Quantitative estimation of ultrasonic attenuation in a solid in the immersion case with correction of diffraction effects

This paper presents a method of diffraction correction for the log-spectral difference method to estimate quantitatively attenuation of a solid in the immersion case. The correction method is established based on the angular spectrum approach that is used to calculate the echoes from the front and b ack surfaces of the immersed solid. An example is given of a copper plate s ubmerged in water and inspected by a linear array with a cylindrically curv ed surface. The correction method is first applied to a theoretical estimat ion of attenuation which is linearly dependent on frequency. The results ha ve shown that the evaluated attenuation coefficient is in excellent agreeme nt with the exact value. Then the method is applied to a real situation, in which the results have shown that the method yields reasonable evaluated a ttenuation values. This work has demonstrated that the method is able to co rrect effectively the diffraction effect so as to achieve a quantitative es timation of attenuation. (C) 2000 Elsevier Science B.V. All rights reserved .