Researchers Use Expanse to Explore Causes of Friction

A ball bearing piece expanded to view the components that make it up.

Leonardo Da Vinci – an artist, scientist and inventor recognized by many for his famous works such as the Mona Lisa and the Creation of Adam – made several contributions to human society, including sketch designs for the ball bearing (a rolling device used to create space between moving parts). His conception of the device was a way to reduce the friction of a rotating axis in his design for a helicopter – another creation of the Renaissance man. 

Now, several hundred years later, researchers who understand more about friction still puzzle over how and why it exists between seemingly smooth surfaces. 

To address this question, a team of engineering scholars from Johns Hopkins University used the Expanse supercomputer at the San Diego Supercomputer Center at UC San Diego to create simulations to model the friction between two rough surfaces coated with fatty acids. The simulations from Expanse showed that the junctions between the peaks of the original rough surfaces controlled what is termed “frictional aging” – the increase of friction when two surfaces in contact are at rest.

The scientists’ cutting-edge research combined friction experiments, molecular simulations and a multiscale theoretical model to examine the molecular mechanisms underlying structural frictional aging and its transient friction response on the macroscopic scale. 

Their study was published in a paper titled From Molecular to Multiasperity Contacts: How Roughness Bridges the Friction Scale Gap in American Chemical Society Nano.

When we simulated this situation at the nanoscale level, we were very surprised that the original nanoscale roughness of the surface made a difference – not just the fatty acids. Think of a frying pan – it is a seemingly smooth surface because it has a coating to make it this way, but at the nanoscale level, this pan is rough as it is not possible to make the surface completely smooth.

Lucas Frerot, postdoctoral scholar at Johns Hopkins

You can read more about this story here (Published March 29, 2023): Expanse Supercomputer Helps Researchers Understand What Causes Friction between Smooth Surfaces

Project Details

Institution: SDSC (San Diego Supercomputer Center)
University: UC San Diego
Funding Agency: The work on Expanse was funded by the National Science Foundation Extreme Science and Engineering Discovery Environment (XSEDE)
Allocation Number: TG-MAT210003

The science story featured here, allocated through August 31, 2022, was enabled through Extreme Science and Engineering Discovery Environment (XSEDE) and supported by National Science Foundation grant number #1548562. Projects allocated September 1, 2022 and beyond are enabled by the ACCESS program, which is supported by National Science Foundation grants #2138259, #2138286, #2138307, #2137603, and #2138296.

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