基于循环孔洞扩张模型的Q355钢超低周疲劳断裂数值模拟

NUMERICAL SIMULATION OF ULTRA-LOW CYCLE FATIGUE FRACTURE OF Q355 STEELS BASED ON CYCLIC VOID GROWTH MODEL

基于微观断裂力学的循环孔洞扩张模型是进行钢材超低周疲劳断裂分析的有效手段。通过光滑圆棒循环加载试验,确定了Q355钢混合强化模型材料参数;进行了不同加载方式下Q355钢单边缺口试件的超低周疲劳试验,确定了试件的超低周疲劳寿命及其断裂发展过程;建立了单边缺口试件有限元模型,基于有限元分析结果,采用循环孔洞扩张模型对试件的超低周疲劳寿命进行了预测,并通过编写用户子程序,删除断裂单元以模拟试件的断裂扩展过程,对试件的超低周疲劳断裂全过程进行了数值模拟。数值模拟结果与试验结果基本吻合,验证了循环孔洞扩张模型对钢材超低周疲劳断裂全过程数值模拟的适用性。

The cyclic void growth model(CVGM) is based on micromechanics of fracture and can effectively deal with the ultra-low cycle fatigue(ULCF) fracture of structural steels. Smooth bar specimens were tested under cyclic loading to determine the material constants in the combined hardening model of Q355 steels. Single-edge notched plate specimens were tested under different cyclic loadings. The ULCF lives and the development of the ULCF fracture were obtained for all test specimens. Finite element(FE) models were established for the singleedge notched plate specimens. The ULCF lives of these specimens were predicted by the CVGM based on the results of the FE analysis. By programming a user subroutine, the fractured elements were removed from the FE models to simulate the fracture propagation during the loading. The entire process of the ULCF fracture of each test specimen was numerically simulated. The simulation agreed well with the test results, which verified the applicability of the CVGM to the numerical simulation of the ULCF fracture of structural steels.