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采用扫描电镜和图像分析对高强韧X80管线钢的拉伸断口特征进行观察以及统计分析,根据断口特征参数设计孔洞体胞模型,并应用有限元数值模拟计算研究孔洞扩张比的演化规律。结果表明,在低应力三轴度的条件下,随着等效应变的增加,夹杂物导致的孔洞体积扩张比也不断缓慢增加,等效应变与孔洞体积扩张比的自然对数成正比,线性关系吻合良好,在后期高应力作用下应考虑M-A岛二次形核形成的孔洞片导致韧性断裂。在任何加载的条件下,对于高的应力三轴度,有限元数值模拟计算孔洞扩张比的演化规律与传统的R-T模型有较大的差异,夹杂物导致的孔洞体积扩张比迅速增加,最终由孔洞间韧带颈缩引起韧性断裂。
Scanning electron microscopy and image analysis were used to observe and analyze the tensile fracture characteristics of high tensile strength and toughness X80 pipeline steel. Hole cellular model was designed according to the fracture parameters and the evolution of pore expansion ratio was studied by finite element numerical simulation. The results show that under the condition of low stress triaxiality, the volumetric expansion ratio of pores caused by inclusions also increases slowly with the increase of equivalent strain, and the equivalent strain is proportional to the natural logarithm of the volumetric expansion ratio of pores. The linearity The relationship is in good agreement. Under the action of high stress at the later stage, the holes formed by secondary nucleation of MA island should be considered to cause ductile fracture. Under the condition of any loading, the evolution law of hole expansion ratio calculated by finite element numerical simulation is quite different from the traditional RT model for high stress triaxiality, and the volume expansion ratio of holes caused by inclusions increases rapidly. Finally, Neck between the necking neck caused by ductile fracture.