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一、概述机械加工中,任何加工工艺过程都会在工件中造成残余应力。例如,在焊接过程中,由于工件受到不均匀的加热与冷却,产生的残余应力尤为严重。在加热过程中,远离焊缝的较冷金属阻止局部受热金属的膨胀;加之在冷却过程中,金属的收缩又受到较冷金属的制约,因此焊接结构中的残余应力往往高达屈服应力的水平。在某些情况下,要采取专门的措施消除这些残余应力,否则,残余应力的存在可能严重妨碍焊接结构的使用性能。例如:当残余应力已达屈服点时,只要一施加工作应力,就会引起塑性变形。当在残余应力区存在有缺陷或应力集中时,有可能引起裂纹的扩展,或导致脆断。
First, an overview Mechanical processing, any processing process will cause residual stress in the workpiece. For example, residual stresses are particularly severe during the welding process due to uneven heating and cooling of the workpieces. In the heating process, the colder metal away from the weld prevents the expansion of the locally heated metal. In addition, the shrinkage of the metal during cooling is controlled by the colder metal, so the residual stress in the welded structure tends to be as high as the yield stress. In some cases, special measures should be taken to eliminate these residual stresses, otherwise the residual stress may seriously impede the performance of the welded structure. For example: When the residual stress has reached the yield point, as long as the application of work stress, it will cause plastic deformation. When there is a defect or stress concentration in the residual stress region, it is possible to cause crack propagation or to cause brittle fracture.