Estudo da viabilidade da termografia para a detecção de falhas decorrentes de fadiga por contato em engrenagens cilíndricas de dentes retos.

Abstract

This research aims to evaluate if thermography can detect an increment to the temperature field, which characterizes the presence of failures due to contact fatigue in cylindrical gears of spurs, from its face. The motivation arose from the study on Tribology, where it was found that the emergence of failures in machine elements, has as one of its main characteristics the increase of friction and consequent heat generation. The research is classified as applied, quantitative, explanatory, experimental and bibliographical. The methodology used used a bench of tests previously designed for thermographic tests, composed of the following mechanical elements: electric motor controlled by frequency inverter, vibration dampers, shafts, bearings, thermal insulation and gears. Thermal tests were carried out from the frame of the pinion, where temperature values were measured from its face for the following operating conditions: with and without lubrication in the absence of failures (reference conditions), and with and without lubrication with the implementation of failures (failure status). Anomalies were inserted in order to reproduce problems due to contact fatigue wear in a controlled environment scenario, relative to ambient temperature, relative humidity, engine speed, wind speed, reflected temperature and emissivity. As results, temperature values were defined for the reference conditions, where the condition in which the gear couple was lubricated, presented a lower heat generation and lower temperature variations between the experiments. For the fault state, the collected data of temperature resemble the reference conditions, not showing a disturbance to the thermal field due to the presence of the anomalies. Therefore, it is concluded that it is possible to calibrate via quantitative (active and passive) thermography for cylindrical gears of straight teeth in a laboratory environment, but this was not shown to be feasible in detecting the defects inserted in the surface of the teeth.