Adapting a scaled twin-disc device for tread braking investigations based on an ad-hoc thermal similitude model

The present paper shows the design of a scaled tread braking system to be included in a scaled twin-disc system, to carry out thermomechanical investigations on wheel and shoe materials. The test bench consists of two discs, pressed against each other, simulating the wheel-rail contact. A pneumatic cylinder pushes scaled brake shoes against the wheel tread surface, and a fan-nozzle device improves convection cooling. As a major novelty, both systems are designed to comply with a new thermal scaling method, that is specifically identified to obtain the same temperature field on the scaled twin-disc as for a full-scale system. The paper thoroughly describes the mathematical background of the new thermal scaling method, which is then preliminarily validated with finite element thermal models for both the brake block and wheel. The greatest advantage of the final twin-disc configuration is that it allows to carry out investigations of wheel-rail wear phenomena as well as studies on the thermomechanical interaction between wheels and brake shoes, while adhering to scaling rules that corroborate the validity of the experimental results.