Subjects -> INSTRUMENTS (Total: 63 journals)
Showing 1 - 16 of 16 Journals sorted alphabetically
Applied Mechanics Reviews     Full-text available via subscription   (Followers: 27)
Bulletin of Social Informatics Theory and Application     Open Access   (Followers: 1)
Computational Visual Media     Open Access   (Followers: 4)
Devices and Methods of Measurements     Open Access  
Documenta & Instrumenta - Documenta et Instrumenta     Open Access  
EPJ Techniques and Instrumentation     Open Access  
European Journal of Remote Sensing     Open Access   (Followers: 9)
Experimental Astronomy     Hybrid Journal   (Followers: 39)
Flow Measurement and Instrumentation     Hybrid Journal   (Followers: 18)
Geoscientific Instrumentation, Methods and Data Systems     Open Access   (Followers: 4)
Geoscientific Instrumentation, Methods and Data Systems Discussions     Open Access   (Followers: 1)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 2)
IEEE Sensors Journal     Hybrid Journal   (Followers: 103)
IEEE Sensors Letters     Hybrid Journal   (Followers: 3)
IJEIS (Indonesian Journal of Electronics and Instrumentation Systems)     Open Access   (Followers: 3)
Imaging & Microscopy     Hybrid Journal   (Followers: 9)
InfoTekJar : Jurnal Nasional Informatika dan Teknologi Jaringan     Open Access  
Instrumentation Science & Technology     Hybrid Journal   (Followers: 6)
Instruments and Experimental Techniques     Hybrid Journal   (Followers: 1)
International Journal of Applied Mechanics     Hybrid Journal   (Followers: 7)
International Journal of Instrumentation Science     Open Access   (Followers: 40)
International Journal of Measurement Technologies and Instrumentation Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Metrology and Quality Engineering     Full-text available via subscription   (Followers: 4)
International Journal of Remote Sensing     Hybrid Journal   (Followers: 282)
International Journal of Remote Sensing Applications     Open Access   (Followers: 45)
International Journal of Sensor Networks     Hybrid Journal   (Followers: 4)
International Journal of Testing     Hybrid Journal   (Followers: 1)
Journal of Applied Remote Sensing     Hybrid Journal   (Followers: 83)
Journal of Astronomical Instrumentation     Open Access   (Followers: 3)
Journal of Instrumentation     Hybrid Journal   (Followers: 32)
Journal of Instrumentation Technology & Innovations     Full-text available via subscription   (Followers: 2)
Journal of Medical Devices     Full-text available via subscription   (Followers: 5)
Journal of Medical Signals and Sensors     Open Access   (Followers: 3)
Journal of Optical Technology     Full-text available via subscription   (Followers: 5)
Journal of Sensors and Sensor Systems     Open Access   (Followers: 11)
Journal of Vacuum Science & Technology B     Hybrid Journal   (Followers: 3)
Jurnal Informatika Upgris     Open Access  
Measurement : Sensors     Open Access   (Followers: 3)
Measurement and Control     Open Access   (Followers: 36)
Measurement Instruments for the Social Sciences     Open Access  
Measurement Science and Technology     Hybrid Journal   (Followers: 7)
Measurement Techniques     Hybrid Journal   (Followers: 3)
Medical Devices & Sensors     Hybrid Journal  
Medical Instrumentation     Open Access  
Metrology and Instruments / Метрологія та прилади     Open Access  
Metrology and Measurement Systems     Open Access   (Followers: 6)
Microscopy     Hybrid Journal   (Followers: 8)
Modern Instrumentation     Open Access   (Followers: 50)
Optoelectronics, Instrumentation and Data Processing     Hybrid Journal   (Followers: 4)
PFG : Journal of Photogrammetry, Remote Sensing and Geoinformation Science     Hybrid Journal  
Photogrammetric Engineering & Remote Sensing     Full-text available via subscription   (Followers: 29)
Remote Sensing     Open Access   (Followers: 55)
Remote Sensing Applications : Society and Environment     Full-text available via subscription   (Followers: 8)
Remote Sensing of Environment     Hybrid Journal   (Followers: 93)
Remote Sensing Science     Open Access   (Followers: 24)
Review of Scientific Instruments     Hybrid Journal   (Followers: 23)
Science of Remote Sensing     Open Access  
Sensors and Materials     Open Access   (Followers: 2)
Solid State Nuclear Magnetic Resonance     Hybrid Journal   (Followers: 3)
Standards     Open Access  
Transactions of the Institute of Measurement and Control     Hybrid Journal   (Followers: 13)
Труды СПИИРАН     Open Access  
Similar Journals
Journal Cover
International Journal of Applied Mechanics
Journal Prestige (SJR): 0.793
Citation Impact (citeScore): 2
Number of Followers: 7  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1758-8251 - ISSN (Online) 1758-826X
Published by World Scientific Homepage  [119 journals]
  • Modeling of Thin Plate Flexural Vibrations by Partition of Unity Finite
           Element Method
    • Authors: Tong Zhou, Jean-Daniel Chazot, Emmanuel Perrey-Debain, Li Cheng
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      This paper presents a conforming thin plate bending element based on the Partition of Unity Finite Element Method (PUFEM) for the simulation of steady-state forced vibration. The issue of ensuring the continuity of displacement and slope between elements is addressed by the use of cubic Hermite-type Partition of Unity (PU) functions. With appropriate PU functions, the PUFEM allows the incorporation of the special enrichment functions into the finite elements to better cope with plate oscillations in a broad frequency band. The enrichment strategies consist of the sum of a power series up to a given order and a combination of progressive flexural wave solutions with polynomials. The applicability and the effectiveness of the PUFEM plate elements are first verified via the structural frequency response. Investigation is then carried out to analyze the role of polynomial enrichment orders and enriched plane wave distributions for achieving good computational performance in terms of accuracy and data reduction. Numerical results show that the PUFEM with high-order polynomials and hybrid wave-polynomial combinations can provide highly accurate prediction results by using reduced degrees of freedom and improved rate of convergence, as compared with the classical FEM.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-05-08T07:00:00Z
      DOI: 10.1142/S1758825121500307
       
