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首页> 外文期刊>International Journal of Fracture >Effects of microstructure variability OH intrinsic fatigue resistance of nickel-base superalloys - a computational micromechanics approach
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Effects of microstructure variability OH intrinsic fatigue resistance of nickel-base superalloys - a computational micromechanics approach

机译:镍基高温合金微观结构变异性OH固有疲劳强度的影响-一种计算微力学方法

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摘要

Understanding the effects of microstructure variability on fatigue resistance is a key to selection and design of materials for fatigue applications. The traditional empirical approach rooted in experiments is being increasingly combined with systematic computational modeling. This work is concerned with demonstrating the feasibility of linking effects of microstructure variability on cyclic plasticity at the scale of intrinsic microstructure of a single crystal nickel-base superalloy. The precipitate and the matrix phases of the alloy are modeled explicitly using a physically based crystal viscoplasticity constitutive framework with appropriate scale and spacing effects to reflect dislocation-precipitate interactions. The model is implemented as a user material subroutine within a finite element code. Various realizations of different microstructures are generated using a constrained Pois-son point process. Statistical volume elements (SVEs) with random-periodic boundary conditions are simulated under fully reversed cyclic loading at 650 deg C. Primary cooling y' precipitate size and volume fraction are considered in terms of their effects on the macroscopic stress-strain response and on distributed cyclic microplasticity within the SVE. To compare various microstructures in terms of probability of fatigue crack formation, an appropriate nonlocal measure of cyclic plastic shear strain range is proposed based on percolation of cyclic microplasticity at the scale of the SVE.
机译:了解微观结构变异性对抗疲劳性的影响是选择和设计用于疲劳应用的材料的关键。扎根于实验的传统经验方法正越来越多地与系统的计算模型相结合。这项工作涉及证明在单晶镍基高温合金的内在微观结构尺度上,微观结构变异性对循环塑性的连锁效应的可行性。使用基于物理的晶体粘塑性本构框架,以适当的尺度和间距效应来反映位错-沉淀的相互作用,对合金的析出相和基体相进行显式建模。该模型被实现为有限元代码中的用户材料子例程。使用受约束的Pois-son点过程可生成各种不同的微结构。在完全反向循环载荷下在650℃下模拟具有随机周期边界条件的统计体积元素(SVE)。考虑到主要冷却y'沉淀物的大小和体积分数对宏观应力-应变响应和分布的影响, SVE内的循环微塑性。为了根据疲劳裂纹形成的可能性比较各种微观结构,基于循环微塑性在SVE尺度上的渗滤,提出了一种适当的非局部测量循环塑性剪切应变范围的方法。

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