Dynamic Fracture Behavior And Characteristics Of Pipeline Under Internal Explosion Based On Rate Type Damage Evolution

At present,the numerical simulation is an indispensable method for the prediction of dynamic fracture of combustible gas pipeline explosion.The constitutive model and failure model used in the numerical simulation method greatly determine the accuracy of the prediction results.The results show that the macro material failure is the process of damage formation,evolution and accumulation at the micro and micro level.Some studies have found that the damage evolution of materials under explosion load should depend on strain and strain rate at the same time.The existing failure criteria used to predict the dynamic fracture number of pipeline explosion believe that the crack is initiated when the stress,strain and energy reach the critical value It is difficult to describe the real dynamic fracture mechanical behavior of materials,which leads to the difference between the numerical simulation results and the experimental results.In this paper,supported by the National Natural Science Foundation youth fund project "Research on dynamic crack propagation mechanism and prediction of pipeline under internal explosion based on rate type damage evolution and fluid structure coupling",the research on dynamic fracture behavior and characteristics of pipeline under internal explosion based on rate type damage evolution is carried out.The main research progress and conclusions are as follows:(1)a thermo viscoplastic constitutive model coupled with rate type damage is proposed by combining the thermo viscoplastic constitutive model considering strain hardening,strain rate hardening and temperature softening with the rate type damage evolution law based on the explicit correlation of strain rate based on thermal activation mechanism.Compared with other constitutive models and failure models,it can better describe the real dynamic fracture mechanical behavior of materials.(2)the strain rate,damage and other state variables are added into the stress compensation updating algorithm,and combined with Mises yield criterion and dynamic failure criterion,the thermo viscoplastic constitutive model of coupled rate damage is written into the VUMAT material subroutine interface provided by ABAQUS explicit analysis,and the numerical simulation of Taylor bar impact test is carried out to verify the correctness of the VUMAT subroutine.(3)According to the Chapman Jouguet detonation model and Taylor Zeldovich similar solution,the analytical solution of the flow field after the rapid propagation of detonation wave in the pipe is obtained.The solution can characterize the characteristics of the detonation load distribution with time and space in the pipe,and the detonation load is written into the VDLOAD subroutine provided by ABAQUS in the form of user-defined function to complete the application of detonation load.(4)The dynamic fracture finite element model of pipeline under internal explosion based on rate type damage evolution is established and verified.The results show that the dynamic propagation and bifurcation behavior of the crack and the final fracture morphology of the pipeline under different defect lengths are in good agreement with the experimental results.The numerical prediction method based on rate type damage evolution can reasonably and accurately predict the dynamic fracture process and final fracture morphology of pipeline under internal explosion.