Abstract
Roller bearings support heavy loads by riding on an ultra-thin oil film (between the roller and raceway), the thickness of which is critical as it reflects the lubrication performance. Ultrasonic interfacial reflection, which facilitates the non-destructive measurement of oil-film thickness, has been widely studied. However, insufficient spatial resolution around the rolling line contact zone remains a barrier despite the use of miniature piezoelectric transducers. In this study, a finite-element-aided method is utilized to simulate wave propagation through a three-layered structure of roller-oil-raceway under elastohydrodynamic lubrication (EHL) with nonlinear characteristics of the i) deformed curvature of the cylindrical roller and ii) nonuniform distribution of the fluid bulk modulus along the circumference of the oil layer being considered. A load and speed-dependent look-up table is then developed to establish an accurate relationship between the overall reflection coefficient (directly measured by an embedded ultrasonic transducer) and objective variable of the central oil-film thickness. The proposed finite-element-aided method is verified experimentally in a roller-raceway test rig with the ultrasonically measured oil-film thickness corresponding to the values calculated using the EHL theory.
Highlights
The Rolling bearings are critical supporting components of rotating machinery
The accurate acquisition of the oil-film thickness under operating conditions remains an ongoing challenge for line-contact components such as roller bearings owing to the limited space for the installation of a transducer and the required measurement spatial resolution of the thin oil film at a micrometer or submicron scale
The method of integrating ultrasound simulation and elastohydrodynamic lubrication (EHL) theory improved the measurement accuracy of the ray model
Summary
The Rolling bearings are critical supporting components of rotating machinery. An ultra-thin film of oil, which exists between the roller and raceway and typically forms based on dynamic lubrication effects, can support heavy loads. Roller bearings have nonparallel and curved surfaces; the thickness and stiffness of the oil film between the two surfaces are nonuniformly distributed owing to the varied stresses in the contact, significantly influencing the ultrasonic measurements; the width of the line-contact zone is typically small compared to that of the transducer. Given these complexities, improving the spatial resolution is frequently the focus of this promising technique.
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