An Investigation and 3D Crack Propagation Analysis of High Speed Flexible Coupling of Fighter Aircraft

Abstract

The high speed flexible coupling (HSFC) transmits power from the aircraft engine gear box to the accessory gear box operating at high speed ranging from 10,000 to 18,000 rpm. The HSFC utilizes a series of thin annular, titanium alloy flexible plates, to accommodate larger parallel and axial misalignment that arises on the drive line. During ground testing, failure of flexible plate was observed. As a part of the failure analysis the extensive metallographic studies were done. This study showed that, failure was caused by the presence of Electron beam weld spatter on flexible plate, which was a crucial factor to the fatigue crack initiation phase. In order to complement the cause of failure, a 3D crack propagation simulation by FEA was done to predict the critical flaw size. This combined failure cause analysis approach has served as an efficient tool for optimized product development.