Fatigue Life Estimation of Ultrasonic Impact Treated Welds Using a Local Strain Approach

摘要

It is commonly observed that complex fabricated structures subject to fatigue loading faii at the welded connections. Some problems can be corrected by improved detail design but fatigue performance can also be improved using post-weld improvement methods. Ultrasonic impact treatment (UIT) is a relatively new and efficient post-weld improvement method. The current study presents experimental fatigue strength data of non-load carrying attachments in the as-welded and UIT treated condition. Treated welds were found to have about 50 percent greater fatigue strength. This improvement in strength has been modelled using the local strain approach. Material parameters in the highly cold-worked UIT treated zone have been derived using the Uniform Material Law for fatigue analysis. The stress concentration was computed using FE analysis and mean stress estimates were based on X-ray diffraction measurements of the residual stress state in the treated zone. The predicted degree of improvement was in excellent agreement with the experimentally measured improvement.