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861.
针对堆石料浸水后的湿化变形并不是瞬时产生,而是一个渐进发展过程这一现象,建议将湿化变形进行时变计算。首先采用Prandtl-Reuss流动法则推导了湿化剪切应变分量,然后叠加湿化体积应变分量,获得三维湿化应变分量;通过分析三维湿化应变分量和单轴应力状态下的湿化应变的关系,指出有关文献推导的三维湿化应变分量计算公式不严谨;然后类比于堆石料流变变形计算公式,推导了湿化变形时变计算公式。实例分析表明,湿化引起坝顶沉降随时间逐渐增大,变形稳定的时间与湿化变形速率呈反比关系。 相似文献
862.
863.
<正>A three-dimensional(3-D)approach based on the state space method is proposed to study size-dependent mechanical properties of ultra-thin plate-like elastic structures considering surface effects.The structure is modeled as a laminate composed of a bulk bounded with upper and bottom surface layers,which are allowed to have different material properties from the bulk layer.State equations,including the surface properties of the structure,can be established on the basis of 3-D fundamental elasticity to analyze the size-dependent static characteristics of the thin plate-like structure.Compared with two-dimensional plate theories based size-dependent models for thin film structures in literature,the present 3-D approach is exact,which can provide benchmark results to assess the accuracy of 2-D plate theories and various numerical approaches. To show the feasibility of the proposed approach,a 3-D analytical solution for a simply supported plate-like thin structure including surface layers is derived.An algorithm is proposed for the calculation of the state equations obtained to ensure that the numerical results can reveal the surface effects clearly even for extremely thin surface layers.Numerical examples are carried out to exhibit the surface effects and some discussions are provided based on the results obtained. 相似文献
864.
A boundary-element scheme is proposed for the numerical determination of the stress-strain state of a three-dimensional composite
body, which is an elastic inclusion of arbitrary shape perfectly bonded to an infinite elastic matrix. The scheme involves
the reduction of the original problem to six boundary integral equations for the components of interfacial displacements and
forces and the boundary-element parametrization and discretization of these equations using generalized Gaussian integrals
and topological maps with regularizing Jacobians. Numerical results are obtained for a cylindrical inclusion with rounded
ends in a matrix subject at infinity to constant forces acting along this fiber. The influence of the length-to-radius ratio
of the fiber and the ratio of the elastic moduli of the matrix and fiber on the stresses is examined
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 4, pp. 27–35, April 2007. 相似文献
865.
A Three-Dimensional Hybrid LES-Acoustic Analogy Method for Predicting Open-Cavity Noise 总被引:1,自引:0,他引:1
A three-dimensional (3D) hybrid LES-acoustic analogy method for computational aeroacoustics (CAA) is presented for the prediction
of open-cavity noise. The method uses large-eddy simulation (LES) to compute the acoustic source while the Ffowcs Williams-Hawkings
(FW-H) acoustic analogy is employed for the prediction of the far-field sound. As a comparison, a two-dimensional (2D) FW-H
analogy is also included. The hybrid method has been assessed in an open-cavity flow at a Mach number of 0.85 and a Reynolds
number of Re=1.36×106, where some experimental data are available for comparison. The study has identified some important technical issues in the
application of the FW-H acoustic analogy to cavity noise prediction and CAA in general, including the proper selection of
the integration period and the modes of sound sources in the frequency domain. The different nature of 2D and 3D wave propagation
is also highlighted, which calls for a matching acoustic solver for each problem. The developed hybrid method has shown promise
to be a feasible, accurate and computationally affordable approach for CAA. 相似文献
866.
A method of studying the natural vibrations of highly inhomogeneous shells of revolution is developed. The method is based
on a nonclassical theory of shells that allows for transverse shear and reduction. By separating variables, the two-dimensional
problem is reduced to a sequence of one-dimensional eigenvalue problems. The inverse iteration method is used to reduce these
problems to a sequence of inhomogeneous boundary-value problems solved by the orthogonal sweep method. The capabilities of
the method are illustrated by solving certain representative problems and comparing their solutions with those obtained using
the three-dimensional theory of elasticity, the classical theory of shells, and the refined Timoshenko model
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 9, pp. 38–47, September 2007. 相似文献
867.
Amares Chattopadhyay 《应用数学和力学(英文版)》2007,28(10):1309-1318
The propagation of three-dimensional plane waves at a traction free boundary of a half-space composed of triclinic crystalline material is discussed.A method has been developed to find the analytical expressions of all the three phase velocities of quasi-P (qP),quasi-SV(qSV)and quasi-SH(qSH)in three dimensions.Closed form expressions in three dimensions for the amplitude ratios of reflection coefficients of qP,qSV and qSH waves in a triclinic medium are obtained.These expressions are used for numerically studying the variation of the reflection coefficients with the angle of incidence.The graphs are drawn for different polar angle and azimuth.Numerical results presented indicate that the anisotropy affect the reflection coefficients significantly in the three dimensional case compared to the two-dimensional case. 相似文献
868.
Three-dimensional elasticity solutions for static bending of thick functionally graded plates are presented using a hybrid semi-analytical approach-the state-space based differential quadrature method (SSDQM). The plate is generally supported at four edges for which the two-way differential quadrature method is used to solve the in-plane variations of the stress and displacement fields numerically. An approximate laminate model (ALM) is exploited to reduce the inhomogeneous plate into a multi-layered laminate, thus applying the state space method to solve analytically in the thickness direction. Both the convergence properties of SSDQM and ALM are examined. The SSDQM is validated by comparing the numerical results with the exact solutions reported in the literature. As an example, the Mori-Tanaka model is used to predict the effective bulk and shear moduli. Effects of gradient index and aspect ratios on the bending behavior of functionally graded thick plates are investigated. 相似文献
869.
研制了步进摩擦分析测试平台,可用于检测人体在静止及运动路面上的步进摩擦特性.该平台主要由六自由度摇摆台、三维测力台和数据采集系统三部分构成,六自由度摇摆台可提供六个自由度的任意组合运动,用来模拟舰船、海浪和地震等工况;三维测力台可测量出人体在行走时的三维力和力矩;数据采集系统将六自由度运动平台和三维测力台的输出数据采集并保存到计算机中,用来分析人体运动时的步进摩擦特性.采用研制平台进行了一组试验,结果表明:人在上、下坡行走时的垂直地面反作用力与在水平路面行走时的垂直地面反作用力具有不同的分布规律,并且垂直地面反作用力均随坡度角的增大而减小. 相似文献
870.
铝质蜂窝结构由于其优良的物理和机械性能被广泛地应用于工程结构,因而对其力学性能的研究也成为越来越重要的课题。本文通过摆锤冲击实验,研究了蜂窝铝的动态压缩性能及低速冲击吸能特性。结果表明,在球形摆锤冲击下,蜂窝铝结构具有很好的冲击吸能特性,其变形特征与准静态变形类似。研究中通过高速摄像系统和加速度传感器记录摆锤的加速度衰减过程,通过投影光载波技术获得受冲击蜂窝铝板表面的压缩行为和三维变形形貌。最后利用有限元方法进一步分析了蜂窝铝结构中内部损伤形式等实验中无法观测的现象,并对蜂窝铝结构参数对其吸能行为的影响进行了详细的讨论。 相似文献