• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-29
Xiang Gao, Junchuan Niu, Zhihui Liu, Jinxin Tian

The recumbent patients on ambulance stretcher experience multi-dimensional excitations due to road roughness. In order to isolate the multi-dimensional vibrations validly, a novel ambulance stretcher system based on 4-PUU parallel mechanism with Magneto-Rheological dampers is proposed. Firstly, the kinematic and dynamic equation are deduced by geometric relation and Lagrange equation respectively. Subsequently, the vibration isolation performance is investigated in time and frequency domain. The robustness of LQR algorithm is addressed with parameters perturbation by deducing Lyapunov equation. Further, selecting RMS values as the index of vibration isolation performance, the index which includes geometric parameters perturbation, mass and spring uncertainties is discussed. Simulations demonstrate the stretcher system can effectively isolate multi-dimensional vibrations in sensitive frequency range for supine patients with perturbation and uncertainties. The RMS values show different characteristics because of altering Jacobin matrix of the stretcher.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-07
Jiayin Dai, Yongshou Liu, Huichao Liu, Changxu Miao, Guojun Tong

In this article, we study the thermo-elastic vibration of axially functionally graded material (FGM) pipe conveying fluid considering temperature changes. The governing equation based on Euler–Bernoulli beam theory is solved by differential quadrature method. The FGM properties are defined by the property ratios and the volume fraction functions. Power volume fraction function and exponent volume fraction function are compared. We also use sigmoid volume fraction functions so that the exclusive influence of function distribution can be isolated from that of total material proportions. The property ratios’ effects of elasticity and thermo-elasticity gradient are also discussed. Based on the numerical results of first-order dimensionless frequencies and critical flow velocities, concerning thermo-elasticity gradient can theoretically change the stability of the pipe. And the influences of the pure distribution on the first-order critical flow velocities are much smaller than that of the varying total proportions of the component materials. These conclusions will hopefully be used as reference for FGM pipe designing and fabricating.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-29
Zhan Zhao, Chuang Feng, Youheng Dong, Yu Wang, Jie Yang

This paper investigates the nonlinear bending behaviours of functionally graded trapezoidal nanocomposite plates reinforced with graphene platelets (GPLs) under thermo-mechanical loading by employing finite element method. The modified Halpin–Tsai model and rule of mixtures are adopted to determine the Young’s modulus, Poisson’s ratio and the thermal expansion coefficient of the nanocomposites. The influences of a number of factors, including the distribution pattern, concentration and size of GPLs, plate geometry and temperature, on the nonlinear bending of the nanocomposite plates are comprehensively investigated. Numerical results demonstrate that dispersing a small amount of GPLs into nanocomposites can significantly enhance the nonlinear bending performance of the trapezoidal plates. The trapezoidal plates with more GPLs dispersing close to the top and bottom surfaces has the minimum bending deflection and are less sensitive to the temperature increases. GPLs with fewer layers and larger surface area are better reinforcing fillers than their counterparts. Moreover, the plates with bigger bottom angles are found to have better bending performances. However, when the bottom angles are greater than 75°, the variation of the bottom angles will have limited effects on the bending behaviours of the trapezoidal plates.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-02

This paper presents a study on the effects of the SMA wires’ characteristics on tuning the stability of a capacitive micro-resonator. In the proposed model, pre-strained SMA wires have been embedded in a double clamped resonant microbeam which is actuated electrostatically. The governing equations of the system have been introduced and then an eigen-value problem has been adopted to investigate stability. Galerkin-based numerical methods have been used to solve the governing equation of motion for obtaining the motion trajectories of the beam. The effects of the number of SMA wires, their diameter, pre-strain and temperature on the pull-in instability and frequency response of the resonator have been shown. Critical values of recovery stress and SMA temperature for avoiding instability, with and without applying DC voltage have been obtained. The results have shown that by changing each of the SMA parameters, one can reach a needed magnitude of recovery stress as well as transmitted longitudinal force to the host beam, and consequently control and tune the stability and resonance frequency of the micro-resonator.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-02-22
Ruixia Yao, Fei Su, Ronghai Mao