  • In Vivo Measurement of the Mechanical Properties of Facial Soft Tissue
           Using a Bi-Layer Material Model
    • Authors: Huixin Wei, Xuliang Liu, Anna Dai, Linan Li, Chuanwei Li, Shibin Wang, Zhiyong Wang
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      In vivo characterization of facial soft tissue is of great significance for facial plastic surgery, animation and dermatology. This paper presents an in vivo experimental method to characterize the macroscopic mechanical properties of facial soft tissue. In this method, a bi-layer material (BLM) model is established with the skeleton as the substrate under the facial soft tissue and the relationship between the mechanical properties of soft tissue and force–displacement curve is obtained. A novel indentation apparatus is also developed to experimentally measure the force-displacement curve of the facial soft tissue in vivo. Using the apparatus, experiments were conducted on artificial skins to verify the theoretical model. Experiments on facial soft tissue were finally conducted on four volunteers to obtain Young’s moduli at five facial locations using an optimal indenter whose radius is determined by the verification experiment. Our experiment results indicate that a slight difference is observed in Young’s moduli of facial soft tissue among different volunteers and indentation location. At locations of the left-hand cheek near the lips (NE) and center of the left-hand jaw (CJ), Young’s moduli [math] are relatively large ranging from 2.653[math]kPa to 4.437[math]kPa. Nevertheless, at other locations of the center of the cheek (CC), left-hand zygomatic region (ZYG) and left-hand cheek near the lips (NL), the contact forces are smaller, and Young’s moduli [math] are between 1.649[math]kPa and 3.395[math]kPa.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-05-08T07:00:00Z
      DOI: 10.1142/S1758825121500344
       
