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International journal of applied mechanics
Imperial College Press
International journal of applied mechanics

Imperial College Press

1758-8251

International journal of applied mechanics/Journal International journal of applied mechanicsEISCI
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    Dynamic Response of Rectangular Sandwich Tubes with Metal Foam Core Under Blast Loading

    Zhang, JianxunGuo, Haoyuan
    24页
    查看更多>>摘要：In this paper， the dynamic response of clamped rectangular sandwich tubes with metal foam core under transverse blast loading is analytically and numerically studied。 First， based on the theory of the solid beam subjected to transverse blast loading， a semi-empirical analytical solution for the dynamic response of rectangular hollow metal tube is given subjected to transverse blast loading considering local denting effect and combined axial force and bending moment。 Then， based on the analytical solution for the dynamic response of the metal tube， a semi-empirical analytical solution for the dynamic response of clamped rectangular sandwich tubes with metal foam core under transverse blast loading is obtained。 The numerical calculation for the dynamic response of clamped rectangular sandwich tubes is carried out。 The numerical results locate between the upper and lower bounds of the analytical solution。 Next， using the least square method， an analytical method to predict the maximum deflection of sandwich tubes is given under no experimental or numerical data conditions based on the existing data。 The present analytical method can be used to predict the dynamic response of clamped rectangular sandwich tubes with metal foam core under transverse blast loading。 Also， the comparison of energy absorption between rectangular sandwich tube with metal foam core and rectangular hollow tube for the same mass is conducted。 It is shown that the sandwich tube is better than the hollow tube in terms of energy absorption in large deflection。
      原文链接:
    • NSTL
    • World Scientific

    Controlled Bi-Axial Buckling and Postbuckling of Thin Films Suspended on a Stretchable Substrate with Square Prism Relief Structures

    Zhang, XiaoyangYu, QingminWu, HuapingCheng, Huanyu...
    17页
    查看更多>>摘要：Stretchable electronics have spurred rapid developments from curvilinear devices to bio-integrated diagnostic and therapeutic devices。 The wavy configuration in the device components on a stretchable elastomeric substrate surface plays a prominent role in simultaneously achieving high areal coverage and stretchability without compromising the electric performance， resulting in unique applications in stretchable and flexible light-emitting diodes (LEDs)， batteries， supercapacitors， and photovoltaics。 In this study， we investigate the buckling behaviors of stiff thin films on the top surface of a biaxially pre-strained elastomeric substrate with square prism micro-patterned structures。 Based on energy minimization， a theoretical model is established to study the buckling profiles and the maximum strain for different pre-strain levels along two directions， which agrees reasonably well with those obtained by the finite element analysis (FEA)。 After revealing the effect of the center-to-center distance in micro-patterned structures and the interfacial contact width between the film and substrate on the buckling behavior， the elastic stretchability of the system is studied。
      原文链接:
    • NSTL
    • World Scientific

    Nonlinear Solution of a Piezoelectric PN Junction Under Temperature Gradient

    Guo, Ming KaiQin, Guo ShuaiLu, ChunshengZhao, Ming Hao...
    17页
    查看更多>>摘要：By considering the nonlinear coupling of piezoelectricity， thermoelectricity and pyroelectricity， this paper investigated the polarization effect related to temperature gradient in a thermo-piezoelectric PN junction。 The analysis is based on a perturbation method and the one-dimensional nonlinear theories of thermo-piezoelectric semiconductors。 It is shown that as thermal load increases， the linear solution gradually separates from the nonlinear one， in which the third-order solution is basically coincident with the nonlinear numerical solution of COMSOL。 It is found that the electromechanical fields， carrier transport characteristics and turn-on voltage have a fast response to temperature gradient。 By using the perturbation method， the approximate nonlinear solution of a thermo-piezoelectric PN junction can be obtained。 Furthermore， the possibility of thermal manipulation is evident in a piezoelectric PN junction。 These findings will be instructive to a good understanding of the electromechanical coupling characteristics of a PN junction and beneficial to development of a new method for its property modulation。
      原文链接:
    • NSTL
    • World Scientific

    Improved Differential Quadrature Finite Element Method for Free Vibration of Mindlin Plates with Arbitrary Elastic Boundaries

