Session: PTG-02-02: Gear Analysis, Materials, and Fatigue 2

Paper Number: 115149

115149 - A Novel Ultrasonic Fully Reversible Bending Fatigue Test Specimen for Simulated Gear Tooth Bending Fatigue 

Traditional helicopter and potential future urban air mobility (UAM) vehicle transmissions possess gearing that experience lives greater than 10⁹ fatigue cycles in operation. Currently, fatigue life prediction of gears exceeding 10⁷ cycles are based on empirical correlations, since collection of fatigue data beyond 10⁷ cycles is impractical with traditional fatigue testing methods. Ultrasonic fatigue testing enables fatigue testing in excess of 10⁹ cycles in as few as 14 hours. In this paper, a novel ultrasonic bending fatigue specimen is presented. The novel specimen can simulate a gear tooth under bending fatigue including all heat treatment and residual stress effects. Correspondingly it may provide a possible path to screening different gear steel materials, validating gear designs for very high cycle fatigue, and developing heat treatments or material surface treatments. The resulting specimen has the possibility to reduce material development time, reduce required safety factors, and correspondingly reduce weight of gearboxes. In the specimen design is discussed in detail, testing is performed to validate operating principles, and an initial fatigue data set of 8 specimens is presented. Prelimnary results show that the new testing method is promising for enabling better understanding of gear steel material fatigue past 10^7 cycles. 

Presenting Author: Thomas Tallerico NASA Glenn Research Center

Presenting Author Biography: Thomas Tallerico is an aerospace research engineer at NASA's Glenn Research Center. He received both his bachelor's and master's degrees in mechanical engineering from the University of Pennsylvania. His current areas of research include traditional and superconducting electric motors, magnetic gears, and ultrasonic fatigue of gear steels.

Authors:

Zachary Cameron NASA Goddard Space Flight Center
Thomas Tallerico NASA Glenn Research Center