Elastic-Plastic Local Deformation and Collapse of Shells in Contact

通过数值和实验研究了壳在相互接触时发生的大弹塑性变形和坍塌过程。建立了估算壳体与刚体或壳体接触或碰撞时所受损伤的基本知识。提出了一种有限互滑接触问题的数值分析算法，并在有限元法的基础上采用罚函数法建立了该算法。对球壳和圆柱壳的接触问题进行了数值模拟，讨论了接触屈曲和坍塌过程的细节。研究结果表明：(1)接触面的摩擦条件起着重要的作用。(2)如果摩擦系数不是很小，粘着（不相互滑动）下的变形会持续到相当大的程度，从而使两体（壳）都受到显著的损伤。(3)当摩擦系数较小时，接触表面发生相互滑动，发生弹性卸载的物体在滑动后表现为刚体，对另一个物体造成严重损伤。(4)因此，损伤的估计需要知道物体在接触表面抵抗摩擦力的局部剪切变形刚度。通过对球壳和圆柱壳接触屈曲过程的实验观察，讨论了非对称变形对屈曲稳定性的影响，这种影响很难用理论分析来估计。

Large elastic-plastic deformation and collapsing process occurred in shells in contact with each other have been examined numerically and experimentally. Basic knowledge to estimate the damage suffered by the shell on the occasion of contact or collision with the rigid body or the shell has been established.An algorism of numerical analysis for the contact problem involving finite amount of mutual sliding has been developed and the penalty function method is used for the algorism to build in the numerical procedure based on the finite element method.The numerical simulations of the contact problems of spherical and cylindrical shells were performed and the details of the contact buckling and collapse process were discussed. The following results have been obtained concerning the damage of contact of the shells: (1) The condition of friction on the contact surface plays very important role. (2) If the frictional coefficient is not so small, deformaion under sticking (without mutual slide) continues up to the considerable amount and as a consequence, the both bodies (shells) suffer remarkable damage. (3) If the frictional coefficient is small, mutual sliding on the contact surface occurs and the body in which the elastic unloading results behaves like the rigid body after sliding and the serious damage is caused to the other body. (4) Therefore, the estimation of the damage necessitates to know the local rigidity of shear deformation of the body resisting the frictional force in the contact surface.From the experimental observations of the contact bucking of the spherical and cylindrical shells, the role of the non-symmetric deformation is discussed on the stability of the buckling process, which is very difficult to estimate by theoretical analysis.