Turbine Engine Frangible Bearing Support Design

Project goal: To design a frangible bearing support that will withstand higher fatigue loads. Stricter Federal Aviation Administration regulations require that new propulsion turbine engines be able to withstand more severe icing conditions. On these engines, the number one bearing support is designed to break in the event of fan blade separation. This “blade-out” event causes a severe rotating shaft imbalance. To reduce the load that would be transferred to the engine, the bearing support is designed to break away from the engine frame and allow the engine shaft to whirl. The bearing support was modified from having six individual fuse ligaments to using a solid rim ligament around the entire circumference. This design reduces stress concentrations, thus decreasing fatigue from icing conditions. Stresses calculated using finite element analysis software were used to determine ligament thickness and surrounding fillet radii that would fulfill the breaking load and fatigue life requirements. To validate the FEA results, a physical test was performed using a simplified test specimen. Custom tooling was used to simulate the in-engine mounting conditions and radial loads were applied via a hydraulic press. Deflection and strain data were collected to compare with the finite element analysis model.