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1.
Abstract

The elastostatic problem of an orthotropic body having a central inclined crack and subjected at infinity to a uniform biaxial load is considered. It is assumed that the crack line does not coincide with an axis of elastic symmetry of the body. The problem must be considered as one of general orthotropy, due in particular to the fact that the elastic coefficients of the material change with rotation of the reference system. The stress fields at the crack tip are reported and the presence of the non‐singular terms underlined. The Strain Energy Density Theory is extended to orthotropic materials. It is assumed that the Critical Strain Energy Density Factor has a polar variation. The crack initiation is determined via minimization of the ratio of the strain energy density over the material critical strain energy density, pointing out the effects of orthotropy and load biaxiality. The effects of the non‐singular terms on crack growth for different orthotropic materials is also studied, underling the relation between orthotropy and non‐singular terms.  相似文献   
2.
Since wood products for structural elements, especially cross‐laminated timber (CLT), have gained importance in the building sector, the need for appropriate and reliable design codes for such wood products has become essential. For the improvement and development of design concepts, a profound knowledge about the mechanical behaviour of these products is necessary. For this reason, this work focuses on global failure mechanisms and the corresponding evolution of different crack modes in CLT plates, depending on geometric and/or material related properties. Therefore, plate‐bending experiments on three‐ and five‐layered CLT plates were carried out. In addition to standard evaluation methods, each specimen was cut into small cubes to identify the failure modes inside the plates. Regions with dominant shear failure, tensile failure, delamination and mixed failure modes could be captured and connected to geometry and loading situation. Based on this evaluation, well‐known but not yet in detail described effects, such as the ductile structural behaviour of CLT plates, can be explained. Moreover, the evolution of rolling shear failure modes as well as from which point the progressive failure highly affects the plate stiffness is investigated and analysed in detail.  相似文献   
3.
H. M. Wang  H. J. Ding 《热应力杂志》2013,36(12):1169-1185
The thermoelastic dynamic solution of a multilayered orthotropic hollow cylinder in the state of axisymmetric plane strain is obtained. By the method of superposition, the displacement is divided into two parts: one is quasi static and the other is dynamic. The quasi-static solution is derived by the state-space method, and the dynamic solution is obtained by the separation-of-variables method coupled with the initial parameter method as well as the orthogonal expansion technique. The present method is suitable for a multilayered orthotropic hollow cylinder consisting of arbitrary layers and subjected to arbitrary axisymmetric thermal loads. Numerical results are finally presented and discussed.  相似文献   
4.
分析了叉指形电极(IDEs)1-3型压电纤维复合材料传感元件的结构特点和电场特性,构建了压电纤维传感元件的本构方程,并建立了IDEs1-3型压电纤维传感元件的有限元模型,探索了IDEs关键尺寸和压电纤维直径及间隔对传感元件传感性能的影响.结果表明:该传感元件X向产生的电位移大小约为Y向产生电位移大小的3倍,正交异性更加明显,能清楚区分不同方向的应力波;选择合适的纤维间隔,减小电极中心距、电极面宽度和纤维直径能有效的改善传感元件的传感性能.  相似文献   
5.
Based on the Wilkins two-dimensional algorithm, a method is developed for the numerical study of the geometrically and physically nonlinear axially symmetrical dynamic stress-strain state of multilayer thick-walled cylindrical elastoplastic shells with different spiral reinforcement structures. A numerical study of the specific features in the nonlinear dynamic behavior of single-and two-layer cylinders is carried out for different reinforcement configurations and loading amplitudes. Translated from Problemy Prochnosti, No. 6, pp. 110–121, November–December, 2008.  相似文献   
6.
Exact analytical solutions have been obtained of a one-dimensional dynamical problem for an incompressible elastic radially inhomogeneous helically orthotropic thick-walled cylinder under plane strain conditions, loaded with nonsteady internal or external pressure. Necessary and sufficient conditions for the existence, uniqueness and physical adequacy of the solutions have been established. Convergence of wave solutions for slightly compressible cylinders to the analytical dependences obtained for incompressible cylinders has been analytically proved. __________ Translated from Problemy Prochnosti, No. 2, pp. 114–123, March–April, 2006.  相似文献   
7.
The exactness and stability of the Wilkins method in the investigation of the stress-strain state of axisymmetric anisotropic elastic shells, including thick-walled ones, have been studied for different values of artificial viscosity, pulse load rise and fall time, and different deformation process durations. A comparison of numerical calculations, performed by means of an application software package developed by V. A. Romashchenko on the basis of the Wilkins method, with experimental results, known numerical data, and with calculations using the computation kernel LS-DYNA 3D has been carried out.  相似文献   
8.
锚固正交各向异性岩体的三维粘弹-粘塑性有限元分析   总被引:4,自引:3,他引:1  
首先,从经过系统锚杆加固的正交各向异性岩体中取出的表征单元,然后,根据“等效材料”的概念,在一定的简化条件下,建立其本构方程,破坏准则及粘弹-粘塑性模型并将其引入三维有限元程序中,以地下洞室开挖为算例来考察锚固前后围岩的流变动态,从而得出有益的认识和结论。  相似文献   
9.
李涛  张秋华 《工程力学》2002,19(4):123-126
大多数金属材料在承载时产生了各向异性强化的特点,因此,对这一类材料特性的深入研究显得十分必要,正确建立及分析理论模型将对在实际工程中的应用提供很好的理论依据。本文在R.Hill屈服准则下提出了无量纲化的解析应力解,讨论了屈服参数2>h时,正交异性材料平面应力问题的应力场及应力特征场,利用应力微分平衡方程得到了决定特征曲线特征的参数。结果说明特征线一般互不正交。特别地分析了平头冲压边界附近的情况,得到了各应力状态不同区域的应力特征场,应用数值分析的方法对过渡区进行了计算。  相似文献   
10.
遗传算法的改进及其在各向异性介质参数反演中的应用   总被引:1,自引:0,他引:1  
傅旦丹  何樵登 《石油物探》2002,41(3):293-298
目前,常规的遗传算法对变异进程不能实行控制,当变异概率取得较大时,就会以极大的几率使种群中很多成员出现退化的现象,从而使遗传算法变得象蒙特卡洛方法那样,把大量的计算工作浪费在无意义的空间部分,其结果使常规遗传算法不得不采用很小的变异概率。这样做的结果显然不利于算法作全局搜索,存在易陷于局部极值的缺陷。为在扩大模型空间的搜索范围和保持种群多样性的同时,又能对变异过程进行控制,通过引入Metropolis抽样准则,提出了一种改进的遗传算法。同常规算法相比,改进算法更有利于作全局搜索,具有改善遗传算法全局收敛性的效果。针对正交各向异性介质模型,用改性的遗传算法进行了各向异性多参数反演工作,以说明新方法在处理这样高度非线性最优化问题时的处理效果。  相似文献   
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