  • Contact Area-Based Modeling of Robotic Grasps Using Deformable Solid
           Mechanics
    • Authors: S. J. Dharbaneshwer, Asokan Thondiyath
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      In robotic grasp analysis, contact between an object and a hand is described using point contact models and soft contact models. Although soft contact models estimate both contact area and contact force for grasp analysis, most of the approaches use point contact models to analyze the stability of grasp because of the simplicity involved in computation and modeling. However, grasps suggested by these approaches are not intuitive to execute with and often fail in experiments. Since the hand–object interface is modeled using points, their physical characteristics are not taken into account in the analysis, thereby resulting in failed grasps. In this work, the contact models related to robotic grasping are briefly reviewed, and the discrepancies present in them are identified from a solid mechanics standpoint. Using the constitutive equations available in solid mechanics, these contact models are then reformulated based on contact areas for both deformable hard as well as soft fingertips. By performing Finite Element (FE) simulations of the contact situation considered, the contact models are validated. The proposed models are validated using robotic grasp experiments as well.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-05-08T07:00:00Z
      DOI: 10.1142/S1758825121500381
       
  • Drying-Induced Pressure Rise and Fracture Mechanics Modeling of the
           Sphagnum Capsule
    • Authors: Jingtian Kang, Suixin Liu, Changguo Wang
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      The Sphagnum capsule can disperse spores at an extraordinarily high velocity and acceleration during drying. Briefly, the pressure rise induced by the decrease in the environmental humidity inside the spore chamber causes crack growth between the lid and the capsule wall. At a critical condition, the lid of the capsule suddenly fractures, and the top spores are propelled by the high pressure. Motivated by this phenomenon, we develop a similar mechanics model to study the drying-induced pressure rise and the fracture mechanism of the Sphagnum capsule in this paper. We investigate the drying-induced pressure rise and obtain the deformation configuration for various stiffness ratios of different parts. We also establish a fracture mechanics model and calculate the energy release rate to study the lid separation during the ejection of spores. We find that the energy release rate increases with crack growth when the crack is short, maximizes at an intermediate central crack angle of around [math], and gradually decreases with further increase in the central crack depending on the loading type. Such a nonmonotonic relationship between the energy release rate and the crack length can be readily used to explain the spontaneously fast unsteady crack growth and the following potential crack arrest reported in the literature. The results and the modeling method obtained in this paper can be used to explain similar fracture-related spore launching of plants and design bioinspired structures to realize the drying-induced fast movement.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-04-30T07:00:00Z
      DOI: 10.1142/S1758825121500277
       
  • Time-Dependent Response of Incompressible Membranes based on Quasi-Linear
           Viscoelasticity Theory
    • Authors: Farzam Dadgar-Rad, Nasser Firouzi
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      In this work, large deformation of incompressible, hyperelastic membranes based on the quasi-linear viscoelasticity (QLV) theory is formulated. Time integration algorithm and the expression for consistent fourth-order tangent tensor are presented. The formulation covers isotropic as well as anisotropic polymeric and biological materials. To solve numerical examples, a nonlinear finite element formulation in the Lagrangian framework is developed. Finally, several examples are provided to investigate the applicability of the present formulation. It is found that the numerical results are in good agreement with the analytical and experimental results available in the literature.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-04-30T07:00:00Z
      DOI: 10.1142/S1758825121500368
       
  • The Use of Contravariant Tensors to Model Anisotropic Soft Tissues
    • Authors: Arthesh Basak, Amirtham Rajagopal, Umesh Basappa, Mokarram Hossain
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      Biological tissues have been shown to behave isotropically at lower strain values, while at higher strains the fibers embedded in the tissue straighten and tend to take up the load. Thus, the anisotropy induced at higher loads can be mathematically modeled by incorporating the strains experienced by the fibers. From histological studies on soft tissues it is evident that for a wide range of tissues the fibers have an oblique mean orientation about the physiological loading directions. Thus, we require a mathematical framework of tensors defined in nonorthogonal basis to capture the direction-dependent response of fibers under high induced loads. In this work, we propose a novel approach to determine the fiber strains with the aid of the contravariant tensors defined in an oblique coordinate system. To determine the fiber strains, we introduce a fourth-order contravariant fiber orientation transformation tensor. The approach helps us successfully in determining the fiber strains, for a family of symmetrically and asymmetrically oriented fibers, with the aid of a single anisotropic invariant. The proposed model was fitted with the experimental data from literature to determine the corresponding material parameters.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-04-30T07:00:00Z
      DOI: 10.1142/S1758825121500393
       
