Transverse butt welds as fatigue critical detail of steel towers and monopiles - Influence of the geometrical notch effect on the fatigue resistance

Transverse butt welds as fatigue critical detail of steel towers and monopiles - Influence of the geometrical notch effect on the fatigue resistance. The large dimensions of wind turbines and their components become more and more challenging for the entire supply chain in the wind industry. An efficient manufacturing of components is of an increasing importance in order to withstand the cost pressure and to be competitive on the international market. Welding is the most common joining technique in heavy steel construction. Newly developed high-performance welding techniques may contribute to reduce the number of weld passes and by this the manufacturing time. These alternative welds have to show comparable or even better mechanical-technological properties than the conventionally welded seams. This paper mainly focuses on the evaluation of the fatigue resistance. Samples welded by a newly developed combination of nonvacuum electron beam and submerged arc welding are numerically and experimentally checked against conventionally submerged arc welded samples. Motivated by the question of an optimized fatigue design process as part of a serial production process for tubular tower and monopile, the weld geometry was measured. In order to ensure a wide comparability, measurement standards regarding accuracy and data processing were defined. The measured weld profiles were prepared for FE-simulations of the theoretical notch factor Kt. It is possible to predict the fatigue critical weld transition by means of the maximum Kt. Combining the test results with the statistical evaluation of the notch factors, a definite correlation between fatigue life and geometrical notch effect can be shown.