1992 Volume 41 Issue 464 Pages 765-769
A measurement system of transit time of ultrasonic waves propagating through the thickness of plates under plane-stress state was developed, which is an improvement of the zero-crossing method with a personal computer and a high resolution digital memory or oscilloscope.
In this system, thirty pairs of the first and second echo profiles stored in a digital oscilloscope are averaged in a personal computer, and then the rising portion of the averaged wave profile is enlarged on a screen of the computer and fitted to a straight line. The transit time of the echo is determined by the ordinate of the cross point of the straight line and the zero line. This system can measure the transit time to an accuracy of 1ns for shear waves propagating through an aluminum specimen.
The acoustoelastic constants of a 2017-T3 aluminum plate of which rolling direction was parallel to the uniaxial tensile direction were found as follows; the constant for initial anisotropy=6.5×10-3, the stress-birefrigent coefficient=-34×10-6MPa-1.
Using these constants, the principal stress difference of the residual stress in an annulus which was shrink-fitted to a shaft was measured. The tangential and radial residual stress components were separated with the elastic solution of plane axisymmetric stress field. They were in good agreement with the analytical results.
