Fatigue performance of tungsten inert gas (TIG) and plasma welds in thin sections

The greatest potential for the use of TIG and plasma welding is in the join ing of thin sections, less than 10 mm thickness. This may introduce an addi tional benefit from the fatigue viewpoint, since fatigue strength is expect ed to increase with a decrease in plate thickness. Superior fatigue performance was confirmed for TIG and plasma transverse bu tt, cruciform and non-load carrying fillet welds of a carbon-manganese stee l, all failing from the weld toe, justifying a one class increase in Euroco de 3. Weld details, which failed by fatigue cracking in the weld throat, showed n o influence of welding process. Extensive measurements of the weld toe geometries confirmed that TIG and pl asma welds had more favourable profiles than MMA welds, with lower weld toe angles and larger weld toe radii. Fracture mechanics modelling confirmed t hat the differences in weld toe geometry were consistent with the differenc es in fatigue life actually observed. Weld toe radius appeared to be more s ignificant than weld toe angle. (C) 1999 Elsevier Science Ltd. All rights r eserved.