Citation:
G. Servetti, X. Zhang, Predicting fatigue crack growth rate in a welded butt
joint: The role of effective R ratio in accounting for residual stress effect,
Engineering Fracture Mechanics, Volume 76, Issue 11, July 2009, Pages 1589-1602
Abstract:
A simple and efficient method is presented in this paper for predicting fatigue
crack growth rate in welded butt joints. Three well-known empirical crack growth
laws are employed using the material constants that were obtained from the base
material coupon tests. Based on the superposition rule of the linear elastic
fracture mechanics, welding residual stress effect is accounted for by replacing
the nominal stress ratio (R) in the empirical laws by the effective stress
intensity factor ratio (Reff). The key part of the analysis process is to
calculate the stress intensity factor due to the initial residual stress field
and also the stress relaxation and redistribution due to crack growth. The
finite element method in conjunction with the modified virtual crack closure
technique was used for this analysis. Fatigue crack growth rates were then
calculated by the empirical laws and comparisons were made among these
predictions as well as against published experimental tests, which were
conducted under either constant amplitude load or constant stress intensity
factor range. Test samples were M(T) geometry made of aluminium alloy 2024-T351
with a longitudinal weld by the variable polarity plasma arc welding process.
Good agreement was achieved.