共查询到20条相似文献,搜索用时 125 毫秒
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高体积百分比颗粒增强聚合物材料的有效粘弹性性质 总被引:1,自引:0,他引:1
聚合物材料通常表现为粘弹性性质.为了改进聚合物材料的力学性能,通常将某种无机材料以颗粒或纤维的形式填充到聚合物中,从而得到增强、增韧的聚合物基复合材料.提出了一个新的细观力学模型,用于预测颗粒增强聚合物复合材料的有效粘弹性性质,尤其针对高体积百分比的颗粒夹杂复合材料,该方法基于Laplace变换和双夹杂相互作用的弹性模型.计算了玻璃微珠/ED-6复合材料的有效松弛模量以及恒应变率下的应力应变关系.计算结果表明在高体积百分比下该文方法比基于Mori Tanaka方法预测的粘弹性效应明显减弱. 相似文献
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任意荷载下成层粘弹性地基的一维固结 总被引:5,自引:0,他引:5
针对成层粘弹性地基模型,运用Laplace变换及矩阵传递法求解了任意荷载下成层粘弹性地基一维变形问题,得到了频域内的通解,通过Laplace逆变换,即可计算成层粘弹性地基在任意荷载下的一维变形.Terzaghi一维固结理论解是本文的一个特例.结合三层地基的算例,可以看到粘弹性地基的固结相对于弹性地基有个滞后过程,但随时间最终趋于一致;循环荷载下粘弹性多层地基固结时,其有效应力和变形都呈振荡增长,且不与荷载同步,而要相对滞后.此外,通过一工程实例,对该方法的可靠性进行论证,以证明该法确能指导工程实践. 相似文献
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采用厚壁筒在内压作用下的应力强度因子作为参考载荷的应力强度因子,通过权函数方法推导出了内壁带二维径向边裂纹的旋转厚壁筒的应力强度因子公式.这些公式可用于计算旋转厚壁筒在不同裂纹深度、转速、材料和尺寸情况下的应力强度因子.算例表明该文的公式具有良好的精度.同时还研究了旋转圆筒应力强度因子随裂纹深度和内外径比之间的变化规律,方便了工程应用. 相似文献
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采用复变函数方法,研究了在法向均布荷载作用下,含两个不等边裂纹椭圆孔的无限大板平面问题,得到了裂纹尖端的应力强度因子的解析解.并通过有限元软件计算了应力强度因子的数值解,与解析解进行对比,吻合较好.另外,研究了随着裂纹和椭圆孔尺寸变化时应力强度因子的变化规律.可以看出应力强度因子随椭圆孔的长短半轴之比和裂纹长度的增大而增大. 相似文献
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研究倾斜荷载作用在黏性流体与热弹性微极蜂窝结构固体界面上时,荷载倾斜角的影响.假设倾斜荷载是法向荷载和切向荷载的线性组合.为求解该问题,对时间变量进行Laplace变换,对空间变量进行Fourier变换.通过引入势函数,获得了变换域中应力、温度分布和压力的表达式.利用数值逆变换技术,求得问题的物理解.同时,得到了频域中的表达式,以及变量适当变化时稳态情况下的表达式.用图形显示不同荷载源和荷载倾角变化时的响应.并且讨论了一些特殊情况. 相似文献
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The problem of multiple arbitrarily oriented planar cracks in an infinite magnetoelectroelastic space under dynamic loadings is considered. An explicit solution to the problem is given in the Laplace transform domain in terms of suitable exponential Fourier integral representations. The unknown functions in the Fourier integrals are directly related to the Laplace transform of the jumps in the displacements, electric potential and magnetic potential across opposite crack faces and are to be determined by solving a system of hypersingular integral equations. Once the hypersingular integral equations are solved, the displacements, electric potential, magnetic potential and other quantities of interest such as the crack tip intensity factors may be easily computed in the Laplace transform domain and recovered in the physical space with the help of a suitable algorithm for inverting Laplace transforms. 相似文献
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Probability models are formulated for the availability (probability of being operative, i.e. not failed or down at fixed or random time t) of a variety of simple repairable systems. Single-exponential approximations of the time-dependent approach to long-run availability are presented. Problems of non-parametric estimation of time-dependent system availability from data are addressed by way of the empirical Laplace—Stieltjes transform. Uncertainty assessments are made by classical asymptotics (delta method) and by bootstrapping. 相似文献
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A comprehensive outline is presented for obtaining the Laplace transforms of the transition probability density functions
and of the first-passage-time densities for one-dimensional time-homogeneous diffusion processes in the presence of absorbing
and/or reflecting boundaries. In particular, the Laplace transform of the transition probability density function in the presence
of pairs of reflecting boundaries are explicitly obtained. Symmetric diffusion processes are then specifically considered
and explicit closed-form relations are then obtained for the hyperbolic diffusion process in the presence of absorbing and/or
reflecting boundaries. The special cases of the Brownian motion and of the Hongler process are finally analyzed. 相似文献
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针对饱和软黏土,结合引入弹壶元件改进的分数阶Kelvin模型,同时考虑土体内应力沿深度变化的特点,利用Laplace变换推导获得其一维固结半解析解.首先,通过与文献中的试验结果及文献中的理论结果对比,说明了该模型的有效性;其次,详细地分析了不同分数阶阶数、不同总应力比以及不同分级线性加载等因素对饱和软黏土固结沉降以及孔隙水压力的影响,再现了饱和软黏土的固结沉降机理,以期为工程实践提供相关的理论基础. 相似文献