This study analyzes the influence of bonded and unbonded interface conditions on the anti-penetration performance of a ceramic/metal composite target and determines the associated mechanism. The 3D finite element and 3D smoothed particle hydrodynamics simulation results revealed that a bonded ceramic/metal target exhibited better anti-penetration performance than an unbonded target, and the associated mechanism was determined. Notably, the bond strength between the ceramic and metal backplate plays an important role in the formation of the ceramic conoid, and the ceramic conoid that formed in the bonded target effectively consumed the kinetic energy of the projectile, thereby improving the anti-penetration performance of ceramic composite armor. To verify this conclusion, we also compare and analyze the anti-penetration performance of interface bonded and unbonded metal/metal composite targets. The results show that due to the absence of the ceramic conoid, the interfacial bonding conditions have little influence on the anti-penetration performance of a metal/metal composite target.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2018-11-26
B. K. Jha, M. C. Ray

This paper is concerned with the derivation of exact solutions for the responses of piezoelectric bimorph energy harvesters composed of laminated composite beam substrates. An electro-elastic finite element model is also developed based on the layer wise first order shear deformation theory for computing the responses of the bimorphs under general boundary and loading conditions. Both series and parallel connections of the piezoelectric layers of the bimorphs are considered. The responses computed by the finite element model excellently match with that obtained by the exact solutions. The induced electric potential in case of the bimorph in which the piezoelectric layers are connected in series is significantly larger than that in case of the bimorph with piezoelectric layers connected in parallel. If the thickness of the piezoelectric layers and the substrate remain same, the piezoelectric bimorph composed of antisymmetric angle-ply substrate beam is capable of inducing more electric potential than the bimorphs with cross-ply substrate beams. Also, if the bimorph is cantilever, it induces significantly more electric potential than when it is simply supported. Optimum thickness of the piezoelectric layers of the bimorph and unimorph harvesters has been determined. Most importantly, it is found that the bimorph with its piezoelectric layers connected in series performs significantly better than the unimorph if the mass and volume of the piezoelectric layers and the substrates remain same. The results presented here may serve as the benchmark results for verifying experimental and numerical models.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-31
Mohammadamin Jamshidi, Jamal Arghavani, Ghazaleh Maboudi

In the present study, an attempt is made to present the governing equations on the post-buckling of two-dimensional (2D) FGP beams and propose appropriate optimization procedure to achieve optimal post-buckling behavior and mass. To this end, Timoshenko beam theory, Von-Karman nonlinear relations, virtual work principle, and generalized differential quadrature method are considered to derive and solve governing equations and associated boundary condition (Hinged–Hinged) for an unknown 2D porosity distribution. Proposed method is validated using the papers in the literature. The optimization procedure including defining porosity distributions (interpolations), post-buckling function and Taguchi method is then proposed to optimize the post-buckling path and minimize the mass of the 2D-FGP beams. Results indicate that, great improvement can be achieved by optimizing the porosity distribution; for an identical mass, the post-buckling paths of optimum points are closer to desired path (dense structure). The difference between uniform and non-uniform porosity distributions is more (58% higher post buckling function), at higher values of the mass. Optimum distributions mostly have the higher values of porosity at center line of the beam and minimum values at outer line. Analysis of variance is also provided to create a better understanding about design points contributions on the post-buckling path.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-02
Ibrahim Guven, Kenan Cinar

A method based on X-ray micro-CT was introduced to create realistic representative volume elements (RVE) for particulate-filled composite materials. The method is applicable to most composite systems, and can be utilized to improve artificial computer algorithms by presenting the number, the dimension, and the orientation of filler particles inside the RVEs. Three different shapes of glass fillers (spherical, flake, and fiber) and filler mass fractions (5%, 10%, and 15%) were introduced to epoxy resin to demonstrate the capability of micro-CT to create RVEs. Two kind of RVEs were created; voxel-based and geometry-based. Voxel-based RVEs were created from binary segmentation of images taken from micro-CT. Geometry-based RVEs were created after reconstruction of voxel-based RVEs to eliminate the stepped-like appearance of non-orthogonal interfaces. These RVE’s were then used in the finite element analysis to find the effective mechanical properties such as Young’s modulus, shear modulus, Poisson’s ratio of the samples. In order to assess the numerical findings, compression tests were performed according to ASTM D695. Also, spherical fillers were distributed inside a volume artificially using an algorithm and RVEs were created. The number and the dimension of the spherical fillers were supplied from X-ray micro-CT and optical microscopy, respectively. The elastic moduli found using RVEs created from the algorithm is close to the elastic moduli found using RVEs created from X-ray micro-CT.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-02
Ahmet Emin Senturk, Ahmet Sinan Oktem, Alp Er S. Konukman

