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Lebensdauervorhersage für integralgegossene Turbinenräder unter Berücksichtigung kurzer Risse am Beispiel der Nickelbasis-Legierung IN 713 C
Life assessment for integral turbine wheels in consideration of short cracks on example of the nickel base alloy IN 713 C
Constant and variable amplitude fatigue tests on unnotched specimens under strain controlled axial loading and on notched specimens under load controlled bending were carried out in order to investigate the transferability of unnotched specimens data to components. In this case the notched specimen represents the component, the turbine wheel. The operational conditions of a turbine wheel, high temperatures, hold times, different loading rates and the fatigue sequence Hot Turbistan, were included in the investigations. Short crack propagation was measured in a scanning electron microscope by identification of load markers on the rupture surface. Additionally CT-specimens were tested in order to determine crack propagation of long cracks. Using these test results and corresponding safety factors a better life assessment for turbine wheels is possible, if the concepts of Safe-Life-, Damage- Tolerance and Total-Life are applied.