Hiroki Toda

R-value Acoustoelastic Analysis of Residual Stress in a Seam Welded Plate

R-value acoustoelastic analysis method (R-method) is proposed for a nondestructive residual stress measurement. Application of this method to the measurement of residual stress in a seam welded plate shows it to be promising with the potential to measure residual stress within an error of 10 MPa.

Texture-Induced Acoustic Anisotropy due to Compressive Deformation (Effects of Strain-Rate and Temperature)

A texture-induced acoustic anisotropy originated by plastic deformation under compression is investigated for copper and aluminum polycrystalline metals making use of a birefringent effect of a polarized ultrasonic wave to study the effects of strain-rate and temperature in the deformation process. A variation in acoustic anisotropy appears to be influenced by both strain-rate and temperature for copper, but it definitely does not appear for aluminum.

Scattering-induced error in longitudinal wave velocity measurement.

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.