材料参数对韧性材料高应变率拉伸碎裂过程的影响

Grady-Kipp将一个与断裂能量相关的内聚断裂模型引入Mott[1]的刚性卸载波分析，导出一个预测韧性材料在高速拉伸碎裂过程中产生碎片的平均尺度的计算公式[2]。为定量评估Grady-Kipp公式的适用程度，采用数值方法模拟了具有不同材料参数的一维弹塑性杆在高应变率拉伸过程中的碎裂现象。通过改变材料的断裂能 、密度 和应变率敏感系数c，模拟了杆在不同应变率 下的碎裂过程，研究了材料参数对碎裂时的碎片尺度、表观断裂应变和断口温升等的影响。通过对应变率和碎片尺寸进行无量纲化，证实Grady-Kipp公式在广泛的材料参数范围内能较好地预测碎裂过程中发生的碎片平均尺寸。

HIGH STRAIN RATE TENSILE FRAGMENTATION PROCESS OF DUCTILE MATERIALS AND THE EFFECTS OF MATERIAL PARAMETERS

By introducing a cohesive fracture model into the Mott[1] momentum diffusion analysis,Grady and Kipp[2] deduced a formula for predicting the average size of the fragments during a ductile fragmentation process.To quantitatively evaluate the accuracy of the Grady-Kipp formula,in this paper,we numerically simulated the fragmentation processes of an elastic-plastic bar undergoing initially uniform high strain rate tensile deformation.The key material parameters,including the fracture energy Gc,the material density ρ,yield stress A and the strain-rate sensitivity C,were varied intentionally for evaluating their effects on the fragmentation process.The average fragment sizes were calculated for a wide range of the prescribed strain rates and the material parameters.It was concluded that the Grady-Kipp model provides reasonably close predictions of the lower limit of the ductile fragment sizes,though slight deviations exist in the cases when the fundamental assumptions in the Grady-Kipp analysis do not apply.