Study On Dynamic Mechanical Properties And Fracture Failure Behavior Of DP980 High-strength Steel Under Impact Load

The issue of vehicle crash safety and energy conservation and emission reduction has become an important topic in the world today.Vehicle body structures are closely related to vehicle crash safety performance.High strength steel is widely used in vehicle body structures,and the study of its mechanical properties has become increasingly critical in recent years.This paper analyzes the static and dynamic mechanical properties of DP980high-strength steel through quasi static and dynamic tensile experiments.Based on quasi static and dynamic rheological stress-strain curves,a Johnson Cook dynamic constitutive model was established.A modified dynamic constitutive model for DP980 high-strength steel was established by modifying the strain strengthening term of the Johnson-Cook dynamic constitutive model.The correlation between the Johnson Cook constitutive model and the modified model and the experimental data was calculated,and it was found that the modified model was more suitable for DP980 high-strength steel.Five tensile specimens with different stress states were designed and subjected to tensile tests.The fracture strain of DP980 high-strength steel at room temperature was studied using DIC technology.The evolution of stress triaxiality before fracture was determined using numerical simulation.It was found that the evolution of fracture strain and stress triaxiality of DP980 high-strength steel conformed to the Johnson-Cook fracture model.Based on this,a dynamic fracture model of DP980 high-strength steel was established.Based on the VUMAT interface of ABAQUS,a modified dynamic constitutive model and a dynamic fracture model for DP980 high-strength steel were developed.Through the same numerical simulation comparison between the Johnson-Cook model included in ABAQUS and the modified model,the reliability of the secondary developed modified model was verified.A Johnson-Cook model and a modified model were established to simulate bullet penetration.The dynamic mechanical properties of DP980 high-strength steel subjected to bullet penetration in the two models were analyzed,including strain rate changes,maximum failure stress,penetration depth,and plastic energy absorption.The differences in mechanical properties of the materials characterized by the two models were analyzed.According to different application scenarios,it is proposed which thickness of DP980 high-strength steel should be used to achieve better economic benefits in ensuring collision safety,providing guidance for practical applications.