Ultrasonic Testing of Compressor and Turbine Blades for Fatigue Cracks

1959 ◽  
Vol 31 (2) ◽  
pp. 51-54 ◽  
Author(s):  
J. Schijve
Keyword(s):  
Ultrasonic Testing ◽  
Fatigue Cracks ◽  
Turbine Blades ◽  
Compressor And Turbine Blades

scholarly journals Use of an Inverse Method for the Design of High Efficiency Compressor and Turbine Blades With Large Change in Radius

1984 ◽  
Author(s):  
G. Meauzé ◽  
A. Lesain
Keyword(s):  
Inverse Method ◽  
High Efficiency ◽  
Radial Flow ◽  
Turbine Blades ◽  
Large Change ◽  
Airfoil Optimization ◽  
Time Marching ◽  
Flow Compressor ◽  
Compressor And Turbine Blades ◽  
Made In

Extension of the time-marching computations of flows in 2-D blade cascades to the case of cascades with variable radius and stream tube thickness. One of the specific cases analyzed is that of purely radial cascades. Direct and inverse calculations are made, in non-viscous subsonic or supersonic flows, with or without shock waves. Examples of the design of high efficiency airfoil optimization for radial flow compressor rotors or Stators or inward flow turbine inlet guide vanes are presented.

The Stress Problem of Vibrating Compressor Blades

1955 ◽  
Vol 22 (1) ◽  
pp. 57-64
Author(s):  
Jan R. Schnittger
Keyword(s):  
Turbine Blades ◽  
General Nature ◽  
Compressor Blades ◽  
Stress Problem ◽  
Simplified Analysis ◽  
Compressor And Turbine Blades

Abstract In order to demonstrate the general nature of the actual vibrations of compressor and turbine blades, the author undertakes a simplified analysis in which a single stiff blade, with one translational and one pitching mode, is studied. It is shown that all problems of stress in vibrating compressor blades whether they arise from forced or self-sustained vibrations may be related to the magnitude of finite mechanical or aerodynamic disturbances.

Magnetic Barkhausen Noise Technique for Early Stage Fatigue Prediction in Martensitic Stainless-Steel Samples (invited)

2021 ◽  
pp. 1-18
Author(s):  
Zi Li ◽  
Bharath Basti Shenoy ◽  
L. Udpa ◽  
Yiming Deng
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Power Plants ◽  
Early Stage ◽  
Fatigue Cracks ◽  
Turbine Blades ◽  
Barkhausen Noise ◽  
Magnetic Barkhausen Noise ◽  
Operating Cycle ◽  
Microstructure Changes

Abstract Martensitic grade stainless steel is generally used to manufacture steam turbine blades in power plants. The material degradation of those turbine blades, due to fatigue, will induce unexpected equipment damage. Fatigue cracks, too small to be detected, can grow severely in the next operating cycle and may cause failure before the next inspection opportunity. Therefore, a nondestructive electromagnetic technique, which is sensitive to microstructure changes in the material, is needed to provide a means to estimate the specimen’s fatigue life. To tackle these challenges, this paper presents a novel Magnetic Barkhausen noise (MBN) technique for garnering information relating to the material microstructure changes under test. The MBN signals are analyzed in time as well as frequency domain to infer material information that are influenced by the samples’ mate- rial state. Principal Component Analysis (PCA) is applied to reduce the dimensionality of feature data and extract higher order features. Afterwards, Probabilistic Neural Network (PNN) classifies the sample based on the percentage fatigue life to discover the most correlated MBN features to indicate the remaining fatigue life. Furthermore, one criticism of MBN is its poor repeatability and stability, therefore, Analysis of Variance (ANOVA) is carried out to analyze the uncertainty associated with MBN measurements. The feasibility of MBN technique is investigated in detecting early stage fatigue, which is associated with plastic deformation in ferromagnetic metallic structures. Experimental results demonstrate that the Magnetic Barkhausen Noise technique is a promising candidate for characterizing.

Production of Realistic Flaws and Their Meaning for Ultrasonic Testing

2019 ◽  
Vol 5 (3) ◽  
Author(s):  
Jiri Hodac ◽  
Pavel Mares ◽  
Jaromir Janousek ◽  
Martin Linhart
Keyword(s):  
Staff Training ◽  
Ultrasonic Testing ◽  
Phased Array ◽  
Fatigue Cracks ◽  
Ultrasonic Test ◽  
P 75 ◽  
Array Technology ◽  
Ultrasonic Echo ◽  
Ultrasonic Phased Array ◽  
Test Result

This work is designed to artificially create test specimens with flaws that behave the same way as real-function flaws when observed by nondestructive testing (NDT) technologies. Thus, the understanding of the detection limitations of NDT methods is needed. In this study, real, realistic, and artificial flaws were compared by ultrasonic phased array technology. Fatigue flaws, which belong to the most common structural issues (Ruzicka, M., Hanke, M., and Rost, M., 1987, Dynamicka Pevnost a Zivotnost, CVUT, Prague, Czech Republic, p. 75), are investigated. Measurements have revealed significant differences in the amplitude of ultrasonic echo from fatigue cracks in distinct phases of crack propagation. Studied specimens with realistic flaws have demonstrated their quality for calibration, staff training, and NDT system qualification. More realistic test specimens will increase ultrasonic test result reliability.

