1. Fatigue cracking tests

1.1 Introduction

By plotting the Wöhler curve, we can determine the fatigue strength, which can be considered as the maximum stress the material can withstand without crack initiation after a given service life. However, experience has shown that, in parts in service, there may be machining, welding or casting defects, or corrosion pitting, from which a fatigue crack can propagate. This is particularly true of real structures, where most of the service life is taken up by crack propagation. For this reason, in addition to endurance initiation resistance [M 4 170] , the study of crack propagation is necessary. It is also the only way of accurately determining the residual service life of a part with...