This study aimed to find an appropriate content of water-based friction modifier that will be able to reduce squeal noise without a significant impact on the coefficient of adhesion. A twin-disc machine was used, and the angle of attack of 4 ° simulates sharp curve conditions. The frictional behavior of nine water-based compositions was investigated for dry and wet films. During these experiments, the sound pressure level and the coefficient of adhesion were monitored. The results showed that the presence of solid lubricant in the composition is needed to achieve a long retentivity; however, its higher content can cause low adhesion. The composition with lower solid lubricant content and particles for friction modification with lower Mohs hardness was found to be suitable for further experiments. Moreover, comparison of recorded signals revealed that there is a bilinear dependence between the coefficient of adhesion and the sound pressure level.

Wheel squeal noise research requires many repeatable experiments under controlled driving conditions. While it is difficult to control those conditions on the real track, test rigs are designed. For the experimental validation of the models describing the wheel-squeal noise and other dynamic-related phenomena, suitable experimental models must be utilized. The aim of this paper is to present the design of the twin-disc test rig for the study of the wheel-squeal phenomena. This test rig utilizes a dynamic model of the track-train interaction and uses real train wheel for a more realistic representation of the emitted noise. This twin-disc test rig is intended for research into the mechanisms of the wheel squeal noise formation and for the development and validation of a prediction model. In particular, the influence of weather conditions and the presence of various friction layers in the contact will be addressed.