Damage monitoring of SiC/SiC turbine blisk under overspeed rotation testing using X-ray computed tomography and natural frequency

Abstract

In this paper, the SiC/SiC turbine blisk was fabricated and tested to rupture under overspeed rotation. Under the overspeed rotation testing, the natural frequency of 24 blades and disk were tested using the force hammer−sound pressure sensor method, and the internal defects and damages inside the SiC/SiC turbine blisk were observed and analyzed under the computed tomography and digital imaging system. After overspeed rotation rupture, the fracture surface of the blisk was observed under the scanning electronic microscope, and a large number of fibers’ pullout was observed. Relationships between the rotation speed, internal damage evolution, and the natural frequency degradation in the blisk were established. After 98,000 R.P.M. rotating speed experiment, the natural frequencies of the blade and the disk decreased obviously. The frequency of more than half of blades decreased by 1.5−2.0%, with 13 blades in total; 17% of blades decreased by 1.0−1.5%, with 4 blades in total. The natural frequency of the disk also decreased with the increase of the rotating speed, and the natural frequency of the first three order decreased from 1.0 to 1.5%.

Prediction of fatigue limit stress in C/SiC composites: Effect of stochastic load spectrum

“…During operation of CMCs hot‐section components, stochastic overloads may occur during cyclic‐fatigue loading 30,31 . In the present analysis, three typical stochastic loading spectrums (as shown in Figure 1) were considered in the FLS analysis, as follows: Under cyclic fatigue loading at peak stress σ p , the constant stochastic stress σ s occurs at cycle number N 1 , N 2 , and N 3 with cyclic duration Δ N . Under cyclic fatigue loading at peak stress σ p , the increasing stochastic stresses σ s1 , σ s2 , and σ s3 occur at cycle number N 1 , N 2 , and N 3 with cyclic duration Δ N . Under cyclic fatigue loading at peak stress σ p , the decreasing stochastic stress σ s1 , σ s2 , and σ s3 occur at cycle number N 1 , N 2 , and N 3 with cyclic duration Δ N . …”

“…During operation of CMCs hot-section components, stochastic overloads may occur during cyclic-fatigue loading. 30,31 In the present analysis, three typical stochastic loading spectrums (as shown in Figure 1) were considered in the FLS analysis, as follows:…”

Stress Analysis and Life Prediction of a Ceramic Matrix Composite Vane Using a Micromechanics-Based Approach

“…Uses of CMCs however add complexities in part fabrication [5]. Considerable advances have been made since the 1980s in using CMCs to make combustor liners [6][7][8], nozzle flaps [7,9], vanes [8,[10][11][12][13], blades [14], bladed disks [15], and shrouds [16,17], though a number of these applications remain experimental. Commercially, the major aircraft engine companies have made significant investments in the development and manufacture of CMC hot-section components for use in turbine engines [18,19] and, in some cases, CMC parts are currently being flown on civilian aircrafts [20].…”