Session: 01-16-02: Congress-Wide Symposium on NDE & SHM: Ultrasonic Waves for Material Characterization and Damage Assessment

Paper Number: 119909

119909 - Effects of High-Intensity Focused Ultrasound on Bonding Characteristics of Laminated Thin Materials 

            High-Intensity Focused Ultrasound (HIFU) is mainly used in biomedical scenarios for therapeutic applications, such as tissue ablation, histotripsy through cavitation, and lithotripsy in the kidneys. In this study, we investigate the effects of HIFU on materials, specifically the onset of damage in bonded thin-film laminates with varying adhesive conditions. HIFU stimulation of laminates is distinct for adhesion assessment as it is non-contact and can be controlled spatially and temporally. HIFU is unique since it can alter the strength of adhesion layers locally at depth, as HIFU waves have highest intensity at its focus, as opposed to on the surface with other types of approaches. The testing setup consists of a 2.5 MHz HIFU transducer (H-108, Sonic Concepts, USA) sonicated with a 400-Watt amplifier (1040L, E&I Ltd., USA), as well as adhesively bonded thin-film laminates, which are both suspended within a water tank using a three-axis stage. The stage is rated at a precision level of 0.05 mm, which allows for highly precise positioning of the laminates in relation to the HIFU transducer. Before the adhesion test, the free pressure field of the HIFU focal region is qualitatively measured using a hydrophone (NH0200, 0.2 mm needle, Precision Acoustics, UK). Then, the HIFU sonication of the laminate is captured in-situ using a high-speed camera to visualize fast-acting time-dependent changes such as delamination. The thin-film laminates once sonicated with the HIFU transducer, exhibit varying visible spot colorization, size, and movement into or away from the adhesive layer. These changes are expected to be due to the excitation level and duration of the HIFU waves, as well as the bond conditions in the adhesive layer. The laminates are then inspected using a scanning Laser Doppler Vibrometer, high-fidelity optical microscope, profilometer, and Raman spectroscopy to correlate excitation level, position, and duration, with the alteration of the laminate. Furthermore, we attempt to establish a correlation between damage spot size and coloration, and bond condition. Numerical simulations using finite-element analysis have been conducted to further understand the mechanical and heating effects of HIFU on thin film laminates and corroborate our experimental results. These simulations use heat transfer modeling for thermal analysis, as well as the cohesive zone model for mechanical analysis of the adhesion layer. The acoustic domain is simulated using the Westervelt wave equation to include nonlinear wave effects. Our findings help us predict and understand the HIFU induced effects on the adhesive strength and failure mechanisms of the thin film laminates, and demonstrate a smaller, localized understanding of strength in adhesive layers. 

Presenting Author: Jacob Brody Georgia Institute of Technology

Presenting Author Biography: Jacob Brody is a second year doctoral student in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. He currently works in the Smart Structures and Dynamical Systems laboratory under the advisement of Dr.Alper Erturk. The primary focus of his research is exploring the high-strain rate applications of High Intensity Focused Ultrasound within materials testing.

Authors:

Jacob Brody Georgia Institute of Technology
Prabhakaran Manogharan Georgia Institute of Technology
Alper Erturk Georgia Institute of Technology
Nathan Moore Sandia National Laboratories