Effect of tool pre-heating on the fatigue behavior of lubricant-free additive friction stir deposition repairs of AA7050 aircraft fastener holes

IF 6.8 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue Pub Date : 2025-09-08 DOI:10.1016/j.ijfatigue.2025.109272

I.Y. Hidalgo , V.A. Rojas , N.I. Palya , N. Zhu , L.N. Brewer , G.W. Kubacki , P.G. Allison , J.B. Jordon

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Abstract

This study demonstrates the successful repair of fastener holes in AA7050-T7451 plates using twin-rod additive friction stir deposition (TR-AFSD), a solid-state additive manufacturing technology. Oversized holes surrounded by blend-out regions, simulating the removal of corrosion-damaged areas that are commonly found around fastener holes, were repaired via TR-AFSD using the same AA7050 feedstock materials without any pre-sprayed graphite lubricant. Two repair strategies were evaluated: Repair Methodology A (RM-A), where the tool directly engages the substrate, and Repair Methodology B (RM-B), which incorporates a preheating dwell on a sacrificial plate to enable instantaneous material flow upon deposition. RM-B reached the peak axial forge force (26.16 kN) faster than RM-A, thereby enhancing volumetric filling and densification. Optical and electron microscopy revealed defect-free, metallurgically bonded interfaces, while cross-sectional hardness profiles showed no significant differences between the two repair methodologies. Under tension–tension (R = 0.1) fatigue loading at a 25 MPa constant stress amplitude, samples repaired with RM-B achieved an average fatigue life of 27,918 ± 2,817 cycles, compared to 24,800 ± 1,766 cycles for unrepaired, oversized controls. These results highlight the novelty and effectiveness of TR-AFSD in restoring structural integrity and improving fatigue resistance in aerospace-grade aluminum components.

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刀具预热对无润滑油添加剂搅拌摩擦沉积修复AA7050飞机紧固件孔疲劳行为的影响

本研究展示了采用双棒添加剂搅拌摩擦沉积（TR-AFSD）这一固态增材制造技术成功修复AA7050-T7451板的紧固件孔。通过TR-AFSD，使用相同的AA7050原料进行修复，无需预喷涂石墨润滑剂，通过混合区域包围的超大孔，模拟了紧固件孔周围常见的腐蚀损坏区域的去除。研究人员评估了两种修复策略：修复方法A (RM-A)，工具直接与基板接合；修复方法B (RM-B)，在牺牲板上安装预热装置，以实现沉积时的瞬时材料流动。RM-B比RM-A更快达到峰值轴向锻造力（26.16 kN），从而增强了体积填充和致密化。光学和电子显微镜显示无缺陷，冶金结合界面，而横截面硬度剖面显示两种修复方法之间没有显着差异。在25 MPa恒定应力幅下的拉伸-拉伸（R = 0.1）疲劳载荷下，使用RM-B修复的样品的平均疲劳寿命为27,918±2,817次，而未修复的超大尺寸对照组的平均疲劳寿命为24,800±1,766次。这些结果突出了TR-AFSD在恢复航空级铝部件结构完整性和提高抗疲劳性方面的新颖性和有效性。

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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.