Abstract The ductile fracture in ferrous materials during cylinder upsetting was predicted using an ellipsoidal void model to show the validity of the proposed model. The simulation and experiment of cylinder upsetting were performed using five types of ferrous bars. Seven kinds of prestrains different in magnitude were introduced in the bars by drawing, and special attention was paid to the effect of the prestrain on ductile fracture during cylinder upsetting, which was scarcely paid attention to in earlier studies. A specimen for the plane-strain tensile test obtained from a bar was proposed to obtain a material constant on ductile fracture. Both in the simulation and in the experiment, with increasing the prestrain, the axial strain at fracture initiation monotonically increased, whereas the circumferential strain at fracture initiation monotonically decreased. The effect of the prestrain on the circumferential and axial strains at fracture initiation calculated using an ellipsoidal void model substantially agrees with that obtained experimentally, whereas the effect of the prestrain on the circumferential and axial strains at fracture initiation calculated using conventional ductile fracture criteria considerably differs from that obtained experimentally. Hence, the validity of the ellipsoidal void model was confirmed.

中文翻译：

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使用椭圆体空洞模型预测圆柱镦粗过程中黑色金属材料的韧性断裂

摘要 使用椭球体空隙模型预测了黑色金属材料在圆柱体镦锻过程中的韧性断裂，以证明所提出模型的有效性。使用五种类型的铁棒进行了气缸镦粗的模拟和实验。通过拉拔在钢筋中引入了7种大小不同的预应变，特别关注了预应变对圆柱镦锻过程中韧性断裂的影响，这在早期的研究中很少受到关注。提出了从棒材获得的用于平面应变拉伸试验的试样，以获得关于延性断裂的材料常数。在模拟和实验中，随着预应变的增加，断裂开始时的轴向应变单调增加，而断裂开始时的周向应变单调减小。使用椭圆体空隙模型计算的预应变对断裂起始时的周向和轴向应变的影响与实验结果基本一致，而使用常规韧性断裂标准计算的预应变对断裂起始时的周向和轴向应变的影响有很大不同从实验获得的。因此，证实了椭圆体空隙模型的有效性。而使用常规韧性断裂标准计算的预应变对断裂开始时的周向和轴向应变的影响与实验获得的结果大不相同。因此，证实了椭圆体空隙模型的有效性。而使用常规韧性断裂标准计算的预应变对断裂开始时的周向和轴向应变的影响与实验获得的结果大不相同。因此，证实了椭圆体空隙模型的有效性。