Ultrasonic birefringence effect - its application for materials characterizations

The availability of ultrasonic probes to generate linearly polarised shear waves in components on the one hand, and the possibilities to measure ultrasonic time-of-flight with sufficient accuracy on the other hand, render the application of acoustic birefringence possible. The similarity to the better known optical birfrengence became obvious by experimental investigations using a solid under applied stress as well as by the theoretical treatments of the acousto-elastic effects. The major applications of the acoustic birefringence effect are the characterisation of stress states in the bulk of components and the characterisation of texutre and testure-related properties of rolled parts and semiproducts. Both stress and texture cause an elasti anisotropy of the component. The birefringence of a lineary polarised shear wave, polarised parallel to each of the two principal axes, respectively, yield quantitative results. The state of the art is illustrated by two application of industrial relevance.