A STRESS VECTOR-BASED CONSTITUTIVE MODEL FOR COHESIONLESS SOIL (Ⅱ)-APPLICATION

The stress vector-based constitutive model for cohesionless soil, proposed by SHI Hong-yan et al., was applied to analyze the deformation behaviors of materials subjected to various stress paths. The result of analysis shows that the constitutive model can capture well the main deformation behavior of cohesionless soil, such as stress-strain nonlinearity, hardening property, dilatancy, stress path dependency, non-coaxiality between the principal stress and the principal strain increment directions, and the coupling of mean effective and deviatoric stress with deformation. In addition, the model can also take into account the rotation of principal stress axes and the influence of intermediate principal stress on deformation and strength of soil simultaneously. The excellent agreement between the predicted and measured behavior indicates the comprehensive applicability of the model. Biography: SHI Hong-yan (1962-), Associate Professor, Doctor     

残余应力对压力容器破坏模式的影响分析

破前漏(简称LBB)是压力容器、核电站设备结构设计与评价中的一个重要准则.表面裂纹准静态扩展的几何形貌变化规律的预测是破前漏(LBB)评判十分重要的课题之一.本文对特定焊接残余应力场加载作用下,含三维表面裂纹的压力容器模型,用有限元软件(ABAQUS)进行了表面裂纹准静态扩展模拟计算,得到在此残余应力场作用下应力强度因子沿裂纹前缘的分布规律.结合外载引起的应力强度因子,就可以判别裂纹的扩展形貌,从而判断结构是否满足LBB要求.     

非均匀介质有限元法

提出适合非均匀介质应力分析的有限元法．文中在有限单元内部采用等参变换方法模拟材料特性的变化，算例表明该法计算效率高，计算精度好．     

多层材料结构的界面裂纹尖端复应力强度因子

本文建立了一种多层材料复合结构的界面裂纹问题分析模型。当两种材料之间插入第三种薄层弹性材料,裂纹位于第三种材料与第一或第二种弹性材料的界面上,且插页材料3~#的厚度相对于裂纹尺寸或平面内其他尺寸很小时,可以得到该问题裂纹尖端的复应力强度因子通式。本文用有限元法对结果进行了数值验证,并进行了有关问题的讨论。     

Micromechanics of residual stress and texture development due to poling in polycrystalline ferroelectric ceramics

This paper presents micromechanics based analysis of elastic strain and changes in the texture of poled polycrystalline ferroelectric PZT ceramics for direct comparison with synchrotron X-ray measurements. The grains are modelled as spherical inclusions, to which transformation strains are assigned depending on the fractions of different ferroelectric domains. Eshelby's inclusion problem with the classical self-consistent method is applied to evaluate the elastic state of the grains. In particular, the elongation due to lattice elastic strain is calculated as a function of inclination Ψ relative to the polar axis. The ratio of diffraction peak intensities, corresponding to the domain fractions, is also expressed as a function of Ψ. This analysis identifies the special character of the reflection, for which the lattice strain along in the stress free state is independent of ferroelectric domain population and hence unaffected by poling. The elongation due to the lattice strain parallel to and peak intensity ratio are expressed in terms of the overall macroscopic strain of a poled specimen, each having a dependence.     

孔隙压力作用下圆形巷道围岩的蠕变分析

在原有的岩土流变理论基础上,与渗流力学原理相结合,考虑孔隙压力及孔隙度在岩石蠕变过程中对于岩体变形的影响,在弹性解答的基础上,通过Laplace变换(对应性原理)得出解析解．在一定的假设条件下,利用弹性力学基本方程、蠕变方程及有效应力原理(Terzaghi有效应力方程),采用H-K体模型作为本构方程,将孔隙压力引入到围岩蠕变方程中．给出在孔隙压力作用下的蠕变曲线,并与不考虑孔隙压力和定孔隙压力条件下蠕变曲线相比,其更接近于实际．     

Non-Newtonian effects of second-order fluids on double-layered porous Rayleigh-step bearings

Theoretical study of double-layered porous Rayleigh-step bearings with second-order fluid as lubricant is presented. An approximate method for the solutions of the governing fluid film equations for a porous region is proposed. The expressions for the pressure distribution, load capacity and frictional coefficient are obtained in compact form. Calculations of the dimensionless load capacity, frictional force and frictional coefficients are presented for specific values of the material parameters. It is found that the double porous layer yields an increase in the load capacity and ensures decrease in frictional force at the porous lining as compared with the conventional porous Rayleigh-step bearings. The maximum dimensionless load-carrying capacity is found to occur at a slightly larger step ratio as compared with the conventional porous Rayleigh-step bearings.     

一种求解层合圆柱壳的杂交应力单元

根据修正的余能原理，推导出一种求解复合材料层合圆柱壳的杂交应力单元。取用六面体等参单元，此单元反映了各层材料性质不同及应力分布沿整个厚度不连续现象，同时计入横向剪切变形和法向挤压变形，适用于厚层壳体。文章通过实例说明此单元能准确求出各层内的应力值，实用价值高。     

吊车压轨器强度的实验测试

宽厚板厂房的行车轨道在行车运行时承受来自行车水平导向轮的水平推力，该水平推力可能导致压轨器破坏，为确保压轨器的安全设计，采用平面光弹性、三维光弹性进行实验测试，分析在最不利工况下，各种压轨器所承担的水平推力份额，压轨器的变形和应力分布，给出强度分析评估，确定系统中各个压轨器以及固定螺栓的关键部位的应力水平。     

Equivalence Theorems on the Propagation of Small-Amplitude Waves in Prestressed Linearly Elastic Materials with Internal Constraints

By extending the procedure of linearization for constrained elastic materials in the papers by Marlow and Chadwick et al., we set up a linearized theory of constrained materials with initial stress (not necessarily based on a nonlinear theory). The conditions of propagation are characterized for small-displacement waves that may be either of discontinuity type of any given order or, in the homogeneous case, plane progressive. We see that, just as in the unconstrained case, the laws of propagation of discontinuity waves are the same as those of progressive waves. Waves are classified as mixed, kinematic, or ghost. Then we prove that the analogues of Truesdell"s two equivalence theorems on wave propagation in finite elasticity hold for each type of wave. This revised version was published online in August 2006 with corrections to the Cover Date.