STP624: Standards for Quantitative Nondestructive Examination

    Tittmann, BR
    Member of technical staff, director of structural materials, and member of technical staff, Science Center, Rockwell International, Thousand Oaks, Calif.

    Thompson, DO
    Member of technical staff, director of structural materials, and member of technical staff, Science Center, Rockwell International, Thousand Oaks, Calif.

    Thompson, RB
    Member of technical staff, director of structural materials, and member of technical staff, Science Center, Rockwell International, Thousand Oaks, Calif.

    Pages: 17    Published: Jan 1977


    Abstract

    In this report, the subject of ultrasonic standards is reappraised in terms of history, philosophy of calibration, and future needs. In answer to the critical need for a procedure to calibrate ultrasonic systems for quantitative nondestructive examination (NDE), a new calibration standard and procedure is proposed.

    The calibration standard proposed is the far-field sphere (cavity or inclusion embedded in a solid or a ball suspended in a liquid). As a result of recent work, the sphere now is understood well theoretically and experimentally and can be reproduced and fabricated in a solid, for example, by diffusion bonding techniques. A major advantage of the sphere is that it has no preferential orientation, the transducer alignment is not critical, and it allows multipoint checks on a single standard block.

    The backbone of the calibration procedure is an equation which relates the transmitter signal to the received signal in a quantitative way. With the help of this equation, the scattering parameters, namely, the angular dependence, frequency dependence, and amplitude of the differential scattering cross section may be determined from data obtained on a calibration standard. The results may be compared then with the invariant theoretical solution to verify the proper operation of the ultrasonic system. A key feature of the development is the G-factor which is a proposed figure of merit for a transducer. The discussion includes a technique for its simple determination and its use in the calibration procedure.

    Keywords:

    nondestructive tests, ultrasonic frequencies, standards, spheres, scattering cross sections, transducers, calibration, eigenvalues, eigenvectors, flat-bottom holes, attenuation, goniometers


    Paper ID: STP27040S

    Committee/Subcommittee: E07.06

    DOI: 10.1520/STP27040S


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