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高温蠕变下表面多裂纹扩展行为

The analysis of multiple surface cracks growth behavior under the interaction of creep cracks

  • 摘要: 文中将蠕变损伤模型编写到USDFLD用户子程序中,利用有限元分析软件ABAQUS,通过单元失效技术模拟了表面多裂纹干涉条件下裂纹扩展行为.探究了不同裂纹尺寸、残余应力对高温蠕变表面多裂纹干涉效应及裂纹扩展行为的影响.结果表明,表面裂纹形状比、裂纹深度的增大和裂纹间距离的减小,加强了表面多裂纹之间的干涉效应并促进多裂纹的扩展,而残余应力的存在同样加速了裂纹扩展.基于裂纹扩展速率提出了蠕变下表面多裂纹合并准则,即当蠕变干涉因子超过1.27,应当考虑多裂纹的合并,否则多裂纹仍按照单裂纹处理.

     

    Abstract: The damage model was implemented into user subroutine of commercial ABAQUS code to calculate the damage accumulation in each time interval and to simulate the crack growth. The influence of crack configurations and residual stress on crack growth behavior in the presence of multiple surface cracks were studied through the variation of crack growth rate. With the relative surface crack sizes (a/t, a/c,) become larger and the distance between two cracks (s/c) becomes close, the interaction between two surface cracks were enhanced and the crack growth behavior was improved. Besides, the existence of residual tensile stress also accelerated the crack growth rate. According to the change of crack growth rates, the critical value of γcreep for combination of multiple creep surface cracks was assumed to be 1.27. As γcreep ≥ 1.27 two interacting cracks should be considered to combine into a new big crack otherwise they can be treated as isolated cracks, respectively.

     

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