic unloading (springback) effects which must be accurately predicted to avoid quality issues. Finite element simulations typically show lower accuracy in predicting springback than in predicting plastic deformation. The accuracy of springback predictions may be affected by relatively small errors in the computation of the loading stress or the plastic strain contribution, which may result in larger relative elastic unloading strain errors, due to their strength-to-moduli ratios. In this work we address the prediction of the springback effects in aluminum and HHS employing a novel hyperelastic-based multiplicative large strain elastoplasticity model. We demonstrate that employing a simplest Prager-based combined hardening with this formulation, accurate consistent predictions of springback are obtained, even without resorting to typical improvements like strain-dependent elastic moduli or hardening for yield surface shape evolution.
PubDate: 2022-06-08

• Theoretical predictions of dynamic necking formability of ductile metallic

Abstract: Abstract In this paper, we have investigated necking formability of anisotropic and tension-compression asymmetric metallic sheets subjected to in-plane loading paths ranging from plane strain tension to near equibiaxial tension. For that purpose, we have used three different approaches: a linear stability analysis, a nonlinear two-zone model and unit-cell finite element calculations. We have considered three materials –AZ31-Mg alloy, high purity α-titanium and OFHC copper– whose mechanical behavior is described with an elastic-plastic constitutive model with yielding defined by the CPB06 criterion (15) which includes specific features to account for the evolution of plastic orthotropy and strength differential effect with accumulated plastic deformation (48). From a methodological standpoint, the main novelty of this paper with respect to the recent work of N’souglo et al. (42) –which investigated materials with yielding described by the orthotropic criterion of Hill (24)– is the extension of both stability analysis and nonlinear two-zone model to consider anisotropic and tension-compression asymmetric materials with distortional hardening. The results obtained with the stability analysis and the nonlinear two-zone model show reasonable qualitative and quantitative agreement with forming limit diagrams calculated with the finite element simulations, for the three materials considered, and for a wide range of loading rates varying from quasi-static loading up to 40000 s− 1, which makes apparent the capacity of the theoretical models to capture the mechanisms which control necking formability of metallic materials with complex plastic behavior. Special mention deserves the nonlinear two-zone model, as it does not need prior calibration –unlike the stability analysis– and it yields accurate predictions that rarely deviate more than 10% from the results obtained with the unit-cell calculations.
PubDate: 2022-06-07

• Influence of Sheet Metal Pre-forming on Edge Crack Sensitivity using

Abstract: Abstract Especially in the automotive sector, high-strength sheet materials are processed in the manufacturing industry. These steels often show a pronounced sensitivity to edge cracks. Because of this, many edge crack testing methods for a wide variety of stress conditions have been developed to describe the edge crack sensitivity of a material. Only the hole expansion test according to ISO 16630 has been standardized. However, the standardization has some gaps in the process description, which has resulted in test modifications. Another disadvantage is the dependence of the results on the machine operator. In the past, the influence of the shear cutting parameters die clearance, cutting edge geometry, and type of cutting line on the edge crack sensitivity was only calculated for undeformed sheet materials. Not only are shear cutting operations carried out on undeformed sheet blanks in the context of the manufacturing of sheet metal components, but more and more pre-formed sheets are mechanically separated and subsequently further formed. Therefore, it is essential to consider the influence of the type and amount of pre-forming introduced on the sensitivity of a material to edge cracks. The discrete types of pre-forming, uniaxial tension, plane strain, and equi-biaxial stretch forming were introduced to sheet metal blanks using dual-phase steel. The Edge-Fracture-Tensile-Test was used to identify the residual formability of the undeformed and pre-formed specimens. The Edge-Crack-Sensitivity-Factor $${K}_{\mathrm{ec}}$$ , which can be used to predict edge cracks in a finite element forming simulation, was determined from the recorded major strains for selected parameter configurations.
PubDate: 2022-06-04

• An analytical model for designing defect-free sheet metal profiles with
height-variable cross sections manufactured by Flexible Roller Beading

