Study On Grind-hardening Temperature Field And Process Parameter Determination Method

Grind-hardening is a new integrated machining technology which utilizes grinding heat to quench the non-quenched steel directly. In view of its potential applications, quality prediction and active control method has gradually become one of the themes for this technology. The numerical and experimental methods are synthesized in this paper, which provide a reliable forecasting method for optimizing the grind process and controlling the hardening effects forwardly. The contents of research are as follows.A set of grind-hardening experiments are performed, the grinding force and hardness penetration depth (HPD) are measured. Temperature measurements are conducted using the infrared digital video camera TH5104R, which provides distinct infrared images when the workpiece speed is lower than 10mm/s.The statistical probability results of the grains are used to calculate dynamic grinding parameters such as the average abrasive cut-in depth, the average cutting area, the geometry contact area of grinding wheel and workpiece, and so on. Then the original calculation model is amended with the size effect of grinding force. The numerical results are consistent with experimental data. The error between the prediction and experiments is in less than 11 percent. Identifying the actual contact grains with the actual heat source, the heat flux model was established on the basis of the statistical probability, which reflects the grinding process more accurately.The finite element method is used to simulate temperature field based on the forward grinding force model. Temperature field of workpieces and each node's temperature change course are achieved, while the non-steady-state grinding region and the HPD is also predicted. The influence of heat distribution on the grinding temperature filed is analyzed too. Compared with the infrared results, both the temperature field distribution and contour trends are basically the same, and the triangular heat source with la=0.8 lc provide more accurate simulation results, the relative errors are in 8.6%. The numerical and experimental results of HPD are in good agreement, and the maximum error is 10.7%. Overall, Numerical simulation can meet the forecast requirements for the grinding temperature and the HPD well.A critical thermal analysis is presented to calculate the critical heat flux for the film-boiling and the austenitization within the grinding zone. The appearances of the hardening phenomena are predicted which is observed in grinding experiments. It also provides necessary basis for the initial selection of the grinding conditions.The requirement of HPD and the critical thermal analysis model are considered as constraints in this paper. Then the relations corresponding HPD to the heat flux density under the grinding zone are established based on the FEM method in various grinding conditions. The relations corresponding process parameters to the heat flux density under the grinding zone are also developed. Subsequently, the function of grinding parameters and HPD is constructed using two-dimensional interpolation function in three-dimensional space. Thus the procedure of grinding parameters selection is established. A graphical user interface is developed, and practical calculations are conducted. The results of parameters selection are verified by the experiments and the forecasting results to be feasible.