The determination of the stress intensity factor at the crack tips in an initial stretched strip

In this study, the influence of the initial stress to the fracture parameters at a macro-crack tipsin the anisotropic plate-strip is investigated for various regarding geometrical and mechanicalparameters. The investigations are made within the framework of the Three-DimensionalLinearized Theory of Elasticity in the plane-strain state. Corresponding boundary valueproblems are solved numerically by employing FEM. Under FEM modeling the zonecontaining the crack tips the triangle singular with six-nodes are used; for the remaining zoneof the strip the standard rectangular finite elements with nine-nodes are employed. Thefracture parameters are determined by energy method.In the thesis under fracture parameter the SIF- Stress Intensity Factor (K) as well as the ERR-Energy Release Rate (G) is understood. For the cases where the crack location in the strip issymmetric with respect to the strip center the SIF, but in the other cases the ERR isdetermined. Values of the 1-st and 2-nd modes of SIF are determined for the transversalisotropic material, but for the orthotropic material values of the 1-st mode of SIF areconsidered. In these cases it is assumed that the initial strains are small and can be determinedin framework of linear theory of elasticity. The cases where the initial strains are finite onesare also considered for hyper elastic material the mechanical relations for which are given byharmonic type potential. The initial strain state in the considered problems is selected so thatthe suppositions described by Guz (1991) are satisfied.The algorithm and programmes which are used for obtaining numerous new numerical resultsare composed by the author in FTN77. In particular cases, i.e. in the cases where the initialstrains are absent, these results coincide with the corresponding well-known results.The presented investigations are the first attempts for Fracture Mechanics in many particularcases.Keywords: Stress Intensity Factor, crack, energy release rate, initial stress, singular finiteelement, harmonic type potential, finite elements method.JURY:1. Doç. Dr. Nazmiye YAHNİOĞLU (Supervisor) Date:16.12.20052. Prof. Dr. Surkay D. AKBAROV Page:933. Prof. Dr. R. Faruk YÜKSELER4. Prof. Dr. Mehmet BAKİOĞLU5. Prof. Dr. Esin İNAN