Fatigue propagation behavior of multiple internal defects in 6082-T6 aluminum alloy joints: Experiments and numerical simulation

IF 6.8 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue Pub Date : 2025-07-27 DOI:10.1016/j.ijfatigue.2025.109202

Hongliang Qian , Zhihao Chen , Yankai Wang , Yong Liu , Ping Wang

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Abstract

Incomplete fusion defects within aluminum alloy joints formed during welding exhibit a multi-defect distribution, significantly affecting the fatigue behavior of the joints. This study systematically investigates the propagation behavior of single defect, the coalescence mechanism of coplanar defects, and the suppression effect of non-coplanar defects using FRANC3D, with a particular focus on the effects of defect shape, size, and spacing. The results indicate that internal defects evolve into a circular shape during cyclic loading. Defect coalescence accelerates crack propagation in the depth direction and shortens the fatigue life, as confirmed by microstructure analysis of the fracture surface. For coplanar defects with fixed spacing (s = 1 mm) and the size of defect 2 (a₂ = 0.5 mm), variations in the size of defect 1 do not alter the life distribution across different stages, with the life proportions spent in the pre-coalescence, coalescence, and post-coalescence being 65 %, 13 %, and 22 %, respectively. The suppression effect of non-coplanar defects results in a 20 % increase in fatigue life compared to larger single defect, although it remains lower than that of a smaller single defect.

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6082-T6铝合金接头多内部缺陷疲劳扩展行为：试验与数值模拟

铝合金接头在焊接过程中形成的不完全熔合缺陷呈多缺陷分布，严重影响接头的疲劳行为。本研究利用FRANC3D系统地研究了单个缺陷的传播行为、共面缺陷的聚结机制以及非共面缺陷的抑制效果，重点研究了缺陷形状、尺寸和间距的影响。结果表明：在循环加载过程中，内部缺陷演化为圆形；断口组织分析表明，缺陷合并加速了裂纹在深度方向的扩展，缩短了疲劳寿命。对于固定间距（s = 1 mm）和缺陷2尺寸（a2 = 0.5 mm）的共面缺陷，缺陷1尺寸的变化不会改变其在不同阶段的寿命分布，其在聚结前、聚结和聚结后的寿命比例分别为65%、13%和22%。与较大的单一缺陷相比，非共面缺陷的抑制作用使疲劳寿命提高了20%，但仍低于较小的单一缺陷。

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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.