Modeling stress-strain nonlinear mechanics via entropy changes on surface wetting using the Born-Oppenheimer approximation

Abstract

The process of stress-strain nonlinear deformation is fundamental to almost all branches of science and engineering. Although the mechanical mechanisms of such process are well studied, the governing atomic processes that take place inside solids during mechanical loading remains unclear. In this work, new equations to characterize the stress-strain nonlinear deformation from entropy changes on surface wetting are presented. The evolution of entropy changes during mechanical loading is calculated based on the Born-Oppenheimer approximation, wherein electronic, nuclear, electron-phonon, and phonon-phonon coupling interactions are treated independently. Further measurement and modelling of water contact angles at different strain loadings for NiTi, steel, and aluminum systems, within the elastic and the early plastic domain, are performed to validate the derived equation. These results may enable a paradigm shift from energy-force to entropy-centric research while offering exciting possibilities in NDT inspection, featureless fluid navigation, and anti-biofouling fields.

Keywords

• Surface wettability
• Young's modulus
• Elastic-plastic deformation
• Entropy
• Born-oppenheimer approximation