Dynamic Modeling of Brake Systems with Disc Friction and Caliper Flexibility: Stick-Slip Vibration Analysis

Stick-slip vibration often occurs during high-speed train braking, posing risks to braking component integrity and train operational safety. While structural characteristics significantly influence this vibration, the action mechanisms remain unclear. To explore their influence rules, this study adopts the vehicle–track coupling dynamics method and establishes a novel vehicle dynamics model incorporating disk–pad interface nonlinear friction (described by the Stribeck model with tribologically tested parameters), complex contact interactions (polygonal contact model), and brake caliper flexibility. The model is validated via on-track tests, which confirm its accuracy in capturing brake system stick-slip behaviors under combined disk–pad sliding and wheel–rail rolling friction excitations. Subsequently, the influence of caliper flexible deformation on brake system vibration characteristics and interface interactions during stick-slip vibration under different braking forces and speeds is investigated. Results show that flexible brake calipers exhibit more complex stick-slip vibration characteristics under varying braking conditions, whereas rigid models tend to overestimate braking dynamic responses and fail to capture caliper resonance induced by stick-slip at specific speeds. Thus, the flexible caliper model enables more accurate characterization of actual service dynamic responses. These findings provide effective methodologies and engineering guidance for optimizing brake system dynamic performance and structural design.