Keywords : Mathematical model
Engineering and Technology Journal,
2010, Volume 28, Issue 19, Pages 922-932
In this study the fatigue behavior of an aluminum alloy designated 2024 – T3
under constant and variable amplitude of stresses is considered. The applied load
adopted is a rotating bending one, the cross Section of the laboratory samples is
circular with a diameter of (6.74mm). All tests were carried out under a stress ratio
of R = - 1 and at room temperature condition. The study consists of two parts
experimental and theoretical. The experimental part includes carrying out
laboratory tests on two groups of specimens the first group was tested under
constant stress amplitude to establish the S-N curve of the specimen's material,
while the second group was tested under variable amplitude of stress to assess the
effects of the accumulated fatigue damage. The theoretical part of the study
includes a review of previous literature adopted to derive a theoretical and
mathematical model depending upon the variation of the stresses obtainedby
some previous theories, taking into consideration low and high stress levels, and
even post yield.
The derived model is denoted as elastic-plastic model for the evaluation of life
time of machinery parts. The linear theory of Miner and the theory of Elastic
Cracks Propagation are also studied throughout the theoretical part of the study.
In order to assess the capability of the two theories with the derived model: a
comparison is held between the experimented results and the results obtained by
applying the two theories.
It is noted that results obtained by applying the two theories are lower
(underestimates) than those obtained from the experimental study and that results
obtained by the suggested derived model are in better agreement than those
obtained by the two theories.