The effect of cold expansion on improving the fatigue life of fastener holes

The objective of this study was to establish the effects of cold expansion, chamfering, bolt clamping, and their combinations on the fatigue life of an aluminum-lithium alloy single plate. Fatigue tests were conducted to quantify the antifatigue effects of the different techniques. A scanning electron microscope was used to perform fracture analyses of the used specimens, and the residual stresses were measured using an X-ray diffraction device. In addition, threedimensional finite element models of the specimens were established and used to characterize their stress states, and the Smith-Watson-Topper method was used to predict the fatigue lives of the specimens. The fatigue test results showed that all the considered processes improved the fatigue life of the pristine specimen. The most effective was a combination of 3.2% cold expansion, 1-mm chamfering, and bolt clamping using a 6.4-N m torque, which improved the fatigue life of the pristine specimen by a factor of 15.5. The finite element method results also revealed that this combination decreased the maximum stress and confirmed its superiority in relation to the other fatigue-life enhancement techniques in terms of the anti-fatigue effect. The Smith-Watson-Topper method underestimated the specimen fatigue life, but the accuracy satisfied engineering requirements.

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“…3 Therefore, the fatigue-life improvement of structural joints is an important subject for aircraft designers.…”

Section: Introductionmentioning

confidence: 99%

Effects of chamfering, cold expansion, bolt clamping, and their combinations on fatigue life of aluminum–lithium alloy single plate

Huang

Guan

et al. 2018

Advances in Mechanical Engineering

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“…These studies used 3% to 5% CX, where the percentage represents the amount by which the hole radius increases as the mandrel is pulled through the hole (at maximum expansion). Chakherlou and Vogwell [9] conducted an analytical and experimental study regarding CX holes. The experimental results showed a significant improvement in fatigue life of CX samples compared to as-drilled samples (generally by a factor of 10 in the number of cycles to failure).…”

Section: Introductionmentioning

confidence: 99%

Residual Stress From Cold Expansion of Fastener Holes: Measurement, Eigenstrain, and Process Finite Element Modeling

Ribeiro

Hill

2017

Journal of Engineering Materials and Technology

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Cold expansion (CX) is a material processing technique that has been widely used in the aircraft industry to enhance fatigue life of structural components containing holes. CX introduces compressive hoop residual stresses that slow crack growth near the hole edge. The objective of this paper is to predict residual stresses arising from cold expansion using two different finite element (FE) approaches, and compare the results to measurement data obtained by the contour method. The paper considers single-hole, double-hole, and triple-hole configurations with three different edge margins. The first FE approach considers process modeling, and includes elasticplastic behavior, while the second approach is based on the eigenstrain method, and includes only elastic behavior. The results obtained from the FE models are in good agreement with one another, and with measurement data, especially close to the holes, and with respect to the effect of edge margin on the residual stress distributions. The distribution of the residual stress and equivalent plastic strain around the holes is also explored, and the results are discussed in detail. The eigenstrain method was found to be very useful, providing generally accurate predictions of residual stress.

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“…According to statistics, composite laminates joint is the weakest part of the structures where 60%e80% of structure failure occurs at the fastening joints [1]. The interference fit technology of joint was proved that it can improve the fatigue life of metal structures observably [2,3], but also was pointed out by the McDonnell Douglas Corporation that interference-fit joining improved the fatigue life of carbon epoxy composites [4e6]. Interference fit joints require drilling holes and pressing into the metal pin, which causes nonuniform residual stress and damage to the joints.…”

Section: Introductionmentioning

confidence: 99%

Stress distribution modeling for interference-fit area of each individual layer around composite laminates joint

Song

Yuan

Zhang

et al. 2015

Composites Part B: Engineering

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The effect of cold expansion on improving the fatigue life of fastener holes

Cited by 165 publications

References 17 publications

Effects of chamfering, cold expansion, bolt clamping, and their combinations on fatigue life of aluminum–lithium alloy single plate

Effects of chamfering, cold expansion, bolt clamping, and their combinations on fatigue life of aluminum–lithium alloy single plate

Residual Stress From Cold Expansion of Fastener Holes: Measurement, Eigenstrain, and Process Finite Element Modeling

Stress distribution modeling for interference-fit area of each individual layer around composite laminates joint

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