Under constant amplitude loading, a single variable (K) or Kmax are required in crack
growth relationships. The transferability of fatigue laws, obtained under constant amplitude loading
to variable amplitude fatigue, requires at least an additional variable, whose evolution with crack
length accounts for the interactions effects between cycles of different types. This paper presents an
analysis of fatigue crack growth tests on M(T) specimens made of a medium carbon steel. The
specimens are subjected to repeated blocks of cycles made up of one or several overloads separated
by a variable number of baseline cycles and two baseline stress ratios. The main objective of this
study is to better understand the mechanisms at the origin of interactions effects due to the presence
of overloads (or underloads) at different locations of each block loading. Results have shown that
the interaction effects are closely related to the cyclic plastic behaviour of the material and also the
so-called Bauschinger effect.
A Fatigue Crack Growth Prediction Model with Load Interaction Effects Using Crack Closure Concept, Xiaohua CHENG, Kentaro YAMADA
