1.引言 在现代世界上,各种车辆、船舶、飞行器的数量越来越多,速度越来越快,碰撞事故也随之日益增加,每年都要造成严重的生命和财产损失。因此,近20多年来,碰撞问题已引起许多国家的严重关注。解决这个问题的主要途径,是研究与提高各种车辆、船舶、飞行器结构的耐撞性(structural crashworthiness),参见[1—4]。同时,在某些特定的工况(例如飞行器的紧急着陆,核电站和高速公路旁重要设施的防护等等)下,已有结构难以满足吸 1. INTRODUCTION In the modern world, more and more kinds of vehicles, ships and aircraft are flying faster and faster, and collision accidents are also increasing. Every year, serious losses of life and property are caused. Therefore, the collision problem has caused serious concern in many countries in the past two decades or so. The main way to solve this problem is to study and improve the structural crashworthiness of all kinds of vehicles, ships and aircraft structures [1-4]. At the same time, there are structures that are difficult to satisfy under some specific operating conditions (such as emergency landing of aircraft, protection of nuclear power plants and important facilities beside freeways)