Melezhyk I. Development and application of a technique for a crack resistance estimation calculation of high-temperature power machines elements with cracks

Subject of investigation is crack growth kinetics, survivability and structural failure at presence of a crack. The dissertation purpose is development and application of a technique for a crack resistance estimation of high-temperature power machines elements, working in conditions of low-cycle fatigue and creep of material. Research methods: methods of brittle fracture mechanics, modelling of kinetics of cracks in designs at multimode service conditions till criticality emersion, the FEM, A.V. Ovchinnikov's interpolation method, Euler's step-by-step method for numerical integration. The developed technique allows considering stress redistribution at crack propagation, complexity of the stress state near the crack tip, stress relaxation at creep, asymmetry of a cycle of a loading, etc. For elements of complicated geometry with a crack the method of stress intensity factor determination with use of the FEM is offered. For the first time the problem of kinetics of a crack in root joint of shovels with disks of turbomachines is solved. Influence on settlement survivability of a rotor of turbine K-300-240 with a crack in boring of the axial channel of spread of material characteristics, stress relaxation and change of semiaxises of an elliptic crack at its extending is investigated. Survivability of a wall of the vessel irradiated from within, with a crack on its internal surface taking into account change of material characteristics from temperature and radiation bombarding radiation is estimated. The obtained results are used at performance of a business agreement and at preparation of the draft of a new standard deed. Results of investigations can be used in power-mechanical engineering and energetics.