Mechanisms of fatigue crack growth in 7050-T6 aluminium alloy

IF 6.8 2区材料科学 Q1 ENGINEERING, MECHANICAL International Journal of Fatigue Pub Date : 2025-05-01 Epub Date: 2025-01-21 DOI:10.1016/j.ijfatigue.2025.108830

L.P. Borrego , J.S. Jesus , R. Branco , J.A.M. Ferreira , F.V. Antunes , D.M. Neto , E.R. Sérgio

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Abstract

Fatigue crack growth (FCG) is usually associated with cyclic plastic deformation at the crack tip. However, this damage mechanism loses dominance for relatively low stress intensity factor ranges (ΔK), and a lower boundary must be considered in numerical modelling. So far, the definition of this lower boundary and its variation with the stress ratio remain unclear This paper studies FCG in CT specimens made of 7050-T6 aluminium alloy, submitted to different load ratios. A multi-linear behavior was observed in Paris law regime, independently of stress ratio. SEM analysis showed that ductile striations are observed at high ΔK, while at low ΔK a cleavage mechanism is observed. A numerical analysis was developed, assuming the dominance of cyclic plastic deformation, which overestimated the experimental results obtained for low ΔK. The comparison of the size of cyclic plastic zone, r_pc, with the grain size, ρ, indicated that plastic deformation loses dominance when r_pc < ρ.

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7050-T6铝合金疲劳裂纹扩展机理

疲劳裂纹扩展（FCG）通常与裂纹尖端的循环塑性变形有关。然而，这种损伤机制在相对较低的应力强度因子范围内失去优势（ΔK），在数值模拟中必须考虑较低的边界。本文研究7050-T6铝合金CT试样在不同载荷比下的FCG。在巴黎法律制度下观察到多线性行为，独立于应力比。SEM分析表明，在高ΔK处出现韧性条纹，在低ΔK处出现解理机制。在假设循环塑性变形占主导地位的情况下，进行了数值分析，高估了低ΔK时的实验结果。循环塑性区尺寸rpc与晶粒尺寸ρ的比较表明，当rpc <时，塑性变形失去主导地位；ρ。

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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.