Experimental Study on Wear and Fracture in Aeronautical Gear Transmissions

This work presents some of the results obtained from an extensive experimental test campaign performed at the Department of Mechanical Nuclear and Production Engineering (DIMNP) of Pisa University with the partnership of Avio Propulsione Aerospaziale S.p.A. This test campaign, that is still being performed, is concerned with the characterization of teeth damage in high performance gear transmissions, such as aeronautical ones, characterized by high levels of velocity and load. Damage detection and monitoring have been pursued during all the tests in order to achieve a better understanding of causes and evolution of teeth damage. Moreover, to investigate the effects of different parameters on teeth damage, tests with different load, velocity, teeth geometry, materials and surface finishing, have been performed. The surface conditions of the gear teeth have been investigated using in particular two different instruments: a computer-controlled stylus profilometer able to perform 3D investigations and a scanning electron microscope (SEM) recently provided by a software for surface reconstruction. Qualitative and quantitative changes in surface roughness have been detected. Besides the experimental activity, numerical analyses have been also started for finding theoretical criteria for surface damage prediction; some few obtained results are presented. Due to the vastness of the work performed, only a survey of the main results obtained till now is presented in the paper.