Fatigue Damage Evaluation of Compressor Blade Based on Nonlinear Ultrasonic Nondestructive Testing

Pengfei Wang,Weiqiang Wang,Bingbing Chen,Sanlong Zheng,Zengliang Gao

doi:10.3390/jmse9121358

Abstract

Nonlinear ultrasonic testing is highly sensitive to micro-defects and can be used to detect hidden damage and defects inside materials. At present, most tests are carried out on specimens, and there are few nonlinear ultrasonic tests for fatigue damage of compressor blades. A vibration fatigue test was carried out on compressor blade steel KMN, and blade specimens with different damage degrees were obtained. Then, the nonlinear coefficients of blade specimens were obtained by nonlinear ultrasonic testing. The results showed that the nonlinear coefficient increased with the increase in the number of fatigue cycles in the early stage of fatigue, and then the nonlinear coefficient decreased. The microstructures were observed by scanning electron microscopy (SEM). It was proven that the nonlinear ultrasonic testing can be used for the detection of micro-cracks in the early stage of fatigue. Through the statistical analysis of the size of the micro-cracks inside the material, the empirical formula of the nonlinear coefficient β and the equivalent crack size were obtained. Combined with the β–S–N three-dimensional model, an evaluation method based on the nonlinear ultrasonic testing for the early fatigue damage of the blade was proposed.

Highlights

The second-order nonlinear coefficient β can be expressed with A2/A12 [27,28,29]
The frequency dispersion characteristics of ultrasonic guided waves caused the generation efficiency of the second harmonic to be very low in general, and the signal of the second harmonic was very weak, which is inconvenient for actual measurement
The frequency dispersion characteristics of ultrasonic guided waves caused the generation efficiency of the second harmonic to be very low in general, and the signal of the second harmonic was very weak, which is inconvenient for actual measurement. 7Ifofthe phase velocities of the fundamental frequency Lamb wave mode and the double frequency Lamb wave mode excited in the solid plate are equal, the obvious Lamb wave accumulation secondsecond harmonic signal signal can be can measured

Summary

Introduction

The acoustic parameters measured by the existing ultrasonic technology in the linear range generally have a relatively small response to the early damage changes of materials and structures, and the degradation of mechanical properties cannot be quantitatively characterized. Recent studies have shown that nonlinear ultrasonic technology can overcome the shortcomings of linear ultrasonic techniques that are not sensitive to material or structure damage changes in the early and mid-term. The reason for this is that the nonlinear effect of ultrasonic propagation in materials is closely related to material performance degradation. Material performance degradation will cause the generation of nonlinear harmonics of ultrasonic propagation [2,3,4,5]

Methods

Results

Discussion

Conclusion