Material characterization with the ultrasonic microscope

An effective method for material characterization with a scanning acoustic microscope (SAM) is presented. The elastic parameters Young's modulus and bulk modulus and the density are determined from one single reflection signal. In contrast to established methods a calibration specimen is not required. Additionally, the thickness of the specimen can be estimated with two reflection signals at different focus positions. The new method evaluates the parameters of the surface echo, the longitudinal backwall echo and the mode converted transverse wave backwall echo. With estimated material characteristics, a simulation is set up and results are compared to the measured reflection parameters. Accordingly, the material characteristics are iteratively adapted until a minimum error criterion is reached. This approach can deliver results as accurate as the ultrasonic simulation. The results of a new and fast ray-trace based simulation will be verified with reference measurements and finite element simulations combined with a sound-field measurement.