Monitoring and diagnostics of stresses in reciprocating machines

Abstract This work presents a study for monitoring stresses in links of reciprocating machines by means of indirect measurements. A model of such a machine is a slider-crank mechanism actuated by an asynchronous electric motor with reduction gear. For this study, an experimental simulation apparatus was constructed, composed of a reciprocating machine, a direct-current tachometer as diagnostic sensor, and the necessary instrumentation for measurement of loads acting on the slider and thus stresses on the connecting rod. The excellent agreement between the theoretical and experimental results shows the validity of the solution for monitoring and diagnostics of reciprocating machines using a simple direct-current tachometer connected to an A/D converter and then to a PC able to execute the fast Fourier transforms of the acquired signals. The proposed method is particularly useful when direct measurements of stresses are difficult or particularly laborious. It also allows continuous monitoring of the machine throughout its life time, with user access or denial to computerized information, as desired.