Formation Mechanism Of Hardening Layer Obtained By Pre-stressed Hardening Grinding And Prediction

Grinding hardening is a new technology which integrates grinding and hardening together. It makes the surface layer of the work-piece hardened by using the grinding heat and grinding force. Pre-stressed machining can change the residual stress of surface layer of the work-piece. Pre-stressed hardening grinding is a new technology which integrates hardening grinding and pre-stressed machining together.This paper has studied the mechanism of ordinary grinding,analyzed and calculated main grinding elements, such as grinding force and grinding heat and distribution proportion. It has analyzed the hardening causes of the surface layer, researched the different effects of grinding heat and grinding force on surface hardening layer. At last,it has analyzed effects of pre-stress on surface hardening layer and put forword the standard of judgment on hardening layer.This paper has studied the formation mechanism of hardening layer by pre-stressed hardening grinding experiments. The experiment choosed 45 steel as the grinding material and selected different grinding depths, test-piece feed rates and pre-stresses. The next experiment has observed the organization phase transition of cross-section by metallographic microscope and measured the hardness of some locations on the hardening layer. On the basis of experiment results,this paper has concluded the distinct effects of different grinding conditions and pre-stresses on surface hardening layer.Based on the theoretical analysis and experiment result, this paper has carried out the simulation of pre-stressed hardening grinding process with ANSYS finite element software. It has worked out thermal field distribution and equivalent plastic strain of work-piece. According to the principle of thermal phase transition, this paper has predicted thickness of surface hardening layer. According to the work hardening theory, this paper also predicted the properties of hardening layer formed by grinding force. At last,this paper makes a simulation of pre-stress hardening grinding and put forward the discipline about effects of pre-stress on surface hardening layer.This paper has showed surface hardening layer is formed by thermal phase transition and work hardening. But thermal phase transition is the main reason. The effects of pre-stress on grinding hardening layer mostly reflected in work hardening. When exerted pre-stress, the equivalent plastic strain of layer becomes weak. The bigger pre-stress exerted, the weaker equivalent plastic strain of layer is.This paper has put forward a new prediction method and established a prediction system by GUI which can help people predict the grinding hardening layer thickness and choose better grinding parameters. It provides a simple and effective prediction method for the actual processing.