Back by popular demand, the Beyond the Cutting-Edge plenary symposium presented by the editors of Tribology Letters highlights some of the best papers published in the peer-reviewed journal.
Wednesday, November 15, 2023
Sessions 5D 8:00 – 11:30 am
8:00 - 8:30 am
3771598: More on Mouthfeel: Imbibing Bubbly Beverages
Thomas Reddyhoff, Sorin Vladescu, Connor Myant, Imperial College London, South Kensington, London, United Kingdom; Sophie Bozorgi, Guy Carpenter, Kings College London, London, United Kingdom; Stefan Baier, Motif FoodWorks, Boston, MA
The perception of carbonation is an important factor in beverage consumption which must be understood in order to develop healthier products. This presentation describes the effects of carbonated water on oral lubrication mechanisms involved in beverage mouthfeel and hence taste perception. Friction was measured in a compliant PDMS-glass contact simulating the tongue-palate interface (under representative speeds and loads), while fluorescence microscopy was used to visualize both the flow of liquid and oral mucosal pellicle coverage. Results from tests, in which carbonated water is entrained into this contact, reveal two distinct tribological mechanisms - namely bubble-induced starvation and salivary pellicle removal. Both of these will modulate the flow of tastants to taste buds and are suggested to be important in the experience of taste and refreshment. For example, this may be one reason why flat colas taste sweeter.
8:30 - 9:00 am
3935552: Linking Strength, Friction, and Ordering in Metallic Glasses
Nicolas Argibay, Ames National Laboratory, Ames, IA; Michael Chandross, Sandia National Laboratories, Albuquerque, NM
The friction and strength of shearing metal interfaces was previously linked to grain size in a predictable way for pure metals and dilute alloys, although the accuracy of these correlations was shown to be limited to inert conditions where oxidation and adsorbates have a negligible effect on interface properties. Recent work shows that macroscale friction experiments can also be used to probe the fundamental strength of structurally and chemically disordered alloys, including metallic glasses, with predictable results again limited to inert environments. We show how tribological experiments are being used to inform development of a theoretical framework for the strength of alloys as a function of their structural and chemical ordering and discuss opportunities for alloy composition and structure optimization to promote desirable mechanical behavior.
9:00 - 9:30 am
3756396: The Ultrafast Finger Snap is Mediated by a Frictional Skin Latch
Elio Challita, Raghav Acharya, Saad Bhamla, Georgia Tech, Atlanta, GA; Mark Ilton, Harvey Mudd College, Claremont, CA
The snap of a finger is a ubiquitous human motion that has been used as a form of communication across human cultures throughout millennia. Using high-speed imaging, we present the first study of the dynamics of finger snapping. We show that the finger snap can achieve angular accelerations of 1.6 × 106 °/s−2 in 7 ms making it one of the fastest movements the human body can produce. Our analysis shows that friction between finger pads acts as a latch in controlling this ultrafast movement. Using an experimental and mathematical approach, we show how skin friction lies in an optimally tuned regime enabling it to play a dual role in both loading potential energy and mediating the release of that energy during the finger snapping motion. Our work provides design insight towards the frictional complexity in many robotic and ultra-fast energy-release structures.
10:00 - 10:30 am
3933692: Linking Molecular Structure and Lubrication Mechanisms in Tetraalkylammonium Orthoborate Ionic Liquids
Filippo Mangolini, Jieming Yan, Hsu-Ming Lien, University of Texas at Austin, Austin, TX
While ionic liquids (ILs) have attracted wide interest as potential lubricants owing to their unique properties (e.g., high thermal stability) and good tribological properties, our understanding of the mechanisms by which ILs reduce friction and/or wear is still elusive. Here, we synthesize a homologous series of halogen-free ILs, namely tetraalkylammonium orthoborate ILs, and combine macroscale tribological experiments with surface-analytical measurements to gain insights into the relationship between the IL molecular structure and their lubrication mechanisms/performance. The results of steel-vs.-steel tribological tests indicate an improvement of the friction-reducing properties of these ILs as the length of the alkyl chains attached to ammonium cations increases. Based on ex situ X-ray photoelectron spectroscopy (XPS) analyses of the surface chemistry of steel after sliding tests, a phenomenological model is proposed for the observed tribological behavior.
10:30 - 11:00 am
3761773: Tribotronic Control and Electrochemical Properties of Nanofluid Interfaces
Jacqueline Krim, Caitlin Seed, Biplav Acharya, Alex Smirnov, North Carolina State University, Raleigh, NC
We have employed Quartz Crystal Microbalance (QCM) and cyclic voltammetry (CV) methods to explore nanotribological and electrochemical attributes of platinum or gold electrodes immersed in nanosuspensions of charged species (nanoparticles, ionic liquids, nanodiamonds). The setup consists of a QCM immersed in a nanosuspension whose sensing electrode faces a nearby counter electrode. An electric field perpendicular to the QCM surface is created when a potential is applied between the two electrodes, which allows the charged constituents in the suspension to be repositioned. QCM measurements are able to detect differences in friction under various field conditions, and thus detectably tune the friction in both nanoparticle and ionic liquid systems. CV simultaneously monitors the system's electrochemical attributes. The versatility, speed, and simplicity of QCM for friction measurements renders it an ideal tool for the rapidly expanding research area of tribotronics.
11:00 - 11:30 am
3764635: Nanosensors for In Situ Measurement of Pressure and Temperature in EHD Contacts
David Philippon, Tarek Seoudi, Nicolas Fillot, Lionel Lafarge, Nicolas Devaux, Philippe Vergne, INSA Lyon - LaMCoS, Villeurbanne, France; Alexandre Mondelin, SKF Aerospace France, Châteauneuf-sur-Isère, France
A new methodology based on the photoluminescence properties of non-intrusive nanosensors is presented for in situ measurement of pressure and temperature in lubricating confined films. Pressure and temperature calibrations of these sensors dispersed in a selected fluid were established through experiments in diamond anvil cells (DAC). Afterwards, measurements were carried out in elastohydrodynalic (EHD) contacts involving different contacting paired materials (glass, steel, Si3N4 and sapphire) and submitted to various operating conditions. The experimental results were compared with numerical simulations. Experimental pressure profiles obtained in isothermal experiments show a very good agreement with the values predicted by the numerical model. Non-isothermal cases were also carried out. Temperature rises in the central zone of EHD contacts involving various material pairs were measured and compared to predictions, leading to a very satisfying agreement.