Simultaneous Determination of Orientation and Thickness in Anisotropic Media

Ultrasonic travel-time techniques are commonly utilized for thickness determination in parts where the properties of the material are well characterized. Typically, this use has been limited to isotropic materials ( where the ultrasonic velocity used to determine the thickness is independent of the direction of propagation in the material ). For anisotropic materials, the situation is considerably more complicated due to the directional dependence of the ultrasonic velocity. If the orientation of the material is known, then the same approach used for isotropic samples can be used for thickness determination, providing one properly accounts for the known anisotropy in velocity. When the orientation and thickness are both unknown, a new approach must be utilized to avoid errors arising from the intrinsic variation in the ultrasonic velocity due to anisotropy.