  • Limit Elastic Analysis of Functionally Graded Rotating Disks Under
           Thermo-Mechanical Loading
    • Authors: Royal Madan, Shubhankar Bhowmick
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      In this work, the thermo-mechanical limit elastic speed analysis of functionally graded rotating disk has been reported. Three different material models, i.e., power law (P-FGM), sigmoid law (S-FGM), and exponential law (E-FGM), along with varying disk profiles, namely uniform, tapered, and exponential disk profiles, are considered. The methodology adopted is variational principle wherein the solution has been obtained by Galerkin’s error minimization principle. Halpin–Tsai method was used to estimate the modulus, modified rule of mixture for yield strength, and the rule of mixture for density and coefficient of thermal expansion. This study aims to analyze the effects of material models, grading indices, aspect ratio, and disk geometry on disk performance when subjected to combined thermal and mechanical loadings. Finite element analysis has been performed to validate this study and good agreement between both the methods is seen. The study shows a substantial difference in the limit speed for different disk profiles changing from uniform thickness to exponentially varying thickness. The von Mises stress distribution and location of yielding at limit speed are shown for different indices, material models, and disk profiles. In P-FGM, limit speed decreases with the increase in grading indices whereas in E-FGM, limit speed decreases with the decrease in grading indices. For increase in aspect ratio, limit elastic speed decreases in all the cases.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-04-21T07:00:00Z
      DOI: 10.1142/S1758825121500332
       
  • Implicit Material Point Method with Convected Particle Domain
           Interpolation for Consolidation and Dynamic Analysis of Saturated Porous
           Media with Massive Deformation
    • Authors: Zhiqiang Hu, Yu Liu, Hongwu Zhang, Yonggang Zheng, Hongfei Ye
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      A coupling convected particle domain interpolation based implicit material point method (ICCPDI) is developed in this paper for the long-time consolidation and dynamic problems of fully saturated porous media involving massive deformation. In the method, the implicit formulas based on the u-p form governing equations are derived to overcome the time step size limitation within the conventional explicit method and in turn improve the computational efficiency particularly for consolidation problems. Then, the CPDI technique is adopted to eliminate the numerical noises occurring while material points crossing cell boundaries in the massive deformation of solid skeleton. Moreover, an extended material point penalty method is proposed to effectively treat the boundary constraints in the coupled system by avoiding introducing an auxiliary boundary layer. Numerical simulation results of several representative examples demonstrate the accuracy and efficiency of the proposed ICCPDI method to predict the consolidation and dynamic responses of saturated porous media with massive deformation.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-04-12T07:00:00Z
      DOI: 10.1142/S175882512150023X
       
  • Elasticity Solution for Bending and Frequency Behavior of Sandwich
           Cylindrical Shell with FG-CNTRC Face-Sheets and Polymer Core Under Initial
           Stresses
    • Authors: M. Safarpour, A. Alibeigloo
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      This paper explores the high-accuracy analysis of bending and frequency response of the sandwich cylindrical shell with functionally graded (FG) carbon nanotubes reinforced composite (FG-CNTRC) face-sheets and polymeric core under the effect of initial axial stress and various mechanical loading based upon the three-dimensional theory of elasticity for various sets of boundary conditions. The sandwich structure is composed of multilayers with uniformly dispersed carbon nanotubes (CNT) in each fictitious layer of face-sheets, but its weight fraction changes layer-by-layer along the thickness direction. With the aid of compatibility conditions, the sandwich structure with three layers is modeled. Analytical bending and frequency solutions are obtained for simply supported shells. Also, the state-space based differential quadrature method (SS-DQM) is employed to determine the bending and frequency response of the sandwich cylindrical shell by considering various boundary conditions. The bending response of the sandwich cylindrical shell is obtained under the impact of various mechanical loadings. The influences of several parameters, such as initial stress and various mechanical loadings are investigated on the bending and frequency of the structures. The results of the presented study can be served as benchmarks to assess the validity of the conventional two-dimensional theory.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-04-07T07:00:00Z
      DOI: 10.1142/S1758825121500204
       
