High-intensity, Wideband Ultrasonic and Resonant Acoustic Investigations for Material Testing and Characterization

High-intensity and nonlinear acoustic and ultrasonic testing of materials is a relatively new frontier in mechanical characterization of materials. In the first part of this dissertation research, ultrasonic transmission is taken to the extreme with high-intensity focused ultrasound (HIFU) as a non-contact method of producing focused energy spatially and temporally. Although it has been well investigated in the biomedical field, HIFU has not been explored as a dynamic, high-strain-rate characterization technique for materials. Here, we report the potential of HIFU as a stress-generating apparatus for material testing. Specifically, it is shown that adhesively bonded thin-film soft laminates can be selectively delaminated at the interface via HIFU, demonstrating its capacity as a compact, non-contact mechanism of shock wave generation. In the second and third parts, acoustic transmission intensity is increased with secondary harmonic generation (SHG) and nonlinear resonance acoustic spectroscopy (NRAS), respectively. In the third part, an S-parameter-based approach, particularly the bisection de-embedding method is also proposed for accurately measuring the wave speed and attenuation of materials, significantly expanding the effective bandwidth of transducers employed for testing. These methods are used for testing the nonlinear elastic responses of various advanced materials. The proposed work outlines the numerical and experimental work to complete the dissertation.