Study on the influence of the grinding chatter on the workpiece’s microstructure transformation

Grinding chatter is a kind of self-excited vibration which does not need external motivation. However, the internal motivation exists in the form of the grinding force. The grinding force is time-varying due to the regeneration effects between the grinding wheel and the workpiece. Generally, the chatter strength is reflected by the grinding force, which affects the distribution of the grinding temperature field by adjusting the heat flux. Moreover, the dynamic temperature generated within the grinding area is applied to cause the materials microstructure transformation of the workpiece’s surface. Consequently, the materials microstructure transformation of the workpiece’s surface is affected by the grinding chatter as well. In order to investigate the relationship between the material microstructure transformation and the chatter strength, a new hybrid model which combines the finite difference method (FDM) and the cellular automaton (CA) method is established accordingly. Coupled by the chatter factor, the FDM verified by the Jager theory model is applied to obtain the distribution of the dynamic grinding temperature field. It can be proved that the grinding temperature goes up with the increase of the grinding chatter. Combined with the dynamic temperature field, the CA model is firstly applied to simulate the austenization which includes the nucleation, growth, grain coarsening, and carbon diffusion process. The results indicate that the grain size expands with the increase of the grinding chatter, which results in the low mechanical properties of the material. Then, the martensite’s nucleation with the grinding chatter started in the calculated austenite microstructure. Afterwards, the martensite with the grinding chatter grows up in the calculated austensite microstructure. From the experiment and the simulation, it can be concluded that the martensite content decreases with the increase of the grinding chatter. According to the above conclusions, it proves that better mechanical properties can be obtained by wakening the impact of the grinding chatter.