Study on the stability of compressive residual stress induced by high-frequency mechanical impact under cyclic loadings
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RESEARCH PAPER
Study on the stability of compressive residual stress induced by high-frequency mechanical impact under cyclic loadings with spike loads Hector Ruiz 1
&
Naoki Osawa 1 & Sherif Rashed 2
Received: 19 December 2019 / Accepted: 15 July 2020 # International Institute of Welding 2020
Abstract In this study, the residual stress simulations of the out-of-plane gusset welded joints examined by Leitner et al. (2016) in Aswelded and HFMI-treated conditions which are performed by Ruiz (2018, 2019) are reviewed and verified. Based on the reviewed simulation’s results, the changes of residual stress under constant amplitude and compressive spike loads with various stress amplitudes are simulated. Sensitivity analyses of the simulation parameters in stress response simulation are carried out, and recommendations on residual stress relaxation simulation are proposed. From the residual stress relaxation simulation results, the following are found: (1) for constant amplitude cyclic loading cases, the residual stress induced by HFMI treatment shows considerable relaxation. The longitudinal component of the residual stress shows a slight increase when the maximum stress of the cyclic loading is large, about 44.5%; (2) for spike followed by constant amplitude cyclic loading cases, the residual stress shows considerable relaxation. The degree of the relaxation becomes more significant with the increase of spike load and/or the maximum stress in the constant amplitude loading except the longitudinal stress component on the top face. The longitudinal residual stress near top face shows considerable improvement showing around 21% of increment compared with the as-peened condition. Keywords Cyclic Loading . High-frequency mechanical impact treatment . Fatigue strength improvement . Welding
1 Introduction The advantage of removing potential threats of the harmful tensile residual stresses (RS) and exploiting the beneficial compressive stresses by mechanical treatments is already known in the welding communities. A mechanical post-weld treatment such as high-frequency mechanical impact (HFMI) has been found to exhibit a significant fatigue life enhancement of welded joints. The effectiveness of HFMI treatment is primarily based on three effects: the local work hardening, Recommended for publication by Commission XIII - Fatigue of Welded Components and Structures * Hector Ruiz [email protected] 1
Department of Naval Architecture and Ocean Engineering, Osaka University, Osaka, Japan
2
Joining and Welding Research Institute, Osaka University, Osaka, Japan
introduction of compressive RS and the rounded weld toe [1–11]. A concern regarding the relaxation of the RS induced by HFMI treatment has become an important topic in welding community. Measurements by Tai [12] indicated that the compressive RS was reduced just after the first loading cycle. This was confirmed by Miyashita [13] for laser peening treatment. For variable amplitude loadings, Yildirim [14] analysed the change of RS in longitudinal stiffene
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