Fatigue crack propagation for an aircraft compressor under input data variability

Abstract

The quantification of all the uncertainty sources affecting the phenomenon of fatigue crack-growth is essential to enhance competitiveness in designing more high-performance products, e.g. aircraft engines. This work reports crack propagation simulations for a first-stage compressor of a turbo-fan engine, by considering the impact on life prediction accuracy given by geometrical tolerances, material variability and actual rotational speed. Crack-growth simulations were developed by Finite Element Method (FEM) considering the variability of the fillet radius between blades and disk, so as to derive the distribution of Stress Intensity Factors (SIF) along the crack size as a function of both fillet radius and rotational speed. Consequently, a NASGRO formulation, calibrated on Ti6Al4V test data, was implemented in a MATLAB routine in a stochastic way so as to derive the residual life predictions for the component. Statistical evaluations were made and the contributes of all the considered uncertainty sources were compared and classified.