QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
Print ISSN : 0288-4771
Quantitative Assessment of Root Shape on Fatigue Strength of Welded Joint with Backing Strip
Dong Uk LeeKohsuke HorikawaYoshiaki Arata
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1988 Volume 6 Issue 1 Pages 158-164

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Abstract

It is known that stress concentration is occured at root of welded joint with backing strip by misalignment, as the misalignment causes eccentricity to load. However, it is hard to avoid misalignment in field welded joints of steel deck plate.
In this paper, fatigue behaviors were investigated on welded joints with backing strip which were fabricated by overhead position.
The stress concentration factors of various root shapes were analyzed by the finite-element method. Estimating equation from root radius and root angle was derived based upon FEM results.
The fatigue strengths for 2 million cycles were calculated from the fatigue test results, then the stress concentration factor for required fatigue strength was obtained.
The results obtained in this reports are as follows;
1. The fatigue lives of specimens with misalignment 2.0 and 3.0 mm were inferior to that of specimens without misalignment, and the fatigue life was largely decreased at misalignment 4.0 mm for manual weled and CO2 welded joints.
2. Even slag inclusion and blow hole were existed in weld metal, they did not cause crack initiation. The fatigue cracks were mainly initiated at the weld root of specimen.
3. The stress concentration factor was mostly influenced by the misalignment.
4. Whether the root shape was convex or concave, the stress concentration factor was n ainly influenced by shape of toe at base metal side.
5. The stress concentration factor can be obtained by the estimating equation, which consists of eccentricity to load and shape of toe at the base metal side.
6. The stress concentration factor to satisfy required fatigue strength was given in relation to toe radius and flank angle.

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