Fatigue process zone at notches

Fatigue macrocrack initiation is considered to be a two-parameter process. It is governed by the local stress range and a certain linear parameter of the material, the process (prefracture) zone size, d*. The value of d* determines the fatigue stress concentration factor, K-f, and quantitative criterion, a(i) = d*, for the micro- to macrocrack transition. The experimental and calculational methods for parameter d* estimation are analyzed. The value of K-f for the beam and CT specimens based on the author's approach and calculated by the well-known equations of Neuber and Peterson are compared. (C) 2001 Elsevier Science Ltd. All rights reserved.