The viscosity of the grease to use performance impact - bearing knowledge

by:Waxing     2020-05-29
Lubricating oil viscosity decreases with the increase of temperature, so the same kind of lubricating oil, owing to the different temperature, different viscosity. This stay is called 'viscosity Temperature characteristic '. The glue of the grease - More complicated than the lubricating oil temperature properties, sticky - because this kind of structure system Temperature characteristics and subject to change with the change of the shear. The viscosity of the grease under a certain temperature is variable with the change of shear rate changes. The viscosity is called similar viscosity, the international unit of measurement for palmer ( Card) 。 Seconds ( Pa• s) 。 The similar of the grease don't obey Newton's laws of fluid viscosity, along with the increase of the shear rate reduced. Due to relative motion between the layers of grease, the structure frame was damaged, so the higher the shear rate and the heavy skeleton structure failure, and similar viscosity reducing of grease. When the shear rate continues to increase, similar grease viscosity since he no longer changes close to the base oil viscosity, and keep the Newton fluid properties. Called the change rule of similar grease viscosity and shear rate viscosity Speed characteristic. An increasingly bitter viscosity change with shear rate, the energy loss. Can generally similar grease according to the low temperature viscosity value to determine the grease used in low temperature limit. Grease of similar viscosity with temperature rising and falling, but relatively slow, just as one of the base oil of one percent or a few thousands of points. Because grease flow resistance, has a part is determined by the intensity of skeleton structure, and the skeleton structure is affected by temperature is small, so the glue of the grease - Temperature characteristic is better than oil. — Generally speaking, in the use of grease temperature range of viscosity change is a lot smaller than base oil. The viscosity of the grease - Thickener used in the temperature properties depends on the features and usage, as well as the phase properties of soap oil system, and the relationship between the viscosity of base oil is smaller. The nature of the lubricant viscosity change with shear rate, enables it to be used on the mechanical speed change often have a special adaptability. When high speed, low requirement of lubricant viscosity, the grease structure destruction intensified, fiber orientation, lower viscosity. When the speed is slow for lubricant viscosity is bigger, and grease at low shear rate viscosity is bigger. Grease viscosity changing with the shear rate basic meets the requirement of mechanical speed change on the lubricant viscosity. Grease in the cutting speed is small viscosity friction and the lubrication parts starting has much to do. Because the grease in the cutting speed hours the viscosity, so at this time, such as the viscosity of the grease will increase the starting resistance. The viscosity of the grease increases, especially in the low temperature will make the cold starting is affected, even cause difficulties. Mechanical actually starts, to overcome the grease in the cutting speed hours needed for the flow resistance force is much bigger than overcome force needed for the ultimate strength. 5 pa ( 7 gf /平方厘米) 5 s - 1 when the flow resistance of 2452 pa ( 25 gf / cm2) , thus it can be seen, the viscosity of the grease in low temperature and low shear rate for large effect on the cold starting performance of the grease. For low temperature or wide temperature range with grease needs its viscosity at low temperature.
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