On the precision and Accuracy of the acoustic birefringence technique for stress evaluation

This paper presents a numerical procedure for estimation of the precision and accuracy of the acoustic birefringence technique for evaluation of residual and applied stresses in civil structures and components. This procedure accounts in an automatic and systematic way for the uncertainties in the input data and their propagation throughout the calculations. The acoustic birefringence is defined from the speeds of two mutually orthogonal volumetric waves of normal incidence, but when the use of a pulse-echo measurement system is feasible, the birefringence can be defined directly from the time-of-flight of the waves, since they travel the same physical space. The times-of-flight of the waves are estimated by coupling the mathematical techniques of cross correlation and data interpolation, whereas the material’s acoustoelastic constant is determined via a weighted linear regression. As an example, the estimation of the precision and accuracy in the evaluation of the stresses in a beam under bending is discussed.