Antifriction Bearing Sleeves for Diagnostics and Energy Harvesting

Roller ball bearings are the most common and one of the most important components in rotating machinery. Bearings, in general produce vibrations which can be harvested to produce energy and analysis of these vibrations can also be used to determine the condition of ball bearing. In this paper we discuss how to use the bearings for energy harvesting and conditioning monitoring in machines. A sleeve, padded with piezoelectric material, is designed to solve the dual purpose. Piezo electric materials have the ability to generate an electric field or electric potential in response to applied mechanical strain. Tests are conducted on the good and defective bearings to study the effectiveness of the sleeve. Phase fluctuation based processors are found to be effective in ball bearing condition monitoring. For condition monitoring the signature responses for a given time period are studied. At a constant speed of increase in load leads to an increase in voltage generated. For a single non-coated piezo film, voltage varies from 383 mV at 80 lbf to 683 mV at 320 lbf at 40Hz. With the increased stacking of non-coated piezo films at 320 lbf, voltage generated shows an increase of 23 %. Nano-coating mixture (Ferrofluid and Zinc oxide nanoparticles) causes an additional piezoelectric effect on the surface of piezo film as ZnO acts as an additional source of electrons, due to its ability to emit charges at room temperature. The single piezo film configuration at 320 lbf generates a voltage of 663 mV while the voltage increases 2.1 times for a single nano-coated piezo film. Introduction of defects causes increases in the contact stress at the asperities leading to an increase in the vibrations and forces. Also, an increase in vibration and force, leads to an increase in the voltage generated. For a single piezo film configuration, in a normal bearing, the voltage generated is 663 mV while a defective bearing gives a voltage of 698 mV.