Influence of morphological characteristics on the mechanical properties and failure mechanisms of legacy butt welds

Abstract

This paper describes an investigation carried out to explore the relationship between the morphological characteristics, mechanical properties, and failure modes of legacy butt welds. A total of 31 tension coupons were cut out of butt-welded tubular structures which had been in service for over 50 years. Monotonic tension tests were conducted to investigate the mechanical behavior and the failure modes of the welds. A digital image correlation (DIC) system was used to monitor the strain distribution on the cut-out surface of the coupons. Results showed that morphological imperfections such as misalignment and plastically deformed regions near the welding zone reduced the capacity and ductility of the weld. Data from the DIC system revealed that fracture at the welding zone initiated from pre-existing imperfections.