1997 Volume 37 Issue 12 Pages 1245-1250
The effect of the relative humidity of the laboratory air on the fatigue crack growth rate in 8090 Al-Li alloys has been examined. The constant ΔK fatigue crack growth tests under programmed humidity cycle conditions were carried out to quantify the extent of the increase in fatigue crack growth rates due to the relative humidity. The obtained results are compared to the da/dN-ΔK relationships obtained from the constant amplitude dynamic load fatigue crack growth tests. It was found that the intrinsic fatigue crack growth rate increase with the relative humidity, but the extent of the increase was found to be considerably small compared to the growth rate difference between the laboratory air and vacuum conditions. The constant ΔK test at a high stress ratio under programmed humidity cycle conditions was effective for detecting the relatively small humidity effect on the fatigue crack growth rate.