Development and Comparative Evaluation of Reduced-scale Krauss Friction Tester based on Similarity Theory

Based on the similarity principle, the basic parameters of the reduced-scale Krauss tester were derived from the full-scale Krauss tester by using the dimensional analysis method. The main structure of the Krauss testing machine had been made, and some components and parts such as brake system, servo loading system and torque measuring system had been designed and manufactured. The same batch and molded NAO brake friction material had been rigorously evaluated on two Krauss testers following ECE R-90 procedure as per the ‘‘Economic Commission for Europe” (ECE) regulations and these parameters such as friction torque, brake pressure, friction coefficient, test temperature and time had been discussed. The results showed that the reduced-scale Krauss tester was faster response than that of the full-scale Krauss tester in the process of brake growth and brake release, the brake completion time was about 370 ms ahead of schedule. However, the full-scale Krauss tester had a slower response and the brake completion time delay was about 240 ms. During the entire test, the average coefficient of friction was closer and the relative error is 6.3%, and the maximum and minimum values of the friction coefficient appeared at the same brake sequence, test section and brake cycle. The test temperature had good linear correlation in the whole test process. The total test time for reduced-scale Krauss tester was about 4/5 of full-scale Krauss tester. In each test, if the same other conditions existed, the power cost of the reduced-scale Krauss tester is 20.79 % of the power cost of the full-scale Krauss tester when the ECE R-90 test program was executed. From the comparison of the main test indexes, the test data of the scaled Krauss test machine reflected the fluctuation and correlation of the test data of the full-scale Krauss test machine to a certain extent, providing a new test equipment for the brake friction material.