Research on Hardening Mechanism of Grinding Part Surface Affected Layer in Small Cutting Depth
|Keywords||grinding mechanism hardening temperature field thermal-mechanical coupling prediction|
Grinding hardening technology is a technology that makes the surface layer of the work-piece hardened by using the coupling between grinding heat and grinding force. This technology will improve the hardness of the surface layer and produce hardening layer. This technology could combine grinding with heat treatment process and streamline processes, reduce energy consumption, improve productivity and economic benefits.This paper has studied the mechanism of ordinary grinding, calculated main grinding elements, such as grinding contact arc length, the efficient edge’s number of the grinding wheel, grinding force and grinding heat distribution proportion. It has also analyzed the hardening causes of the surface layer, researched the different effects and coupling relationship of grinding heat and grinding force on surface layer hardening in theory. That is, considering the comprehensive effect of the transformation of organization and dislocation, the lattice distortion, slip. Last, it has put forward the theoretical formula model.This paper has studied grinding hardening technology by experiments. The experiment chose45steel as the grinding material and selected different grinding depths and test-piece feed rate without grinding liquid. The next experiments have measured the surface hardness and the surface roughness of test-piece and observed the organization phase transition of cross-section by metallographic microscope. This paper has analyzed the experiment results and confirmed the distinct effects of different grinding conditions on the hardening of surface layer.Based on the theoretical analysis, this paper has carried out the thermal simulation about the hardening process of surface grinding and cylindrical grinding with ANSYS finite element software. It has come to the distribution of the temperature field and its change course and predicted the thickness of hardening layer according to the principle of phase transition. Based on the analysis and prediction of the temperature field, this paper has carried out the thermal-mechanical coupling simulation, predicted the thickness of hardening layer again according to the results of thermal-mechanical coupling simulation and carried on analyses between the two prediction results. It has analyzed the simulation results of surface grinding and the experiment results of surface grinding comparatively, verified the accuracy of experiment and simulation.This paper has established a prediction system of grinding hardening layer thickness using1stOpt software and MATLAB software based on experiment results and a large number of simulation results. This system provides a method of selecting theoretical initial value of grinding parameters for practical machining.This paper showed it is feasible that obtains grinding hardening layer like that it is heat-treated. Grinding heat is the main reason that the work-piece emerges hardening layer and grinding force only plays a small auxiliary role. Bigger grinding depth and lower work-piece feed speed could improve the thickness of the surface hardening layer, but grinding wheel speed has no significant impact on the thickness of the surface hardening layer.