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비선형 탄성-음향 효과를 이용한 비선형 탄성 계수의 계측과 금속재료의 특성평가
장경영,좌등척송,Sato, Takuso 대한기계학회 1993 대한기계학회논문집 Vol.17 No.8
In this paper, a new method to estimate stress status in metal nondestructively by using nonlinear dependency of sound speed on stress is proposed. For the purpose, equivalent nonlinear elastic constants up to fourth-order are introduced and a new characteristic parameter given as a function of these constants is presented. And a concrete system to measure the characteristic parameter is constructed by electromagnetic pumping wave and ultrasonic probing wave system. Some experimental results for Al alloy showed that the estimation of stress status in metal is possible by the proposed method.
2차원 초음파 회절격자를 이용한 음향-광3차 상관기의 구성
장경영,Jang, Gyeong-Yeong,Sato, Takuso 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.1
Third order correlation funciton is to be advantageous to detect unique features embedded in various random signals that are undetectable with second order correlation or power spectrum. In this paper, we will introduce optical modulator which consists of a laser light source, 2-dimensional ultrasonic diffractor cell with signal controlling circuitry, and a CCD camera connected to personal computer for image processing. With this modulator, the third order correlaiton pattern of signal can be immediately obtained at the camera due to parallel nature of optical computing.