Rudavskiy D. Life time determination of metallic materials and welded joints under cyclic loading and hydrogenation

The dissertation is devoted to the problem of the hydrogenated structural elements residual life time estimation. The diffusion problem for hydrogen concentration determination in welded joints is formulated and numerical solution is obtained. A number of energy approaches based on the models for fatigue cracks initiation and propagation were proposed. The calculation models of fatigue microcrack initiation near the hydrogenated stress notch tip and its growth up to the macro size are formulated. The obtained equations allowed to estimate a full period of macrocrack initiation. The calculation model of fatigue crack growth propagation in hydrogenated inhomogeneous materials for plane stress state is built. A fatigue crack propagation path and a weld joint residual life time can be found by the obtained equations. It is shown that calculation results correlate well with the well known experimental data.Some important examples of the residual life time of the welds are considered with the help of proposed models.