Optimization And Experimental Research On The Process Parameters Of High Pressure Forming In Subframe

With the continuous development of the automobile industry,lightweight technology has gradually become one of the important development directions of the future automobile industry.As an advanced manufacturing process,internal high-pressure forming technology has been widely used in automobile and many other fields due to its advantages of good quality,high efficiency and light weight.However,due to the complicated forming mechanism and the difficulty in making process parameters,it is difficult to apply the internal high pressure forming process.In this paper,an automobile subframe is taken as the research object,and the internal high-pressure forming process of the part is studied by numerical simulation and multi-objective optimization combined with experimental research,which provides a theoretical guidance for the subsequent development of relevant parts’ internal high-pressure forming process parameters.The specific research contents are as follows:Based on the theory of plastic forming,the characteristics of stress and strain in the bulging area and the influence of basic process parameters on the forming quality are revealed.The size structure of the automobile subframe is analyzed,and the process plan of pre forming and internal high pressure forming is selected.The basic process parameters in the forming process are determined by theoretical calculation,and the evaluation method of the forming results,such as the degree of section distortion and the law of wall thickness distribution,is given.The finite element models of preform and hydroforming are established by the finite element software.Based on the idea of control variables,the down pressure of the upper die,the replenishment amount,the loading path and the friction coefficient in the process of preform are determined,and the influence of the process parameters on the wall thickness distribution of the formed parts is analyzed.Finally,the forming process is preliminarily determined by synthesizing various factors The optimal process parameters are:the upper die pressing amount is 160mm,the feeding amount is 15mm,the loading path is loading path 3,the feeding speed is 0.88mm/ms,and the friction.coefficient is 0.03.At this time,the maximum thinning rate is 16.23%,and the maximum thickening rate is 16.36%.Through the research and comparative analysis of the theory and method of multi-objective optimization,the non dominated sequencing genetic algorithm NSGA-II is selected;the reasonable design variables,objective functions and constraints are selected,the mathematical model of multi-objective optimization is established,and the reasonable optimization process is designed;the integration of LS-DYNA and iSIGHT is used,and the most important process in the internalpressure forming process is based on the preliminary optimal process parameters The maximum thinning rate and thickening rate of the parts are 15.63%and 15.03%respectively,3.7%and 9.6%lower than the same period of last year.Based on the parameters obtained from calculation and simulation optimization,the in high-pressure forming process of automobile subframe is tested and studied.The compari between the test results and numerical simulation results shows that there are slight errors the numerical simulation results and the actual test results,but the overall trend is consistent,the reliability is high.The factors that lead to the errors are analyzed.