Process Study Of Residual Stresses In Milling 2024 Aluminum Alloy

The technical requirements of aluminum alloy aviation integral structural parts in terms of materials,structure,technology,etc.are more complex and precise than those of structural parts in other fields.The processing of such parts is generally obtained by casting,forging and other methods,and then through Cutting process to get the finished product.The most commonly used processing method for aerospace integral structural parts is milling.In the milling process,the residual stress generated by the milling process is one of the important factors that cause the machining deformation of the parts.Therefore,the residual stress generated by the cutting process can be controlled to improve the deformation of aerospace structural parts.In this paper,2024-T4 aluminum alloy is the research object,through the establishment of milling model and test two methods,the distribution of residual stress after milling is studied,and the cryogenic treatment process is used to control the residual stress generated by milling,and The mechanism has been studied,and the main research contents and conclusions are as follows:(1)The finite element model of milling 2024 aluminum alloy in two-dimensional plane was established based on ABAQUS.Coupling analysis of temperature and displacement was carried out.The changes of temperature and stress field of workpiece by changing cutter structure parameters and milling parameters during milling 2024 aluminum alloy were simulated.The results showed that: Under different milling processes,processing and distribution of residual stress in the depth direction basic consistent,with the increase of distance from the milling surface and present a "scoop" shape distribution,namely,in depth direction of residual tensile stress of the machined surface has been gradually reduced,in a certain depth into the residual compressive stress,the maximum stress state,and gradually reduce along with the depth direction,It eventually fluctuates around 0 MPa.(2)Four factors and three levels orthogonal experiments were used to simulate the milling process,and the distribution of residual stress on the workpiece surface under different milling parameters was analyzed.The influence of different factors on residual stress after milling was analyzed by range method,and the optimized milling process group was obtained.The milling residual stress values in the actual machining process were obtained through experiments on the optimized process parameters,which verified the effectiveness of the simulation model.The optimal process parameters for the minimum residual stress in milling 2024 aluminum alloy were obtained as follows: spindle speed 4000r/min,cutter path S-type milling,milling depth1.5mm,milling width 6mm.Compared with the simulation results,it can be seen that the distribution of residual stress measured by the test is basically consistent with the simulation results,which indicates that the simulation model can be used as a reference standard for actual production.(3)Adopt different cryogenic treatment process for milling of thin-walled box class sample after the completion of cryogenic treatment,through the blind hole method to measure the sample surface residual stress,and metallographic microscope and scanning electron microscopy(SEM)observation and analysis was carried out on the microstructure of aluminum alloy,cryogenic treatment process was studied on the influence law of milling surface residual stress and micro mechanism.The results show that the fluctuation of residual stress in the depth direction decreases obviously after cryogenic treatment,which indicates that the cryogenic treatment can effectively improve the stress stability of residual stress in the depth direction after milling 2024 aluminum alloy.From the microscopic aspect,after cryogenic treatment,the grain of aluminum alloy is complete and distributed thinly,some internal defects disappear,and some impurities on the surface of the matrix are dissolved.At the same time,the cryogenic treatment promotes the diffusion and precipitation of the second strengthening phase,so the distribution of residual stress of 2024 aluminum alloy is affected.