Anisotropic nonlocal damage model for materials with intrinsic transverse isotropy
Anisotropic nonlocal damage model for materials with intrinsic transverse isotropy
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DOI：
10.1016/j.ijsolstr.2018.01.020
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发表时间：
2018-05
影响因子：
3.6
通讯作者：
Jin Wencheng;C. Arson
中科院分区：
文献类型：
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作者：
Jin Wencheng;C. Arson
本文给出了具有本征横向各向同性材料的各向异性损伤模型的理论公式和数值实现。裂纹的萌生和扩展由四个等效应变量度控制的唯象损伤演化规律来模拟。后者的构造是为了区分材料在拉伸和压缩时沿垂直于层理平面的方向和在层理平面内的机械响应。为了避免软化引起的网格依赖，用非局部应变替换等效应变，非局部应变定义为通过两个内部长度参数缩放的邻域上的加权平均。有限元方程用正常的平面弧长控制算法求解，该算法允许在捕捉回或捕捉通过的情况下通过极限点。通过对页岩进行的三轴压缩试验，对不同的约束条件和相对于层理平面的加载方向进行了模型校准。高斯点模拟证实，该模型成功地捕捉到了单轴抗拉强度相对于层理方向的变化。三点弯曲试验和压裂试验的有限元模拟表明，非局部增强确实避免了网格依赖，损伤过程区的轴向和横向尺寸由两个特征长度来衡量。结果进一步表明，无论是拉伸还是压缩，损伤过程区都是方向相关的。该模型可以用于任何类型的织构脆性材料；它允许在宏观响应中表示几种并行的损伤机制，并解释控制损伤过程区的破坏机制。
This paper presents the theoretical formulation and numerical implementation of an anisotropic damage model for materials with intrinsic transverse isotropy. Crack initiation and propagation are modeled by phenomenological damage evolution laws, controlled by four equivalent strain measures. The latter are constructed so as to distinguish the mechanical response of the material in tension and compression, along the direction perpendicular to the bedding plane and within the bedding plane. To avoid mesh dependency induced by softening, equivalent strains are replaced by nonlocal counterparts, defined as weighted averages over a neighborhood scaled by two internal length parameters. Finite Element equations are solved with a normal plane arc length control algorithm, which allows passing limit points in case of snap back or snap through. The model is calibrated against triaxial compression tests performed on shale, for different confinements and loading orientations relative to the bedding plane. Gauss point simulations confirm that the model successfully captures the variation of uniaxial tensile strength with respect to the bedding orientation. Finite Element simulations of three-point bending tests and compression splitting tests show that nonlocal enhancement indeed avoids mesh dependency, and that the axial and transverse dimensions of the damage process zone are scaled by the two characteristic lengths. Results further show that the damage process zone is direction dependent both in tension and compression. The model can be used for any type of textured brittle material; it allows representing several concurrent damage mechanisms in the macroscopic response and interpreting the failure mechanisms that control the damage process zone.