Rational design for a friction unit of a disc-shoe brake

Abstract

In this study, we develop a rational design for a friction unit provided that restrictions are imposed on the fly-wheel masses of rotating elements and the onset of a thermal stabilization state. The input calculation data were the braking torque, specific pressure in the friction pair, angular velocity and the diameter of the brake disc hub. The geometric programming method was used at the preliminary stage to calculate the design and operational parameters of a discshoe brake. Further, the parameters were refined based on the conditions of mutually exclusive factors (energy intensity and braking time) and the stress-strain state. On the basis of the proposed rational design for a friction unit, a software application for calculating in the DELPHI programming language was developed. The ranges of design parameters were determined at the preliminary design stage: a brake disc diameter from 0.237 to 0.37 m; the width of working surfaces from 0.0335 to 0.1 m; and the thickness of half-discs from 0.012 to 0.026 m. The final result of the rational design method was the specified ranges of design parameters: diameter from 0.31 to 0.324 m; width from 0.041 to 0.0485 m; and thickness from 0.0148 to 0.0151 m. The developed method of rational design reduces the diameter ranges of the designed brake disc in comparison with the preliminary calculation by 9.5 times, while the ranges of the width of the working surfaces are reduced by 8.9 times, and the thickness range – by 46.6 times. At the final stage, the secondary design and operational parameters of the friction unit were determined: the areas of the working and non-working surfaces of the friction pairs and the coefficient of their mutual overlap. The proposed method of rational design reduces the selected range of design parameters, which will provide a more rational choice of compliance with their specified performance characteristics.