High Cycle Fatigue Testing of Turbine Blades Under Biaxial Loading

Although technologies derived under the Integrated High Performance Turbine Engine Technology (IHPTET) initiative should result in higher performance of gas turbine engines, the durability of engine components continues to be one of the most important design issues which impacts their affordability and robustness. It is currently very difficult to measure or predict the fatigue life of engine components under the elevated temperature environment. To measure and predict engine components fatigue life under these conditions we propose a feasibility study and preliminary design for high cycle fatigue testing of turbine blades under biaxial loading based on both numerical modeling and experimental study. Three-dimensional thermal-mechanical finite element models will be constructed for a turbine blade under biaxial loading, i.e., centrifugal force and transverse vibration loading, to simulate the structural response under operational conditions.Based on the life element modeling, several critical designs of the biaxial fatigue testing mechanism will be proposed and further investigated. They include the attachments at the blade dovetail and at the tip of the airfoil, and the frequency and displacement range of the vibration actuators. A preliminary design of a four-post test frame will be performed. Small scale fatigue test on turbine blades using existing test frame will also be performed to investigate the structural response of the turbine blade under vibration loading.After the completion of the above mentioned Phase I effort, a high cycle fatigue test system will be designed and constructed to test the durability of turnbine blades under biaxial loading in Phase II.