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991.
In this paper, elastoplastic stress-strain behavior during tensile deformation of an aluminum alloy matrix composite containing
alumina circular and non-circular particles is analyzed. In terms of cell models in conjunction with continuum plasticity
theory, various periodic arrays of particles are assumed in a three-dimensional finite element simulation. The geometrical
effects of particle volume fraction, shape, aspect ratio, array and distribution, as well as non-circular particle orientation
on the overall elastoplastic stress-strain behavior are examined in view to design optimum microstructures of the composites.
The project supported by the National Natural Science Foundation of China and the State Education Commission of China 相似文献
992.
Jong-Shyong Wu Lieh-Kwang Chiang 《International Journal of Solids and Structures》2003,40(26):7425-7448
For the cases of using the finite curved beam elements and taking the effects of both the shear deformation and rotary inertias into consideration, the literature regarding either free or forced vibration analysis of the curved beams is rare. Thus, this paper tries to determine the dynamic responses of a circular curved Timoshenko beam due to a moving load using the curved beam elements. By taking account of the effect of shear deformation and that of rotary inertias due to bending and torsional vibrations, the stiffness matrix and the mass matrix of the curved beam element were obtained from the force–displacement relations and the kinetic energy equations, respectively. Since all the element property matrices for the curved beam element are derived based on the local polar coordinate system (rather than the local Cartesian one), their coefficients are invariant for any curved beam element with constant radius of curvature and subtended angle and one does not need to transform the property matrices of each curved beam element from the local coordinate system to the global one to achieve the overall property matrices for the entire curved beam structure before they are assembled. The availability of the presented approach has been verified by both the existing analytical solutions for the entire continuum curved beam and the numerical solutions for the entire discretized curved beam composed of the conventional straight beam elements based on either the consistent-mass model or the lumped-mass model. In addition to the typical circular curved beams, a hybrid curved beam composed of one curved-beam segment and two identical straight-beam segments subjected to a moving load was also studied. Influence on the dynamic responses of the curved beams of the slenderness ratio, moving-load speed, shear deformation and rotary inertias was investigated. 相似文献
993.
A general nonlinear theory for the dynamics of elastic anisotropic circular cylindrical shells undergoing small strains and moderate-rotation vibrations is presented. The theory fully accounts for extensionality and geometric nonlinearities by using local stress and strain measures and an exact coordinate transformation, which result in nonlinear curvatures and strain-displacement expressions that contain the von Karman strains as a special case. Moreover, the linear part of the theory contains, as special cases, most of the classical linear theories when appropriate stress resultants and couples are defined. Parabolic distributions of the transverse shear strains are accounted for by using a third-order theory and hence shear correction factors are not required. Five third-order nonlinear partial differential equations describing the extension, bending, and shear vibrations of shells are obtained using the principle of virtual work and an asymptotic analysis. These equations show that laminated shells display linear elastic and nonlinear geometric couplings among all motions. 相似文献
994.
Strain recovery after the cessation of shear was studied in model immiscible blends composed of polyisobutylene drops (10–30%
by weight) in a polydimethylsiloxane matrix. Blends of viscosity ratio (viscosity of the drops relative to the matrix viscosity)
ranging from 0.3 to 1.7 were studied. Most of the strain recovery was attributable to interfacial tension, and could be well-described
by just two parameters: the ultimate recovery and a single retardation time. Both these parameters were found to increase
with the capillary number of the drops prior to cessation of shear. For blends that had reached steady shear conditions, the
ultimate recovery decreased with increasing viscosity ratio, whereas the retardation time increased with increasing viscosity
ratio. The retardation time was well-predicted, but the ultimate recovery was over-predicted by a linear viscoelastic model
developed previously by Vinckier et al. (Rheol Acta 38:65–72, 1999). 相似文献
995.
岩石力学位移反演分析回顾及进展 总被引:67,自引:0,他引:67
回顾综述了岩石力学反演分析的研究进展,重点介绍了位移反分析法的分类、结果评价及研究特点,讨论了需进一步探讨的问题. 相似文献
996.
剪切散斑:一种光学测量技术及其应用 总被引:3,自引:0,他引:3
本文综述了剪切散斑测量技术及其成功的应用领域。剪切散斑技术是一种基于激光的全场、非接触表面变形(位移或应变)测量技术,它无需特殊的隔震装置,克服了因参考光束给全息干涉技术所带来的诸多限制。因此,它是用于现场测量的一个有效工具。剪切散斑测量技术已经得到了工业界的普遍认同,尤其是在工业无损检测方面更显示出了它的极大优势,它可以通过识别被诱发的异常变形来显示物体的内部缺陷。剪切散斑的应用还包括应变测量、材料特性表征、残余应力评估、泄漏探测、振动分析和三维形貌测量等。 相似文献
997.
A boundary integral method was developed for simulating the motion and deformation of a viscous drop in an axisymmetric ambient Stokes flow near a rigid wall and for direct calculating the stress on the wall. Numerical experiments by the method were performed for different initial stand-off distances of the drop to the wall, viscosity ratios, combined surface tension and buoyancy parameters and ambient flow parameters. Numerical results show that due to the action of ambient flow and buoyancy the drop is compressed and stretched respectively in axial and radial directions when time goes. When the ambient flow action is weaker than that of the buoyancy the drop raises and bends upward and the stress on the wall induced by drop motion decreases when time advances. When the ambient flow action is stronger than that of the buoyancy the drop descends and becomes flatter and flatter as time goes. In this case when the initial stand-off distance is large the stress on the wall increases as the drop evolutes but when the stand-off distance is small the stress on the wall decreases as a result of combined effects of ambient flow, buoyancy and the stronger wall action to the flow. The action of the stress on the wall induced by drop motion is restricted in an area near the symmetric axis, which increases when the initial stand-off distance increases. When the initial stand-off distance increases the stress induced by drop motion decreases substantially. The surface tension effects resist the deformation and smooth the profile of the drop surfaces. The drop viscosity will reduce the deformation and migration of the drop. 相似文献
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