Preliminary Finite Element Analysis of a Compressor Disk in the TF3O Engine.

AMRL has been developing expertise in finite element analysis PEA of engine components, particularly compressor and turbine discs. The fourth stage Low Pressure Compressor LPC disc of the TF3O engine in the F-111 aircraft was chosen as the first component for detailed analysis after being identified as a prime candidate for the retirement-for-cause lifting methodology. This report describes a preliminary study of the stresses in this component. Two benchmark examples which show close agreement between PEA stress results and analytical solutions are presented. The PEA results confirm the critical location for low cycle fatigue failure specified by the OEM. The assembly loads are shown to significantly increase the mean and peak stresses but not the cyclic stress range. The thermal stresses are shown to be an order of magnitude smaller than the stresses caused by the rotation of the disc. The analysis shows that the most severe stresses produced in the disc under typical engine operating conditions are much lower than the yield stress of the disc material Ti-8-l-l, which suggests a very conservative design. Recommendations are made for developing models that will more realistically represent the loads on the disc and the interaction with other components in order to determine whether the design is really as conservative as the current analysis suggests.