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991.
992.
This study is concerned with the modeling of interphases in elastic media in general, and in composite materials in particular. The aim is to replace a boundary value problem consisting of a three-phase configuration, say that of fiber-interphase-matrix, by a simpler problem which involves the fiber and matrix only, plus certain matching conditions which simulate the interphase. The simplest of such known representations replaces a thin interphase by a “perfect contact interface” (a single surface) across which the displacements and tractions are assumed to be continuous. Another classical model replaces a thin and soft interphase by a “spring-type interface”, across which the tractions are continuous, but the displacement field undergoes a discontinuity. In the present paper, a Cosserat shell model of the interphase is derived which successfully models the original interphase in a unified manner, for the full range of its material parameters relative to those of the neighboring media. The model is derived in the setting of three-dimensional linear elasticity with small deformations and displacements. Comparisons with an existing exact solution of a coated fiber in an infinite matrix show that it performs extremely well even for moderately thick interphases. 相似文献
993.
Mehdi Khojastehpour 《Journal of the mechanics and physics of solids》2004,52(10):2235-2262
This article discusses localized bifurcation modes corresponding to shear band formation and diffuse bifurcation modes corresponding to bulge formation for cylindrical soil specimen subjected to an axisymmetric load under undrained conditions. We employ the tangential-subloading surface model, which exhibits the characteristic regimes of the governing equations: elliptic, hyperbolic and parabolic. Also, conditions for shear band formation, shear band inclination, diffuse bulging formation, and the long and short wavelength limits of diffuse bulging modes are discussed in relation to material properties and their state of stress, i.e. the stress ratio and the normal-yield ratio. Tangential-plastic strain rate term is required for the analyses of shear band and diffuse bulging. The shear band and the diffuse bulging are generated in not only normal-yield but also subyield states and they are severely affected by the normal-yield ratio describing the degree of approach to the normal-yield state. 相似文献
994.
成功建立了Hahn-Tsai复合材料模型的非线性杂交应力有限元方程,采用Newton-Raphson迭代法求解结构的非线性位移方程。在迭代过程中,为了提高计算效率可采用简单迭代法由节点位移求解单元应力场。但是,当载荷增加到一定程度以后,非线性应力场由于循环迭代而无法收敛,显然,一般的加速方法不能解决这种循环迭代的发散问题。因此,本文发展了一种确实有效的非线性应力场迭代新方法,在不增加计算工作量的情况下,不仅极大地提高了收敛速度,而且对于较大载荷也能够很好地收敛,从而解决了大载荷下非线性杂交元方法失败的关键问题。数值算例表明该方法是确实可行的。 相似文献
995.
996.
弹塑性随机振动系统中恢复力数学模型的若干形式 总被引:2,自引:0,他引:2
本文基于弹塑性随机振动系统恢复力数学模型的统一形式,提出了能考虑刚度下降段和系统在滞变过程中强度退化的四种恢复力数学模型,为适应系统在多次强随机干扰下的反应分析需要,根据试验结果,提出了经受过强随机干扰的有损伤系统的恢复力模型,并建立了相应的数学表达式,最后针对钢筋砼框架结构在主余震作用下的弹塑性地震反应分析给出了具体算例。 相似文献
997.
In nonlinear elasticity the exact geometry of deformation is combined with general constitutive relations. This allows a very sophisticated interaction of deformations in different material directions. Based on the Cosserat theory for planar deformations of nonlinearly elastic rods we demonstrate some paradoxical bending effects caused by a nontrivial interaction of extension, flexure, and shear. The analytical results are illustrated by numerical examples. 相似文献
998.
Marie-Noëlle BussacPierre Collet Gérard Gary Ramzi Othman 《Journal of the mechanics and physics of solids》2002,50(2):321-349
When using a classical SHPB (split Hopkinson pressure bar) set-up, the useful measuring time is limited by the length of the bars, so that the maximum strain which can be measured in material testing applications is also limited. In this paper, a new method with no time limits is presented for measuring the force and displacement at any station on a bar from strain or velocity measurements performed at various places on the bar. The method takes the wave dispersion into account, as must inevitably be done when making long time measurements. It can be applied to one-dimensional and single-mode waves of all kinds propagating through a medium (flexural waves in beams, acoustic waves in wave guides, etc.). With bars of usual sizes, the measuring time can be up to 50 times longer than the time available with classical methods. An analysis of the sensitivity of the results to the accuracy of the experimental data and to the quality of the wave propagation modelling was also carried out. Experimental results are given which show the efficiency of the method. 相似文献
999.
Starting from the general stress-strain relation for a linear Boltzmann-Volterra material, which is in agreement with the principle of inertia, a new identification procedure is proposed. Instead of running one long-range relaxation experiment, following asingle suitably specified deformation history, material characterization is done using the data ofn short relaxation experiments followingn different deformation histories. To interpret these data a direct non-iterative algorithm has been developed. Compared with other methods, for example curve fitting by using Gauss' method, this direct method is numerically stable and allows a simple direct evaluation of the error due to the scattering of experimental data. The method has been applied to the determination of the relaxation times of an unsaturated polyester material. 相似文献
1000.
Dr.Th. Th. Steinkopff Dr. M. Sautter Dr. J. Wulf 《Archive of Applied Mechanics (Ingenieur Archiv)》1995,65(7):496-506
Übersicht Zur Simulation des elastoplastischen Verformungsverhaltens und von Versagensprozessen in grob mehrphasigen Materialien verwenden wir die Methode der Mehrphasigen Finiten Elemente. Der Verzicht auf die ausschließliche Verwendung einphasiger Finiter Elemente gestattet die spannungs-/Dehnungsanalyse an komplizierten Realgefügen. Die vorgestellten Beispiele für Verformungs- und Versagensanalysen stellen die Leistungsfähigkeit der Methode der Mehrphasigen Finiten Elemente hinsichtlich Modellieraufwand, Konvergenz und Zuverlässigkeit der Resultate unter Beweis.
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