Topographic Temperature: A Maximum-Entropy State Description of Running-In Surfaces

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Hauptverfasser: Brodmann, Boris, Eifler, Matthias
Format: Preprint
Veröffentlicht: 2025
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author Brodmann, Boris
Eifler, Matthias
author_facet Brodmann, Boris
Eifler, Matthias
contents Surface topography governs tribological performance, yet conventional parameters describe either amplitude statistics or spectral content in isolation. We introduce a scale-dependent framework that represents surface height and directional gradient as conjugate coordinates of a structural phase space. The elastic reference energy derived from Persson's contact mechanics theory defines a metric that couples surface geometry to the elastic half-space response. A maximum-entropy formulation yields a canonical state density. In the Gaussian limit this formulation recovers Persson's spectral description exactly, showing that the power spectral density is a complete contact mechanical descriptor only under Gaussian statistics. The associated Lagrange multiplier defines a topographic temperature in the sense of Grmela's multiscale thermodynamics and embeds the areal subsystem within a scale-dependent boundary potential. The framework is validated experimentally using ground and honed AISI 52100 steel discs before and after running in. The ground surface contracts toward lower entropy and elastic energy, whereas the honed surface expands into previously unoccupied states. These opposite trajectories become transparent only in the coupled height-gradient representation and highlight the role of the principal directional gradient for scale-aware surface metrology.
format Preprint
id arxiv_https___arxiv_org_abs_2503_01286
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Topographic Temperature: A Maximum-Entropy State Description of Running-In Surfaces
Brodmann, Boris
Eifler, Matthias
Signal Processing
Optics
Surface topography governs tribological performance, yet conventional parameters describe either amplitude statistics or spectral content in isolation. We introduce a scale-dependent framework that represents surface height and directional gradient as conjugate coordinates of a structural phase space. The elastic reference energy derived from Persson's contact mechanics theory defines a metric that couples surface geometry to the elastic half-space response. A maximum-entropy formulation yields a canonical state density. In the Gaussian limit this formulation recovers Persson's spectral description exactly, showing that the power spectral density is a complete contact mechanical descriptor only under Gaussian statistics. The associated Lagrange multiplier defines a topographic temperature in the sense of Grmela's multiscale thermodynamics and embeds the areal subsystem within a scale-dependent boundary potential. The framework is validated experimentally using ground and honed AISI 52100 steel discs before and after running in. The ground surface contracts toward lower entropy and elastic energy, whereas the honed surface expands into previously unoccupied states. These opposite trajectories become transparent only in the coupled height-gradient representation and highlight the role of the principal directional gradient for scale-aware surface metrology.
title Topographic Temperature: A Maximum-Entropy State Description of Running-In Surfaces
topic Signal Processing
Optics
url https://arxiv.org/abs/2503.01286