Abstract: Abstract Following the industrial change from mass production towards serial customization flexible technologies are becoming increasingly important. Therefore, the novel forming process “flexible roller beading” (FRB) is developed, which enables the continuous production of sheet metal profiles with customizable variable cross-sectional height and exploits the lightweight potential of profile-based constructions. To guarantee the quality and further processability of the profiles, component defects—primarily sheet wrinkling in the profile flange—must be avoided. The occurrence of wrinkling is affected by various geometric parameters of the targeted profile. This makes an empirical determination of the material-dependent process limits inefficient due to the expensive computational times of numerical simulations and effort of experimental test executions. Therefore, a mathematical model is developed which allows the analytical prediction of the process instabilities causing sheet wrinkling. The presented paper includes the description of the mechanical characteristics of FRB based on numerical and experimental investigations. The predictive analytical model derived from these findings determines the maximum longitudinal compressive stress in the profile flange, which is responsible for the wrinkling formation, based on the relevant geometric characteristics. By the comparison of the calculated occurring longitudinal compressive stress with the material-specific critical stress, sheet wrinkling can be predicted and failure-free profile geometries can be efficiently designed. The generality of the analytical model, independent of the profile geometry, is validated by experimental tests.
PubDate: 2022-05-28

• Real-time prediction by data-driven models applied to induction heating
process

Abstract: Abstract Data-driven modeling approach constitutes an appealing alternative to the finite element method for optimizing complex multiphysics parametrized problems. In this context, this paper aims at proposing a parametric solution for the temperature-time evolution during the multiphysics induction heating process by using a data-driven non-intrusive modeling approach. To achieve this goal, firstly, a set of synthetic solutions was collected, at some sparse sensors in the space domain and for properly selected process parameters, by solving the full-order finite element models using FORGE® software. Then, the gappy proper orthogonal decomposition method was used to complete the missing data. Next, the proper orthogonal decomposition method coupled with the nonlinear sparse proper generalized decomposition regression method was applied to find a low-dimensional space onto which the original solutions were projected and a model for the low-dimensional representations was, therefore, created. Hence, a real-time prediction of the temperature-time evolution and for any new process parameters could be efficiently computed at the predefined positions (sensors) in the space domain. Finally, spatial interpolation was carried out to extend the solutions everywhere in the spatial domain by applying a strategy based on the nonlinear dimensionality reduction by locally linear embedding method and the proper orthogonal decomposition method with radial basis functions interpolation. It was shown that the results are promising and the applied approaches provide good approximations in the low-data limit case.
PubDate: 2022-05-27

• Evaluation of the mechanical properties and deformability of metal-based
composite sheets made of thin stainless-steel sheets and carbon fiber
reinforced plastics

Abstract: Abstract Ultra-lightweight sheets with excellent deformability are required for the development of new air vehicles, as well as greener conventional vehicles. Carbon fiber reinforced plastic (CFRP) has a high specific rigidity and strength but is too expensive to be used in general machine parts. Using CFRP enhances the properties of the material itself. Furthermore, developing the usage of the material also makes the mechanical properties higher. The purpose of this paper is to combine both methods and produce a material with better rigidity and deformability. The new structure was proposed considering the moment of inertia of area. This structure was excellent not only in terms of rigidity but also in the moldability of the core. In addition, the effects of the structure dimensions on the moldability, bonding strength and flexural rigidity were determined using finite element (FE) analysis and experiments. By comparing the results of the FE analysis conducted under pure bending conditions with three-point bending experiment, it was found that the FE analysis of pure bending fails to predict the three-point bending stiffness because the shear stress has a significant effect on the experimental measurements. By modifying the model from pure bending to three-point bending, the experimental results were well reproduced by the 3D FE analysis.
PubDate: 2022-05-16

• Novel approach to optimize the mechanical properties of Cu-Al composite
wires

Abstract: Abstract The present study is concerned with the mechanical properties of Cu-Al wires manufactured via cold drawing. The common approach for improving the tensile strength of drawn wires is to optimize the operational parameters. Those parameters include the die geometry, amount of area reduction at each pass, drawing speed, lubrication and so on. Optimization helps homogenize the plastic deformation during wire drawing. That in turn minimizes the undesirable effect of processing-induced tensile residual stresses forming near the wire surface. The current investigation introduces a novel optimization approach to modify the residual stress distribution with a focus on the fiber-matrix configuration rather than the operational parameters. To that end, residual stress distributions in the two configurations I- conventional copper-clad aluminum and II- so-called “Architectured” wires were compared at the same Cu/Al volume fraction. The comparison was performed using the finite element analysis. Experimental stress–strain curves, numerical residual stress profiles, and equivalent plastic strain contours were then plotted for both conventional and novel configurations. The findings suggest that the novel composite wires offer remarkably better tensile behavior along with other already-known electrical and thermal advantages. This could be ascribed to their architectural features such a continuous copper network and fine Al fibers. Therefore, the new fiber-matrix configuration could remove the need for optimization of various operational parameters or post-drawing treatments for a given wiredrawing set-up.
PubDate: 2022-05-06

