Experimental and theoretical study of harmonic generation at contacting interface

Area of Science:

• Solid Mechanics
• Materials Science
• Nonlinear Acoustics

Background:

• Contacting interfaces exhibit nonlinear behavior under mechanical load.
• Second harmonic generation is a key indicator of interface nonlinearity.
• Understanding interface nonlinearities is crucial for applications like non-destructive testing.

Purpose of the Study:

• To experimentally evaluate the second harmonic generation of a contacting interface.
• To theoretically model the nonlinear behavior of the interface using a nonlinear interface model.
• To identify interfacial stiffness parameters and evaluate the nonlinearity parameter.

Main Methods:

• Two aluminum blocks were mated to form a contact interface and subjected to normal compressive loading.
• A 5 MHz longitudinal toneburst wave was transmitted through the interface.
• The transmitted wave's fundamental and second harmonic components were extracted to determine a nonlinearity parameter.

Main Results:

• The nonlinearity parameter was calculated as the ratio of the second harmonic amplitude to the squared fundamental amplitude.
• Linear and second-order interfacial stiffness parameters were identified from the contact pressure dependence of the fundamental amplitude.
• The theoretical model showed good qualitative agreement with the experimental results for the contact pressure dependence of the nonlinearity parameter.

Conclusions:

• The study successfully evaluated the second harmonic generation behavior of a contacting interface.
• The developed nonlinear interface model effectively describes the experimental observations.
• The findings contribute to a better understanding of interface nonlinearities and their characterization.