Marginally dispersive ultrasonic waveguides
First Claim
1. A method for ultrasonically measuring selected physical parameters of a specimen, said method including improvements comprising the steps ofgenerating ultrasonic waves having a characteristic wavelength, andconfiguring a marginally dispersive waveguide for transmitting the ultrasonic waves into the specimen in a selectively dispersive manner, the configuring step including the steps ofselecting waveguide diameters over the length of the waveguide so the phase velocity of the ultrasonic waves in the waveguide, averaged over the entire length of the waveguide, exceeds ninety percent of the square root of the ratio of Young'"'"'s Modulus to waveguide material density,selecting waveguide diameters so that said diameters are less than one wavelength and greater than twenty-five percent of wavelength over substantially the entire length of the marginal dispersive waveguide.
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Abstract
Methods and apparatus for ultrasonically measuring selected physical parameters of a test material or structure are achieved by selecting and configuring waveguides for transmitting extensional, longitudinal, shear, Rayleigh and Lamb waves into media in a marginally dispersive manner. Marginally dispersive transmission is defined by specific criteria of velocity and waveguide diameter. Methods and apparatus for acoustically isolating the waveguides to permit leakage are included, as well as a method of extension to flexural mode conversion to launch flexural waves into a medium.
137 Citations
68 Claims
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1. A method for ultrasonically measuring selected physical parameters of a specimen, said method including improvements comprising the steps of
generating ultrasonic waves having a characteristic wavelength, and configuring a marginally dispersive waveguide for transmitting the ultrasonic waves into the specimen in a selectively dispersive manner, the configuring step including the steps of selecting waveguide diameters over the length of the waveguide so the phase velocity of the ultrasonic waves in the waveguide, averaged over the entire length of the waveguide, exceeds ninety percent of the square root of the ratio of Young'"'"'s Modulus to waveguide material density, selecting waveguide diameters so that said diameters are less than one wavelength and greater than twenty-five percent of wavelength over substantially the entire length of the marginal dispersive waveguide.
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35. In apparatus for ultrasonically measuring selected physical parameters of a specimen, the apparatus comprising means for generating ultrasonic waves having a characteristic wavelength, the improvement comprising
marginally dispersive waveguide means for transmitting the ultrasonic waves into the specimen in a selectively dispersive manner, the marginally dispersive waveguide means including a marginally dispersive waveguide constructed from at least one selected material, said waveguide being characterized by a length and selected diameters, said diameters being such that the phase velocity of the ultrasonic waves in the waveguide, averaged over the entire length of the waveguide, exceeds ninety percent of the square root of the ratio of Young'"'"'s modulus to waveguide material density, each of said diameters being less than approximately one wavelength and greater than approximately twenty-five percent of wavelength over substantially the entire length of the waveguide.
Specification