Proposta de um transdutor capacitivo para medição da espessura do filme de óleo lubrificante em ensaio de desgaste por deslizamento

Abstract

The main way to reduce wear between bodies that slide over each other is through the introduction of a layer of lubricating material, consisting of a material with lower shear stress than that of the solid surfaces, or the interface between them, which leads to a reduction in the coefficient of friction. For the purpose of laboratory investigations in order to measure the thickness of the lubricating film that forms between surfaces in relative motion, different methods have been developed that make use of different physical principles such as, for example, ultrasonic, optical or with the use of capacitors. This paper proposes the design of a capacitive sensor to carry out this measurement in a block-on-ring type test, which is made from the calculation of the theoretical capacitance of the system formed by the test piece and the counterbody and then the other components of the electrical circuit are dimentioned and adjusted through circuit simulations in the Proteus software. Those simulations show that the sensor is capable of measuring capacitances of the order of magnitude of nF and with these measurements it is possible to estimate the thickness of lubricating films less than 10 μm.