A novel method to improve fatigue behaviors of holed structures based on electromagnetic force

Abstract

In this study, a novel method stress wave strengthening (SWS) process based on electromagnetic force was proposed to improve the fatigue life of holed structures. Corresponding tests were carried out to explore the fatigue performance of SWS. Cold expansion (CE) was also investigated for comparison. The fatigue life of SWS and CE samples were evaluated, moreover, the mechanisms of fatigue failures and life enhancements were also discussed. Results showed that double-side SWS extended fatigue life significantly and reduced stiffness degradation more effectively with respect to CE process. Moreover, fatigue cracks commonly appeared at mid-planes of hole surfaces and horizontally grew in SWS samples, which differed a lot from CE samples. Through the residual stress measurement, it is seen that more uniform residual stress along axial direction can be obtained by SWS compared to CE, which can explain the fatigue life enhancement and failure mechanism of SWS method.

Investigation on fatigue performance of open‐hole plates treated by dynamic cold expansion under large expansion size based on electromagnetic loading

“…Several novel processes, which are based on the traditional CE process, were reported in literatures, such as electromagnetic CE, [27][28][29][30] symmetric CE, 31,32 friction stir expansion, 33 ultrasonic impact assistant expansion, 34 and stress wave strengthening. 35 Although these processes can achieve more uniform compressive residual stress and prolong fatigue life compared to the traditional CE process, yet they need more complex tools or procedures, thereby causing more time and cost. Hence, it is more efficient to improve the CE process itself without adding any other tools or procedures.…”

Modified Split Mandrel Method and Equipment to Improve the Fatigue Performance of Structural Components with Fastener Holes

“…In the last few years, various dynamic hole cold working methods have been presented, which have a common technical basis: an electromagnetic load. They implement two concepts: mechanical cold working methods based on electromagnetic driving [17,18] and a non-contact electromagnetic cold hole expansion process based on radial pulsed electromagnetic force [19,20]. For example, Guo et al [17] proposed a novel dynamic cold expansion method using the mandrel driven by a driving head through the electromagnetic dynamic force.…”

“…Their method reduces expansion resistance, generates more uniform hole diameter distribution along the hole axial direction after cold expansion, and exhibits higher fatigue life compared to static mandrel coldworking. Additionally, Guo et al [18] proposed a novel stress wave strengthening method based on electromagnetic force to improve the fatigue life of plate-holed structures. Their double-side stress wave strengthening method extended the fatigue life of 6061-T6 aluminum alloy holed-plate samples compared to cold expansion, while their single-side stress wave strengthening exhibited lower fatigue life than cold expansion.…”