Katsuhisa Shibata

Ultrasonic Measurement of Rotation of Principal Axis of Plastic Anisotropy and Change of Elastic Stiffness of Prestrained Polycrystalline Sheet Metal.

It is desired to develop the identification scheme of the principal axis of plastic anisotrypy of polycrystalline sheet metal to the improvement of calculation accuracy of formability. Elastic anisotropy is due to texture, it is same cause with plastic anisotropy, therefore, plastic anisotropy can be measured through phase velocity measurement of an ultrasonic wave. The rotation of the principal axis and the change of elastic constants of a sheet metal for press forming during plastic deformation are identified with the phase velocity of Rayleigh wave. It is demonstrated that the principal axis rotates independently of the material fiber.

Two-Dimensional Vibration Intensity Measurement by Wave Composition.

As a method to measure the vibration intensity on a thin plate, wave composition method is presented. Sensors are arranged on the circle, so measurement is easier with this method than with traditional finite difference method, it arranges them on an array. Good measurement accuracy is expected because spatial derivation is performed algebraically employing Fourier transform. Simulations of estimation error are done for plane wave field and divergent wave field. Error is small for smaller measurement circle, however, under measurement error at sensors (unavoidable at practical measurement), estimation with smaller measurement circle suffers from this measurement error. Larger circle diameter is suitable for robust measurement. Comparison with traditional finite difference method is performed. Present method shows good accuracy for broad frequency range.

Influence of Support Condition on Loss Factor of Beam of Sandwich Plate.

The influence of the support condition of a beam of a sandwich plate on the modal loss factor is examined. Resonant frequency and modal loss factor are calculated based on Meads theory. While Ungars equation, which is generally employed to estimate loss factor, is valid only for a simply supported beam, a trial of applying it to other support conditions is performed by defining the equivalent half-wavelength, and it is suggested that for support conditions other than simply supported as well, resonant frequency is well predicted by Ungars equation. Only for the simply supported beam, can the modal loss factor be determined uniquely from frequency. For other general support conditions, loss factor depends on the mode order. An experiment is performed with the support condition of both ends simply supported and free, and a similar tendency to these finding is shown. It was demonstrated that the loss factor obtained from antiresonance for symmetrically supported beams corresponds to the modal loss factor for the clamped beam of half length. This is also verified experimentally.

Measuring Condition and Precision of Vibration Intensity Measurement in Plates.

Errors involved in bending vibration intensity measurement consist of systematical errors due to finite difference and random errors. Both errors are investigated through analysis and experimentation. A correction factor is proposed to minimize the errors due to the finite difference for the general measuring condition. The following results are obtained. ( 1 ) The method which uses 9 measuring points is recommended for measuring the intensity in a far-field condition. ( 2 ) The condition to minimize the random errors is proposed; the product of wave number k and the space Δ between sensors is specified in the paper. ( 3 ) The method which uses 4 measuring points gives a larger value than the actual one.