Finite-Element Method-Based Model to Study High-Cycle Fatigue in Turbine Blades

In order to satisfy the defense challenges of the 21st century, more advanced technologies are needed to build aircraft engines that are lighter, compact, and more powerful than existing designs. Turbine blades are highly critical components of an aircraft engine, and high-cycle fatigue is one of the prime reasons for turbine blade failures; thus understanding and prediction of fatigue failure are of the utmost importance. A primary function of the Turbine Engine Fatigue Facility of the Air Force Research Laboratory’s Propulsion Directorate at Wright-Patterson Air Force Base is evaluation of the development of crack initiation and growth in turbine blade components. One major avenue for the inception of a crack under high-cycle fatigue is the use of a shaker table or an applied forcing function imposed by a piezoelectric transducer. In order for a crack to develop in a plate device, one must have appropriate specimen geometry that produces crack initiation. There are many situations where particular plate dimensions are chosen for testing but a crack never initiates even at the designated endurance limit. This paper presents a method, based on finite-element evaluation, that determines if plate geometry does lead to high-cycle fatigue (HCF) cracking. Furthermore, it justifies the use of a concentrated load as a representation for an aerodynamic forcing function. If the method is followed, a researcher can study the crack-growth scenario within the HCF environment.