Effect of the density of pillar-patterned substrates on the contact mechanics: Transition from top to mixed contact with a detailed pressure-field description

TL;DR

This study investigates how the pattern density of pillar-patterned substrates influences the transition from top to mixed contact with a spherical lens, combining experiments, simulations, and theory to map contact regimes.

Contribution

It provides a comprehensive phase diagram linking physical parameters to contact regimes, integrating experimental, numerical, and theoretical insights.

Findings

Identified boundaries between contact regimes

Developed a phase diagram for contact transition

Combined multiple approaches for comprehensive analysis

Abstract

Different contact regimes between a spherical lens and a periodically patterned substrate are observed, when they are pressed against each other. Top contact occurs when only the highest substrate sections touch the lens, whereas mixed contact implies that both the highest and the lowest substrate sections come into contact with the lens. In this paper, we study how the pattern density of the substrate, along with its physical properties and those of the lens, determine the transition from top contact to mixed contact. Experiments and numerical simulations had been performed, as complementary approaches to obtain data, and a theoretical analysis has been developed to gain insight on the effect of the physical parameters on the contact transition. As a result, a phase diagram is presented, in terms of the load and the contact radius, that combines the observations of the three approaches (experimental, numerical, and theoretical), unveiling the boundaries of three contact regimes: (1) deterministic-driven contact, (2) top contact, and (3) mixed contact.