The Influence of Yield Strength and Fracture Toughness on Fatigue Design Procedures for Structural Steels

摘要

The failure of welded structures by fatigue can be viewed as crack growth between two flaw sizes forming fixed boundary conditions. The initial condition is a rapidly initiated or pre-existing flaw, and the terminal condition is the critical flaw at failure. This report outlines the modes of failure and methods of analysis for fatigue design for structural steels ranging in yield strength from 30 to 300 ksi. Fatigue crack propagation characteristics of steels seldom vary widely in response to broad changes in yield strength and fracture toughness. However, strength and toughness do vary widely among structural steels and thereby exert profound effects on the fatigue failure process. By applying the principles of the NRL Ratio Analysis Diagram, an analysis shows that the ratio of plane strain fracture toughness to yield strength can be employed to determine fatigue design procedures. (Author)