Influence of Plate Geometry on the Welding Residual Stresses from Submerged Arc Welding in Offshore Steel Structures

In the offshore wind industry, welding-induced distortion and tensile residual stresses have become a major concern in relation to the structural integrity of a welded structure. Particularly, the continuous increase in size of welded plates and joints needs special attention concerning welding induced residual stresses.

These stresses have a negative impact on the integrity of the welded joint as they promote distortion, reduce fatigue life, and contribute to the stress corrosion cracking and brittle fracture in the weld components. This paper deals with the influence of plate thickness and plate geometry on the welding induced residual stresses from submerged arc welding.

It also investigates whether the assumption of residual stresses up to yield strength magnitude is valid in welded structures as stated in the Eurocode 3, DNV and IIW design guidelines. Submerged arc welding (SAW) is used to make a fully penetrated butt weld in 10 mm, 40 mm, and 50 mm thick steel plates with both circular hollow section and flat plate geometry.

The base material is thermomechanically hot-rolled low-carbon fine-grained S355ML steel in accordance with the European standard DS/EN 10025-4. The welding residual stress state is investigated by means of experiments, and in accordance with existing production procedures to find the magnitude of the residual stresses.

Experiments include welding and hole-drilling measurements of near-surface residual stress distribution.