Three-dimensional mode-I crack growth analyses with FCPAS in machinery and structure elements

Although some cracks seen in engineering structures can be approximated by two dimensional modeling and analysis techniques, most of them are three dimensional in nature and they appear in the form of surface, corner or embedded cracks. Furthermore, in many engineering problems which involve cracks and cyclic loads, the fatigue crack propagation life of the component under consideration can be significant part of its overall mechanical life. Though some crack propagation problems are truly three-dimensional, i.e., crack faces evolve into non-planar surfaces, there are many structural problems that involve planar fatigue crack propagation under mode-I stress intensity factor as a crack driving force. In this thesis study, some mode-I fatigue crack propagation practical cases which are seen in industrial application studies with with real three dimensioned part geometry are analized and presented. In the analysis mode-I fatigue crack progress propagation analysis procedure is applied and the results are verified with literature data. Distributions of crack tip stress intensity factors on crack front are calculated using enriched finite elements. The purpose of this study to apply and provide analysis procedure that is developed in FCPAS before for plate and cylindirical geometries, on more complex geometries for mode-I crack propagation problems which are seen in energy, transportation and aviation area. In this context, five applications have been chosen; 1) fatigue crack propagation on UIC 60 rail, 2) fatigue crack propagation in power-plant pipe, 3) fatigue crack propagation in helicopter lift frame, 4) fatigue crack propagation in turbine model, 5) fatigue crack propagation in plate with countersunk holes. The results obtained from the analyses have good agreement with literatüre and are observed to be compatible with each other when compared with the results found in the literature. Thus, this study shows that the calculation of life on common mode -I crack propagation with the presented procedure can be used on the aforementioned technology areas.