PVD Sputtered Thin-Film Sensors Integration in Rolling Bearings for Condition Monitoring
The global economic and ecological change requires new innovation in the application of conventional machine elements such as gears and rolling bearing systems. The motivation is to save resources, to use machine elements more efficiently or to increase the fatigue life of systems. Rolling bearings are used for example in wind turbines and must function reliably over their entire lifetime. Unplanned rolling bearing failures are connected with high costs. To determine the operational status, condition monitoring systems (CMS) are used for monitoring. These CMS only work in combination with specific sensors (vibration, temperature) and measurement processing of the signals. This presentation is about the integration of thin-film sensors in rolling bearings and the development of integrated smart measurement technology. The sensors are applied within a thrust cylindrical roller bearing washer by means of a PVD sputter process and can measure signals such as strain and temperature directly in the rolling contact. This must be embedded within an electrically insulating system. For this purpose, a multilayer system is deposited on the surface. Aluminum oxide is used for insulation and wear protection. The development and challenge of the system is to guarantee a sufficient wear protection layer. For this purpose, the prepared systems were stressed under stationary operating conditions and an attempt was made to characterize the service life of the coating systems.On the one hand, the failure of the insulation and wear protection layer (less than 4 µm) could be determined by the specific location of an acceleration sensor.In addition, a method was developed to quantify the wear or abrasion by means of complex impedance measurements.The layer systems are tested and evaluated on an FE8 test rig at the Institute of Machine Design and Tribology (IMKT) in Hanover. The experiment demonstrated that the production of sensors and application in bearings are feasible.