考虑应力三轴度影响的30CrMnSiNi2A钢韧性断裂研究

On ductile fracture of 30CrMnSiNi2A steel considering effects of stress triaxiality

30CrMnSiNi2A钢是一种在军工领域应用广泛的低合金高强度钢。针对结构完整性的评估问题,采用试验和数值计算结合的方法研究了30CrMnSiNi2A钢的韧性断裂特性。对光滑圆棒试件在不同温度下进行准静态和动态拉伸试验,并通过有限元迭代方法标定了材料的Johnson-Cook动态本构模型参数,分析了温度和应变率对30CrMnSiNi2A钢断裂行为的影响。开展了缺口圆棒拉伸、缺口平板剪切和圆柱压缩试验,计算了各试件对应的平均应力三轴度和断裂应变,给出了应力三轴度在-1/3~1.5区间内的断裂应变变化曲线,分别确定了Johnson-Cook和Bao-Wierzbicki失效模型参数。研究表明,30CrMnSiNi2A钢的断裂应变与应力状态密切相关,且在不同的应力三轴度区间内曲线单调性差异较大,Bao-Wierzbicki失效模型较好地描述了这种钢在不同应力状态下的断裂特性。

30CrMnSiNi2A steel is a high-strength low-alloy steel and it is widely used in the defense industry. Its ductile fracture properties were investigated by using a combined experimental-numerical approach to address the need for assessment of structural integrity. The parameters of the Johnson-Cook constitutive model were obtained through quasi-static and dynamic tensile tests on round bar specimens at different temperatures and relevant finite element method iterations. The effects of strain rate and temperature on fracture were studied. The tensile tests on notched round bar specimens were performed to calibrate the fracture strain in the range of high positive stress triaxiality. The tensile tests on butterfly plates and compression tests on short cylindrical specimens covered the fracture properties in the range of low and negative stress triaxiality. The finite element models were computed and the fracture loci in the space of the effective plastic strain to fracture and the stress triaxiality in a wide range from-1/3 to 1.5 were constructed. The parameters of the Johnson-Cook fracture model and BaoWierzbicki fracture model were calibrated. It is shown that stress triaxiality has a significant effect on the fracture of 30CrMnSiNi2A steel and the monotonicity of the fracture loci varies in different stress triaxiality range. The Bao-Wierzbicki model is capable of predicting the fracture patterns of the 30CrMnSiNi2A steel in different stress states.