Frequency Characteristics of Acoustic Emission Signal from Fatigue Crack Propagation in 5083 Aluminum by Joint Time-Frequency Analysis Method

J. Ocean Eng. Technol. 2003;17(3):46-51.

NAM KI-WOO;LEE KUN-CHAN;

Dept. of Materials Science and Engineering, Pukyong National University;Graduate School, Pukyong National University;

시간-주파수 해석법에 의한 5083 알루미늄의 피로균열 진전에 의할 음향방출 신호의 주파수특성

남기우;이건찬;

부경대학교 재료공학과;부경대학교 대학원;

핵심용어: Joint Time-Frequency Analysis Method 시간-주파수 해석법, Fatigue Crack Propagation 피로균열전파, Stress Ratio 응력비, Load Cycle 하중반복속도, Acoustic Emission 음향방출, Nondestructive Evaluation 비파괴평가

Abstract

Acoustic emission (AE) signals, emanated during local failure of aluminum alloys, have been the subject of numerous investigations. It is well known that the characteristics of AE are strongly influenced by the previous thermal and mechanical treatment of the sample. Possible sources of AE during deformation have been suggested as the avalanche motion of dislocations, fracture of brittle particles, and debonding of these particles from the alloy matrix. The goal of the present study is to determine if AE occurring as the result of fatigue crack propagation could be evaluated by the joint time-frequency analysis method, short time Fourier transform (STFT), and Wigner-Ville distribution (WVD). The time-frequency analysis methods can be used to analyze non-stationary AE more effectively than conventional techniques. STFT is more effective than WVD in analyzing AE signals. Noise and frequency characteristics of crack openings and closures could be separated using STFT. The influence of various fatigue parameters on the frequency characteristics of AE signals was investigated.