In this investigation, an efficient fatigue life computation method under variable amplitude loading of structural components has been proposed. Attention in this study is focused on total fatigue life estimation of aircraft structural components. Flat specimens with central hole made of quenched and tempered steel 13H11N2V2MF were tested as representatives of different structural components. Total fatigue life of these specimens, defined as sum of fatigue crack initiation and crack growth life, was experimentally determined. Specimens were tested by blocks of positive variable amplitude loading. Crack initiation life was computed using theory of low-cycle fatigue (LCF) properties. Cyclic stress-strain curve, Masing's curve and approximate Sonsino's curve were used for determining stress-strain response at critical point of considered specimens. Computation of crack initiation life was realised using Palmgren-Miner's linear rule of damage accumulation, applied on Morrow's curves of LCF properties. Crack growth life was predicted using strain energy density method. In this method, the same LCF properties were used for crack initiation life and for crack growth life computations also. Computation results are compared with own experimentally obtained results.KEY WORDS: crack growth, crack initiation, FEM, strain energy density method, total fatigue life prediction Ó

This study focuses on the estimation of residual life of damaged thermal power plant components. The high-pressure turbine housing was chosen as an example of thermal power plant component where, during the years of exploitation, damage appeared in the form of dominant crack. Residual life estimation procedure, based upon experimental and numerical methods has been introduced and applied. Material properties were determined experimentally both at room and operating temperature, while all necessary calculations were performed by the special finite element method, so-called X-FEM. The residual life estimation of the damaged high-pressure turbine housing was performed by applying the Paris's law for crack growth analysis.

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The thermomechanical buckling and postbuckling behavior of layered composite shell type structure are considered with the finite element method (FEM) under the combination of temperature load and applied mechanical loads. To account for through-thickness shear deformation effects, the thermal elastic, Higher-Order Shear deformation Theory (HOST) is used in this study. The refined higher order theories, that takes into account the effect of transverse normal deformation, is used to develop discrete finite element models for the thermal buckling analysis of composite laminates. Attention in this study is focused on analyzing the temperature effects on buckling and postbuckling behavior of thin shell structural components. Special attention in this paper is focused on studying of values of the hole in curved panel on thermal buckling behavior and consequently to expend and upgrade previously conducted investigation. Using FEM, a broader observation of the critical temperature of loss of stability depending on the size of the hole was conducted. The presented numerical results based on HOST can be used as versatile and accurate method for buckling and postbuckling analyzes of thin-walled laminated plates under thermo-mechanical loads.