Study on the effect of stress redistribution in different notched specimens of DD6 on the life of combined high and low cycle fatigue under high temperature

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue Pub Date : 2024-11-19 DOI:10.1016/j.ijfatigue.2024.108713

L. Liu, Z.X. Wen, Z.F. Yue, J.D. Wang, H.S. Gao

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Abstract

Under combined high and low cycle fatigue (CCF) loading, the multi-axial stress state induced by geometric discontinuities of different notch forms under the same stress amplitude can result in significant differences in fatigue performance of DD6 alloy. Therefore, it is of great importance to study the CCF behavior of Ni-base single-crystal alloy samples with differing notch geometries at the high temperatures. In order to obtain an approximate CCF lifespan, different stress amplitudes need to be applied to DD6 specimens with different notch forms. In this study, two kinds of notched DD6 plate specimens with [001] orientation were studied by CCF test at 760 °C, and the amplitudes of stresses were acquired under the same service life level. The effect of stress redistribution, in particular stress triaxiality, was evaluated on CCF lifetime of the DD6 specimens. A damage model with anisotropy considering stress triaxiality effect was suggested. The results indicated that the conventional stress–strain variables could not reflect the trend of CCF lifetime for different geometrical notched DD6 specimens, whereas the stress triaxiality at the CCF load peak could. A modified Basquin model was introduced for predicting CCF life according to the stress triaxiality at the peak loading. It can accurately and efficiently estimate the CCF life of two kinds of notched DD6 plate specimens, and the life prediction results fall within a scatter band of ±3 times of fatigue life.

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研究 DD6 不同缺口试样中的应力再分布对高温下高低循环组合疲劳寿命的影响

在高低循环疲劳（CCF）联合加载下，相同应力振幅下不同缺口形状的几何不连续性引起的多轴应力状态会导致 DD6 合金的疲劳性能出现显著差异。因此，研究具有不同缺口几何形状的镍基单晶合金样品在高温下的 CCF 行为具有重要意义。为了获得近似的 CCF 寿命，需要对具有不同缺口形式的 DD6 试样施加不同的应力振幅。本研究在 760 ℃ 下通过 CCF 试验研究了两种具有 [001] 取向缺口的 DD6 板试样，并获得了相同使用寿命水平下的应力振幅。评估了应力再分布，特别是应力三轴性对 DD6 试样 CCF 寿命的影响。提出了一种考虑到应力三轴效应的各向异性损伤模型。结果表明，传统的应力-应变变量无法反映不同几何缺口 DD6 试样的 CCF 寿命趋势，而 CCF 载荷峰值处的应力三轴性却可以。根据加载峰值时的应力三轴度，引入了一个修正的 Basquin 模型来预测 CCF 的寿命。该模型能准确有效地估算两种缺口 DD6 板试样的 CCF 寿命，且寿命预测结果在疲劳寿命±3 倍的散布带内。

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来源期刊

International Journal of Fatigue 工程技术-材料科学：综合

CiteScore

10.70

自引率

21.70%

发文量

619

审稿时长

58 days

期刊介绍： Typical subjects discussed in International Journal of Fatigue address: Novel fatigue testing and characterization methods (new kinds of fatigue tests, critical evaluation of existing methods, in situ measurement of fatigue degradation, non-contact field measurements) Multiaxial fatigue and complex loading effects of materials and structures, exploring state-of-the-art concepts in degradation under cyclic loading Fatigue in the very high cycle regime, including failure mode transitions from surface to subsurface, effects of surface treatment, processing, and loading conditions Modeling (including degradation processes and related driving forces, multiscale/multi-resolution methods, computational hierarchical and concurrent methods for coupled component and material responses, novel methods for notch root analysis, fracture mechanics, damage mechanics, crack growth kinetics, life prediction and durability, and prediction of stochastic fatigue behavior reflecting microstructure and service conditions) Models for early stages of fatigue crack formation and growth that explicitly consider microstructure and relevant materials science aspects Understanding the influence or manufacturing and processing route on fatigue degradation, and embedding this understanding in more predictive schemes for mitigation and design against fatigue Prognosis and damage state awareness (including sensors, monitoring, methodology, interactive control, accelerated methods, data interpretation) Applications of technologies associated with fatigue and their implications for structural integrity and reliability. This includes issues related to design, operation and maintenance, i.e., life cycle engineering Smart materials and structures that can sense and mitigate fatigue degradation Fatigue of devices and structures at small scales, including effects of process route and surfaces/interfaces.