  • A New Method for Predicting Double-Crack Propagation Trajectories of
           Brittle Rock
    • Authors: Qingqing Shen, Qiuhua Rao, Quan Zhang, Zhuo Li, Dongliang Sun, Wei Yi
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      Multi-crack propagation is investigated mainly by experimental measurement and little by theoretical prediction. The classical fracture criteria can better predict tensile fracture under arbitrary loading conditions (pure tensile, pure shear and mixed-mode), but have difficulty in predicting shear fracture. In this paper, Mode I and Mode II SIFs of branch-cracks initiated by the original cracks were calculated by the complex function and superposition method, and a new theory of multi-crack propagation was established based on the criterion of maximum tensile-shear SIF ratio. Theoretical results of two collinear cracks under uniaxial compression show that the cracks initiate more easily at [math] (the crack inclination angle) than other angles. Coalescence of branch-crack only occurs at [math] with the maximum crack propagation length. Peak stress [math] reaches minimum when [math] (inner friction angle of rock), and the larger the [math], the closer to the compressive strength of rock the [math]. Mechanism of the crack initiation and propagation are all Mode I under uniaxial compression. Uniaxial compressive test results of red sandstone (the rock material is assumed to be homogeneous) pre-cracked specimens agree well with predicted results of the crack initiation, stable and unstable propagation, which can prove the validity of the new multi-crack propagation prediction method.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-04-07T07:00:00Z
      DOI: 10.1142/S1758825121500265
       
  • Investigation of Droplet Impinging on a Heated Porous Surface Under
           Various Working Conditions; A Mathematical Modeling
    • Authors: Mohammad Azadeh, Hamidreza Khakrah
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      This study numerically investigated the behavior of a Newtonian droplet impacting a heated porous surface. In this regard, a two-phase finite volume code was used for laminar flow. The time adaptive method was applied to enhance the accuracy of results and better convergence of the solving process. Also, the dynamic grid adaptation technique was adopted to predict the liquid-air interface precisely. The results were first validated against experimental data at different Weber numbers. Then the effect of variations in the droplet temperature was investigated on the spreading factor. The obtained results revealed that the rise in droplet temperature led to an increase in the maximum spreading diameter due to the reduction in the effects of viscosity, density, and surface tension. In the next step, the effects of droplet impact on the hydrophilic and superhydrophobic surfaces with the porosities of 20–80% were evaluated. The obtained results revealed that the increase in the surface porosity caused a decrease in the droplet diameter during the impact time. Also, at high surface porosity values, the decline in the contact angle influence on the droplet dynamic behavior was observed.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-03-31T07:00:00Z
      DOI: 10.1142/S1758825121500150
       
  • Reduced-Order Model Description of Origami Stent Built with Waterbomb
           Pattern
    • Authors: Guilherme V. Rodrigues, Marcelo A. Savi
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      Origami-inspired structures have found many innovative applications in engineering fields. The expressive volume changes intrinsically related to their geometry is very useful for different purposes. Nevertheless, the mathematical description of origami structures is complex, which makes the design a challenging topic. This work deals with the use of reduce-order models for the origami description. A cylindrical origami structure with waterbomb pattern, called origami stent, is of concern. A reduced-order model (ROM) is developed based on kinematics and symmetry hypotheses. Afterward, a finite element analysis (FEA) is developed based on a nonlinear bar-and-hinge model. Numerical simulations are carried out evaluating the ROM validity range. Rigid and non-rigid situations are investigated showing that ROM is able to be employed for origami description.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-03-31T07:00:00Z
      DOI: 10.1142/S1758825121500162
       
