人们总希望一部机械使用寿命长、重量轻、效率高又安全可靠,这就要求组成一部机械的零部件具有优良的性能。能否设计出既安全可靠、体积小重量轻,又耐用的零部件,不仅要考虑结构灵巧,还要采用先进的生产工艺,充分发挥材料的性能。如为了安全可靠,过多的考虑韧性和塑性,那么产品必然粗大、笨重、 People always hope that a mechanical long life, light weight, high efficiency and safety, which requires the formation of a mechanical parts with excellent performance. Can design a safe, reliable, small size, light weight, and durable parts, not only to consider the structure smart, but also the use of advanced production technology, give full play to the performance of materials. If in order to be safe and reliable, too much to consider toughness and plasticity, then the product must be bulky, bulky,