Análise de óleos lubrificantes sob a ótica da termografia em ensaios de atrito cisalhante.

Abstract

The aim of this work is to evaluate the Thermography ability to monitor the behavior of the lubricating oils SAE 20W50 API SJ and ISO VG 10 from the thermal point of view until the moment of the lubricating film rupture, characterized by the sudden elevation in the friction, noise, vibration and temperature in shear friction tests. The methodology used is based on the analysis of thermograms that indicate temperature profiles during the friction tests and at the moment of mechanical failure, comparing these results with those obtained by a thermocouple. Thus, it is possible to obtain information that can be used as noninvasive visual references during a friction situation. The specimens, consisting of cylindrical SAE 1045 steel pins, are rubbed against a wear ring consisting of a weld-locked bearing under the condition of a boundary lubrication regime. Tests were performed under increasing load conditions up to 180 N at 10, 15 and 20 Hz (600, 900 and 1200 rpm) rotations. The results show the qualitative and quantitative capacity of the Thermography in the detection of lubrication failures, considering the emissivity of the lubricating oil film equal to 0.82. In addition, the temperature peaks associated with scuffing shown by Thermography are larger than those shown by the thermocouple, which facilitates the visualization of this phenomenon. It will be concluded that the Thermography can be used for detecting the breakdown of the lubricant film in pin-on-ring friction tests.