Investigation of Nonlinear Mechanics Pertaining to Amplitude Filters and Rolling Contact
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Mork, Nehemiah Steven
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Abstract
The first half of this work investigates a novel filtering approach for acoustic signals in periodic media that is dependent on the signal amplitude. Two unique hierarchical unit cells are presented resulting in high-pass as well as low-pass amplitude dependent filtering of acoustics signals. The amplitude filtering effects of each nonlinear unit cell are first predicted using a series of numerical simulations, then supported using an analytical nonlinear harmonic balance analysis, and verified using a series of experimental tests using fabricated lattices and nonlinear unit cells. The second half of this work transitions focus to the nonlinear mechanics present in frictional rolling contact between an elastomeric roller and rigid substrate. We experimentally verify the friction-induced memory effect in quasistatic elastomeric rollers under normal and tangential loading by utilizing digital image correlation (DIC). We then present a novel procedure for implementing DIC for dynamic loading scenarios when material convects through a region of interest allowing for higher resolution in the region of interest compared to current methods. We demonstrate the proposed method by analyzing the region of the roller sidewall along the roller-substrate contact region during dynamic rolling. This analysis allows for imaging the evolution of the strain state in the roller from quasistatic steady state, through the transient regime, and finally reaching a dynamic steady state. Understanding frictional contact may also prove valuable in roller design and shed light onto rolling instabilities and their effects on global roller mechanics. The presented dynamic DIC method presents a new method for studying a wide range of dynamic loading scenarios.
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2024-04-09
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Dissertation