This conference paper was submitted for presentation at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

The load carrying structure of modern railway coaches is designed using aluminium profiles in case of passenger coaches or mainly steel plates in case of freight waggons. Both structures are fabricated by welding the parts together leading to a large number of welds which have to withstand the imposed loads. The actual paper will focus on a code conforming fatigue assessment of the structures. Although most of the welds used are full penetration seam welds fillet welds have to be used in some areas and would be beneficial for cost savings. Accordingly, the use of fillet welds and especially one-sided fillet welds and their assessment is of large economical interest. There is a commonly used practical rule for fillet welds using a weld thickness a of 0.7-times the sheet thickness t. Accordingly, the stresses in the weld are higher than in the sheet. An efficient FE modelling scenario however does not model each weld with the according thickness in a design phase. In addition, a fillet weld, is subjected to a local bending load when a global tension load is applied to the attached sheet of a T-joint connection. This bending moment, caused by the eccentricity of the weld to the joint induces additional stresses to the weld which have to be taken into account for a fatigue prediction. Therefore, correct weld stresses in fillet welds have to be calculated in a postprocessing step taking into account the reduced cross-section and the additional bending. The realistic effect of the additional bending of the weld depends on the actual geometric circumstances. The effect will be low when welding a tube with a small diameter onto flat plate since local bending is suppressed by the curvature. On the other hand, the bending will be significant when a flat plate is welded onto a flat sheet or in case of a large rectangular tube on a flat plate. The influence of the local bending will be shown for these examples. A modelling and postprocessing procedure automatically generating the welds (from parts or part properties) and assessing those welds according to Eurocode and or DVS1612 and DVS1608 respectively will be presented for an aluminium passenger coach and a steel freight wagon.