Non-reversible dry friction oscillator: design and measurements

A Coulomb oscillator with a variable normal force has been designed and man ufactured to carry out a wide range of experimental dynamic analysis, espec ially the study of the non-reversibility of dry friction characteristics. T he design choice was based on the criteria of accuracy of the mathematical model and flexibility in terms of parameter changes such as the natural fre quency of the system, coefficient of friction and normal force. The system consists of a block mass attached to two coil springs and a dry frictional damper in which the friction force is varied by a pneumatic actuator. This allows a constant pressure between sliding surfaces to be maintained. The e xperimental set-up, the calibration procedure for the clamping device and t ypical results are presented. Experimental non-reversible dry friction char acteristics are discussed.