  • Thermo-Acoustic Effects on the Natural Frequencies of Vibration of an
           Elastic Rectangular Panel
    • Authors: Manuel Gascón-Pérez
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      In this paper, the thermo-acoustic behavior of a rectangular panel fully immersed in a compressible fluid at rest is investigated. A boundary element method (BEM) has been employed taking into account the Kirchhoff–Helmholtz (K-H) integral equation for the acoustic pressure and with the fluid-plate interface boundary condition the acoustic pressure jump over the panel is calculated. The thermal effects are considered regarding in the form of a uniform increment of temperature of the panel and are analyzed in order to prevent the buckling phenomena. The deformation modes of the panel correspond to the vacuum case. Applying a collocation method for the panel equation, the natural frequencies are obtained. The effects of several geometric parameters regarding different thermal loads on these frequencies are evaluated. Furthermore, the influence of the wave number for different temperatures of the panel on the acoustic damping ratio is evaluated, as well as the acoustic radiation efficiency for the different modes. The verification of the method is proven with other works.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-03-31T07:00:00Z
      DOI: 10.1142/S1758825121500198
       
  • Modeling for Cyclic Plasticity of Gradient Nanostructured Metals and
           Fatigue Life Prediction
    • Authors: Wufan Chen, Haofei Zhou
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      This paper proposes a theoretical model for the description of tension-compression cyclic plasticity of gradient nanostructured (GNS) metals. The gradient grain size effect is considered by introducing the Hall–Petch relation for local yield stress and strain hardening. With the experimentally measured grain size distribution profile, the average axial stress can be calculated for cylindrical GNS metal specimens. The model was verified using experimental data obtained from 316L stainless steel treated by surface mechanical rolling treatment (SMRT). Moreover, the corresponding strain energy for cyclic plasticity can be calculated from the constitutive equations, providing an energy-based approach to explain the fatigue life of gradient 316L stainless steel.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-03-29T07:00:00Z
      DOI: 10.1142/S1758825121500216
       
  • An Improved Sub-Step Composite Time Integration Formulation With Enhanced
           Performance on Linear and Nonlinear Dynamics
    • Authors: W. B. Wen, S. Y. Deng, T. H. Liu, S. Y. Duan, W. Q. Hou, X. D. Xia
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      An improved time integration scheme is proposed for linear and nonlinear dynamics. The proposed scheme has two free parameters which control numerical dissipation and accuracy effectively. Basic properties including spectral stability, algorithmic accuracy, algorithmic damping, period elongation and overshooting behavior are investigated. The influences of algorithmic parameters on these properties are quantified. The effectiveness of the proposed scheme for linear and nonlinear dynamics is evaluated through some numerical examples. Analytical and numerical results demonstrate that the proposed scheme has the following significant characteristics: (1) desirable accuracy can be obtained for various linear and nonlinear problems, when compared with other effective schemes; (2) for nonlinear problems, new scheme also shows good performance; (3) the proposed scheme has simple formulation and good compatibility for various dynamic problems, and thus, is a promising candidate for practical analysis.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-03-25T07:00:00Z
      DOI: 10.1142/S1758825121500174
       
  • Experimental Investigation on the Performance of Signal Processing Tools
           for the Analysis of Mechanical Vibrations in Rotor Rubbing
    • Authors: Eduardo Rubio, César Chávez-Olivares, Alejandro Cervantes-Herrera
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      Rubbing is an important problem in machinery industry which occurs when a rotating element hits a stationary part. This rotor-to-stator rub may result in the catastrophic breakdown of the machine. In this work, the phenomenon of rotor rubbing is analyzed from the perspective that the signal analysis tools that are in use today to detect this defect emphasize or highlight particular aspects of the studied phenomenon. So, sometimes it is necessary to use more than one tool to deepen the understanding of the problem. For this purpose, laboratory tests were performed on a rotor system with a rubbing mechanism, while mechanical vibrations were measured with an accelerometer and a data acquisition system. Experiments were carried out for fixed rotor speed, and for run-up and run-down rotor speed conditions. The analysis approach included various processing tools to study their capabilities in rubbing detection: Root Mean Square (RMS), Fourier transform, Wavelet transform and Hurst exponent. Fixed rubbing conditions show similar results for RMS and Hurst exponent on the information obtained. For variable run-up and run-down rotor speed conditions, the Hurst exponent shows predictability, a fact that can be used for rub detection. However, the Wavelet and Fourier Transforms operated in a very distinct way. Although both transforms give frequency information, Fourier transform results in a more detailed frequency analysis, while the Wavelet transform can give time localization of the rubbing phenomenon.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-03-25T07:00:00Z
      DOI: 10.1142/S1758825121500186
       
