Design and Simulation of a Back-to-Back Test Rig for Ultra High Cycle Fatigue Testing of Gears Under Fully Reversed Load

Gear units for turbomachinery, especially in the aerospace sector, place high demands. In addition to the high power density, the demands are also increased regarding the operating temperatures compared to automotive applications. Furthermore, the high operating speed excites vibrations in the higher frequency range, which also poses challenges for the transmission design in terms of NVH. The high dynamics of over 12 000 rpm combined with the high number of load cycles under fully reversed load (N > 10⁸) that an aviation planetary gearbox experiences makes load capacity tests with standardized back-to-back test rigs uneconomical or even impossible due to the extremely long testing times. To enable the Ultra High Cycle Fatigue (UHCF) testing, a high-speed back-to-back test rig was developed. In addition to the design, particular focus is placed on the thermal and dynamic simulation of the test rig. These two aspects are the basis for a safe commissioning and a successful testing. In the area of thermal simulation, the behavior of the test rig components in the operating temperature range from room temperature to T > 100°C is investigated regarding the thermal expansion and the resulting tolerances. The dynamic simulation deals with the vibration behavior of the test rig. Special focus is placed on the tooth mesh frequency and the natural frequencies of the components. As a result, the operating points for testing are defined and the operational safety is ensured. In addition, for providing a basis for the investigation of aircraft transmissions, the paper shows fundamental ideas for the design of high-speed back-to-back gear test rigs.

Authors: Johannes Lövenich, M. Trippe, O. Malinowski, J. Brimmers, S. Neus, C. Brecher

ISBN: 978-1-64353-105-2