Pressure-dependent thermal contact conductance in a spindle interference-fit interface: A two-layer macro–micro design framework

Thermal contact conductance at a spindle shaft–rotor interference-fit interface evolves with the mechanical contact state and thereby affects interfacial heat flow, shaft temperature, and thermal deformation. Existing studies often treat rough-surface heat transfer, assembly and surface parameters, and interface morphology separately, limiting coordinated control of global thermal response and local contact pressure. This study develops a two-layer macro–micro computational framework that couples pressure-dependent rough-surface heat transfer with thermomechanical design. A finite-element model updates thermal contact conductance according to contact pressure, roughness, and hardness. Within the investigated ranges, conductance increases with interference magnitude and decreases with roughness and hardness. The first layer uses Kriging-assisted multi-objective optimization to select the single-sided radial interference, roughness, and hardness under non-cooled and internally cooled conditions. The resulting thermomechanical state is transferred to the second layer, where interface morphology is designed to redistribute local pressure. Across four selected solutions, the maximum absolute relative discrepancy between surrogate predictions and finite element re-evaluations is 1.57%. Relative to the corresponding selected non-cooled cases, the selected internally cooled cases show 33.8%–33.9% lower maximum shaft temperatures and 67.2%–75.6% lower front-end thermal deformations; these differences also include changes in the selected parameters. Interface morphology design reduces the contact-pressure standard deviation by 88.9%–99.0%. The framework therefore treats rough-surface thermal contact as a design-dependent multiphysics boundary and links interface heat-transfer characterization to global thermomechanical response and local pressure regulation.