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Shock and Vibration
Volume 2017, Article ID 4568460, 11 pages
https://doi.org/10.1155/2017/4568460
Research Article

Research on Fatigue Damage of Compressor Blade Steel KMN-I Using Nonlinear Ultrasonic Testing

1School of Mechanical Engineering, Shandong University, 17923 Jingshi Road, Jinan, China
2Engineering and Technology Research Center for Special Equipment Safety of Shandong Province, 17923 Jingshi Road, Jinan, China
3Research Center of Safety Guarantee and Assessment to Special Equipment, Shandong University, 17923 Jingshi Road, Jinan, China
4Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education, 17923 Jingshi Road, Jinan, China

Correspondence should be addressed to Weiqiang Wang; nc.ude.uds@gnawqw

Received 21 June 2017; Revised 13 September 2017; Accepted 26 September 2017; Published 19 October 2017

Academic Editor: M. I. Herreros

Copyright © 2017 Pengfei Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The fatigue damage of compressor blade steel KMN-I was investigated using nonlinear ultrasonic testing and the relation curve between the material nonlinearity parameter β and the fatigue life was obtained. The results showed that the nonlinearity parameter increased first and then decreased with the increase of the fatigue cycles. The microstructures were observed by scanning electron microscopy (SEM). It was found that some small defects like holes and pits appeared in the material matrix with the increase of the fatigue cycles, and the nonlinearity parameter increased correspondingly. The nonlinearity parameter reached the peak value when the microcracks initiated, and the nonlinearity parameter began to decrease when the microcracks further propagated to macrocracks. Therefore, it is proved that the nonlinearity parameter can be used to characterize the initiation of microcracks at the early stage of fatigue, and a method of evaluating the fatigue life of materials by nonlinear ultrasonic testing is proposed.