Experimental characterization and analysis of wet belt friction and the vibro-acoustic behavior

The robustness and noise warranty costs of rubber belts used for power transmission are directly affected by the frictional properties under varying environmental conditions. This paper presents an experimental characterization and analysis of the friction and vibro-acoustic behavior of automotive ribbed rubber belts under wet conditions. The experimental results show that the static friction under wet condition is higher than the corresponding kinetic friction by 40%-1040% for different belts; and the wet static friction is also much higher than the dry static friction. The wet kinetic friction is lower than the dry kinetic friction by about 30-40%. The occurrence of wet static friction is associated with the strong noise of the belt system. The spectrogram analysis of recorded sound demonstrates that the sound exhibits an impulsive sound pattern with broadband frequency extending to 20 kHz. In this study, the belt vibration is also measured and the spectrum results correlated with those of the sound measurement. The capillary effect, dry adhesive effect and the boundary lubrication effect are discussed based on adhesion models, which are used to correlate with experimental results and to interpret the effects of relevant parameters. The presented results are based on the start-up running of a newly developed belt-pulley test rig, which are different from some published results based on SAE Standard J2432. The test rig based on SAE Standard J2432 is actually operated as water lubricated coast-down, which is not applicable to characterizing the friction properties of belt in wet start-up running.