Modeling the Evolution and Collective Frictional Behavior of Microscale Viscoelastic Contacts at High Sliding Speeds

Yuval Tal

Submitted September 7, 2025, SCEC Contribution #14871, 2025 SCEC Annual Meeting Poster #TBD

Microscale contact mechanics governs the frictional and sliding behavior of natural surfaces, playing a key role in earthquake dynamics. Here, I explicitly model the collective frictional behavior and contact evolution of a microscopically rough interface between 2-D viscoelastic bodies. The model employs a generalized Maxwell viscoelastic formulation for bulk contact deformation, and local microscopic shear resistance is either proportional to the normal stress or determined solely by the material shear strength, depending on the level of local normal stress. Moreover, the local frictional formulation includes the direct effect of logarithmic velocity strengthening, but not the evolution effect, which naturally emerges from bulk viscoelastic deformation. To simulate frictional sliding, these constitutive relationships are implemented into the mortar finite element method, which accommodates non-matching meshes and continuously updates the contact geometry, enabling large slip relative to the contact scale.

I focus on the frictional behavior of an analog material, PMMA (Polymethyl methacrylate), taking advantage of available experimental data on its viscoelastic properties, contact evolution, and frictional response during sliding. I begin by tuning the viscoelastic parameters to reproduce the experimentally observed logarithmic increase in effective elastic properties from low quasistatic to high dynamic strain rates. I then simulate frictional sliding at velocities ranging from 10-6 to 1 m/s, showing that this viscoelastic effect can explain several phenomena observed at these sliding velocities. These include a decrease in contact area and macroscopic frictional resistance with increasing sliding velocity, but an increase in the average local frictional resistance of the contacts themselves, in the absence of significant thermal effects.

Citation
Tal, Y. (2025, 09). Modeling the Evolution and Collective Frictional Behavior of Microscale Viscoelastic Contacts at High Sliding Speeds. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)