The viscosity and strength limits reflect the characteristics of non-Newtonian fluids in lubricating grease, that is, the fluidity changes with shear velocity.
The viscosity of grease is usually represented by apparent viscosity or similar viscosity. When explaining the viscosity, temperature and shear rate must be specified. Similar viscosity indicators can be used to control its low temperature flowability and pumpability.
The strength limit of lubricating grease refers to the minimum shear stress required to cause the grease to start flowing, also known as the ultimate shear stress. The strength limit is a function of temperature. The higher the temperature, the smaller the strength limit of the grease. The lower the temperature, the greater the strength limit of the grease. Its size depends on the type and content of the thickener, and also has a certain relationship with the preparation process. The strength limit of lubricating grease has great practical significance: grease will not lose from the lubricating components because it has a certain strength limit; But if its strength limit is too large, it will cause difficulty in starting the lubricated machinery or consume too much energy.