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1 前言 1.1 工艺应力变形问题的重要性机器零件的失效可能出现在制造、存放和运行三种状态下。在制造过程中的失效,如零件在铸造或热处理中开裂。在锻造中产生超标缺陷,在焊接中产生过大变形等等,大多是由于工艺过程中产生的内应力所引起,结果导致废品增加,甚至使零件根本制造不出来。在存放中的零件失效,如轧辊在存放中自行开裂,机床床身在存放中变形,大多因残余应力引起。残余应力是工艺过程中内应力变化发展的最终结果。零件在运行服役中失效,通常认为主要由工作负荷所引起。但工艺过程中遗留下来的损伤、缺陷、裂纹以及残余应力常常是这类失效的诱因。
1 Preface 1.1 The Importance of Creep Problems The failure of machine parts may occur under three conditions of manufacture, storage and operation. In the manufacturing process of failure, such as parts in the casting or heat cracking process. In forging excessive defects, excessive deformation in the welding and so on, mostly due to the internal stress generated during the process, resulting in increased waste, or even make the parts simply can not come out. In the storage of parts failure, such as roller self-cracking in the storage, machine bed deformation in the storage, mostly due to residual stress. Residual stress is the end result of the development of changes in the internal stress during the process. Parts that fail to operate in service are generally considered to be mainly caused by work loads. However, the damage, defects, cracks and residual stresses that are left in the process are often the cause of such failures.