Predicting Fatigue Crack Growth Rate in Welded Aluminium Alloys: Effective Stress Ratio and Crack Closure Corrections

摘要

Fatigue crack growth rates through welding residual stress fields were calculated by two approaches: a) superposition method using the effective stress ratio in empirical crack growth laws; b) crack closure approach using the effective stress intensity factor range. Finite element method is used to calculate the residual stress intensity factor and the crack opening stresses. Residual stress redistribution due to crack extension is also modelled. Both methods are validated by measured crack growth rates obtained by constant amplitude load or constant stress intensity factor range tests using M(T) specimens made of two materials (2024-T351 & 2198-T3) fabricated by two welding processes: VPPA and FSW. Results indicate that both the effective stress ratio and effective SIF range can be used for predicting crack growth rates for the configurations studied in this work.