Modelling of cavity nucleation under creep-fatigue interaction
Modelling of cavity nucleation under creep-fatigue interaction
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DOI：
10.1016/j.mechmat.2021.103799
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发表时间：
2021-03-04
影响因子：
3.9
通讯作者：
Chen, B.
中科院分区：
文献类型：
--
作者：
Hu, J. -D.;Xuan, F. -Z.;Chen, B.
建立了蠕变-疲劳相互作用下的空穴成核模型，简称CH模型。 CH 模型的关键是通过自洽方案来解释蠕变变形。这样可以在 500-600 摄氏度的温度范围内评估 316 型不锈钢中晶界滑动 (GBS) 和晶体变形对空腔成核的综合影响。CH 模型预测，在长期的应力保持期间，局部正应力将渐近接近非零饱和值。这与蠕变下的连续成核过程一致。 CH 模型已用于计算各种载荷波形情况下的空腔成核率，其中包括瞬态和稳定载荷期间施加的应力和时间。结果，确定了可以使空腔成核最大化的负载波形特性。首先，预压保持时间需要较长，而负载反转时间需要较短。其次，如果以时间效率为首要考虑，拉伸保持时间可以在一定程度上缩短。第三，所有上述与时间相关的参数都有其最佳值，具体取决于温度和蠕变速率。第四，不平衡应力有利于张力，提高了成核率，应力范围是控制因素。总之，CH 模型为蠕变疲劳测试程序的设计提供了重要的指导，旨在促进蠕变空化损坏。这种基于机制的模型为蠕变疲劳相互作用的复杂性提供了基本解释。
A cavity nucleation model under creep-fatigue interaction, abbreviated as CH model, has been established. The key aspect of the CH model is accounting for the creep deformation through a self-consistent scheme. This allows the combined effect of grain boundary sliding (GBS) and crystal deformation on cavity nucleation to be assessed in Type 316 stainless steel over the temperature range of 500-600 degrees C. The CH model predicts that the local normal stress asymptotically approaches a non-zero saturation value over a long period of stress hold. This aligns with the continuous nucleation process under creep. The CH model has been used to calculate the cavity nucleation rates under various load-waveform scenarios, which include the stress and time applied during the transient and steady loadings. As a result, the load waveform characteristics that can maximise the cavity nucleation are identified. First, the pre-compressive hold time needs to be long, whereas the load reversal time needs to be short. Second, the tensile hold time can be shortened to some extent if time efficiency is the primary concern. Third, all the above-mentioned time-related parameters have their optimum values depending on the temperature and creep rate. Fourth, the unbalanced stress hold in favour of the tension enhances the nucleation rate, and the stress range is the controlling factor. In summary, the CH model provides an important guide to the design of creep-fatigue testing programme with the desire to promote creep cavitation damage. This mechanistic-based model provides underlying interpretations to the complexity of creep-fatigue interaction.