Experimental measurements of oil films in a dynamically loaded journal bearing

This paper describes the design of a journal bearing test platform capable of high accuracy film thickness measurements via ultrasonic transducers permanently embedded in both the bearing and rotating shaft. A bespoke hydraulic loading system with programmable valves allowed the application of dynamic loads with defined loading patterns, including the simulation of loading patterns found in real components such as automotive connecting rod bearings. Tests under a range of rotation speeds, temperatures and loading profiles have allowed the detailed analysis of film thickness response to rapidly changing loads. Unlike conventional methods, the ultrasonic technique offers a non-invasive direct measurement of the shaft-bearing interface, thus enabling the study of phenomena such as squeeze film effects. Measurements have been achieved by applying a novel referencing method, referred to as the snapshot technique. Via this method, squeeze time was shown to reduce with increasing shaft rotation speed, applied load and bearing temperature. Results have been compared against inductive sensors and numerical techniques with good agreement observed.