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Low-Cycle Fatigue Behavior of Fiber-Laser Welded, Corrosion-Resistant, High-Strength Low Alloy Sheet Steel

Published

Author(s)

Jeffrey W. Sowards, Erik A. Pfeif, Matthew J. Connolly, Joseph D. McColskey, Stephanie L. Miller, Brian J. Simonds, James R. Fekete

Abstract

Incorporation of high-strength steels into ground vehicles provides a weight-savings advantage by using thinner sections of material, which increases vehicle efficiency. Advanced welding techniques such as fiber laser welding are a potential method for joining the high-strength steels that can greatly increase productivity. However, weld fatigue is also a primary design consideration for implementation of laser-welded sheet. Much of the previous fatigue work on fiber laser welded sheet steel has focused on stress-controlled fatigue testing. Therefore, this paper presents an optimized fiber laser welding procedure for butt welds of high-strength low-alloy steel sheet, and subsequent fully-reversed, strain-controlled low-cycle fatigue testing on weld material. Existing low cycle fatigue models adequately describe fatigue behavior of the laser welds. The results show that weld low cycle fatigue strength is significantly increased relative to base metal due to formation of martensite in the weld caused by rapid cooling inherent to laser welding. Weld fatigue life was shorter than base metal when plastic strains were high, but were close to base metal at lower plastic strains. Fatigue specimens containing weld failed at both base metal and in the weld indicating that there is some competition between weld cyclic fatigue strength and stress concentration effect at the weld fusion zone.
Citation
Materials and Design
Volume
121
Issue
5

Keywords

fiber laser beam welding, high strength low alloy steel, low cycle fatigue, microstructure- property relationships, residual stress, sheet steel
Created February 21, 2017, Updated November 10, 2018