Performance analysis of grease
From: Author: Publish time:2018-05-23 10:11 Clicks:0
The rheological properties of grease are the characteristics of flow and deformation of grease when subjected to external forces.
1, when the grease is not affected by external forces, it can remain as solid as a solid shape, that is, it will not lose automatically when it is stationary.
2, when it is subjected to weak external forces, it produces elastic deformation. After removing the external force, it can return to its original position and shape, showing the elastic characteristics of solid.
3. When the exerted external force is large enough, the grease is deformed and flowing, so it can no longer automatically recover to its original position and shape, so the starting torque of the grease on the mechanical parts is larger than that of the liquid lubricating oil.
4. During the flow of grease, the apparent viscosity (or similar viscosity) of the system decreases with the increase of shear stress and the orientation of the soap fibers in different degrees. At this stage, the apparent viscosity of the grease decreases with the increase of shear rate.
5. In the case of high shear stress (high shear speed), the flow of grease, like Newton fluid, can keep a constant, and no longer change with the change of shear speed.
Thixotropy of lubricating grease means that when the lubricating grease is shear, the viscosity decreases and softens, and when the shear force stops, the consistency will gradually recover. When the grease is subjected to shearing, the contact part between individual soap fibers forming a continuous skeleton begins to slide to the point of disengagement, causing the system to deform to flow. In the long term or high shear effect, the soap fiber itself will also be damaged and cut, so the consistency is reduced. After shearing, the structure skeleton begins to recover. However, the rearrangement of soap fibers takes a certain time, so the recovery of consistency is a slow process, and the reformed skeleton is different from the original one.
The rheology and thixotropy of grease are of great importance to the use of grease. In the lubrication process of gear and bearing, the consistency of the grease is reduced because of the relative sliding or rolling of the friction pair. Under the effect of high shear force, the grease on the friction surface can form a fluid shape, which is beneficial to the lubrication of the mechanical parts. Once the operation is stopped, the consistency of the grease is restored to a certain level. For the bearings, the grease can be kept inside the bearing and not lost; for the gearbox, the grease can be sealed to a certain consistency to avoid the leakage of the gear box.
The knowledge of rheology and thixotropy of the above grease is compiled by Jiucheng lubricants. Welcome to reprint!