结构金属材料机加工影响层硬化软化的表征与研究

A lot of experimental results show that the higher the strength of engineering metallic materials, the larger their half-width values of X-ray diffraction profile and microhardness. The two parameters therefore are often used to characterize the hardening and softening of machining affected layers of the materials. But the test results of this research item demonstrate that the half-width values of the grinding affected layers of two kinds of steels in hard state markedly decrease, even if they are work-hardened in the grinding process. Obviously, the wrong conclusion will be drawn if using the half-width as the characterization parameter for describing the hardening and softening of the grinding affected layers of such materials. Both theoretical analysis and X-ray diffraction tests indicate that the superficial plastic deformation in grinding can decrease the micro-stress (micro-strain) of the materials, and thereby reduce the half-width of X-ray diffraction profile. The hardening and softening of machining affected layers will be more effectively characterized using superficial yield strength, which can be measured by the use of a method established in this item. A criterion for the static relaxation of residual stresses and a method for calculating the relaxation amount have been proposed. The results obtained from calculation and experiment coincide with each other.

针对机加工影响层残余应力的特点提出一种测量该影响层不同深度部位屈服强度的方法，以此方法做工具研究影响层的机加工硬化软化，这种硬化软化在循环载荷作用下的稳定性、以及它对残余应力弛豫的影响。有关成果可为表面完整性研究提供一种新的测试手段，并有助于进一步阐明机加工工艺条件和表面完整性间的关系，以及它们对加工件疲劳性能的影响。