Aeromechanical Modeling of Rotating Fan Blades to Investigate High-Cycle and Low-Cycle Fatigue Interaction

Abstract

Gas turbine engine components are subject to both low-cycle fatigue (LCF) and highcycle fatigue (HCF) loads. To improve engine reliability, durability and maintenance, it is necessary to understand the interaction of LCF and HCF in these components, which can adversely affect the overall life of the engine while they are occurring simultaneously during a flight cycle. A fully coupled aeromechanical fluid-structure interaction (FSI) analysis in conjunction with a fracture mechanics analysis was numerically performed to predict the effect of representative fluctuating loads on the fatigue life ofbliskfan blades. This was achieved by comparing an isolated rotor (IR) to a rotor in the presence of upstream inlet guide vanes (IGVs). A fracture mechanics analysis was used to combine the HCF loading spectrum with an LCF loading spectrum from a simplified engine flight cycle in order to determine the extent of the fatigue life reduction due to the interaction of the HCF and LCF loads occurring simultaneously. The results demonstrate the reduced fatigue life of the blades predicted by a combined loading of HCF and LCF cycles from a crack growth analysis, as compared to the effect of the individual cycles. In addition, the HCF aerodynamic forcing from the IGVs excited a higher natural frequency of vibration o f the rotor blade, which was shown to have a detrimental effect on the fatigue life. The findings suggest that FSI, blade-row interaction and HCF I LCF interaction are important considerations when predicting blade life at the design stage of the engine. The lack of available experimental data to validate this problem emphasizes the utility of a numerical approach to first examine the physics of the problem and second to help establish the need for these complex experiments.

A practical nonlinear damage accumulation method to predict the life and crack propagation of blade subjected to multilevel cyclic fatigue loads

“…The SIF K of blade corner crack is usually extracted 37–40 using an approximated plate model proposed by Newman. 41 Considering centrifugal stress S t and aerodynamic moment M , the approximated plate model with a quarter round crack is shown in Figure 17.…”

“…At present, the fatigue life prediction is still very important in the design of engineering blade. However, very few papers have investigated the life and crack propagation of a blade subjected to MCF using a nonlinear damage accumulation method numerically, 27 and the multiaxial stress state of the blade is rarely considered in engineering practice. 10 In this article, the method based on Chaboche's nonlinear damage model is used to investigate a compressor blade subjected to MCF of SCF and working aerodynamic force (WAF).…”

Experimental determination of IGV preswirl effect on impeller blade vibration in an unshrouded centrifugal compressor

“…2,8 However, the IGV induced blade fatigue failure was reported in a high specificpower radial inflow turbine stage. 9 Dhopade and Neely 10 studied the axial compressor blade vibration due to upstream inlet guide vanes. Results indicated the aerodynamic forcing from the IGV excited the vibration of the rotor blade, which was shown to have a detrimental effect on the blade fatigue life.…”

Study on the fatigue life and damage accumulation of a compressor blade based on a modified nonlinear damage model

“…Nevertheless, the loading conditions of a compressor blade are so complicated that the improvement in prediction model of fatigue life should take into account the material properties, the structure characteristics, and the failure modes of the blade. Several sorts of load contribute to the fatigue process of a compressor blade that can increase the damage accumulation rate so as to decrease the fatigue life . Many loading parameters, such as the mean stress and the stress ratio, can affect the damage accumulation .…”

“…Several sorts of load contribute to the fatigue process of a compressor blade that can increase the damage accumulation rate so as to decrease the fatigue life. 19 Many loading parameters, such as the mean stress and the stress ratio, can affect the damage accumulation. 20,21 As the loading parameters vary throughout the fatigue process, the corresponding cyclic hardening and cyclic softening phenomena alternate correspondingly.…”