Rudavskyy D. Methods for estimation of the residual life-time of structure elements by making use of the magneto-elastic and acoustic emission parameters

The object of the research is the processes of fatigue and hydrogen cracking of metal structural elements, and dynamic elastic fields caused by mentioned processes in structural materials. The research aim is to develop the methodological bases of structures state and residual life estimation using elastic wave parameters. The proposed methodology is based on calculation models built using fracture mechanics energetic approach. The relationships of energy conservation law in thermodynamics; finite elements and Runge-Kutta numerical methods; physical experiments, statistical methods of data processing are applied at the dissertation. Calculation models of microcrack initiation and its growth up to the macrocrack size near penny-shaped micronotch are built at the work. Calculation model of subcritical period determination of plane fatigue crack propagation for elastoplastic three-dimensional body is developed. Calculation model of plane crack growth in the three-dimensional body under action of static loading and hydrogen-contained environment is formulated. The new method of ferromagnetic materials diagnostics is developed. Based on carried out theoretical and experimental investigations the methodological principles of metal structures residual lifetime estimation using data of acoustic emission monitoring are developed at the work. Research results have been used for acoustic emission diagnostics of bridges over the rivers Dniester and Dnipro; oil-pumping stations "Chyzhivka", "Zhulyn", "Pleschivka", "Novyny", "Dolyna", "Kurovychi", "Karpaty", "Drohobych", "Skole", "Solochyn", "Brody", as well as for the diagnostic of locomotive power units at the "Lviv locomotive repair plant". Obtained results can be used in research and development centres and factory laboratories that solve the problems of diagnostics the technical state of long-term usage metal structure elements with cracks for residual life estimation. Among them are branches of "Naftogaz of Ukraine", Ternopil Ivan Pul'uj National Technical University (Ukraine), Paton Electric Welding Institute of NAS of Ukraine, Pisarenko Institute for Problems of Strength of the NAS of Ukraine and others.