三轴应力场中不同形状孔洞的长大及其新模型

Growth and its new model of voids with different shape in triaxial stress fields

对不同形状孔洞在从光滑试样到裂纹试样这样广泛三轴应力场中的长大规律 ,本文通过控制体胞宏观应力三维度的方法进行了精确的有限元分析 ,计算结果表明 :(1)孔洞的体积改变和形状变化是孔洞演化的两种基本机制 ,在不同的三轴应力场中 ,这两种机制的作用不同 ;(2 )现有模型对孔洞长大规律的描述是不准确的 ,由它们得到的临界孔洞扩张比参数 HGC与临界孔洞体积分数 f C不具备一一对应关系 ,因此不能很好地反映孔洞的实际扩张。在此基础上 ,提出了一个描述孔洞长大的新模型 ,与四种常用的现有模型相比 ,该模型不仅能更好地描述不同三轴应力场中孔洞的长大 ,而且能反映不同应力三维度水平下材料破坏模式的变化。

By means of controlling the macroscopic stress triaxiality of the cell, the finite element (FE) simulation analyses have been carried on the growth mechanism of voids with different shape in the wide triaxial stress fields from the smooth bar to the crack sample. The FE calculation results show: (1)the shape change and volume change are two kinds of basic mechanism of void growth, and their uses to voids growth are different in the different samples with different stress triaxiality levels. (2)the known void growth models presented by other researcher have larger error describing void growth in different samples. Based on these, in the present paper, the authors present a new void growth model. Compared with other known four kinds model, the new model can response the comprehensive use of shape change and volume change to the void developing, so it can describe effectively the void growth in different triaxial stress fields, and this new model can response the change of fracture mechanism of materials in different sample.