Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Proposal on a practical numerical simulation technique of HFMI treatment for welded joints
Peiyuan Dai1, Phyo Myat Kyaw1, Donghui Ma3, Jun Okada3, Masahito Honnami3 ,Sherif Rashed2, Naoki Osawa1,
1. Department of Naval Architecture & Ocean Engineering, Osaka University, Suita, Osaka, Japan
2. CAE Lab, Nishinomiya, Hyogo, Japan
3. Technical Research Institute, Hitachi Zosen Corporation, Taisho, Osaka, Japan

ABSTRACTand Khurshid, Leitner, Barsoum & Scheider (2017) investigated theinfluence of the FE mesh, hardening model and various peening
parameter, namely impact velocity, contact force and permanent
indentation depth, on stress induced by HFMI treatment. Two types ofsimulations, displacement controlled (DC) simulations and force
controlled (FC) simulations were used and compared in their work.
Ruiz, Osawa & Rashed (2020) and Schubnell, Carl, Farajian,Gkatzogiannis, Knödel, Ummenhofer, Wimpory & Eslami (2020)
focused on the stability of RS in HFMI treated welded joints undercyclic loading. They studied the relaxation behavior of HFMI-induced
RS by a 3-step simulation including welding, HFMI and under externalload. The validation was carried out by comparing simulated RS with
X-ray and neutron diffraction measurements.

This study proposes a numerical simulation system for the highfrequency mechanical impact (HFMI) treatment that can consider thewelding residual stresses (RS). The validity of the HFMI simulation
process is examined by a HFMI-treated flat plate. Then, theeffectiveness of the proposed simulation system is demonstrated byusing a gusset welded joint model. A stress interpolation code isemployed to transfer welding RS data from coarse mesh to fine mesh as
initial load of HFMI analysis. The proposed calculation systemfacilitates the accurate estimation of RS after HFMI treatment by
allowing the consideration of welding RS through the interpolation
process.

An analytical framework for HFMI simulations has been established in
the research works mentioned before. However, it has so far been achallenge to develop a practical numerical analysis system forestimating HFMI-induced RS in welded structures with the balance ofcomputational efficiency and accuracy. Numerical simulation of HFMI
treated joints is usually divided into two steps. The welding simulation
is firstly performed using thermal elastic-plastic finite element method(TEP-FEM), and then explicit dynamic FEA of HFMI treatment iscarried out considering initial load of welding RS obtained by thewelding analysis. To facilitate the transfer of stress distribution between
these two steps, many researchers (Yuan & Sumi, 2016; Leitner,Khurshid & Barsoum, 2017; Ruiz, Osawa & Rashed, 2020; Schubnell,Carl, Farajian, Gkatzogiannis, Knödel, Ummenhofer, Wimpory & Eslami,2020; Tang, L, Ince, A & Zheng, J , 2020; Hanji, Tateishi, Kano &Shimizu, 2021) have adopted the strategy in which same finite element(FE) mesh is applied in both welding and HFMI simulation processes.
For welding analysis, sufficient agreement between simulations andexperiments can be achieved by using a FE mesh with element lengthof 1 mm at welds and heat affected zone (Deng, Kiyoshima, Ogawa,Yanagida & Saito , 2011; Deng, Zhang, Pu & Liang, 2017). However,HFMI simulation requires a finer mesh because the HFMI-induced RS
has more drastic local variation in treated zone compared to thewelding RS. The ratio of element size in the treated region / pin tip
radius should be less than 0.1 (Ruiz, Osawa & Rashed, 2019), forexample, pin with 1.5 mm radius tip and the element size less than
0.15×0.15×0.15 mm. Applying such ultra-fine mesh in welding
analysis results in unnecessary waste of computing resources,

KEYWORDS: HFMI simulation; Welded joints; Stress interpolation;
Residual stress.

INTRODUCTION
Welding is a crucial thermal processing, widely used in shipbuilding
and offshore industries. However, welding residual stresses (RS), flaws
and other weld defects often occur during fabrication and reduce thefatigue performance of welded structures. Post-weld treatments such as
high-frequency mechanical impact (HFMI) treatment has exhibitedstrong potential for improving the fatigue strength of welded joints. The
beneficial effect of HFMI treatment is primarily based on introductionof compressive RS, improvement of the local work hardening andreducing notch effect at the weld toe (Marquis and Barsoum, 2016). To
estimate the fatigue life of HFMI treated structures, it is necessary to
numerically investigate the RS field in HFMI treated welded joints.
Some basic research involving numerical simulation of HFMI treatment
has been studied by researchers in the last decade. Baptista, Infante &Branco (2011) proposed a fully dynamic analysis process of thehammer peening techniques on a welded joint. The hammering
simulation was performed by explicit finite element analysis (FEA)
program, considering the Chaboche Kinematic-hardening material
model and different peening parameter which are experimentally
determined. This fully dynamic model shows higher efficiency thanpreviously static one, allowing for more complex and closer to realcomponent simulation. Foehrenbach, Hardenacke & Farajian (2016)

2990