Reduction of stiffness in timing belts: experimental tests

Abstract - The detection of the loss of stiffness, whether localized or distributed, in timing belts by analyzing the vibrations of the pulley's supports is presented in this work. The envelope analysis tool was used for the vibration analysis, because it allows extracting the diagnostic useful signal, purifying the overall vibratory signal from structural vibrations and from noise. Two experimental cases are presented here. First case examines the measurements made in the laboratory on a special test bench for synchronous belt drive and considering belts in which a local reduction in stiffness was purposely created. The second case concerns the experimental measurements carried out on the distribution mechanism of an internal combustion engine in which the reduction of stiffness of the belt is caused by the normal wear after a long working period. In both cases, in the spectrograms obtained from the signal processing with the envelope tool, it was possible to relate the amplitude of the peak at the belt revolution frequency with the reduction of stiffness of the timing belt.