Thixotropy of greases and low-speed operation of rotational plastoviscometers and rolling bearings

Summary A typical property of greases, as plastic disperse systems, is their thixotropy (reversible destruction of their structure due to deformation). In relation to this, if the rate of their formation drops below a certain critical value it becomes practically very difficult or even impossible to attain steady conditions of their flow. This is observed both in rotational plastoviscometers and in rolling-contact bearings, and is manifested in more or less sharp fluctuations of the resistance moments. The critical value of the rate of deformation depends on the nature of the grease and the rigidity of the braking device or the power reserve of the drive, decreasing when these values are increased. When soap greases are deformed they become anisotropic, which, when the direction of deformation is changed, tells perceptibly on their resistance to deformation and results in fluctuations of the resistance moments in rolling bearings.