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Research

My research revolves around tribology, the science of surfaces. I am particularly interested in the modeling of rough contact interfaces and how understanding these interfaces can help modeling friction and wear of solids.

For a complete list of publications, see my ORCID profile.

Rough contact interfaces

Virtually all real surfaces (from geological fault faces to hard drives, from roads to cartilage) are rough if one looks closely enough. This means that contact between two solids is never perfect, or even smooth: the solids only touch in sparse areas with complex geometries. The “true contact area” is typically only a few percent of the apparent area of contact (the macroscopic dimensions of the solids), and it is from the surface interactions at this “true contact area” that properties like friction and wear emerge (see friction and wear below).

Many natural surfaces exhibit a fractal-like behavior: as one “zooms-in” on roughness, one discovers more roughness at smaller scales.

A rough surface

The fact that surface roughness does not have a characteristic scale makes contact interfaces challenging to model, because all roughness scales can be relevant and should be accounted for. Things become even more complex when non-linear material behavior comes into play.

During my doctoral work, I have developed an efficient numerical method to model contact of rough surfaces with elastic-plastic materials (such as metals). Below is a picture of such a simulation, where we can see the plastic zones that develop due to the heterogeneous contact pressure.

Plastic zones in a rough contact

Such simulations are possible thanks to the use of Fourier-domain Green’s functions that I derived (cf. The Mindlin Fundamental Solution - A Fourier Approach). I have implemented this Fourier-based numerical method for elastic-plastic contact in an open-source code called Tamaas, which is a hybrid C++/Python library for simulating all sorts of contact situations. Feel free to check out the tutorials.

Nanoscale tribology

Although understanding roughness is fundamental to understand the macroscopic properties of friction and wear, understanding of these phenomena at the nanoscale is equally important. This is why I am interested in the small-scales mechanisms of friction and wear, keeping in mind that these mechanisms interact with the surface roughness in the sparse contact area and give rise to the macroscopic properties we can observe and measure.

In particular, I am interested in ductile evolution of surface roughness in polymers and how the sliding velocity can affect this evolution. Below is a molecular dynamics simulation of an asperity collision in a polymer glass.

Wear of a polymer asperity

I am also interested in the friction properties of fatty acid monolayers, which form a system simple, yet rich enough to observe and study complex friction dynamics.

Scientific Communication

I believe proper scientific communication, targeted at peers but also at the greater public, is an important part of a researcher’s work. To create figures that appeal to the people outside the scientific field, I use cutting edge (open-source) tools like Blender. I recently made a render from roughness measured on a nanoscrystalline diamond surface by Luke A. Thimons and co-workers (doi:10.57703/ce-4r74d), which was used in a press release for the Contact.Engineering open platform, whose goal it is to standardize rough surface analysis, facilitize that analysis and the open sharing of data, in the spirit of reproducibility.

nanocrystalline diamond surface

I also believe visuals are the opportunity for science to meet art, and artistically appealing visuals can be the start of a scientific conversation.

contact pressures in the style of Andy Warhol

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