Abstract A dislocation and gradient-based crystal plasticity finite element study of fatigue has been carried out for nickel-based superalloy RR1000 in order to investigate detrimental non-proportional effects on fatigue life. Six differing multiaxial loading cycles including both proportional and non-proportional paths have been addressed and a critical stored energy density criterion employed for fatigue life. Non-proportional paths are shown to lead to higher numbers of intragranular slip system activations, reflecting experimental observations. These give higher geometrically necessary dislocation (GND) densities resulting from slip system interaction occurring through latent hardening effects in the model. The higher GND densities in turn drive up local stress and stored energy densities, thereby leading to lower predicted fatigue lives, in keeping with non-proportional fatigue experiments in the alloy considered. Intragranular slip system interaction may be the mechanistic explanation for non-proportional effects in fatigue of engineering alloys.

中文翻译：

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镍基高温合金非比例疲劳中滑移系统相互作用、GND密度和储能的晶体塑性研究

摘要 为了研究非比例对疲劳寿命的不利影响，对镍基高温合金 RR1000 进行了基于位错和梯度的疲劳晶体塑性有限元研究。解决了六个不同的多轴加载循环，包括比例和非比例路径，并采用了疲劳寿命的临界存储能量密度标准。非比例路径被证明会导致更多的粒内滑移系统激活，这反映了实验观察。这些提供了更高的几何必要位错 (GND) 密度，这是由模型中潜在硬化效应产生的滑移系统相互作用引起的。较高的 GND 密度反过来会增加局部应力和储存能量密度，从而导致较低的预测疲劳寿命，与所考虑合金的非比例疲劳实验保持一致。晶内滑移系统相互作用可能是工程合金疲劳中非比例效应的机理解释。