Numerical Simulation And Cracking Characteristics Of 22MnB5 High Strength Steel Hot Stamping

With the improvement of people's living standards,private cars start to enter every family,so the global car usage has increased rapidly.However,the problems of environmental pollution,energy waste and resource shortage have also arisen.Therefore,the automobile industry has solved the above-mentioned problems in the development of automobiles through various methods.Nowadays,in order to meet the demand for lightweight vehicles,high-strength steel is introduced into the body structure materials.The high-strength steel material has the characteristics of high strength and excellent mechanical properties,and its hot forming strength can reach 1500 MPa.However,due to the effect of thermal-mechanical coupling,cracking defects will occur during the hot stamping process,which seriously affects the forming quality of the parts.The method of numerical simulation and experiment was used to study the hot stamping process and fracture characteristics,as follows:1.Obtain the true stress and strain of the material at 600?,700? and 800? through hot tensile test and calculation and can be found from the curve: In the forming process of 22MnB5 high-strength steel material,the initial forming temperature and the strain in the forming process Velocity has a greater influence on its flow strain.The flow strain required for sheet metal deformation decreases with increasing temperature and increases with increasing strain rate.Arrhenius-type constitutive model of the material is established by the stress and strain obtained through the experiment.The material parameters in the constitutive equation are fitted by Origin calculation,so as to obtain the material stress and strain calculated in the constitutive equation.Compared with the real stress and strain obtained from the test,it is concluded that the constructed Arrhenius constitutive model can well reflect the stress-strain curve changes of 22MnB5 high-strength steel material under different initial forming temperatures and strain rates.2.According to the national standard,set up the bulging test conditions of 22MnB5 high-strength steel material,establish the forming limit curves of the sheet material at 600?,700? and 800? by numerical simulation.The point increases with increasing temperature.By comparing with the forming limit line obtained by experiment,it is found that the forming limit line obtained by the two fits better,thus verifying the reliability of the simulation model.Simulated the forming effect of the material at 700?,750?,800? and 850? when the material reached fracture,it is concluded that 22MnB5 high-strength steel material has a good forming effect at 700?.3.Based on the thinning rate,the effect of various forming process parameters on the fracture characteristics of the material during the forming process of 22MnB5 high-strength steel was studied through numerical analysis.It was found that: with the blank holder force,friction coefficient,strain rate and mold gap The increase,the forming thinning rate of the material increases,and the tendency of cracking defects during the forming process also increases.4.Using the response surface analysis method to study the comprehensive impact of various process parameters on the forming of 22MnB5 high-strength steel material,it was found that during the forming process,the blank holder force and the friction coefficient and the interaction between the two have a greater impact on the thinning rate of the formed part,Mold gap and strain rate have the second influence.The optimal process parameter combination(blank holding force 1.493 MPa,friction coefficient 0.475,strain rate 10.116s-1,mold gap 2.287mm)was obtained by optimizing the response surface model,and the reliability of the results was verified by simulation.