Motivated by the need for three-dimension methods for interface calculations that can deal with topology change, we describe a generally applicable numerical method built from Youngs technique. The usefulness of the method is illustrated by moving interface restructure in each mix cell and calculation of transport volume among cells.

This paper presents a theoretical analysis of the large deformation problem of a plastic spherical shell impacted by a missile. Firstly, a deformation mode of the spherical shell is given by introducing isometric transformation. Secondly, the large deformation problem of a rigid-plastic spherical shell is solved. A comparison between the theoretical results and the experimental ones indicates that the two groups of results are in conformity with each other.

目的 研究球形塑性壳在撞击载荷作用下的动态破坏行为。方法　通过引入等度量变换，给出了球壳的变形模态;利用能量平衡给出了壳体在撞击载荷作用下大变形动态破坏的运动控制方程；采用Runge-Kutta方法求解了该运动控制方程。 结果　给出了冲击力，窝陷半径和中心点位移随时间的变化关系以及最大窝陷半径、最大中心点位移和最大冲击力随弹体速度的变化关系。结论　本文结果与实验结果有比较好的一致性。

On the basis of yon Karman equations and using the general bifurcation theory, the elastic instability of an orthotropic elliptic plate whose edge is subjected to a uniform plane compression is discussed. Following the well-known Liapunov-Schmidt process the existance of bifurcation solution at a simple eigenvalue is shown and the asymptotic expression is obtained by means of the perturbation expansion with a small parameter. Finally, by using the finite element method, the critical loads of the plate are computed and the post-buckling behavior is analysed. And also the effect of material and geome-tric parameters on the stability is studied.

Under the action of external loads, the critical condition of fracture in ductile materials is closely re-lated to the strong interactions among internal microdefects at the later stage of deformation. By means of Riemann's analytical integration, necessary conditions for the internal necking between adjacent elliptical voids under plane strain conditions are studied. The influences of the aspect ratio of elliptical voids, the distance between two voids, and the angle of the straight line connecting the central points of two voids with respect to the tensile direction on the above-mentioned necessary conditions are also discussed.