Dynamic evolution of thermal erosion at the armature-rail interface via a three-dimensional fully-coupled multiphysics model

Abstract Extreme thermal erosion at the armature-rail interface stems from severe nonlinear coupling among electromagnetic, thermo-mechanical, and phase-change fields under mega-ampere hypervelocity sliding. To overcome the intrinsic limitations of traditional decoupled or idealized models, a three-dimensional transient fully-coupled multiphysics framework is established. This methodology synchronously resolves magnetic diffusion, contact stress redistribution, dynamic contact impedance, and wear evolution within a unified formulation. Validated against experimental post-launch morphologies, the model dismantles conventional damage criteria: severe erosion localization does not strictly coincide with peak current density zones. Instead, damage progression is dictated by the synergistic co-evolution of interfacial electrical conductivity under the joint influence of transient current density and contact stress. Furthermore, a distinct staged evolution pattern of thermal erosion is identified, fundamentally governed by the dynamic composite heat-source competition between dominant contact Joule heating and transiently amplified frictional-shear dissipation. The framework quantitatively captures a U-shaped, non-monotonic temporal evolution of contact impedance, elucidating the initial mechanical hysteresis and the antagonistic interplay between pressure-enhanced conduction and thermal-induced structural degradation. This work unveils the invisible transient contact states during electromagnetic launch, providing a robust theoretical foundation for designing long-life, erosion-resistant sliding electrical contacts.