Investigation Of Crashworthiness For Hot Stamping Thin-wall Structure Considering Damage

Vehicle lightweight is one of the important means of vehicle energy saving and emission reduction.In recent years,with the gradual reduction of the mass of the car,the safety of the car has become an important aspect of attention.Taking both lightweight and car safety into vehicle design consideration has become one of the important scientific issue in the automotive field.In order to improve the safety of vehicles,the strength of automotive metal steel also gradually increased.The tensile strength of automobile advanced high strength steel can reach at 1800 Mpa.Furthermore,with the application and development of hot stamping technology,a kind of graded strength auto parts appears in the human vision.However,with the strength increment,its ductility will decrease correspondingly.In the process of automobile collision,the damage will inevitably appear in the process of crushing.The occurrence of damage will play an important influence on the deformation form of the structural crushing process,thus affecting the impact resistance of the structure.Therefore,it is very necessary to study the crashworthiness of hot stamping thin-walled structures with considering the damage.In this paper,the damage behavior of the high strength material after hot stamping is studied based on the continuum damage theory,and the damage factors are introduced into the analysis of the anti-collision performance of the typical vehicle body thin-wall structure.Firstly,hot stamping technology is used to explore the material property of 22MnB5 quenched under different processes.In this paper,the typical temperature(600?)quenching process is selected to conduct the research on the damage behavior of the material.Through the preparation of the typical U-shaped parts,the dynamic crushing experiment is carried out on the universal press at the set speed,and the working conditions are compared with the simulation.The results show that the specimen will inevitably occur damage behavior under certain pressure,and the occurrence of the damage will cause the brittle fracture characteristics of the sample,and continue to absorb the energy in a broken way.Subsequently,based on the GISSMO damage model,the relationship between the failure strain and the stress triaxiality of the material after high strength quenching is explored by the combination of experiment and simulation,and the full field strain distribution is measured by the design of the tensile sample covering the triaxiality range(0~0.7)and the DIC optical measurement technique.The B-spline curve is used to fit the data points.The grid dependency evaluation is further carried out.Consequently,the GISSMO damage model of the material after hot stamping and quenching is more consistent with the description of the actual crash.Finally,the GISSMO model is introduced into the simulation of the anti-collision performance of a typical hot stamping thin-wall structure.The impact of the damage factors on the impact resistance of the structure is investigated by using the energy absorption(EA)and the peak force(PCF)as the evaluation index.The study shows that the impact performance considering damage factor on the hot stamping high strength material after quenching is analyzed.Considering the numerical simulation of damage,the accuracy of the simulation will be improved.The error of energy absorption between experiment and simulation is 4.14%,which is 19.36% lower than the simulation without considering damage,and the error is 23.5% of the simulation without considering damage.It has little effect on the peak force,but it has a certain decrease in the energy absorption.In addition,the corresponding research is extended,and the corresponding data are used to study the crashworthiness of thin-wall structures with variable intensity hot stamping.