Stress concentration in T-butt joints: Effects of weld strength and loading patterns

Abstract

Understanding the behavior of stress concentration factor (SCF) due to variations in manufacturing conditions and in-service loading patterns is crucial for ensuring the integrity and preventing failure of welded joints. This study investigates the effects of weld strength and loading patterns at varying stress levels on SCF behavior in thin T-butt welded joints made from different base metal (BM) steel grades. Welding calculations were initially performed for six T-butt welded specimens under various weld strength conditions and BM steel grades to predict welding residual stress (WRS), with some results validated against measured data from the literature. A series of elastic-plastic stress analyses were then conducted to calculate the SCF under different cyclic loading patterns. The applied loading patterns included pure constant amplitude loading (CAL) and CAL combined with a single tensile overload (OL), with various stress levels applied in both patterns. The effect of WRS was also considered in the SCF calculations. The results showed that the SCF generally increased with higher CAL stress levels and decreased with higher OL stress levels for a given weld strength and BM steel grade. Furthermore, under-matching weld strength resulted in the lowest SCF, while over-matching weld strength produced the highest SCF for a specific BM steel grade and stress level. Thus, selecting the appropriate weld strength is critical for reducing SCF and minimizing the likelihood of crack initiation in T-butt welded joints subjected to cyclic loads. Additionally, residual stress redistribution was analyzed to support the findings of this study.