The aim of this thesis is both, to identify the optimal conditions for the application of high frequency hammering and to predict the effects on the fatigue behaviour of treated welded joints. This work is part of a project that aims at proposing an approach, applicable industrially, to enhance the fatigue life of new welded structures. Such a method should also extend the fatigue life of existing structures. The first part of this thesis presents the various effects of hammering based on the results of the literature. In additions, experimental tests are performed, from which a number of recommendations have been implemented. An indirect method is then presented to estimate, using instrumented spherical indentation, the local properties of a weld assembly to model treatment. Two direct numerical methods have also been proposed. The first one enable us to simulate quickly the treatment of high frequency hammering, while the second is used to estimate the possible relaxation of residual stresses generated by the treatment, following fatigue loading. The proposed approach is then applied to various treatment conditions. The comparison between numerical results obtained allows for the evaluation for the main parameters and to identify future tendencies. Finally, further comparisons made with experimental results show a good agreement for the validation of the approach.