Mean Velocity Scaling and Friction Coefficient Estimation for Rough Surface Turbulent Boundary Layers in Turbomachines

2014 ◽  
Author(s):  
Ju Hyun Shin ◽  
Seung Jin Song
Keyword(s):  
Flat Plate ◽  
Rough Surface ◽  
Boundary Layers ◽  
Turbine Blades ◽  
Axial Compressor ◽  
Turbulent Boundary Layers ◽  
Flat Plates ◽  
Mean Velocity ◽  
Coefficient Estimation ◽  
Compressor And Turbine Blades

Based on flat plate results, mean velocity and friction coefficient estimation methods are proposed for rough surface turbulent boundary layers on axial compressor and turbine blades. The ratio of the displacement thickness to boundary layer thickness (δ*/δ) was first suggested by Zagarola and Smits (1998) for smooth pipe flows. The same parameter is proposed in this paper to scale the normalized mean velocity defect of smooth and rough surface flat plate turbulent boundary layers with zero, favorable, and adverse pressure gradients. The available mean velocity defect profiles of smooth and rough surface boundary layers from axial compressor and turbine blades are also scaled and compared to the flat plate results. Irrespective of the Reynolds number (Reθ), pressure gradient (K), and roughness (k), δ*/δ provides appropriate scaling for collapsing the flat plate and turbomachinery data. From the results, a new one-variable power law based on δ*/δ is proposed to estimate the mean velocity profile. The proposed power law can accurately estimate boundary layers on flat plates, compressor blades, and turbine blades. Finally, a new empirical Cf correlation is proposed for rough surface turbulent boundary layers under pressure gradients. The proposed Cf correlation is based on that of Bergstrom et al. (2005) and newly incorporates the acceleration parameter K. It can accurately estimate Cf in turbulent boundary layers of rough surface flat plates as well as those of smooth turbine blades.

Effects of Warping and Pretwist on Torsional Vibration of Rotating Beams

1984 ◽  
Vol 51 (4) ◽  
pp. 913-920 ◽  
Author(s):  
K. R. V. Kaza ◽  
R. E. Kielb
Keyword(s):  
Aspect Ratio ◽  
Torsional Vibration ◽  
Equations Of Motion ◽  
Turbine Blades ◽  
Mode Shapes ◽  
Compressor Blades ◽  
Rotating Beams ◽  
Special Cases ◽  
Torsional Frequency ◽  
Compressor And Turbine Blades

The effect of pretwist and warping on the torsional vibration of short-aspect-ratio rotating beams is examined for application to the modeling of turbofan, turboprop, and compressor blades. The equations of motion and the associated boundary conditions by using both Wagner’s hypothesis and Washizu’s theory are derived and a few minor limitations of the Wagner’s hypothesis, as applied to thick blades, are pointed out and discussed. The equations for several special cases are solved in a closed form. Results are presented indicating the effect of warping, pretwist, and rotation on torsional vibration of beams as aspect ratio is varied. The results show that the structural warping and pretwist terms have a significant effect on torsional frequency and mode shapes of short-aspect-ratio blades whereas the inertial warping terms have negligible effect. Since the torsional frequencies and mode shapes are very important in aeroelastic analyses by using modal methods, the structural warping terms should be included in modeling turbofan, turboprop, compressor, and turbine blades.

scholarly journals Comparative study of protective coatings for heat resistance

2020 ◽  
Vol 23 (1) ◽  
pp. 41-48
Author(s):  
A. V. Zorichev ◽  
G. T. Pashchenko ◽  
O. A. Parfenovskaya ◽  
V. M. Samoylenko ◽  
T. I. Golovneva
Keyword(s):  
Phase Composition ◽  
Heat Resistance ◽  
Temperature Change ◽  
Thermal Fatigue ◽  
Protective Coatings ◽  
Fatigue Cracks ◽  
Turbine Blades ◽  
Cyclic Temperature ◽  
Thermal Fatigue Cracks ◽  
Cyclic Temperature Change

Modern gas turbine engines operate under changing temperature loads. Therefore, one of the important characteristics of the protective coatings used on the turbine blades is their high resistance to the occurrence and development of cracks under mechanical and thermal loads. The applied effective systems of internal heat removal of the cooled turbine blades lead to an increase in their heat stress. At present, cracks arising from thermal fatigue are one of the common defects of the protective coatings used on turbine blades. The heat resistance of coatings at high temperatures is determined by three factors: the shape of the part on which the coating is applied, the thickness of the coating and the phase composition of the surface layers or the maximum aluminum content in the coating. Therefore, when choosing a protective coating for these operating conditions, it is important to know the impact of these factors on the thermal stability of the coating. The paper presents a comparative study of various coatings on their resistance to crack formation under cyclic temperature change. The dependence of the heat resistance of the considered coatings on the method of their application and phase-structural state is established. Especially valuable is the established mechanism of formation and propagation of thermal fatigue cracks depending on the phase composition of the initial coating. It is shown that the durability of protective coatings with cyclic temperature change depends on the chemical composition of the coating and the method of its formation. The dependence of the formation of thermal fatigue cracks on the samples with the coatings under study on the number of cycles of temperature change is established.

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