| The mechanical properties and damage of steel are the key issues in the research of engineering material structures.With the vigorous development of China’s manufacturing industry,the market has increasingly demanded product quality.In the fields of automobiles,aviation,and ships,advanced steels at home and abroad have been widely used.In this paper,two new imported steel materials with different mechanical properties are used.According to the working conditions of different stress states of the steel during the engineering use phase,the mechanical properties experiment of the steel under quasi-static state and the dynamic mechanical property experiment of Hopkinson tie rod are designed.During the loading process,through the results of experiments and finite elemen t simulations,the damage of the steel under different stress states was obtained.The applicable scope of different failure equations was analyzed.The fracture cross section of the specimen was observed in combination with the SEM scanning electron microscope to obtain the material.Fracture mechanism under different stress states.The details are as follows:1.In order to reflect the stress state of the materials under different loading conditions in the project,the triaxiality theory of stress is introduced,and eight kinds of round bar tensile test specimens with different notch radii of two steel materials are designed.Tensile and torsional combined test pieces,pure torsion test pieces,and compression test pieces.Five kinds of dynamic tensile test specimens with different notch radii are designed.The mechanical properties of two steels are obtained through mechanical property experiments.The damage parameters of SWRCH10A steel and the law of the strain at the moment of sample failure with the triaxiality of stress are obtained.This determines the damage initiation strain th reshold for SWRCH10A steel during loading.2.Through the experimental results,the parameters of J-C damage model are fitted,and the material damage model parameters of two kinds of steel under different stress state are obtained.By fitting the parameters of J-C constitutive model,the constitutive parameters of the two steels under dynamic loading are obtained.Based on the Zerilli-Armstrong model and the theory of crystal micro dislocation,the properties of SWRCH10A steel are improved,and the SWRCH10A damage constitutive model considering the thermal activation effect damage is obtained.By fitting the test data,the model parameters are determined,and the relationship between the damage parameters and the stress triaxiality is obtained.Finite element simulation was performed on the experimental process,and the load-displacement curve and stress-strain curve were compared in the experiment and simulation,and good simulation results were obtained.And through the finite element post-processing program,the triaxiality distribution of the stress on the fracture section of the specimen,the equivalent plastic strain distribution,and the first principal stress distribution were obtained.The simulation results of two different materials are compared with the simulation results of quasi-static and dynamic loading conditions.The applicable range of ductile strain damage model and J-C damage model was analyzed,and the relationship between fracture strain and stress triaxiality was obtained.The damage evolution equation of SWRCH10A steel at high strain rate was established.3.According to the observation of the fracture surface of the specimen by SEM scanning electron microscope,the fracture mechanism of the material under different stress states is obtained,and the fracture mechanism of the material changes regularly with the stress triaxiality. |
PDF Full Text Request