Abstract
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 anti-fatigue 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, three-dimensional 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.
Highlights
Stress concentration around the edge of a hole in an aircraft structural joint is known to facilitate fatigue cracking,[1,2] and most aircraft accidents have been found to be due to fatigue failure.[3]
The above-mentioned works only considered the effect of cold expansion and bolt clamping, or cold expansion and chamfering on fatigue-life enhancement, and not a combination of all three processes, namely, chamfering, cold expansion, and bolt clamping. Building on these previous studies, this study explored methods for enhancing the anti-fatigue effect in a single plate by combining cold expansion, bolt clamping, and chamfering
The circumferential residual stress distributions on the middle plane (see Figure 11(b)) of all the CE specimens (C, non-C, BC, and non-BC) are similar. This indicates that the residual stress distribution in the middle region of the hole edge is mainly determined by cold expansion rather than chamfering or bolt clamping
Summary
Stress concentration around the edge of a hole in an aircraft structural joint is known to facilitate fatigue cracking,[1,2] and most aircraft accidents have been found to be due to fatigue failure.[3] the fatigue-life improvement of structural joints is an important subject for aircraft designers. Various techniques are used in the aircraft industry to improve the fatigue behavior of joints, such as cold expansion,[4] shot peening,[5] laser shock,[6] and interference fitting.[7] Cold expansion is the most commonly used method owing to its convenience and low cost. The process involves the insertion of an oversized mandrel into the joint hole and pulling it out from the other.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