  • A Thermodynamic-Consistent Model for the Thermo-Chemo-Mechanical Couplings
           in Amorphous Shape-Memory Polymers
    • Authors: Lu Dai, Rui Xiao
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      Chemically-responsive amorphous shape-memory polymers (SMPs) can transit from the temporary shape to the permanent shape in responsive to solvents. This effect has been reported in various polymer-solvent systems. However, limited attention has been paid to the constitutive modeling of this behavior. In this work, we develop a fully thermo-chemo-mechanical coupled thermodynamic framework for the chemically-responsive amorphous SMPs. The framework shows that the entropy, the chemical potential and the stress can be directly obtained if the Helmholtz free energy density is defined. Based on the entropy inequality, the evolution equation for the viscous strain, the temperature and the number of solvent molecules are also derived. We also provide an explicit form of Helmholtz free energy density as an example. In addition, based on the free volume concept, the dependence of viscosity and diffusivity on the temperature and solvent concentration is defined. The theoretical framework can potentially advance the fundamental understanding of chemically-responsive shape-memory effect. Meanwhile, it can also be used to describe other important physical processes such as the diffusion of solvents in glassy polymers.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-03-25T07:00:00Z
      DOI: 10.1142/S1758825121500228
       
  • Understanding and Controlling Hexagonal Patterns of Wrinkles in
           Neo-Hookean Elastic Bilayer Structures
    • Authors: Teng Zhang
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      A controlled surface wrinkling pattern has been widely used in diverse applications such as stretchable electronics, smart windows, and haptics. Here, we focus on hexagonal wrinkling patterns because of their great potentials in realizing anisotropic and tunable friction and serving as a dynamical template for making non-flat thin films through self-assembling processes. We employ large-scale finite element simulations of a bilayer neo-Hookean solid (e.g., a film bonded on a substrate) to explore mechanical principles that govern the formation of hexagonal wrinkling patterns and strategies for making nearly perfect hexagonal patterns. In our model, the wrinkling instabilities are driven by the confined film expansion. Our results indicate robust hexagonal patterns exist at a relatively small modulus mismatch (on the order of 10) between the film and substrate. Besides, the film expansion should not exceed the onset of wrinkling value too much to avoid post-buckling patterns. By harnessing the imperfection insensitivity of one dimension sinusoidal wrinkles, we apply a sequential loading to the bilayer structure to produce the nearly perfect hexagonal patterns. Lastly, we discuss the connection between the simple bilayer model and the gradient structures commonly existed in experiments.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-03-25T07:00:00Z
      DOI: 10.1142/S1758825121500241
       
  • Identification of the Model of Nonlinear Elasticity in Dynamic Experiments
    • Authors: Marina Sokolova, Yuri Astapov, Dmitrii Khristich
      Abstract: International Journal of Applied Mechanics, Ahead of Print.
      Dynamic methods for identifying a model of a nonlinearly elastic deformable body are considered. By the effective phase velocities of longitudinal and transverse waves propagating along and across the axis of the compressed bar, it is possible to determine five elastic constants of the second and third orders included in the model relations. Calculation formulae are obtained and an example of determining the dependence of phase velocities on the preliminary deformation for polyamide 6 is given. The influence of preliminary deformations on polar diagrams of wave velocities is investigated.
      Citation: International Journal of Applied Mechanics
      PubDate: 2021-03-25T07:00:00Z
      DOI: 10.1142/S1758825121500253
       
 
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