Hybrid graphene/hexagonal boron-nitride (G/h-BN) has shown significant physical properties and has been fabricated recently. Structural defects, such as Stone–Wales (SW) and vacancy, unavoidably exist in the interface of hybrid G/h-BN during the growth process. In this study, the interfacial thermal resistance (ITR) of armchair and zigzag hybrid G/h-BN with vacancy and SW defects is systematically investigated, using molecular dynamics (MD) simulations. Our results indicate that armchair edge hybrid G/h-BN possesses higher normalized ITR than the zigzag one. In addition, vacancy and SW defects introduced important influences on the ITR of hybrid G/h-BN. The ITR of hybrid G/h-BN is studied with two distinct sections. In the first section, various types of atoms, such as C, N and B, vacancy defects located throughout the interface of armchair and zigzag hybrid G/h-BN are studied. Our MD simulations results show that when the number of vacancy defect is increased, the effect of C atom vacancy defect on the normalized ITR of hybrid G/h-BN is higher than other atoms. On the other hand, the influence of B atom vacancy defect on the normalized ITR is lowest. In the second section, CC and BN types of SW defects positioned along the interface of armchair and zigzag hybrid G/h-BN are investigated. The results of this study demonstrate that CC type of SW defect shows higher normalized ITR than BN type one by increasing the SW number of defects. The obtained results in this study may open new insights for potential applications of thermal transport and control for the hybrid G/h-BN type structures.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-16
Richa Goyal, Satish Kumar

The dispersion properties of Love waves are utilized for the fabrication of sensor devices in the different material environments. This study involves the propagation of Love wave in a double-layered structure consisting of two finite layers of viscoelastic and piezoelectric material lying over the semi-infinite size-dependent micropolar substrate. The bottom substrate of the structure is modeled as, the material with microstructural properties. The real and damping dispersion relations are obtained analytically in closed form expression under both the cases of electrically open and short conditions. The coupling constant and characteristic length that describe the effect of the microstructure of the micropolar substrate, are studied graphically on Love wave propagation. The effects of piezoelectric layer are shown by considering two different materials of a piezoelectric layer, i.e., $$PZT-5H$$ or $$BaTiO_3$$, along with the internal friction and heterogeneity parameter associated with a viscoelastic layer. The numerical computation and the graphs are given for aluminium-epoxy (substrate), viscoelastic material and $$PZT-5H$$ or $$BaTiO_3$$ (piezoelectric layer). Some of the particular cases are derived from the study by using different relevant conditions.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-01
Motoyuki Murashima, Shouta Yoshino, Masato Kawaguchi, Noritsugu Umehara

In this paper, we provide a detailed account of our efforts in the design, development and prototyping of a novel intelligent surface by adapting initially curved diaphragms. Unlike the shortcomings that characterize current designs of functional surfaces, our adaptive surface design is characterised by simplicity, multifunctionality, adaptability, high flexibility and robustness as well as controlled autonomy. Four aspects of the work are accordingly examined. The first is concerned with the conceptual design of the new functional surface. The second with the development of functional prototypes of intelligent surfaces, showing its characteristics and ease of manufacturing using 3D additive manufacturing. The third with demonstrating the multi-frictional ability of the newly designed surface. Our friction test results show wide range friction control ability from the friction coefficient value 0.3 (same value of material itself) to 3 times higher value 1.1. Finally, we address the challenges that are faced in our new design and the efforts that are currently being adopted to overcome them.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-01-01
Chein-Shan Liu, Botong Li, Chung-Lun Kuo

An almost exact solution is derived for the forced vibration of a composite beam with periodically varying non-smooth interface through a moderate weak-form formulation. The material property of a non-uniform beam is characterized by its flexural rigidity function R(x). In the novel method, R(x) is relaxed to be an integrable function rather than a $${\mathcal{C}}^2$$ smooth function in the usual approach. The R(x)-orthogonal bases in the linear span of all boundary functions are derived such that the second-order derivatives of the bases elements are orthogonal with respect to the weight function R(x). When the deflection of the beam is expressed in terms of the bases, the expansion coefficients can be determined exactly in closed form owing to the R(x)-orthogonality of the bases. The solution obtained is almost exact, since its accuracy can be up to the order $$10^{-15}$$. This powerful method is used to analyze the forced vibration behavior of composite beams with three different periodic interfaces.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-11-25
Yuewu Wang, Anfeng Zhou, Tairan Fu, Wei Zhang

