Nondestructive Monitoring of Stress Relaxation in Welded Steel Plates

This study investigates transverse stress relaxation in welded steel plates. Two different methods of stress measurement were used; strain gages and critically refracted longitudinal $LCR$ waves. The material investigated was ASTM 1008/1010 steel. T-shaped slots were cut from each edge of each specimen in order to provide a uniaxial tension stress field in the area of investigation. After the plates were stress-relieved by annealing, the transverse slots were then welded and allowed to cool. Strain gages were applied to the bridge area joining the middle of the plate and oriented parallel to the long side of the plate. Initial strain gage and ultrasonic measurements were then performed. At different time intervals, cutting through a sample plate’s welds relieved the stresses. Strain gage and ultrasonic measurements were then repeated. Both the strain gage and $LCR$ methods indicate that there is a measurable stress relaxation in the plates, and that it occurs in a time-dependent and predictable manner.