Advances in Fracture and Materials Behavior

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Authors: Tao Hua, Hui Min Xie, Peng Zhang, Fei Yi Du, Bing Pan, Fu Long Dai, Peng Wan Chen, Qing Ming Zhang, Feng Lei Huang
Abstract: The spider silk is considered as a new type of biomaterials with its excellent mechanical properties. The mechanical properties of the spider silk are crucial to their applications. In this study the mechanical properties of spider silk were studied with a micro-tensile system driven by magnet-coil force actuator, which is very effective to measure the properties of low dimensional materials. The Young’s modulus of the spider silk is obtained, the relationship between the mechanical properties of spider silk and time is also acquired.
Authors: Jun Lin Li, Zhong He Sui, Wei Yang Yang
Abstract: Dynamic problems of Yoffe mode crack are studied under antiplane shear impact in infinite orthotropic functionally graded materials. The shear modules in two directions are assumed to vary in terms with power function form of dual parameters of arbitrary time power. By using integral transform-dual integral equations method, the stress field and dynamic stress intensity factor near crack tip are obtained. And the influences of material in homogenous coefficient and graded parameters and crack moving speed to dynamic stress intensity factor are analyzed in virtue of Matlab software. Results show that the dimensionless dynamic stress intensity factor will decrease with the increase of moving speed of crack, which is opposite to the result of the dynamic problem of infinite strip in FGM. And the dimensionless dynamic stress intensity factor will decrease with the increase of graded parameters and rise with the increase of material in homogenous coefficient.
Authors: Yong Li, Xiao Jing Li, Wei Shen Zhu, Qiang Yong Zhang
Abstract: This paper introduces many types of analogue materials in China and other countries in geotechnical model tests. Combined with the study on a few geo-mechanical model tests of significant tunnels and underground openings in Chinese western areas, this paper recommends a new type of analogue material, which is made from iron mineral powder, barite powder, quartz powder and alcoholic solution with rosin. In order to know the physico-mechanical characteristics of this composite material with different mixture ratios, we use specimens to do lots of mechanical experiments such as uniaxial compressive test, quasi-triaxial shear test, triaxial test and Brazilian test. Consequently, the analogue materials with different mixture ratios can be used to physically model different projects, and this analogue material with a certain mixture ratio has been successfully used in the model test of a branching-out tunnel. The results of the model test verify that this new analogue material can be successfully used in all kinds of geotechnical model tests.
Authors: Xi Song, Shi Rong Li
Abstract: Based on Kirchhoff’s assumption of straight normal line of beams and considering the effects of the axial elongation, the initial curvature and the stretching-bending coupling on the arch deformation, geometrically nonlinear governing equations of functionally graded arch subjected to mechanical and thermal loads are derived. In the analysis, it is assumed that the material properties of the arch vary through the thickness as a power function. As a numerical example, the critical buckling load and the corresponding mode shapes of a semicircle arch, with both of the ends fixed, subjected to normally uniform distributed follower force is obtained by the shooting method. The effects of the parameters of material gradient on the critical loads and the deformation of the structure are examined in detail. Equilibrium configurations for different values of the load or temperature rise are plotted. Analysis and numerical results show that the behavior of buckling of the arch is of bifurcation and the buckling modes corresponding to minimum buckling load is asymmetric. In other words, bifurcation buckling occurs prior to the snap-through buckling.
Authors: Xiao Shan Cao, Feng Jin, Zi Kun Wang
Abstract: For the propagation of horizontally shear waves (SH-waves) in a functionally gradient piezoelectric material (FGPM) plate, the governing equations are established by the theory of elasticity. The Airy equations and Airy functions are applied to find the solutions of the equations. Numerical results indicate that: compared with those of SH-waves in a transversely isotropic piezoelectric plate, remarkable difference can be observed for the dispersion properties of SH-waves in a FGPM plate. Material coefficients gradient variation patterns do not affect higher modes dispersion properties of SH-waves in a FGPM plate for electrically open case. While for electrically shorted case, dispersion properties of SH-waves higher modes are affected by the material coefficients gradient variation patterns, remarkable influences can be observed for S0 mode. Influences of materials coefficients gradient variation patterns on cutoff-frequencies of SH-waves are also revealed. The results obtained are meaningful for the investigation and characterization of SH-waves in inhomogeneous media.
Authors: Yao Dai, Xiu Fa Yan, Chang Qing Sun, Wei Tan
Abstract: Crack-tip higher order stress and displacement fields for a mode III crack along the direction of property variation in a functionally gradient material (FGM), which has a power variation of shear modulus along the gradient direction, are obtained through the asymptotic analysis. The asymptotic expansions of crack tip stress fields are derived to explicitly bring out the influence of non-homogeneity on the structure of the stress field. The analysis reveals that only the higher order terms in the expansion are influenced by the material non-homogeneity. Moreover, it can be seen from expressions of higher order stress fields that at least three terms must be considered in the case of FGMs in order to explicitly and theoretically account for non-homogeneity effects on crack tip stress fields.
Authors: P. Xue, J.P. He, Yu Long Li
Abstract: Plastic crushing behavior of thin-walled spheres under various loading cases is studied using Finite Element Method. The entire plastic deformation process is tracked during the post-buckling process. The results are compared with the experimental results reported in literature [13], and very good agreements between the numerical simulation and the experimental result are achieved.
Authors: Masayuki Tai, Anil C. Wijeyewickrema, Olivier Llouquet
Abstract: In this paper, Saint-Venant end effects for plane deformations of transversely isotropic piezoelectric materials are investigated. The stress decay rates in linear piezoelectric strips that are traction free with two kinds of electrical boundary conditions are considered. The characteristic equations for decay rate are obtained for symmetric and antisymmetric deformations. Numerical values are given for the roots with the smallest positive real part, which are associated with the slowest decay. Saint-Venant end effects of piezoelectric materials of crystal class 6mm penetrate much further into strip than those of elastic isotropic materials.
Authors: Maigefeireti Maitireyimu, Masanori Kikuchi, Mamtimin Gheni
Abstract: This article presents a modified FEM Superpostion method (S-FEM) for composite material analysis. Around the reinforcement body, failure and interface fracture may occur in the matrix. So the S-FEM was employed to detect the stress distribution around the reinforcement. One particle in big matrix is studied. Area of twice of particle radium is selected as local field.First, the feasibility of modified S-FEM is verified. And by symmetric analysis, geometric distribution of particle which may influence on the strength of composite material were discussed.
Authors: Mamtimin Gheni, Dong Cheng Yin, Xu Fei Wang, Masanori Kikuchi
Abstract: In this paper, the mathematical model for nonlinear multi-shaped randomly distributed domains in revealable and non-revealbale fields is established by using waveform mesh generation (WMG) method with damp, and made the application function of finite element pre and post handling system. The results show, this method can conduct mesh transformation to any given nonlinear function or given shapes in different scale randomly distributed domain in revealable and non-revealable fields, and obtained some smoothly mesh with matching each boundary and neighboring domains interaction.

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