Volume 3, Issue 6 (November 1975)
An Analysis of the Influence of Mean Stress Intensity and Environment on Fatigue Crack Growth in a New High Strength Aluminum Alloy
The effects of the mean stress intensity factor Km and the range of the stress intensity ΔK on fatigue crack propagation during wholly tensile loading cycles in the aluminum (Al) alloy RR58 in laboratory air and in a 3.5% NaCl solution have been studied using contoured double-cantilever beam specimens. In general the fatigue crack growth rate in NaCl solution was greater than in air under similar conditions except for tests in which high values of the maximum stress intensity factor were used when no significant difference was observed.
Based on the experimental data a relation between the cyclic crack growth rate da/dN and the tensile loading levels has been proposed. The threshold value of ΔK, ΔKth, is approximately 12% higher in air than in the 3.5% NaCl solution, and its value decreases linearly with increasing values of Km.