Fatigue life extension of existing welded structures via high frequency mechanical impact (HFMI) treatment
Journal article, 2021

High-Frequency Mechanical Impact (HFMI) is one of the post-weld treatment methods. In this study, comparative axial fatigue tests were conducted on as-welded and HFMI-treated welded transverse attachment details. The test results demonstrated the efficiency of HFMI-treatment in fatigue life extension of cracked welded structures, providing that the existing crack size is less than 1.2 mm. Cracks were created in some specimens through fatigue testing before HFMI-treatment, while other specimens were not subjected to any fatigue loading prior to treatment. Many of the treated specimens ran out after 10 million cycles of loading when tested at a stress range of 150 MPa. Therefore, the stress range was increased to 180 MPa or 210 MPa. No remarkable difference was found between the fatigue strength of the crack-free and the cracked treated specimens. It was found that the induced compressive residual stress can exceed the material yield limit, and reach a depth larger than 1.5 mm in most cases. The induced compressive residual stress, the local material hardening, the increase in weld toe radius, the change in crack orientation and the shallowness of the crack size were the causatives of the obtained long fatigue lives of the HFMI-treated specimens. Besides, linear elastic fracture mechanics calculations were conducted to predict the fatigue lives of as-welded and HFMI-treated details. The results were in agreement with the experiment. Moreover, the calculations showed that the initial crack size, the clamping stress and the induced compressive residual stress were the main factors behind the scatter in fatigue lives.

Steel bridges

Existing structures

Fatigue life extension

High frequency mechanical impact

Pre-fatigue

Crack repair

Author

Hassan al-Karawi

Chalmers, Architecture and Civil Engineering, Structural Engineering

Rüdiger Ulrich Franz von Bock und Polach

Technical University of Hamburg (TUHH)

Mohammad al-Emrani

Chalmers, Architecture and Civil Engineering, Structural Engineering

Engineering Structures

01410296 (ISSN) 18737323 (eISSN)

Vol. 239 112234

LifeExt - Livslängdsförlängning för befintliga stålbroar

Swedish Transport Administration (TRV 2018/27547), 2018-05-15 -- 2020-11-30.

VINNOVA (2017-02670), 2017-06-08 -- 2019-12-31.

Driving Forces

Sustainable development

Areas of Advance

Building Futures (2010-2018)

Life Science Engineering (2010-2018)

Materials Science

Subject Categories

Construction Management

Infrastructure Engineering

Building Technologies

DOI

10.1016/j.engstruct.2021.112234

More information

Latest update

7/8/2021 9