Session: 16-01-01: Poster Session: NSF-Funded Research (Grad & Undergrad)

Paper Number: 99789

99789 - Measurement of Contact Stiffness of Engineered Surface for Enriched and Novel Nonlinear Wave Propagation in Phononic Material. 

Nonlinearity in phononic materials enables advanced wave propagation features that are not possible in linear media. Phononic materials made by the periodic arrangement of rough contact interfaces have shown unprecedented wave phenomena such as fast-traveling solitary waves and energy transfer between frequencies. These behaviors are a result of the combined effect of periodicity, discrete contact nonlinearity, and micron-sized random asperities contributing to surface roughness. However, there is limited work on characterizing the dependence of the nonlinear stiffness on an engineered surface topography of contact interfaces, which could ultimately enable new nonlinear wave propagation responses in phononic media. This study aims to measure the stiffness of contact interfaces with engineered surfaces with sinusoidal waviness for different combinations of the contact interface such as a wavy-flat interface, wavy-wavy interface with peak-to-peak contact, and peak-to-valley contact. Two different experimental techniques, digital image correlation (DIC) and nonlinear ultrasound, are used to experimentally measure the contact stiffness. In the DIC technique, a high-speed camera in conjunction with a microscope is used to take high-resolution images of the interface under load and is analyzed afterward to capture the displacement field of the interface region which enables to measure the force-displacement relationship and thus the stiffness. On the other hand, the nonlinear ultrasound technique uses a high-frequency ultrasound wave to excite the interface and the resulting reflection wave is recorded. By using this reflection coefficient, the stiffness of the contact interface is measured by an analytically developed model correlating the stiffness to the reflection coefficient with other acoustic and material properties. The results obtained by both methods are compared in their ability to accurately measure contact stiffness and its dependence on precompression. The study also compares the corresponding stiffness value obtained experimentally to that obtained using the finite element method for smooth wavy surfaces. Nonlinear ultrasound always gives the local unloading stiffness and thus has a higher value than DIC measured stiffness, which gives the bulk tangential stiffness. However, the stiffness measured in both measurement methods is expected to follow a power-law relationship with the applied precompression. The DIC provides a straightforward and direct technique for contact interface stiffness measurement while, although complex, the nonlinear ultrasound technique provides diverse capabilities of stiffness measurement correlating different factors such as the amplitude, frequency, and wavelength of the excitation wave with the stiffness. The obtained local interface stiffness will then be used to investigate the global nonlinear wave responses of continuum phononic material with these discrete wavy contact interfaces, by modeling the interfaces as nonlinear springs using the experimental results. Measuring the nonlinear stiffness between different wavy interfaces will enable diverse nonlinear wave propagation in phononic materials with physically realizable nonlinear building blocks, with applications such as wave-controlled devices.

Presenting Author: Md Kamruzzaman University of Illinois Urbana-Champaign

Presenting Author Biography: I have completed my B.Sc and M.Sc. in Mechanical Engineering from Bangladesh University of Engineering and Technology in 2016 and 2019 respectively. Currently, I am pursuing my Ph.D. in Mechanical Engineering at the University of Illinois at Urbana-Champaign. My research mainly focuses on nonlinear wave propagation in phononic materials.

Authors:

Md Kamruzzaman University of Illinois Urbana-Champaign
Kathryn H Matlack University of Illinois Urbana-Champaign