Abstract The most important ability of fracture mechanics is how to apply the material test data obtained by standard specimens with the through-thickness cracks to practical structures where partially penetrating crack growth usually spends most of the service life, but complicated stress states make it difficult to describe the creep crack border stress states effectively. Based on the creep stress intensity factor Kδ(t)-Tz, a crack tip opening displacement based description is proposed to characterize the creep crack border fields for partially penetrating cracked specimens under out-of-plane constraints described by Tz. Comprehensive three-dimensional finite element results show that in the whole range of elliptical parametrical angle and shape factor, the maximum change in Kδ(t)-Tz is within 19% while C(t) changes over 370%, showing that Kδ(t)-Tz is more stable than C(t). At both primary and steady creep stages, the Kδ(t)-Tz description can characterize the crack border stress fields effectively for specimens with surface and corner elliptic cracks. Consideration of the in-plane constraint coefficient Q* is found to be necessary only for embedded elliptic cracked specimens, where the Kδ(t)-Tz-Q* description can provide an accurate prediction of crack border stress fields. The dominance and stability of Kδ(t)-Tz and Tz make the crack tip opening displacement based description potentially to develop creep fracture assessment approaches for high temperature structures.

中文翻译：

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基于裂纹尖端张开位移的部分穿透裂纹试样三维蠕变裂纹边界应力场描述

摘要 断裂力学最重要的能力是如何将具有全厚度裂纹的标准试样获得的材料试验数据应用到实际结构中，其中部分穿透裂纹扩展通常花费大部分的使用寿命，但复杂的应力状态使其难以实现。有效地描述蠕变裂纹边界应力状态。基于蠕变应力强度因子 Kδ(t)-Tz，提出了一种基于裂纹尖端张开位移的描述，以表征在 Tz 描述的面外约束下部分穿透裂纹试样的蠕变裂纹边界场。综合三维有限元结果表明，在椭圆参数角和形状因子的整个范围内，Kδ(t)-Tz的最大变化在19%以内，而C(t)变化超过370%，表明 Kδ(t)-Tz 比 C(t) 更稳定。在初级和稳定蠕变阶段，Kδ(t)-Tz 描述可以有效地表征具有表面和角部椭圆裂纹试样的裂纹边界应力场。发现仅对嵌入式椭圆裂纹试样才需要考虑面内约束系数 Q*，其中 Kδ(t)-Tz-Q* 描述可以提供裂纹边界应力场的准确预测。Kδ(t)-Tz 和 Tz 的优势和稳定性使得基于裂纹尖端张开位移的描述有可能为高温结构开发蠕变断裂评估方法。Kδ(t)-Tz 描述可以有效地表征具有表面和角部椭圆裂纹的试样的裂纹边界应力场。发现仅对嵌入式椭圆裂纹试样才需要考虑面内约束系数 Q*，其中 Kδ(t)-Tz-Q* 描述可以提供裂纹边界应力场的准确预测。Kδ(t)-Tz 和 Tz 的优势和稳定性使得基于裂纹尖端张开位移的描述有可能为高温结构开发蠕变断裂评估方法。Kδ(t)-Tz 描述可以有效地表征具有表面和角部椭圆裂纹的试样的裂纹边界应力场。发现仅对嵌入式椭圆裂纹试样才需要考虑面内约束系数 Q*，其中 Kδ(t)-Tz-Q* 描述可以提供裂纹边界应力场的准确预测。Kδ(t)-Tz 和 Tz 的优势和稳定性使得基于裂纹尖端张开位移的描述有可能为高温结构开发蠕变断裂评估方法。