It is common practice to use symmetrical (Fig. 1) or asymmetrical (Fig. 2) grooves when welding thick materials. This approach primarily helps to control distortion, balance residual stresses, and reduce weld volume. Reducing the weld volume also helps to minimize the accumulation of residual stress.

Some complexities in this design have not been addressed in any Code or Standard. This includes BS EN ISO, ASME, RCC-M, RCC-MRx, or DNV. Perhaps, this is the first time attention is to be brought to this phenomenon.

Fatigue test was conducted on an asymmetrical Double-V welds of S355N+J2 steel with a thickness greater than 60 mm. The results are presented in Fig. 3.

The test showed that failure consistently occurred on the side with the widest capping weld beads, irrespective of how the grooves were made. In other words, under fatigue conditions, the likelihood of failure is highest at the weld toe on the side with the largest capping width.

If this is the case, welds can be designed with this widest side positioned for easy Non-Destructive Testing (NDT). This involves placing this side on the exterior of any component.

During in-service inspections, inspection time can be significantly reduced by focusing only on this part of the weld. In urgent situations, examining just this side may be sufficient to confirm the continued integrity of the structure or component.

Welding process – SAW (121)