• Robustness of deep-drawing finite-element simulations to process
variations

Abstract: Abstract Robustness of numerical models paves the way for efficient compensation of perturbations resulting in deviations from the nominal conditions. This is critical if the numerical simulations will be used to determine closed-loop process control adjustments to assure the final part quality. This work details the procedure to establish and validate numerical process models, through an investigation of deep-drawing of AA1100-O blanks using 3D Servo Press. Of particular interest is the robustness of the deep-drawing simulation models to different process variations and off-design conditions. The experiments are performed on a 3D Servo Press, used as a conventional press, and equipped with a spring-loaded blank holder. From the experiments, the punch force–displacement as well as local features, i.e., flange draw-in and wall-thinning, are obtained. Two types of finite element models of the drawing process are created, one using shell and the other using solid elements. Correspondingly, the plastic anisotropy of the blanks is modeled using the Yld2000-2d (2D) and Yld2004-18p (3D) yield functions. The friction coefficient between the blank and tooling is inversely identified by comparing the simulated punch force–displacement response, flange draw-in and thickness variations with the experimental ones. The robustness of the numerical and material models is confirmed by process variations on the geometry of the blanks, i.e., an initial offset of blank center and elliptical blanks. However, the wrinkling of the flange due to variation of the blank holder force is not captured by the model. A modification to the model, i.e., by introducing appropriate geometric imperfections to the blank, enables it to predict the flange wrinkling. This work investigates the robustness of numerical models to different types of process variations, which is vital in model-based control analyses.
PubDate: 2022-05-03

• Optimization and inverse analysis in metal forming: scientific
state-of-the-art and recent trends

Abstract: Abstract Nowadays, the accuracy and fast result-delivery of numerical simulations allow to perform not simply feasibility and validation tasks but to actually accomplish optimized process designs and solutions for the metal forming industry. This paper present a wide overview of the role of optimization and inverse analysis in the scientific and industrial community of metal forming, including the contribution of the ESAFORM association to this thematic, which is still growing after about three decades of intense research. The number of efficient and effective solutions comprising metal forming and optimization seems to increase year after year. Representative process optimization problems in sheet, bulk, and tube metal forming are presented through significant examples, and the treatment of uncertainty is also shown in stochastic approaches combined with optimization methods. Inverse problems in metal forming, which are solved with the aid of optimization methodologies, are also discussed particularly with emphasis on parameter identification problems and inverse material characterization in mechanical plasticity. The paper also identifies the most recent research trends and formulates some predictions for the future needs of industrial users. This paper shows not only that the relevance of the field of study is still increasing, but also that optimization and inverse analysis in metal forming is playing and will continue to play an important role in the digital transition of the metal forming industry, where simulation still represents the most advanced frontier.
PubDate: 2022-04-27

• Tailored Forming of hybrid bulk metal components

Abstract: Abstract Multi-material bulk metal components allow for a resource efficient and functionally structured component design, with a load adaptation achieved in certain functional areas by using similar and dissimilar material combinations. One possibility for the production of hybrid bulk metal components is Tailored Forming, in which pre-joined semi-finished products are hot-formed using novel process chains. By means of Tailored Forming, the properties of the joining zone are geometrically and thermomechanically influenced during the forming process. Based on this motivation, forming processes (die forging, impact extrusion) coupled with adapted inductive heating strategies were designed using numerical simulations and successfully realised in the following work in order to produce demonstrator components with serial or coaxial material arrangements. The quality of the joining zone was investigated through metallographic and SEM imaging, tensile tests and life cycle tests. By selecting suitable materials, it was possible to achieve weight savings of 22% for a pinion shaft and up to 40% for a bearing bush in the material combination of steel and aluminium with sufficient strength for the respective application. It was shown that the intermetallic phases formed after friction welding barely grow during the forming process. By adjusting the heat treatment of the aluminium, the growth of the IMP can also be reduced in this process step. Furthermore, for steel-steel components alloy savings of up to 51% with regard to chromium could be achieved when using low-alloy steel as a substitute for high-alloy steel parts in less loaded sections. The welded microstructure of a cladded bearing washer could be transformed into a homogeneous fine-grained microstructure by forming. The lifetime of tailored formed washers nearly reached those of high-alloyed mono-material components.
PubDate: 2022-04-27

• Plastic flow localization resulting from yield surface vertices: crystal
plasticity and corner theories of plasticity

