Notch Fatigue Strengths of Several High-Strength Low-Alloy Sheet Steels

Most structural components contain geometric discontinuities or notches. Over the years, several approximate methods have been developed to relate the remote stress (S) to the local stress (σ) and the local strain (ɛ) under conditions of localized plastic yielding during fatigue. Recently, the author has developed a new method of computing the fatigue strength reduction factor (K_f) in the presence of a notch [10]. The method estimates the notch root stresses from strain controlled fatigue data for any given life. The present paper illustrates the application of this technique by presenting data for several HSLA steels. In particular, the data are presented for hot rolled, dual phase, and galvanized sheet steels. It is shown that the K_f values are a function of life level and that this functional dependence is specific to the steel. Practical implications of these data in materials substitution programs are illustrated by calculating the potential thickness reductions when using HSLA steels for fatigue critical applications.