The aim of the present work is to develop a high-order shear deformable beam model and investigate the transient response of a sandwich porous beam when acted upon by a non-uniformly distributed moving mass. It is assumed that the total mass is distributed within a specified distance and has various distribution patterns. The sandwich beam is composed of two functionally graded (FG) facesheets and an FG porous core. The modulus of elasticity of the porous core is graded owing to the continuously variation in porosity in the thickness direction. The open-cell metal foam model is used to evaluate the mass density of the core. A new high-order shear deformation theory is proposed and implemented to develop a reliable and accurate model that can address the vibration responses of the beam. The equations of motion are derived using the Lagrange method, whereas a standard Newmark-β method is employed to solve the time-dependent response. A few numerical examples are discussed to study the effects of various sandwich configurations and different types of mass distributions on the vibration behaviors of the sandwich beam. The results indicate that dispersing the mass toward the two ends of the load to the extent feasible is suitable for preventing large dynamic deflections.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-11-08
L. Y. Lim, S. A. Meguid

Most existing thermal barrier coating (TBC) studies do not account for the depletion of Al in the BC and growth of mixed oxides (MOs). In this complementary study, we modify and extend our earlier (Lim and Meguid in Mater Des, 2019.  https://doi.org/10.1016/j.matdes.2018.107543) coupled finite volume (FV)–finite element (FE) formulations to incorporate diffusion reactions of Al and Cr in the BC. The modified/expanded FV–FE formulations are supported by the introduction of appropriate diffusion–reaction equations and high temperature oxidation model. Three aspects of the work were accordingly examined. Firstly, the FV model is used to describe the diffusion and reaction of Al and O2 in the formation of α-Al2O3. The β-phase rate of depletion predicted by the model agrees well with experimental findings. Secondly, the diffusion of Cr through the TGO that leads to the formation of an external layer of MOs is simulated using the FV model. Our simulations reveal that MOs form in the early stage of thermal exposure, although there are sufficient Al in the BC to sustain the growth of α-Al2O3 phase. We reasoned this to the formation of internal oxides and diffusion cell in the BC. Lastly, we studied the effect of roughness on β-phase depletion and growth of TGO (α-Al2O3 + MOs). We show that β-phase in the peak of undulation depletes faster and the interface between the β + γ phase and γ phase in the BC straightens over time. Furthermore, our results reveal that MOs tend to form in the valley of undulation due to the shorter diffusion path.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-11-08
C. Erdönmez

Wire ropes are one of the most complex shapes due to the helical coiling of wires. It is difficult to generate a meshed model of even the classical circular wire rope. In this paper a more complex form which is known as compacted wire rope is modeled in 3D. The originality of this work is that, it is the first time a multi-layered compacted wire rope is generated and brought to the literature. The written code permits to create any length of compacted independent wire rope core geometry and to change wire radiuses and pitch lengths easily. Meanwhile flexibility of the code makes it easier to generate different kind of compacted independent wire rope core which is ready for numerical analysis. Compacted wire ropes have increased wear resistance and tensile strength. Due to its flattened surface their usage on a sheave or a pulley provides less wearing and breaking of wires while more tensile strength and increased lifetime. With the compaction process diameter of the wire rope decreases which results a decrease on the reaction moment also. This modeling issue can be used to create new type of complex wire rope models in the future.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-11-01
P. Areias, F. Queirós de Melo, J. Carrilho Lopes

Engineering-level accuracy of discretization methods for frictional contact originates from precise representation of discontinuous frictional and normal interaction laws and precise discrete contact techniques. In terms of discontinuous behavior in the quasi-static case, two themes are of concern: the normal interaction (i.e. impact) and the jumps in tangential directions arising from high frictional values. In terms of normal behavior, we use a smoothed complementarity relation. For the tangential behavior, we propose a simple and effective algorithm, which is based a stick predictor followed by corrections to the tangential velocity. This allows problems with impact and stick-slip behavior to be solved with an implicit code based on Newton–Raphson iterations. Three worked examples are shown with comparisons with published results. An extension to node-to-face form in 3D is also presented.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-10-30
Yu Liu, Shenjie Zhou, Kanghui Wu, Lu Qi

On the basis of the couple stress piezoelectric theory including flexoelectric effects, a size-dependent model of a bilayer microbeam consisting of a piezoelectric material layer and an elastic layer has been established. The governing equations along with the boundary conditions of the microbeam model have been obtained from variation principle. The microbeam bending problems have been solved to analyse the electromechanical coupling responses to the applied concentrated force and voltage. Numerical results show that whether under the concentrated force or the voltage, the influence of flexoelectric effects on the equivalent piezoelectric response is larger than that of rotation gradient elastic effects when the size of the microbeam is much larger than the material length scale parameters. However, with the continuous decrease of the beam characteristic size scale, rotation gradient elastic effects have a stronger impact on the electromechanical responses than flexoelectric effects, which leads to a rapid decrease of the equivalent piezoelectric responses. The result also shows that the contribution of flexoelectric effects on the equivalent piezoelectric response increases when the beam size diminishes, which leads to a significant surge of the electromechanical responses compared to the model under the classical piezoelectric theory.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-10-29
Haodong Zhang, Xianmin Zhang, Zhenhui Zhan, Lixin Yang

This paper presents a methodology to study the dynamic response of a parallel robot with multiple lubricated joints. Based on Gümbel’s boundary conditions, the hydrodynamic force of the journal bearing is calculated with the Pinkus–Sternlicht model. Considering the dynamic loads on the multiple lubricated joints, the Pinkus–Sternlicht model is modified to ensure numerical stability of the solution of the system’s equations. A comparative analysis of four joint force models is presented to show the advantages of the modified model for a 3-PRR (P and R represent prismatic and revolute pairs respectively and the underline of the P represents the actuated joint) parallel robot. The improvement in the numerical stability of the modified Pinkus–Sternlicht model is proven. Subsequently, the dynamic behavior of the 3-PRR parallel robot with multiple lubricated joints is analyzed comprehensively, compared with the 3-PRR parallel robot with multiple dry clearance joints. Simulation results demonstrate the validity of the dynamic methodology containing the modified Pinkus–Sternlicht model for the 3-PRR parallel robot with multiple lubricated joints. This dynamic methodology can illustrate the better periodicity of such parallel robots considering lubricated joints.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-10-24
Chao Lin, Wenjie Wei, Shuang Wang, Xiguang Xia, Qingkun Xin

As a new type of gear transmission developed in recent years, curve-face gear transmission has not appeared before. In order to solve the problem of root bending strength of the eccentric straight and helical curve face gear, a calculating method of the tooth root bending strength was proposed. According to the principle of space meshing, differential geometry and design of machinery, the parametric equations of pitch curve was obtained, the pressure angle and the contact ratio in the meshing process were derived. The plane equivalent pitch curve was obtained, and the formula for calculating the equivalent tooth form factor and the equivalent stress correction factor was acquired. The calculation method of the bending strength of the gear pair was established, and the influence of the basic structural parameters on the bending stress was also analyzed in detail. The position of the stress hazard of the eccentric curve-face gear was determined. Through the finite element analysis and transmission experiment, the accuracy of the calculation method of strength of the gear pair was verified.

更新日期：2019-12-11
• Int. J. Mech. Mater. Des. (IF 3.143) Pub Date : 2019-10-18
Liyuan Wang

Surface effect plays an important role in nanosized materials. In this paper, two-dimensional Boussinesq problem with the surface effect is systematically investigated based on Chen–Yao’s surface elastic theory, in which surface effect on mechanical properties of materials is considered based on the concept of surface energy density. The Fourier integral transform method is adopted to derive the contact stress and displacement fields of the Boussinesq problem. As two examples, the deformations induced, respectively, by a uniform distributed pressure and a concentrated force are analyzed in detail. The theoretical result in this paper show that the surface energy density of the indented bulk substrate, as only one additional parameter, serves as an important factor to influence the contact properties in contrast to the classical contact models. The numerical results show that the semi-infinite substrate becomes hardened when the surface effect is considered. Scaling analysis further indicates that only when the ratio of the contact width to the volume surface energy density to the shear modulus is equal, the difference between the theoretical prediction of surface effect and the classical contact solution without surface effect will be significant. The results provide a further understanding of the surface effect of nanomaterials, which should be helpful for the design and accurate evaluation of service performance of nanoscale devices or nanomaterials.

更新日期：2019-12-11
Contents have been reproduced by permission of the publishers.

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