Simulation Study And Experimental Verification Of Cylindrical And Notch Grinding Of 18CrNiMo7-6 Alloy Steel

With the rapid development of modern equipment manufacturing industry,the processing and manufacturing mode of products has changed from the initial forming processing to the processing and manufacturing mode with high precision,good quality and long service life.Grinding can obtain higher machining accuracy and better workpiece surface quality.At present,it has become the main machining means of precision parts manufacturing.However,because the grinding process is the removal process of workpiece materials by many abrasive particles on the surface of abrasive tools,and the shape,size and position distribution of these abrasive particles are random,it is very difficult to study various mechanisms in the grinding process,summarize the grinding rules and predict the grinding results.With the development of high performance computer and software technology,numerical simulation has become an effective means to study grinding process.Through the simulation geometric model of grinding wheel and workpiece established based on the actual grinding process,the material model parameters are calibrated through detailed experiments,combined with the finite element simulation method,the in-depth study of the grinding process can be realized.In order to study the changes of grinding force and grinding heat in the grinding process of 18 CrNiMo7-6 alloy steel and the influence of grinding technology on the grinding results,the grinding process of round bar specimen and V-notch fatigue specimen is numerically simulated in this paper.The main work of this paper is as follows:(1)Firstly,considering Johnson cook(J-C)damage model,the quasi-static tensile tests and finite element simulation of 18 CrNiMo 7-6 alloy steel samples with different notch sizes,tensile tests at low and medium strain rates,SHTB tests and tensile tests at different temperatures were carried out.J-C damage model parameters were calibrated by fitting the experimental results,and the fitting quality shows that the fitting damage parameters are reliable.The rationality of the J-C damage model selected in this paper and the validity of the model parameters are verified by Taylor test and finite element simulation.The research provides parameter basis for grinding simulation process of 18 CrNiMo7-6 alloy steel.(2)Based on the actual cylindrical grinding process,the finite element model of grinding wheel and workpiece is established and simplified to two-dimensional model for analysis.The relationship between main grinding process parameters(wheel speed,workpiece speed,grinding depth)and grinding force,grinding temperature,workpiece surface roughness and residual stress on workpiece surface was studied.Based on the dimension analysis and numerical simulation results,the relevant mathematical model is established.The maximum error between the verified model prediction results and the simulation results is less than 12%.The variation trend of residual stress in the model prediction and simulation is consistent with the experiment.Through the mathematical model,it can be seen that the grinding force is more sensitive to the grinding depth,and the sensitivity of the normal force to the grinding depth is greater than the tangential force.The simulation results show that with the increase of grinding temperature,the residual stress on the workpiece surface increases to the direction of residual tensile stress,and with the increase of grinding force,the residual stress on the workpiece surface increases to the direction of residual compressive stress.(3)The notch grinding process of V-notch fatigue specimens was simulated numerically.Based on the actual V-notch grinding wheel,a grinding wheel finite element model with random shape,posture and position of abrasive particles was established.The established grinding wheel model is in good agreement with the actual grinding wheel morphology.The influence of main grinding process parameters on grinding force,grinding temperature and residual stress on workpiece surface has been analyzed by simulation calculation of single factor and variable.The morphology of notch in the simulated specimen is in good agreement with the experiment.The variation trend of residual stress on notched surface in the simulation is in accordance with the test measurement.Overall,the simulation results are in good agreement with the experimental results.This research provides an idea for using the finite element method to study the grinding mechanism,control the machining quality and establish the grinding simulation model for the complex-shaped parts.