采用实验-数值方法对40Cr和30CrMnSiNi2A两种高强钢三点弯曲试样在不同加载速率的冲击载荷作用下进行了动态断裂韧性的测试, 并对其率相关性进行研究. 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材料动态断裂韧性. 结果表明, 在本工作加载速率范围内(10 6 MPa•m 1/2/s),40Cr钢为解理型断裂, 其动态断裂韧性随加载速率增加的变化趋势不明显；而30CrMnSiNi2A钢则在较大程度上表现为延性断裂的特征, 其动态断裂韧性随加载速率的增加呈明显上升趋势. 并对上述结果进行了宏观和微观机理分析.
ModeⅠdynamic fracture toughnesses KId for high strength steels, 40Cr and 30CrMnSiNi2A, subjected to impact loading with different loading rates were measured using an experimental-numerical hybrid method. The sensitivity of KId to loading rate for the steels were investigated. The tests were performed on three point bending specimens with Hopkinson pressure bar and the time of crack initiation was determined by strain gauge. With 3-D transient finite element analysis, the dynamic stress intensity factor histories under different loading rates were obtained and the dynamic fracture toughnesses were determined by fracture initiation time. The results show that within the loading rate range (10 6 MPa•m 1/2/s), 40Cr steel specimens failed by cleavage fracture, and the KId tendency is not clear with increasing loading rate. 30CrMnSiNi2A steel specimens failed to a large extent by ductile fracture and the KId value increases obviously with loading rate. Mechanisms of the results were discussed macroscopically and microcosmically.
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