Fracture failure analysis of flywheel hub served in heavy-fuel aviation piston engine

The safety of both the crew and aircraft are gravely compromised by flywheel hub fatigue failure in its heavy-fuel piston engine. It is imperative to investigate the root causes and mechanisms behind flywheel hub fracture. In this study, a comprehensive approach combining macroscopic fracture analysis, microstructural evaluation, chemical composition analysis and FEA simulation is employed to systematically investigate the root cause and failure mechanism of flywheel hubs in a heavy-fuel piston engine. Firstly, the failure mode of the flywheel hub is fatigue caused by cyclic loading, as evidenced by the propagation of typical beach markings. The mechanism behind flywheel hub failure is facilitated by severe cyclical loads and design flaws that result in a high concentration of stress between the spokes due to rounding. Furthermore, finite element analysis simulations are conducted under operational conditions utilizing stress and fatigue lifetime analysis to validate the fatigue mechanism. The experimental data is then cross-verified with simulation results, demonstrating a concurrence. Lastly, precautionary measures such as regular non-destructive testing (NDT), geometry redesign, and moderate operation of the power lever are also proposed to address future fatigue issues in flywheel hubs.