引言自从焊接结构得到广泛应用以来,在许多国家中,一些桥梁、船舶、压力容器、管道、贮罐、和建筑机械等金属结构,曾发生过不少脆性破坏事故。由于这种事故具有突然发生不易予防的特点,所以它们的后果是严重的,甚至是灾难性的。其中最著名的有比利时30年代一些钢桥的破坏事故,美国40年代“自由”型万吨货轮的大量破坏事故,最突出的有 INTRODUCTION Since many welded structures have been widely used, in many countries, some brittle failure accidents have occurred in some metal structures such as bridges, ships, pressure vessels, pipes, storage tanks and construction machinery. Because of the sudden and unpredictable nature of such accidents, their consequences are severe and even catastrophic. One of the most notable is the destruction of some of the steel bridges in Belgium in the 1930s, the massive destruction of the “freed” 10,000-ton freighter in the United States in the 1940s, most notably