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Background <p>Structural failures in aircraft subsystems often originate from fatigue-induced crack initiation at stress concentration zones. In this study, the root cause of crack development in the attachment fitting of the oil cooler assembly of a trainer aircraft was investigated, with a focus on developing effective mitigation strategies.</p> Objectives <p>The aim was to identify mechanisms driving crack initiation and propagation in A356 aluminum alloy under operational loading and to propose design modifications that enhance fatigue life and reliability.</p> Methods <p>A combination of experimental and numerical approaches was employed. Fractographic analysis was used to characterize crack morphology and initiation sites. Shaker table testing was conducted to simulate operational vibratory loads, while Finite Element (FE) analysis was performed to evaluate stress distribution and dynamic response. Fatigue life prediction was carried out using Power Spectral Density (PSD)-based inputs.</p> Results <p>Fatigue striations were identified near flange edges and bolted joints, confirming stress concentration as the primary source of crack initiation. Resonance frequencies at 71.5 Hz, 251.6 Hz, and 1720 Hz were found to produce peak vibratory stress amplification. Fatigue life estimation indicated crack initiation at ~352.7 hours. Incorporation of structural damping significantly reduced stress amplitudes, extending the fatigue life by 57%, to approximately 832.4 hours.</p> Conclusion <p>The integrated experimental–computational framework provided a comprehensive understanding of fatigue mechanisms in the oil cooler assembly. The proposed damping-based mitigation approach successfully improved fatigue resistance, contributing to safer and more reliable aerospace components.</p>

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Failure Analysis and Vibration-Induced Fatigue Mitigation in a Trainer Aircraft Oil Cooler Assembly

  • 期刊论文

  • 发表日期：

    2025年8月29日

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  • Jasir Adnan,
  • Haris Ali Khan,
  • Ehsan Ahmad,
  • Taimur Ali Shams,
  • Hammad Akhtar

摘要

Background

Structural failures in aircraft subsystems often originate from fatigue-induced crack initiation at stress concentration zones. In this study, the root cause of crack development in the attachment fitting of the oil cooler assembly of a trainer aircraft was investigated, with a focus on developing effective mitigation strategies.

Objectives

The aim was to identify mechanisms driving crack initiation and propagation in A356 aluminum alloy under operational loading and to propose design modifications that enhance fatigue life and reliability.

Methods

A combination of experimental and numerical approaches was employed. Fractographic analysis was used to characterize crack morphology and initiation sites. Shaker table testing was conducted to simulate operational vibratory loads, while Finite Element (FE) analysis was performed to evaluate stress distribution and dynamic response. Fatigue life prediction was carried out using Power Spectral Density (PSD)-based inputs.

Results

Fatigue striations were identified near flange edges and bolted joints, confirming stress concentration as the primary source of crack initiation. Resonance frequencies at 71.5 Hz, 251.6 Hz, and 1720 Hz were found to produce peak vibratory stress amplification. Fatigue life estimation indicated crack initiation at ~352.7 hours. Incorporation of structural damping significantly reduced stress amplitudes, extending the fatigue life by 57%, to approximately 832.4 hours.

Conclusion

The integrated experimental–computational framework provided a comprehensive understanding of fatigue mechanisms in the oil cooler assembly. The proposed damping-based mitigation approach successfully improved fatigue resistance, contributing to safer and more reliable aerospace components.