Research On Forming Limit Prediction Of 22MnB5 High Strength Steel

The forming limit diagram is the easiest and most effective method on evaluate the formability of the sheet,determine the shape of the mold and stamping process parameters and solve the stamping problem to avoid design failure.High strength steel has advantages of high strength and light weight,and is widely used in the field of lightweight automotive technology to reduce the weight of vehicles,increase the strength and safety of lightweight way.Over the past decade,the development and research of forming technology for high strength steel has been greatly improved.However,the forming limit of high strength steel plate is limited by the strain measurement method,the strain rate and the friction factor in forming,so the research reports on this kind of material are relatively few.Therefore,the subject is 22MnB5 high strength steel as the research object to test for the verification basis,the study using M-K groove theory combined with constitutive equation and finite element simulation method to predict the forming limit diagram.The main contents are as follows:1.According to the principle of plastic mechanics,based on the M-K groove theory,the yield criterion and the plastic constitutive equation are chosen to write the Matlab program to predict the 22MnB5 high strength steel plate forming limit diagram.2.Using the sheet metal forming test machine and XJTUDIC digital image strain measurement analysis system,the forming limit test of different width samples was carried out.By analyzing the on-line real-time monitoring system,the main and secondary strain of each unit at any time of the sheet metal were obtained,Method to calculate the ultimate strain,get the material more realistic shape limit diagram.And the same time,compared with the theoretical prediction data,so as to obtain 22MnB5 high strength steel plate ideal forming limit calculation model,and the impact of parameter analysis.3.Numerical simulation of 22MnB5 high strength steel FLD test using Dynaform.The forming limit diagram is obtained by different method of instability judgment.And the same time,compared with the experimental data to find the most suitable high strength steel sheet instability judgment criteria.Based on the digital image method,the forming test is carried out on the line in real time to obtain the forming limit line of the real test value.It is proved that the theoretical method and the simulation method can successfully predict the forming limit diagram of high strength steel.It can provide theoretical guidance for evaluating the forming performance of sheet metal and the actual production stamping process specification,and can also be used as the judgment basis of limit condition in the finite element simulation.