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The microstructural changes occurring in steels under cyclic loading are responsible for heat dissipation. Therefore, self-heating measurements can be considered as an efficient way to relate fatigue properties to microstructure. However, the dissipative mechanisms are not clearly identified and some questions remain opened. This paper aims to use the experimental estimation of the intrinsic dissipation, in stress amplitude ranges lower than the macroscopic yield strength, to lead to a better understanding of the dissipative mechanisms. First, self-heating measurements enable to evaluate how the free surface affects the spatial distribution of the dissipation sources in the normal direction. Results indicate that, for thin specimens with a high roughness factor, the dissipation sources are mostly activated close to the free surface. Besides, it is experimentally shown that the self-heating curves are not dependent on the mean stress for low stress magnitudes while they are sensitive to the mean stress for higher stress magnitudes. It is deduced that in the loading conditions used to determine the self-heating curves, the dissipative mechanisms imply recoverable strains (anelasticity) for low stress magnitudes and unrecoverable strains (inelasticity) for higher stress magnitudes.

International audience; The dimensioning of composite structures presents the problem of behaviour modelling. This problem comes not only from the specific nature of the involved materials, but also from the reproducibility of the process both on the series scale as well as on the specimen characterisation level, which enables determination of the modelling parameters. In the case of static dimensioning with or without damage, the reproducibility of the mechanical parameters is satisfactory overall, regardless of the implemented experimental procedure. In fatigue dimensioning, the two aspects; process influence and procedure of identification play a major role in the application of the lifetime predictive models. This research has, as a medium-term objective, to partially answer the problems raised previously. The damage model used is based on generalised standard material thermodynamics. This model, coupled with the finite element method, allows simulation of the fatigue behaviour of composite parts.