两种高强钢在高加载速率下的Ⅱ型动态断裂韧性

采用实验-数值相结合的方法对40Cr和30CrMnSiNi2A两种高强钢剪切试样在冲击载荷作用下的Ⅱ型动态断裂韧性进行了测试．实验在Hopkinson压杆系统上完成,试样的起裂时间采用应变片法测得．结合有限元三维动态模拟,得到了不同加载速率下试样动态应力强度因子的时间历程,并由实测的起裂时间确定两种钢的动态断裂韧性．结果表明,在现有加载率范围 (2×106-7×106MPa．m1／2／s)内,两种高强钢试样几乎全部由绝热剪切模式引发断裂,其动态断裂韧性均随加载速率的增加而呈现上升趋势,且在相同加载速率下后者的动态断裂韧性大于前者的动态断裂韧性．并对韧带尺寸对试样断裂韧性的影响进行了研究．

MODE II DYNAMIC FRACTURE TOUGHNESS OF TWO HIGH STRENGTH STEELS UNDER HIGH LOADING RATE

Mode II dynamic fracture toughnesses K IId for high strengthsteels, 40Cr and 30CrMnSiNi2A, subjected to impact loading were measuredusing an experiment-number combined method. The tests were performedon shear specimens with Hopkinson pressure bar and the time of crackinitiation was determined by strain gauge. With 3-D transient finiteelement analysis, the time evolution of dynamic stress intensity factorunder different loading rates was obtained and the dynamic fracturetoughness was determined by fracture initiation time. The results showthat within the loading rate range(2×10 6 -7×10 6 MPa m 1/2/s),almost all the specimens failed by adiabatic shear bands and theK IId values of the two steels increase withincreasing loading rate. The K IId value of 30CrMnSiNi2A islarger than that of 40Cr at the same loading rate. The effect of ligamentsize on fracture toughness was also discussed.