| Abstract: | Singularities leading to the calculation of spurious velocity fields have been observed in the tangent stiffness equations assembled during the finite-element analysis of square blocks of purely cohesive perfectly plastic material. These occur because of weaknesses in conventional implementations of the plastic flow rule. Both twisting and swaying modes occur which interfere with the calculation of uniform velocity fields for blocks responding to uniform applied stress. Various techniques can be used to eliminate the problem. The phenomenon does not eventuate when non-uniform stress fields are acting, so does not affect the solution of practical plasticity problems. |
