WELDOX 700E钢Johnson-Cook本构模型及动态断裂机理

Johnson-Cook constitutive model and fracture mechanism of WELDOX 700E steel

利用拉伸试验机、霍普金森拉杆装置对高强度WELDOX 700E 钢进行了静、动态拉伸力学性能测试,研究了WELDOX 700E 钢的静、动态力学性能,并利用OM、SEM 观察分析了WELDOX 700E 钢不同应变速率下的断裂机理。结果表明: 随着应变速率由0. 000 25 s - 1 提高至4000 s - 1 时,WELDOX 700E 钢的屈服强度提高53. 4%,并伴随有绝热升温现象;同时,通过对试验数据进行本构方程拟合,得到了WELDOX 700E 钢的Johnson-Cook 本构方程: σi = ( 921. 6 + 1147. 2ε0. 81i) ( 1 + 0. 085lnε ·* ) 。静、动态拉伸条件下,WELDOX 700E 钢呈现出典型的微孔聚集型韧窝断裂形貌,显微孔洞以马氏体板条界面、第二相粒子为形核点,在拉伸正应力的持续作用下显微孔洞长大、聚集,直至断裂,且随着应变速率的增加,拉伸试样颈缩区的马氏体板条平均宽度由891 nm 降至395 nm,显微组织形变加剧与强度增加的趋势一致.

The static and dynamic mechanical properties of WELDOX 700E steel with high strength were studied by using tensile tests and split Hopkinson tension bar.The fracture mechanism of WELDOX 700E steel at different strain rates was analyzed by using OM and SEM.The results show that the yield strength of WELDOX 700E steel increases 53.4%as the strain rate increasing from 0.000 25 s-1 to 4000 s-1,also with the phenomenon of adiabatic heating.The Johnson-Cook constitutive equation of WELDOX 700E steel has been obtained through the experimental data asσi=(921.6+1147.2ε0.81 i)(1+0.085lnε·*).The fracture mechanism of WELDOX 700E steel is microvoid accumulation fracture,and there are visible dimples in fracture.The initial points of fracture are martensite phase boundary and secondary phase particle.Under the continuous action of tensile stress,the microvoid grow and aggregate until fracture.The average width of martensite lath at the necked-down section of tensile specimens decreased from 891 nm to 395 nm,and the deformation aggravation of microstructure is consistent with the increase trend of strength.