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Already in the early 1980's, it has been conjectured that the pulsed ultrasonic polar scan (P-UPS) provides a unique fingerprint of the underlying mechanical elasticity tensor at the insonified material spot. Until now, that premise has not been thoroughly investigated, nor validated, despite the opportunities this would create for NDT and materials science in general. In this paper, we report on the first-ever implementation of an inverse modeling technique on the basis of a genetic optimization scheme in order to extract quantitative information from a P-UPS. We validate the optimization approach for synthetic data, and apply it to experimentally obtained polar scans for annealed aluminum, cold rolled DC-06 steel as well as for carbon fiber reinforced plastics. The investigated samples are plate-like and do not require specific preparation. The inverted material characteristics show good agreement with literature, micro-mechanical models as well as with results obtained through conventional testing procedures.

Abstract:In the early 1980's, the ultrasonic polar scan (UPS) technique was developed to assess the fiber direction of composites in a nondestructive way. In spite of the recognition by several researchers as being a sophisticated and promising methodology for nondestructive testing (NDT) and materials science, little advance was made during the following 30 years. Recently however, the UPS technique experienced a strong revival and various modifications to the original UPS setup have been successfully implemented. This revival has exposed several powerful capabilities and interesting applications of the UPS technique for material characterization and damage assessment. This paper gives a short historical overview of the UPS technique for characterizing and inspecting (damaged) fiber-reinforced plastics. In addition, a few future research lines are given, which will further expand the applicability and potential of the UPS method to a broader range of (damaged) materials, bringing the UPS technique to the next level of maturity.

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