断裂过程区应力应变场的数学分析

本文将条状分离区看作是位错连续分布区域,利用复变函数理论及切比雪夫多项式级数展开提出了一种统一的数学分析的方法,用以对均匀材料裂纹前方分离过程区的非线性效应进行有效的,精确的解析分析。避免以前各种模型一般都需要借助于有限元法或其他离散方法才能得到数值解答的难点。本文利用这一新方法,对断裂过程区是内聚力模型,条状屈服区模型的裂纹问题,受约束金属薄膜的裂纹问题,进行了分析计算,并与已有的结果进行了比较,得到了满意的结果。     

TNT炸药动静态变温三轴压缩力学性能的试验研究

介绍了一种高能材料动静态变温三轴压缩试验装置，在熔点以下温度，通过对国产单质炸药ＴＮＴ在中等应变速率（２－４／ｓ）及准静态（３×１０－３／ｓ）条件下三轴压缩力学性能的测试，得出ＴＮＴ的杨氏模量Ｅ、泊松比ν和屈服极限Ｙ，以及当加载速率和温度改变时这些参数的变化规律。并提出三轴应力状态下屈服极限的一种确定方法。该三轴压缩试验装置以及三轴压缩应力状态下力学参数的测试、分析、处理系统为研究高能材料力学性能提供了一套完整的技术和手段。     

The rheology of suspensions of vinylon fibers in polymer liquids. II. Suspensions in polymer solutions

Summary The rheological properties of vinylon fiber suspensions in polymer solutions were studied in steady shear flow. Shear viscosity, first normal-stress difference, yield stress, relative viscosity, and other properties were discussed. Three kinds of flexible vinylon fibers of uniform length and three kinds of polymer solutions as mediums which exhibited remarkable non-Newtonian behaviors were employed. The shear viscosity and relative viscosity ( _r ) increased with the fiber content and the aspect ratio, and depended upon the shear rate. Shear rate dependence of _r was found only in the low shear rate region. This result was different from that of vinylon fiber suspensions in Newtonian fluids. The first normal-stress difference increased at first slightly with increasing fiber content but rather decreased and showed lower values for high content suspensions than that of the medium. A yield stress could be determined by using a modified equation of Casson type. The flow properties of the fiber suspensions depended on the viscosity of the medium in the suspensions under consideration.With 16 figures and 1 table     

润滑剂边界滑移及其对弹流润滑特性的影响

基于润滑剂在弹性流体动力润滑状态下表现出类似塑件固体的非牛顿特性，根据塑性屈服和流体动力润滑理论，建立了考虑润滑剂在固液界面滑移的线接触弹流润滑失效预测模型。计算结果显示：载荷和滑滚比对润滑油膜厚度影响显著；在一定载荷和滑滚比下，润滑油膜将丧失承载能力而破裂。与现有理论及实验数据对比，线接触弹流润滑失效预测模型的计算结果与实验结果具有较好的一致性。     

Numerical plane stress elastic–perfectly plastic crack analysis under Tresca yield condition with comparison to Dugdale plastic strip model

A number of plane stress numerical analyses of the mode I elastoplastic fracture mechanics problem have been performed in the past using the Huber–Mises yield criterion. This study employs instead the Tresca yield condition using an incremental theory of plasticity for a stationary crack. A commercial finite element program is used to solve the opening mode of fracture problem (mode I) for a square plate containing a central crack under generalized plane stress loading conditions. A biaxial uniform tensile traction is applied to the edges of a thin plate composed of a linear elastic non-work hardening material under small strain assumptions. The finite element results are compared with the analytical predictions of the Dugdale plastic strip model for a crack in an infinite plate subject to a biaxial uniform load at infinity.     

On a formulation for anisotropic elastoplasticity at finite strains invariant with respect to the intermediate configuration

The paper is concerned with a formulation of anisotropic finite strain inelasticity based on the multiplicative decomposition of the deformation gradient F=F_eF_p. A major feature of the theory is its invariance with respect to rotations superimposed on the inelastic part of the deformation gradient. The paper motivates and shows how such an invariance can be achieved. At the heart of the formulation is the mixed-variant transformation of the structural tensor, defined as the tensor product of the privileged directions of the material as given in a reference configuration, under the action of F_p. Issues related to the plastic material spin are discussed in detail. It is shown that, in contrast to the isotropic case, any flow function formulated purely in terms of stress quantities, necessarily exhibits a non-vanishing plastic material spin. The possible construction of spin-free rates is discussed as well, where it is shown that the flow rule must then depend not only on the stress but on the strain as well.     

Transition theories of elastic-plastic deformation of metallic polycrystals

Summary A general approach to the problem of determination of elastoplastic behavior of metallic polycrystals at finite deformation is presented. The relation between moving dislocation density and global slip rate for grains is developed. Transition to grain response is obtained by introducing the hardening matrix. Field equations for heterogeneous elastoplastic metals are transformed into an integral equation, using Green functions technique. This allows to find the spin of the lattice related to texture formation.Scale transition is achieved by a self-consistent approximation of the integral equation. New results concerning BCC metals (sheet steel) are presented. They apply to tensile test, Lankford coefficient, initial and subsequent yield surfaces, and evolution of the internal state of the polycrystal: second-order residual stress, stored energy and texture evolution.     

A finite element analysis of the flange earrings of strong anisotropic sheet metals in deep-drawing processes

Flange earrings of strong anisotropic sheet metals in deep-drawing process are numerically analyzed by the elastic-plastic large deformation finite element formulation based on a discrete Kirchhoff triangle plate shell element model. A Barlat-Lian anisotropic yield function and a quasi-flow corner theory are used in the present formulation. The numerical results are compared with the experimental ones of cylindrical cup drawing process. The focus of the present researches is on the numerical analysis and the constraining scheme of the flange earring of circular sheets with strong anisotropy in square cup drawing process. The project supported by the National Natural Science Foundation of China (19832020) and Provincial Natural Science Foundation of Jilin, China (200000519)     

体积分数对基于沸石和硅油的悬浮液的电流变性能的影响

用 HAAKE RV2 0型流变仪 ,在不同外加电场强度和不同颗粒体积分数下测试了基于沸石和硅油的电流变液的剪切应力变化 .结果表明 :随着外加电场强度升高 ,电流变液的零电场粘度急剧增加 ,电流变液的剪切屈服应力增加 ;随着电流变液中沸石颗粒体积分数升高 ,电流变液的剪切屈服强度急剧上升 .这种变化可以用颗粒间作用力与颗粒间距的关系、单位面积的颗粒链数目变化以及多体作用对电流变液性能的影响来解释     

高能电子辐照绝缘厚样品的表面电位动态特性

采用数值计算和实验测量相结合的方法, 阐明了高能电子束照射下绝缘厚样品的表面电位和电子产额动态特性. 结果表明: 由于电子在样品内部的散射和输运, 沿着深度方向, 空间电位先缓慢下降到最小值, 然后逐渐升高并趋近于零; 随着电子束照射, 样品的表面电位逐渐下降, 可至负千伏量级, 电子总产额逐渐增大至一个接近于1的稳定值; 电子束停止照射后, 长时间放置下, 表面电位将逐渐升高, 但带电并不会消除; 表面电位随电子束能量的升高近似线性下降, 随入射角的增大而升高, 而随样品厚度的增大仅略有下降.