金属构件广泛用于国民经济各部门,它们在工作中常因某些原因失去原设计的功能,不能圆满地完成自己的职责而失效,如过量变形、磨损、松动、腐蚀和断裂等。轻者造成设备的滴、漏、跑、胃,影响设备的安全稳定运行;重者可使整个设备或机组发生损坏,造成中毒、烧伤、烫伤、倒塌和火灾,甚至于爆炸.如国外焊接桥梁、船舶、大型储罐、压力容器、气体管道、锅炉汽包、汽轮发电机组等的脆性断裂;美国自由轮螺旋桨、英国航空发动机曲轴、人造卫星涡轮机、大型活塞式压缩机 Metallic components are widely used in various branches of the national economy. They often lose their original design function due to some reasons, fail to fulfill their duties satisfactorily, such as excessive deformation, wear, loosening, corrosion and fracture. Light, causing equipment, drip, run, stomach, affect the safe and stable operation of equipment; severe can make the entire equipment or unit damage, resulting in poisoning, burns, scalds, collapse and fire, or even explosion. , Brittle fracture of ships, large storage tanks, pressure vessels, gas pipelines, boiler drums, steam turbine generators, etc .; the U.S. freewheel propellers, British aeroengines crankshafts, satellite turbines, large piston compressors