Stochastic fatigue of structural steel at a hole
Lutes, Loren D.
Master of Science
Nine steel specimens, each containing a small hole have been tested under three sets of variable amplitude loadings to determine the effect of amplitude variability on fatigue life. Twenty-three constant amplitude tests have also been run at basically four different combinations of mean stress and stress range to determine the S-N curve and to check the variable amplitude test results against a commonly used analytical technique--the Rayleigh approximation. The analytical prediction is based on an S-N curve corrected for the effect of mean stress. The specimens consist of hot rolled A36 Grade 81A steel bar stock of dimension 0.75 inch by 1.50 inch. The loading gives a uniform bending moment about the axis of minimum moment of inertia and the small central hole is orthogonal to this axis. The stochastic loadings used in this study are so-called pseudo-narrowband loadings. The loadings vary from broadband to extremely narrowband. (Abstract shortened with permission of author.)