    Xiang, WeiLi, XinHe, Lina
    29页
    查看更多>>摘要：This paper proposes an improved differential quadrature finite element method (DQFEM) by combining the virtual boundary spring technique with the standard DQFEM， in order to deal with free vibration of Mindlin plates with arbitrary elastic constraints。 The incorporation of the virtual boundary spring technique makes it easy to impose general elastic constraints including some classical boundary conditions and avoids the deficiencies of the classical elimination method， which is widely used to process boundary conditions。 The improved DQFEM formulation for rectangular and curvilinear quadrilateral elements is established。 Convergence characteristics of the present approach are discussed， and the minimum number of nodes to derive convergent results and the appropriate value of the boundary spring stiffness to simulate classical boundary are obtained。 Numerical examples are carried out for Mindlin plates with various boundary conditions and thickness ratios， covering both rectangular and irregular geometries。 By numerical comparisons， the high accuracy and the remarkable efficiency of the present method are demonstrated。 Additionally， adopting the virtual spring boundary can improve the efficiency to some extent compared with the standard DQFEM。
      原文链接:
    • NSTL
    • World Scientific

    Nonlinear Stability Characteristics of Porous Graded Composite Microplates Including Various Microstructural-Dependent Strain Gradient Tensors

    Gao, JingLiu, HaitaoSafaei, BabakSahmani, Saeid...
    23页
    查看更多>>摘要：In this study， the nonlinear buckling and postbuckling characteristics of composite microplates made of a porous functionally graded (PFG) material are scrutinized in the presence of different size-dependent strain gradient tensors as microscale。 Accordingly， for the first time， the effect of each microstructural tensor is analyzed separately on the nonlinear stability of PFG microplates with and without a central cutout。 In order to fulfill this goal， the isogeometric computation approach is engaged to integrate the finite element approach into the nonuniform B-spline-based computer aided design tool。 Accordingly， the geometry of the microplate with a central cutout is modeled smoothly to verify C-1 continuity based upon a refined higher-order plate formulations。 In this regard， the microstructural-dependent load-deflection paths associated with the nonlinear stability of axially compressed microplates are traced。
      原文链接:
    • NSTL
    • World Scientific

    Dynamic Crushing Behaviors of Multi-Layered Gradient Honeycombs with Different Poisson's Ratios: A Finite Element Simulation

    Zhang, Xin-ChunDong, Si-JieAn, Chao-ChaoWu, He-Xiang...
    29页
    查看更多>>摘要：In this work， a new multi-layered gradient honeycomb (MGH) design was proposed by filling structure layer with different Poisson's ratio configurations (e。g。， positive， zero and negative Poisson's ratio) from the perspective of coupling the deformation characteristics with each other to improve in-plane dynamic properties and control energy absorption capacities。 The dynamic behaviors and energy-absorbing characteristics of the MGHs under in-plane impact loadings were investigated by using explicit dynamic finite element (FE) simulation。 This paper mainly focused on the effects of multi-layered gradient arrangements and impact velocities on the dynamic Poisson's ratios， dynamic plateau stresses， crushing load uniformities and specific energy absorption of the MGHs。 A semi-empirical formula for the plateau stresses of the MGHs was presented。 It was shown that through the proper choice of multi-layered arrangements， the MGHs can effectively improve the dynamic crushing behaviors and control energy absorption capacities。 In addition， the dynamic shock enhancement of the MGHs was also investigated by introducing the uniformity index。
      原文链接:
    • NSTL
    • World Scientific

    Thermo-Mechanical Transient Flexure of Glass-Carbon-Kevlar-Reinforced Hybrid Curved Composite Shell Panels: An Experimental Verification

    Sahu, PruthwirajSharma, NitinDewangan, Hukum ChandPanda, Subrata Kumar...
    22页
    查看更多>>摘要：The time-dependent deflection values of the flat/curved hybrid fibre (Glass-Carbon-Kevlar)-reinforced composite panels under the influence of the mechanical loading (UDL and SDL) and the elevated thermal environment are analyzed in this research。 To compute the numerical responses， a higher-order kinematic model is prepared considering the effect of single/double curvature of the shell panel。 The weak form of the governing equation is established through the variational technique。 The steady-state deflections are obtained by solving the discrete form of governing equation of transient vibrations using finite element method (FEM) by employing Newmark's time integration method in MATLAB environment。 The isoparametric Lagrangian element (nine-noded) is adopted to discretize the system equation of the hybrid panels。 The validity of the numerical solutions， computed using the experimental hybrid composite properties， is verified with the experimental (in-house) results as well as with the benchmark results available in the published literature。 Finally， the parametric study of dynamic deflection characteristics of hybrid composite shallow shell panels is carried out by varying the parameters such as curvature ratio， support conditions， hybrid schemes and type of loading in the elevated thermal environment and the results are discussed in detail。
      原文链接:
    • NSTL
    • World Scientific

    Micro-Fracture Simulation of Rock Under Unloading Condition by Grain-Based Discretized Virtual Internal Bond Method

    Yang, YuezongZhang, Zhennan
    22页
    查看更多>>摘要：Rock burst is a multiscale dynamic fracturing process induced by unloading。 To further investigate the dynamic fracturing mechanism of rock burst， a grain-based discretized virtual internal bond (GB-DVIB) method is developed。 The Voronoi diagram is used to discretize the background discretized virtual internal bond (DVIB) mesh to generate the micro-structure of rock。 The bond cell within a Voronoi diagram is termed as the grain cell， characterized by the linear Stillinger-Weber potential。 While the bond cell cut by the Voronoi polygon edge is termed as the interface cell， in which both the tension and the shear failure are considered。 The simulation results suggest that this method can reflect the contact and friction between grains and reproduce the confining pressure-dependency of compressive strength of rock。 With this method， the unloading effects of the in situ stress， the grain size and the heterogeneity on rock failure are studied。 The simulated results show that more tensile cracks and less shear cracks are generated when unloading a higher confining stress。 When the axial stress is fixed， the total created crack area is almost a constant。 The tensile crack area is basically a constant while the shear crack area increases under the condition of a higher axial stress。 With decreasing the grain size， more cracks are generated， but the area ratio of the shear to the tensile cracks is almost a constant。 It is suggested that GB-DVIB is an effective method for the rock burst simulation。 The findings provide deep insight into the rock burst from the standpoint of dynamic fracture。
      原文链接:
    • NSTL
    • World Scientific

    Nonlinear Free Vibration Analysis of In-plane Bi-directional Functionally Graded Plate with Porosities Resting on Elastic Foundations

    Hashemi, SoheilShahri, Pouria KarimiBeigzadeh, SaharZamani, Farshad...
    24页
    查看更多>>摘要：This paper deals with the nonlinear free vibration analysis of in-plane bi-directional functionally graded (IBFG) rectangular plate with porosities which are resting on Winkler-Pasternak elastic foundations。 The material properties of the IBFG plate are assumed to be graded along the length and width of the plate according to the power-law distribution， as well as， even and uneven types are taken into account for porosity distributions。 Equations of motion are developed by means of Hamilton's principle and von Karman nonlinearity strain-displacement relations based on classical plate theory (CPT)。 Afterward， the time-dependent nonlinear equations are derived by applying the Galerkin procedure。 The nonlinear frequency is determined by using modified Poincare-Lindstedt method (MPLM)。 Numerical results are obtained in tabular and graphical form to examine the effects of some system key parameters such as porosity coefficients， distribution patterns， gradient indices， elastic foundation coefficients， aspect ratio and vibration amplitude on the nonlinear frequency of the porous IBFG plate。 To validate the analysis， the results of this paper have been compared to the published data and good agreements have been found。
      原文链接:
    • NSTL
    • World Scientific

    Nonlinear Mechanics of a Smart Biotensegrity Human Foot Prosthesis

    Brandao, AlexSavi, Marcelo A.
    24页
    查看更多>>摘要：This work deals with the nonlinear mechanics of smart bioinspired tensegrity structures。 A minimal regular tensegrity prism actuated by shape memory alloy (SMA) elements is investigated to represent a human foot。 A formulation considering the force density matrix approach is used to model the equilibrium equations of the tensegrity structure based on node mapping。 Lagrange multipliers are employed to represent constraints。 The SMA thermomechanical behavior is described by considering a modified polynomial constitutive model。 Numerical simulations are developed from an optimization procedure employing the Levenberg-Marquardt method。 An investigation of the tensegrity capability to model a human foot is carried out analyzing either mechanical or physiological aspects of the tensegrity prosthesis。 The mechanical performance is compared with high performance prostheses available on the market， showing that it is an interesting alternative with respect to mechanical resistance。 Regarding physiology， foot movements are properly mimicked from SMA actuation。
      原文链接:
    • NSTL
    • World Scientific