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

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 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.

Fatigue response of open hole plates: A finite element simulation investigating the influence of dynamic and static cold expansion processes

“…Additionally, simulation enables the identification of optimal process parameters that yield higher compressive residual stresses and longer fatigue lifetimes. The numerical estimation of fatigue behavior in CE specimens primarily involves two aspects: fatigue crack initiation [26][27][28] and fatigue crack propagation [29][30][31] lifetimes. Regarding fatigue life estimation, there are two common approaches: direct prediction of the total life [32][33][34] or separate prediction of fatigue crack initiation life and propagation life [35][36].…”

Residual stress distribution and fatigue performance investigations of electromagnetic force-based dynamic cold expansion open-holed sheet

“…[16][17][18] Many research studies have proved that CE process can enhance fatigue life for various materials and structures under external cyclic loading. For instance, fatigue life of several types of aluminum alloy structures such as open holes, 19,20 bolted holes, 21,22 double-lap bolted joints, [23][24][25] and bonded joints 26 can be extended by CE process. Holed structures made of other materials such as magnesium alloy, 27 titanium alloy, 28,29 steel, 30 and even composites 31 can also gain some life increments treated by CE method.…”

Research on the Flow-Induced Stress Characteristics of Head-Cover Bolts of a Pump-Turbine during Turbine Start-Up

“…They obtained the stress history of the bolts by acquiring the power generation history for one year and estimated the fatigue life of the bolts based on the accumulated damage [7]. Huang et al used the Smith-Watson-Topper method to predict the fatigue life of a bolt [10]. By calculating the S-N curves under different preloads, Shahani and Shakeri researched the influence of preload on the stress distribution of bolts [11].…”