关联Drucker-Prager条件下等效塑性应变系数

发布时间：2018-10-23 14:00

【摘要】：针对岩石类材料,试图在关联Drucker-Prager条件下建立更一般化的等效塑性应变定义方法,并研究等效塑性应变系数在塑性变形过程中的变化。首先列举了国内外常用的等效塑性应变定义方法,并分析了它们的不合理性。然后从等效应力和等效塑性应变的定义出发,推导出关联Drucker-Prager条件下等效塑性应变系数。结合室内致密砂岩三轴压缩试验,以塑性体应变为内变量,研究了致密砂岩峰后内摩擦角和粘聚力随内变量的变化,进而研究了等效塑性应变系数随塑性变形的变化。研究发现:等效塑性应变系数依赖于屈服准则的选取,等效塑性应变系数为(2/3)~(1/2)是Mises屈服准则下的特例;关联Drucker-Prager条件下等效塑性应变系数C(2/3)~(1/2),并且随着塑性变形的发展而减小最终趋于稳定值;对于岩石类材料,很多有限元软件中不区分具体情况而直接选用C=(2/3)~(1/2)计算等效塑性应变存在较大的误差。
[Abstract]:This paper attempts to establish a more general definition method of equivalent plastic strain for rock materials under the condition of correlation Drucker-Prager and to study the variation of equivalent plastic strain coefficient in the process of plastic deformation. At first, the definition methods of equivalent plastic strain are listed and their irrationality are analyzed. Based on the definitions of equivalent stress and equivalent plastic strain, the equivalent plastic strain coefficient under the condition of correlation Drucker-Prager is derived. In this paper, the variation of internal friction angle and cohesive force after peak of dense sandstone with internal variables is studied, and the change of equivalent plastic strain coefficient with plastic deformation is studied by using plastic body strain as internal variable in the laboratory compact sandstone triaxial compression test. It is found that the equivalent plastic strain coefficient depends on the selection of yield criterion, and the equivalent plastic strain coefficient of (2 / 3) ~ (1 / 2) is a special case under Mises yield criterion. The equivalent plastic strain coefficient C (2 / 3) ~ (1 / 2) is correlated with the Drucker-Prager condition, and decreases with the development of plastic deformation to a stable value; for rock materials, the equivalent plastic strain coefficient C (2 / 3) ~ (1 / 2) decreases with the development of plastic deformation. In many finite element software, there is a big error in calculating the equivalent plastic strain by selecting C = (2 / 3) ~ (1 / 2) directly without distinguishing the specific case.
【作者单位】：中国石油大学石油工程学院;
【基金】：国家自然科学基金优秀青年科学基金(51322404)
【分类号】：TU45

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