High-speed rolling element bearings for aircraft engines are custom-made components and operate under high temperature conditions owing to the elevated rotational speeds and loads. Therefore, assessing the various heat generation sources and mechanisms is worth investigating to accurately quantify the overall power loss within the bearing. In this context, a numerical parametric study was performed to determine and locate various power losses inside an aero-engine cylindrical roller bearing. Then, a thermal network model based on Ohm’s law was developed in order to estimate the operation temperatures of the bearing elements. A series of experiments were carried out on a high-speed rolling-element bearing test rig to validate the numerical predictions; such as bearing component temperatures and overall power loss at specific operating conditions. The numerical predictions based on a hybrid approach showed good agreement with the experimental data.

Roller bearings operating under light loads may suffer from skidding. The latter is more pronounced as the speed increases and may result in extensive wear and reduced service life of the bearing. The main objective of this study is to analyze skidding occurrence in a custom-made all-steel M50 bearing and a hybrid roller bearing subjected to the same operating conditions. The test bearings have a bore diameter of 90 mm, an outer diameter of 125 mm and 26 rollers. The hybrid bearing features silicon nitride (Si3N4) rollers and steel rings (M50 outer ring and M50-NIL inner ring). The bearings feature special channels to allow for under race lubrication of the bearing components in relative motion. A suite of sensors were used and installed to detect skidding and monitor the overall performance of the test bearing such as vibrations and temperature. The effect of the radial applied load, shaft rotational speed, and oil flowrate on roller skidding has been investigated and discussed. Slip ratio for each of the bearings under various speed–load combinations was also determined and analyzed. Turbo-Oil 2380 was used to lubricate the test bearings at a constant temperature of 77 °C. Tests were conducted on a high-speed rolling bearing test rig, and data were recorded using a 24-bit data acquisition system.

Rolling-element bearings (REB) can develop severe damage due to skidding (slipping) between the rolling elements and bearing races. Skidding can be described as gross sliding between the bearing surfaces in relative motion and can result in significant surface distress such as smearing, especially at light loads and high rotational speeds. Under these conditions, skidding occurs between the rolling elements and the bearing races, leading to increased wear (higher friction coefficient), elevated bearing temperature, significant power losses and reduced service life of the bearing. The main objective of this study is to investigate the significance of various sensing technologies (induction, vibration, ultrasound, acoustic and optical) in detecting skidding in standard series roller bearings as well as custom-made roller bearings for aero engine applications. The bearings have a bore diameter of 60 mm and 90 mm, respectively. Jet and under race lubrication techniques have been used to supply oil to the bearings under test. The custom-made aero engine test bearing features special channels to allow under race lubrication of the rollers/races contacts as well as the cage land. The effect of radial load, rotational speed and oil flow on roller skidding have also been investigated and analyzed. Tests have been performed on a dedicated high speed experimental bearing facility and data was recorded using a commercially-available data acquisition system.

Lack of lubrication in rolling-element bearings is a leading root cause of premature failure in induction motors and other electromechanical drives. This study proposes novel vibration-based technologies for diagnosing a lack of lubrication in bearings of induction motors. Two technologies are proposed: the Filter-less spectral kurtosis (FLSK), which quantifies impulsive energy generated by a lack of bearing lubrication, and the fundamental rotational harmonic technology, which captures an increase in the fundamental rotational harmonic magnitude, also induced by a lack of bearing lubrication. Comprehensive experimental trials are performed on a Siemens induction gearmotor, used in airport baggage handling conveyor systems. The experimental results show that both technologies exhibit effective diagnostics.

This paper proposes a novel integrated spectral kurtosis (ISK) technology, which is a new conceptualization for fault diagnosis, and compares it with conventional spectral kurtosis technology. The vibration signals from a gearbox are processed by time synchronous averaging (TSA) and analysed using the spectral kurtosis (SK). The ISK feature is estimated across the entire frequency domain, while the envelope is obtained through SK-based filtering and a Hilbert demodulation. The ISK technology demonstrates the ability to distinguish between healthy and defected gearbox cases, achieving a total probability of correct diagnosis (TPCD) of 91.5% for pinions and 96.1% for gears, whereas the SK-based squared envelope technology provides a limited diagnosis effectiveness, with a maximum TPCD of 80%. The motor current signals are also analysed through harmonic amplitude tracking within the current spectrum. A comparison of the ISK and motor current technologies is also made, showing that the motor current technology reaches a maximum of 90% TPCD for gears, which remains lower than the TPCD for the ISK technology.