中文摘要：

最大塑性功原理又称第二塑性变分原理，在致密体塑性变形分析叶l是运用能量法进行变形力能计算的基础。本文从分析Drucker公设的亢要条件出发，证明了烧结体塑性变形最大塑性功原理的存在，片在该原理的荩础卜，推导出塑性变形的上限功率表达式，并以平面挤压条件下的上限法应用作为实例加以说明。

英文摘要：

Maximum plastic work principle is an important theorem for analyzing plastic deformation which is a foundation to calculate deformation force with energy method. Based on plenary and indispensable condition for Drucker postulate and laws of plastic deformation, the maximum plastic work principle was deduced for PM simered material. Upper bound method was introduced based on the principle. As an applied example upper bound method was used to analyze plane strain extrusion.