縦波音速測定時の超音波散乱に伴う誤差の評価

概要

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The scattering of elastic longitudinal wave on reflection at a free plane boundary is studied using the analytical solution for a two-dimensional wave field generated by strip surface stresses. The variation of the scattered field is calculated with various incident angles of the narrow beams and displayed in polar diagrams, which show a wide range of scattered strength. The calculated result reduces to the specular reflection of the infinite plane wave with the increasing number of beams in the bundle. These results give the basis for estimating the experimental error due to the scattering of the first and second echoes launched by transducers of finite width. The scattering-induced error is well characterized by the ratio of the transducer width to the square root of the specimen thickness, both being normalized by the wavelength. As this ratio increases from zero, the error begins to increase, passes a peak, and then approaches a constant value. To minimize the error, the use of a tranducer is suggested, for which the near-field length is at least four times the specimen thickness.
一般社団法人日本機械学会の論文
1989-04-25