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Hans U. Gerber Marc Goovaerts Nelson DePril 《Journal of Computational and Applied Mathematics》1981,7(4):267-269
The Wiener process with constant drift is modified by a time-dependent retaining barrier that increases at a constant rate and by an absorbing barrier at zero. Explicit expressions in terms of series expansions are derived for the Laplace transform and the probability density function of the time of absorption. 相似文献
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This paper investigates the transient response of a transversely isotropic multilayered half-space under vertical loadings. With the aid of a Laplace–Hankel transform, the global stiffness matrix for a multilayered half-space is acquired by assembling the analytical layer-element of each layer medium. The solutions for the displacements in the time domain are obtained by using the global stiffness matrix equations and a numerical inversion procedure. The accuracy of the proposed method is verified through comparisons with existing solutions for displacements induced by a step and rectangular pulse loading. In addition, selected numerical results for displacements induced by the buried loading are presented to illustrate the effect of transient loading type and material anisotropy on the transient response. 相似文献
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Xiaoshan Chen Yingshan Chen Fahuai Yi 《Journal of Mathematical Analysis and Applications》2012,385(2):928-946
This paper concerns a singular control problem whose value function is governed by a time-dependent HJB equation with gradient constraints. The method is to transform a two-dimensional parabolic variational inequality with gradient constraints into a double obstacle problem with parameter involving two free boundaries that correspond to the investment and disinvestment policies. Moreover we analyze the behaviors of the free boundary surfaces. The main difficulties are to show the free boundary surfaces to be smooth with respect to time and to find the properties of free boundaries with respect to parameter. 相似文献
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Chunrui Li Liancun Zheng Yue Zhang Lianxi Ma Xinxin Zhang 《Communications in Nonlinear Science & Numerical Simulation》2012,17(12):5026-5041
This paper presents an analysis for helical flows of a heated generalized Oldroyd-B fluid subject to a time-dependent shear stress in porous medium, where the motion is due to the longitudinal time-dependent shear stress and the oscillating velocity in boundary. The exact solutions are established by using the sequential fractional derivatives Laplace transform coupled with finite Hankel transforms in terms of generalized G function. Moreover, the effects of various parameters (relaxation time, fractional parameter, permeability and porosity) on the flow and heat transfer are analyzed in detail by graphical illustrations. 相似文献
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Jan Nordstrm 《Applied Numerical Mathematics》1999,30(4):447-457
One way of imposing boundary conditions for the Navier–Stokes equations at artificial supersonic outflow boundaries is to use flux-extrapolation. This procedure is analyzed and compared with variable-extrapolation both for the semi-discrete and continuous problem using the Laplace transform technique. It is shown that flux-extrapolation leads to a loss of accuracy and an extra time growth. The numerical experiments support the analytical results. 相似文献
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非饱和土层一维固结问题的解析解 总被引:5,自引:1,他引:4
对一有限厚度,处于一维受荷状态,表面为透水透气面,底面为不透水不透气面的非饱和土层,依据Fredlund的非饱和土一维固结理论,由液相及气相的控制方程、Darcy定律及Fick定律,经Laplace变换及Cayley-Hamilton数学方法构造了顶面状态向量与任意深度处状态向量间的传递关系;通过引入初始及边界条件,得到了Laplace变换域内的超孔隙水压力、超孔隙气压力以及土层沉降的解;实现Laplace逆变换,得到了时间域内的解析解;用一典型算例,与差分法结果进行对比,验证了其正确性. 相似文献