Research On Continuum Damage Model For Ductile Fracture Of Steel Structures Based On Void Growth Theory

Ductile fracture constitutes a significant failure mode of structural steels,which often causes fracture of components or connections and may result in the collapse of the whole building structures.It is thus necessary to figure out the mechanism of ductile fracture and setup doable numerical approaches for the simulation of the ductile fracture of structural steels.This paper focuses on the ductile fracture simulation models for structural steels.The void growth model and continuum damage model were studied for monotonic loading case.The application of the simulation models was verified by the monotonic tensile test.The main research is as follows:(1)The void growth model under monotonic loading was introduced and detailed analysis of its calculation process was conducted.After study of fracture behavior of relatively large elements in relatively coarse mesh,a continuum damage model was proposed based on void growth model to consider the stiffness degradation of partially-fractured elements in relatively coarse mesh.(2)Tension tests were conducted on eight single-edge notched specimens.The entire ductile fracture procedures and load-displacement curves were determined and studied.(3)The ductile fracture procedures of the single-edge notched specimens were simulated with void growth model.The predicted fracture initiation and propagation agreed well with corresponding test results and the adaptability to the mesh size was also analyzed.The application of void growth model on prediction and simulation of ductile fracture procedures under monotonic loading was verified.(4)Based on the test results of single-edge notched specimens,the parameters of the continuum damage model were calibrated.The ductile fracture procedures of specimens were then simulated with the continuum damage model and the adaptability to the mesh size was also analyzed.Since the simulation results were in reasonable agreement with test results,the application of continuum damage model was verified.(5)Simulation results and computational cost of the two fracture criteria were compared and fracture simulation of two additional specimens was conducted.The results show that both fracture criteria have ability to simulate the ductile fracture,while the computational cost of the continuum damage model is much less than that of void growth model.Based on the experimental study and the finite element analysis method,the application of the two fracture criteria was verified.The proposed continuum damage model can simulate ductile fracture using relatively coarse mesh,which will effectively solve the problems of the poor adaptability to mesh size of finite element analysis and high computational cost based on void growth model.It has great application value to ductile fracture simulation for steel components or connections with complicated configurations.