Numerical study of the Time-of-Flight Pulsed Ultrasonic Polar Scan for the determination of the full elasticity tensor of orthotropic plates

Abstract

A novel approach is presented for the ultrasonic determination of the elastic constants in plate-like structures of an orthotropic material (e.g. composites) using a Time-of-Flight version of the Pulsed Ultrasonic Polar Scan (TOF P-UPS). A forward numerical model of the TOF P-UPS is coupled to an inversion algorithm, based on the genetic optimization principle, targeting the determination of the orthotropic elastic parameters, and the quality of the inversion is demonstrated for synthetic data representative for composites. The advantage of the new approach is that the presented TOF P-UPS inversion method does not require a priori knowledge about the symmetry class of the material, nor about the orientation of the main axes of symmetry. Furthermore, the TOF P-UPS inversion method yields an accurate characterization of the orthotropic elasticity tensor, even when applied to composite plates with small frequency-thickness ratios in which the traditional bulk wave approaches no longer hold. Finally, the robustness of the TOF P-UPS inversion method is demonstrated for noisy data by evaluating the results for a range of signal-to-noise ratios.