焊接残余应力形成机制与消除原理若干问题的讨论

针对目前存在的一些对焊接残余应力形成机制和消除原理传统理论的质疑和不同观点，采用两端拘束杆件和长板各焊接的一维简化模型，分析比较了经受加热与冷却热循环以及直接从高温冷却下来时的应变历史和残余应力产生的机制。结果表明，前者存在残余压缩塑性应变，后者存在残余热收缩应变。两者对产生残余应力的作用完全是等价的，为了统一概念，建议引入固有应变理论。固有应变包括焊接过程中产生的塑性应变，热应变和相变应变，残余应力是在固有应变源作用下构件自动平衡的结果，消除焊接残余应力必须去除固有应变源，此外对若干容易混淆的问题进行了讨论。

Some Discussions on Principle of Causing and Relieving Welding Residual Stress

In order to explain some different views about principle of causing and relieving welding residual stress, a steel bar with two constrained ends and a long welded plate are analyzed as one-dimensional models. Two thennal cycles are used. One includes heating and cooling stages and the other includes only cooling stage directly from high temperature to room temperature. The results show that in the -welds the residual compressive plastic strains are caused in the former case and the residual contractive thermal strains are caused in the second case. Their actions are equivalent for causing the welding residual stress. However it is the best way to introduce the concept of inherent strain which includes the thermal strain ,plastic strain and phase transformation strain caused in welding cycle and can be considered as a source of welding stress. Some relative problems are dbcussed in this paper.