High temperature fatigue crack growth in two metals under constant and variable amplitude loading

Results are presented for fatigue crack growth at elevated temperatures during both constant amplitude and variable amplitude loading. A careful experimental investigation is presented to show that the concept of the effective stress-intensity factor range ΔKIeff can be used to eliminate the load ratio effect on fatigue data and produce one single set of crack growth data. The fatigue crack propagation data corrected for crack closure is then used for comparison of mean crack propagation rates for variable amplitude loads with simple time histories. It is concluded that measured crack closure can not fully explain the discrepancies between measured and predicted propagation rates. A reduction factor fitted to the experimental data could be used to successfully correlate the results.