TWI Frequently asked questions
Fusion welding generates severe mechanical loading near the melt pool. This zone is plastically deformed during welding causing large, tensile residual stresses after welding. This means that stresses near welds usually remaintensile during the application of in-service loads. Cyclic stresses near welds can therefore be fully damaging even if part of the cycle is compressive. Fatigue failure assessment should therefore use the stress range calculated fromthe lowest minimum and the highest maximum stresses caused by the applied cyclic loads.
For fracture assessments, the assumed level of residual stress (for the calculation of crack loading) can be calculated using the methods given in BS 7910 : 2005 ('Guide to methods for assessing the acceptability of flaws inmetallic structures').
