Study On Failure Mode Of Dual-Phase Steel Using Rve Technique

Extensive researches on lightening body weight have been carried out throughout automobile industry for the development of low-carbon economy.Advanced high strength steels are utilized as the body material in more cases,where dual-phase(DP)steel is widely applied in body structure parts.Nowadays,automobile DP steel sheet is mainly manufactured by blanking processing.And its fracture property is always considered as a key factor of automobile safety performance,which is thoroughly studied in this paper.Investigations are focused on the factors of failure mode utilizing micro-mechanic models built by RVE technique.There are two key factors discussed in this paper.The first factor is microstructure.Based on former researches,three characterized microstructures are investigated in this paper,namely ferrite,martensite and ferrite/martensite interface.By analyzing the results acquired from simulating experiments,influence of the three characterized microstructures on crack evolution and crack extension path is investigated statically and dynamically,and conclusions are as follows.Microstructure has a significant influence on the failure mode of DP steel.The progress of crack formation,propagation and coalescence can be manipulated by altering the mechanical properties and microstructural anisotropy of characterized microstructures.Additionally,a model is established to describe the crack distribution in different characterized microstructures.The second factor is geometrically imperfection.Λ-shaped microcracks can be observed on the edge of DP steel sheets manufactured by blanking processing,which are parametrically characterized by introducing geometrical imperfections into the RVE model.By comparing and analyzing results from simulating experiments of different groups,the conclusions are as follows.Micro-cracks on the edge tend to accelerate the formation of inner cracks in the affected area,and when ingrained deep enough and close to inner cracks,it may alter the crack extension path.Additionally,microcracks on the edge tend to impair homogenous distribution of stress in the affected area,which accelerates strain localization in areas with heterogeneous local structure and causes an early fracture.