Fatigue Life Estimates for a Notched Member in a Corrosive Environment (Corrosion)

Abstract

143 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.It is often assumed that the effects of an aggressive environment can be included in fatigue life estimation procedures by determining the material properties in the environment of interest. An analytical and experimental program was conducted to investigate this assumption. Automotive grade aluminum alloy 5454-H32 was selected for this study in laboratory air and 3% sodium chloride solution environments. A simple model where the total fatigue life is considered to be the sum of the portion where fatigue damage is best described by the notch strain field, and the portion where nominal stress and crack length dominate fatigue damage assessment, was used to estimate fatigue lives for center notched plate specimen.Smooth cylindrical specimens were employed to determine the material properties for analyzing initiation life. The environment had a large effect on the initiation resistance of this material in long life region, whereas, at shorter lives the effect was not significant. Center cracked plates were used to determine the crack growth rates. Linear elastic fracture mechanics concepts were employed to estimate crack propagation lives. Approximately a factor of three reduction in crack propagation life was attributable to corrosive environment.Center notched plate specimen with k(,t) = 2.4 and k(,t) = 5.1 were tested in both environments to examine the model. The effect of stress ratio and frequency was also investigated. The accuracy of fatigue life predictions in relation to the experimental data were comparable in 3% sodium chloride solution environment to the result obtained in air.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD