A measurement of ultrasonic attenuation coefficient by frequency response in steels with different grain sizes

摘要

A new evaluation method of ultrasonic attenuation in materials is proposed based on the frequency response property of the material evaluated by employing the sound impulse of a wide frequency band. Borrowing from ordinary system theory, the material to be tested is considered to have a characteristic impulse response, representing its micro-structural non-uniformities and thus resulting in the sound attenuation of the material. The concept is resumed as an attenuation system that simulates the material's micro-structural behavior. Experimental results on a series of specimens, having different grain sizes but all made of a single austenitic stainless steel, showed that the attenuation could properly be evaluated from a single bottom echo in a plate specimen. The attenuation coefficient α, was correlated in this case to the grain size, D, by the equation, αD=H(πD/λ){sup}n, where λ is wave length and H and n are constants. It was also shown that the micro structural change of materials could be evaluated by the energy loss of sound waves passing through the attenuation systems.