Finite element analyses of deformation around holes near a crack tip and their implications to the J‐resistance curve
Finite element analyses of deformation around holes near a crack tip and their implications to the J‐resistance curve
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裂纹尖端附近孔周围变形的有限元分析及其对 J 电阻曲线的影响
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发表时间：
2000
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通讯作者：
I. Gu
中科院分区：
文献类型：
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作者：
I. Gu
对延性裂纹扩展的起始阶段进行了详细的有限元分析。这一过程是通过钝化裂纹尖端前一系列孔洞的生长和合并来模拟的，代表了从大夹杂物中分离出来的孔洞的生长。计算了相邻孔洞之间每个韧带由于孔洞增长而减少的量以及裂纹尖端张开位移（CTOD）。除第一和最后两根韧带外，所有韧带均表现出相似的复位行为，其复位曲线以相同的CTOD增量分开。CTOD增量作为孔洞扩展导致的有效裂纹扩展的函数定义了裂纹尖端张开角，这是在给定条件下裂纹扩展阻力的度量。由于小尺度屈服过程中裂纹扩展导致CTOD增量发生较大变化，因此对于静止裂纹，裂纹起裂点定义为CTOD对J的线性增量偏离点。有效裂纹尖端在每个孔洞处定义为裂纹起裂的韧带减少。因此，j阻力曲线可以由孔洞扩展模型推导出来，并讨论了试样几何形状、裂纹长度和试样尺寸对r曲线的影响。当孔距为初始孔直径的10倍时，计算结果与2024-T351铝合金的实验r曲线一致。
The initiation phase of ductile crack growth is investigated in a detailed finite element analysis. The process is modelled by the growth and coalescence of a series of holes in front of a blunted crack tip, representing the growth of holes separated from large inclusions. The reductions of each ligament between neighbouring holes due to hole growth are calculated as well as crack-tip opening displacements (CTOD). All the ligaments except the first and last show similar behaviour of reduction, with the reduction curves separated in an equal CTOD increment. The CTOD increment as a function of effective crack extension due to hole growth defines crack-tip opening angle, a measure of crack-growth resistance for a given condition. As the CTOD increment changes substantially due to crack extension in small-scale yielding, crack initiation is defined at the point of deviation from the linear increment of CTOD against J for a stationary crack. The effective crack tip is defined at each hole with the ligament reduction of crack initiation. Therefore, the J-resistance curve may be derived from the hole growth model, and hence the effects of specimen geometry, crack length and specimen size on the R-curve are discussed. The calculations for a hole spacing 10 times of the initial hole diameter are in agreement with the experimental R-curve of 2024-T351 aluminium alloy.