A novel method for load line displacement rate partitioning in creep crack growth tests on Type 316H stainless steel
A novel method for load line displacement rate partitioning in creep crack growth tests on Type 316H stainless steel
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316H 不锈钢蠕变裂纹扩展试验中载荷线位移速率划分的新方法
DOI：
10.1016/j.engfracmech.2019.106689
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发表时间：
2020
影响因子：
5.4
通讯作者：
Jones M
中科院分区：
文献类型：
--
作者：
Jones M
表征316H型不锈钢的蠕变裂纹扩展行为对于准确预测高温部件的寿命至关重要，例如在英国先进的气冷反应堆中。蠕变裂纹扩展速率与断裂力学参数C *（被认为决定裂纹扩展过程）之间的相关性可从蠕变裂纹扩展测试中获得。C参数是通过实验确定的，使用一个表达式，该表达式需要蠕变引起的载荷线位移速率的知识。从历史上看，这是通过从实验测得的总载荷线位移中减去弹性和塑性对载荷线位移的贡献值来计算的，这些值是从可用解中获得的。然而，可用于确定塑性贡献的解决方案依赖于生成单轴拉伸数据的幂律拟合，这在大应力范围内难以准确实现。此外，这些表达式不能解释裂纹扩展过程中的应变历史效应。因此，弹性和塑性的贡献往往错误地大，甚至可能超过试验总载荷线位移。提出了一种新的技术，以提供更好的估计蠕变裂纹扩展试验过程中的蠕变贡献的负载线位移速率。该技术采用有限元分析，结合材料特定的单轴拉伸试验数据来模拟实验测试中的裂纹扩展。一个单一的弹塑性蠕变模拟是用来确定单独的弹塑性和蠕变贡献的负载线位移，这意味着，与历史分析，蠕变应力松弛和应变历史的影响，现在可以考虑。结果表明，先进的预测蠕变贡献的负载线位移可以得到使用这种技术。
Characterising the creep crack growth behaviour of Type 316H stainless steel is vital in obtaining accurate predictions for the lifetime of high temperature components, for example in UK advanced gas cooled reactors. The correlation between creep crack growth rates and the fracture mechanics parameter C∗, considered to govern the crack growth process, is obtained from creep crack growth tests. The C∗ parameter is experimentally determined using an expression which requires knowledge of the load line displacement rate due to creep. Historically this has been calculated by subtracting values for the elastic and plastic contributions to the load line displacement, obtained from available solutions, from the total experimentally measured load line displacement. However, the solutions available to determine the plastic contribution rely on generating a power-law fit to uniaxial tensile data, which is difficult to accomplish accurately over a large stress range. In addition, these expressions cannot account for strain history effects during crack growth. Consequently the elastic and plastic contributions are often erroneously large and can even be in excess of the experimental total load line displacement. A novel technique has been proposed to provide improved estimates of the creep contribution to the load line displacement rates during creep crack growth tests. This technique employs finite element analysis that incorporates material specific uniaxial tensile test data to simulate crack growth in an experimental test. A single elastic-plastic-creep simulation is used to determine the separate elastic-plastic and creep contributions to the load line displacement, meaning that, unlike historic analyses, creep stress relaxation and strain history effects can now be accounted for. The results have demonstrated that advanced predictions of the creep contributions to the load line displacement can be obtained using this technique.
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