无相变合金淬火热应力演变机理的理论模型--(1)角端和边缘淬火热应力模型与淬火角端效应

淬火过程中率先引发塑性变形的动力是拉应力,此后拉应力和压应力交替引发塑性变形.拉应力可以诱发压应力的出现.在淬火试样表层可以出现压应力,这不同于传统观点认为淬火表层只能是拉应力的结论.淬火热应力与温度高低关系不大,主要由相对温差(即温度梯度)决定,相对温度高的部分会趋向发展成压应力状态,相对温度低的部分趋向发展成拉应力状态,这是淬火和快速加热产生热应力、塑性变形和残余应力的根本原因.建立了角端、边缘两种淬火热应力模型,提出了淬火角端效应,即在角端拉应力率先引发塑性变形并引起温度梯度、热应力、塑性变形等交替衰减的现象.

The Theoretical Model of the Thermal Stress Evolution Mechanism during Quenching of no Phase Change Alloy--(1) The Corner and Edge Model for Thermal Stress during Quenching and the Corner Effect during Quenching

The plastic deformation during quenching is first induced by tension stress, and then alternative occurrence of tension and compression stress induce plastic deformation. The tension stress may induce compression stress. Compression stress occur in the surface, which is different from conventional view that only tension stress occurs in the surface. The thermal stress during quenching is mainly determined by temperature difference other than temperature. Compression stress occur and develop in the relative high temperature zone, and tension stress occur and develop in the relative low temperature zone. It is the source of thermal stresses, plastic deformation, residual stresses when quenching or quickly heating. The corner and edge models for thermal stress during quenching are established in this paper, and the corner effect, which go with the recession of, temperature grads, thermal stresses and plastic deformation after the first plastic deformation is induced by tension stress, is proposed in the course of quenching.