Influence of the Amplitude of Resonance Vibrations on Fatigue Life of a Compressor Blade with Simulated FOD Damage

Abstract

This work presents the results of the numerical analyses pertaining to the influence of resonance vibration amplitude on the fatigue life of a compressor blade with a defect made by a collision with a hard object (FOD). The research object was the first stage compressor blade of the PZL-10W engine. The numerical simulation of the notch formation was performed for the tested blade. The material fatigue models (for e-N analysis), three cyclic hardening models, and two mean stress correction models were used in the numerical analyses. As a result of the numerical analysis, the information on the distribution of principal stress was obtained. The values of the principal stresses were used for numerical e-N fatigue analysis using the aforementioned models of fatigue, hardening, and mean stress correction. Obtained results were compared to previously published experimental research, where a notch was created at the leading edge in 8 blades. The blades damaged under laboratory conditions were subjected to experimental fatigue tests during which the effect of resonance amplitude on the number of damage cycles was determined. As a result of the comparison work carried out, the impact of the vibration amplitude on the durability of the element with plastic deformation was determined.

Numerical and Experimental Assessment of the Effect of Residual Stresses on the Fatigue Strength of an Aircraft Blade

“…The next step in the performed research was to determine the stress level and prepare the ε-N fatigue models (Manson-Coffin-Basquin equation) [17][18][19][20]30] and models of cyclic hardening (for the Ramberg-Osgood equation) [23,31]. As part of the previous tests [30,31], it was determined that in the case of resonant vibrations of the compressor blade of the PZL-10W engine with a geometric notch with a depth of 0.5 mm located at a height of 3 mm from the blade root, with a known vibration amplitude A = 1.8 mm, the equivalent (Von-Mises) stress reached the highest value in the bottom of the notch, and it amounted to σ eqv = 987 MPa. The maximum principal stresses σ 1max occurred at the same location and were 184 MPa higher [30].…”

“…To prepare a wide range of numerical tests, based on the available literature, 8 fatigue material models were selected for the Manson-Coffin-Basquin equation, based on the numerical fatigue ε-N analysis, which was carried out. The following fatigue models were used in the analysis: Manson's, 4-point Manson's, Mitchell's, Muralidharan-Manson's, Baumel-Seeger's, Ong's, Roessle-Fatemi's, and Median's [17][18][19][20]30,31]. Detailed data on fatigue models were included in Appendix A.…”

“…where: Since the numerical strength analysis of a vibrating blade in the resonance state with an amplitude of 1.8 mm was performed based on a linear-elastic model, it is necessary to use a model taking into account the cyclic hardening (from the Ramberg-Osgood Equation ( 2)), i.e., cyclic strength coefficient (K') and cyclic strain hardening exponent (n'). The Manson's, Fatemi's, and Xianxin's models were selected for the analysis [14][15][16]31]. Some models depend on the fatigue model of the material.…”

Assessment of the Impact of Shot-Peening on the Fatigue Life of a Compressor Blade Subjected to Resonance Vibrations

“…The object of our study was the first stage compressor blade of the PZL-10W turbine engine [ 3 , 4 ]. This blade ( Figure 1 a) is made of the alloy EI-961.…”

“…The working compressor vanes create negative pressure for the air intake, which could be responsible for sucking small elements from the surroundings, such as small stones, grains of sand, and even birds, into the engine. The collision of the rotating blade with harder elements might create a notch on the blade surface [ 3 , 4 , 5 ]. If the notch is located close to the foot of the blade, it is usually the origin of a future crack.…”