Experimental Wear Characterization and Durability Enhancement of an Aeronautic Braking System

Abstract

This paper is focused on the experimental wear characterization of an electromagnetic braking system used for helicopters. The characterization was performed through the evaluation of some monitoring parameters during endurance tests on a test bench and through the visual analysis of the worn surfaces after the tests. The monitoring parameters were the engagement threshold voltage, the release threshold voltage, the inductance, and the braking torque, which are directly correlated with the wear progress. The visual analysis allowed the assessment of the wear extent and the distribution of wear particles at the interfaces. The test performed on the initial base configuration, having ten springs and carbon fibers as friction materials, demonstrated that the braking system had insufficient durability in terms of actuation cycles. The results allowed the design of two new configurations based on different brake architectures and on different friction pairs. One of the new configurations was based on a reduction in the number of springs (eight-spring configuration), and the second one was based on the employment of a different friction material (NAO configuration). Both of these optimized configurations showed enhanced durability and wear resistance, but only the second one showed sufficient durability with respect to the requirements and was defined as acceptable. The final results showed a durability of 3000 actuation cycles for the base configuration, 4385 for the eight-spring configuration, and 35,223 for the NAO configuration. Nevertheless, the analysis of results allowed the cause of the wear phenomena to be studied and eventual further improvements in the system to be suggested.