Abstract: Abstract This article describes the fundamentals and importance of the yield surface vertex effects in plastic flow localization predictions. The yield surface vertex effects are inherent in crystal plasticity based on Schmid law and have been elaborated in phenomenological corner plasticity theories. First, the theoretical importance, experimental evidence and modeling strategies of the yield surface vertices are presented. Next, plastic flow localization analyses using the yield surface vertex effects in previous studies are reviewed. Both full-field analyses by the finite element method and simplified analyses (i.e., Marciniak–Kuczynski-type of approach) are considered. It is also to be noted that conventional plasticity theories (including both phenomenological and crystal plasticity theories) do not involve any intrinsic material length-scale effects. This could lead to drawbacks in applications and plastic flow localization analyses, because these theories do not enable to predict shear bands with width of finite size. We conclude with the presentation and review of recent developments of gradient-enhanced vertex-type plasticity and crystal plasticity theories.
PubDate: 2022-04-27

• Plasticity evolution of an aluminum-magnesium alloy under abrupt strain
path changes

PubDate: 2022-04-22

• Advancements in extrusion and drawing: a review of the contributes by the
ESAFORM community

Abstract: Abstract The present review paper would celebrate the 25 years anniversary of the ESAFORM association by summarizing the studies performed by the delegates of the ESAFORM conference series within mini-symposium “Extrusion and Drawing” and of the papers published in the International Journal of Material Forming in the same fields. The 160 analyzed papers have been divided in four main categories corresponding to the paper main chapters (Hot Metal Extrusion, Cold Metal Extrusion, Polymer Extrusion and Drawing) then further divided in sub-chapters in order to group them in more specific research subjects. The aim of this review paper is then to provide to the reader a complete overview of the investigated topics and of the research trends over the years within the ESAFORM associate researchers.
PubDate: 2022-04-22

• Advances in composite forming through 25 years of ESAFORM

Abstract: Abstract The increase in the number of structural applications of composite materials, especially in the aerospace and automotive industries, has led to a demand for robust models to simulate composite forming processes. The mechanical behaviour of composite materials during forming is relatively complex due to their fibre-matrix composition. Many research studies have been conducted in the past 25-plus years into experimental methods for the characterization of the mechanical behaviours that are exhibited by textile-reinforced composite material systems during forming and into the development of material models to be used in computer codes for forming simulations. These studies have been presented and discussed in the ESAFORM conferences since 1997 and especially in the 'Composite Forming Processes' mini-symposium launched in 2001. This article presents a survey of the research carried out in this context. Mechanical characterization tests specific to composite forming are presented as well as recent analysis techniques such as digital image correlation and X-ray tomography. Three-dimensional mechanical behaviour laws, in particular hypo- and hyperelastic, have been developed and extended to second gradient models. Specific shell approaches have been presented and their application to wrinkling analysis. Resin flow and permeability analysis is another area of research in composite forming processes which are discussed in this article. Research on certain processes is also presented, in particular thermoforming of thermoplastic composites, wet compression moulding, pultrusion, automated fibre placement and three-dimensional printing. This comprehensive review of the works of multiple research groups is a recognition of the breadth and depth of efforts that have been invested into the understanding of the manufacturability of textile-reinforced composite materials.
PubDate: 2022-04-20

• Comparative study of various hardening models for the prediction of
plastic responses under strain path change conditions

Abstract: Abstract This work is aimed at investigating the influence of hardening models on the prediction of plastic responses of sheet metals under strain path change conditions. An enhanced back-stress restoration evolution hardening model was proposed, considering that the back stress accumulated in preloading stages was restored gradually in the subsequent loading stage. A comparative study was conducted between the proposed model and other two hardening models, i.e. Chaboche combined hardening model and Yoshida-Uemori hardening model, in terms of their prediction accuracy of work-hardening and r-value evolution behaviors under reverse and orthogonal loading conditions. The parameters in the models were determined by the experimental results of uniaxial tension and uniaxial compression-tension-compression tests using 6061O aluminum sheet. Associated with the Yld2000-2d yield function, these three hardening models were further employed to simulate a two-stage deep drawing process of a cylindrical cup. The predicted punch load-stroke curves, the height distribution of the drawn cup, and the split-ring springback were compared with the experimental ones. Obvious difference between the predictions was observed in the second drawing stage, which indicates the significant influence of hardening model on the prediction of plastic response under strain path change conditions. Among these three hardening models, the proposed hardening model presented a good prediction result which matched well with the experimental outcome.
PubDate: 2022-04-13
DOI: 10.1007/s12289-022-01673-9

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