| Austempered ductile iron(ADI)is a kind of engineering material with excellent comprehensive mechanical properties that has developed in recent decades.The “Fourteenth Five-Year” development plan of the national foundry industry clearly pointed out that it is necessary to increase the promotion of high-performance ADI in the field of high-end equipment manufacturing.ADI castings have many unique advantages,such as high strength,good toughness and plasticity,wear resistance,low temperature performance,low production cost and good economic benefits.Therefore,due to its excellent comprehensive performance,it has been widely used in engineering machinery,agricultural machinery,mining machinery and automobiles and other fields.However,the difficult machinability of ADI limits its further development,and the exploration of its cutting mechanism has also become a focus of attention.Considering the characteristics of ADI cutting with high strain,high strain rate and high temperature thermo-mechanical coupling deformation,the material deformation process and cutting numerical simulation during ADI cutting are studied in this paper.The main contents were as follows:Firstly,with full consideration of the limited applicability of the constitutive model contained in the material library of DEFORM software,DEFORM is developed by using the user subroutine interfaces of USRMSH and UFLOW.Based on the unique ausferrite microstructure of ADI,the cutting simulation process is modeled using DEFORM as the research platform,including material constitutive model,geometric model modeling,mesh generation,friction heat transfer model and chip generation model.Secondly,the finite element method is used to carry out orthogonal design numerical simulation analysis on the cutting force and cutting temperature of ADI machining.Based on the simulation results,this study analyzed the relationship between the cutting force and three cutting factors: cutting depth,cutting speed,and feed rate.The results show that within a certain range,Fx is positively correlated with cutting depth and cutting speed,and the relationship with feed and cutting speed is not significant;Fy is positively correlated with cutting depth and feed rate,and negatively correlated with cutting speed;Fz is positively correlated with cutting depth,negatively correlated with cutting speed,and the relationship with feed is not significant.The optimal cutting combination with the minimum cutting force as the optimization objective is obtained: v=120～140m/min,f=0.2mm/r,ap=0.5mm.Based on the simulation results,an empirical model of cutting force for cutting ADI is established by using multiple nonlinear regression equations.For the cutting temperature,the cutting speed has the greatest impact.The workpiece temperature and tool temperature increased with increasing cutting speed,cutting depth,and feed rate.Specifically,when the cutting speed increased by 40%,they increased by 9.9% and 50.6%,respectively;when the cutting depth doubled,they increased by 3.9% and 33.5%,respectively;when the feed rate increased by150%,they increased by 5.7% and 37.1%,respectively.Finally,the ADI material cutting verification experiment was carried out,and the comparison between the experimental data and the simulation results showed that the magnitude of the cutting force was in good agreement and the waveform of the cutting force was also consistent.The average error between the simulation model calculation results and the cutting experimental data in the Fx direction,Fy direction,Fz direction and the cutting resultant force F was 13.63%,10.41%,9.88% and 8.57%,respectively.In general,the cutting simulation model can accurately predict the cutting force,and the simulation results are in good agreement with the experimental data.The ADI material constitutive model and the finite element simulation model developed in this paper can accurately simulate and predict the actual processing. |
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