Analysis and Optimization of the Fatigue Damage Accumulation Under Transient Vibrations of Mistuned Bladed Disks

Abstract

This paper develops an efficient method for calculations of stress levels, accumulation of high-cycle fatigue (HCF), and mistuning optimization aimed at the reduction of the fatigue damages for mistuned bladed disks under transient vibrations caused by variation of the rotation speed in the vicinity of resonance frequencies. The expressions for the sensitivities of the stress intensity at critical locations, and fatigue damage at loading cycles concerning the mistuning are derived analytically, providing high accuracy and speed of their evaluations. A gradient-based optimization method based on the sensitivities is applied to find the blade mistuning patterns, providing the minimum and maximum fatigue damage accumulated during gas-turbine acceleration or deceleration of a mistuned bladed disk for extending the service life. The method uses realistic large-scale finite element (FE) modeling for bladed disks, accounting for the varying damping and excitation loads with amplitude and frequency spectrum changing with rotation speed. The method has been implemented in a computer code. The fatigue accumulation caused by the transient vibration has been studied using a realistic bladed disk model. The gradient-based optimization search for mistuning patterns, providing the minimum and maximum fatigue damage accumulation during rotor acceleration is performed.