Bearing torque characteristics of lithium soap greases with some synthetic base oils

Eri Oikawa, Noriyuki Inami, Michita Hokao, Atsushi Yokouchi, Joichi Sugimura

    Research output: Contribution to journalArticlepeer-review

    13 Citations (Scopus)


    This article describes the influence of rheological properties on the bearing torque characteristics of the lithium soap greases with five types of base oils. The greases used had different yield stress depending on the base oils even with the same thickener concentration. Measurement of bearing torque was conducted for a deep-groove radial ball bearing by using a bearing test apparatus. The bearings filled with greases initially exhibited high torque but showed gradual decrease in the torque with prolonged rotation, where the greases with higher yield stress showed larger normalized torque decrease. Observation of bearing after the rotation revealed a tendency that the greases with larger normalized torque decrease had been pushed aside in the raceway by channeling. This implied that the greases with higher yield stress tended to show channeling. On the other hand, the greases with lower yield stress circulated within the bearing by churning and showed smaller normalized torque decrease. These behaviors were explained in terms of the yield stress of the greases and the shear stress to entrain the greases into the contacts. Observation of grease structure was made with atomic force microscopy showed that the greases whose thickener network structure was distributed more densely had higher yield stress.

    Original languageEnglish
    Pages (from-to)575-583
    Number of pages9
    JournalProceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology
    Issue number6
    Publication statusPublished - Jun 2012

    All Science Journal Classification (ASJC) codes

    • Mechanical Engineering
    • Surfaces and Interfaces
    • Surfaces, Coatings and Films


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