The relationship between the rheology of the grease and the vibration behavior of the bearing

Vibration and noise performance is the embodiment of the comprehensive quality level of rolling bearings, and the internal quality of grease as a part of the bearing will have an important impact on the vibration performance of the bearing. On the basis of a comprehensive review of the rheological studies of lubricants by domestic and foreign scholars, the technical indicators and test methods of the experimental instruments used in the institute are introduced in detail, and then the viscosity and shear force of the tested grease under different shear velocities are tested by an apparent viscometer. Through the test, we found that there is a certain correspondence between the rheological properties of the grease and the vibration properties of the bearing.

The apparent viscosity of the grease at a certain shear speed is low and is beneficial to the vibration performance of its bearing, but when the apparent viscosity of the grease is very small, the vibration and noise performance of medium and large bearings with poor machining accuracy is not ideal. The rheological properties of grease play a decisive role in the influence of vibration and noise on small and medium-sized bearings, but have no obvious effect on the vibration performance of micro-sized bearings, which is also in line with the law of system dependence of tribological behavior.

Pay attention to the selection of appropriate grease models, such as several commonly used models in the equipment lubrication manual of Shangqi Group:

1— High-speed bearings, using fully synthetic high-speed bearing grease;

2— High-temperature bearings, using fully synthetic high-temperature motor bearing grease, fully synthetic high-temperature high-speed bearing grease;

3— Heavy-duty bearings, using fully synthetic high-temperature heavy-duty bearing grease;

4— Small and medium-sized bearings or noise reduction, the selection of fully synthetic noise-reducing bearing grease;

5— In the water shower environment, the fully synthetic water-resistant bearing grease is selected;

Generally, brands such as Kluber, Hotolube, and Bosh are used.

Summary. 1. When the relative gap increases, the thickness of the oil film will increase first and then decrease, so there is an optimal relative gap for the bearing capacity, usually about millimeters. 2. The width-diameter ratio also has a great impact on the bearing capacity, the smaller the width-diameter ratio, the more oil is lost from both ends of the bearing, and the more serious the pressure drop in the oil film, which will significantly reduce the bearing capacity.

3. The smaller the eccentricity, the more likely it is to be unstable and produce oil (gas) film oscillation, which reduces the bearing capacity and is easy to destroy. 4. The working load and speed should be matched with the relative clearance and width-diameter ratio, otherwise it will also lead to a decrease in bearing capacity. In the process of starting and stopping, the hydrodynamic bearing can not form an oil film sufficient to separate the two friction surfaces due to the low speed, and it is easy to wear, so the sliding bearing material that can work under direct contact conditions must be selected for the manufacture of bearings or bearing linings.

Hydrodynamic bearings require journal and pad surface geometry to be correct and smooth, with precise alignment during installation.

Hydrodynamic lubrication of the relative clearance of the sliding bearing, the carrying capacity of the sliding bearing, the temperature rise and the running accuracy.

1. When the relative gap increases, the thickness of the oil film will increase first and then decrease, so there is an optimal relative gap for the bearing capacity, usually about millimeters. 2. The width-diameter ratio also has a great impact on the bearing capacity, the smaller the width-diameter ratio, the more oil is lost from both ends of the bearing, and the more serious the pressure drop in the oil film, which will significantly reduce the bearing capacity. 3. The smaller the eccentricity, the more likely it is to be unstable and produce oil (gas) film oscillation, which reduces the bearing capacity and is easy to destroy.

4. The working load and speed should be matched with the relative clearance and width-diameter ratio, otherwise it will also lead to a decrease in bearing capacity. In the process of starting and stopping, the hydrodynamic bearing can not form an oil film sufficient to separate the two friction surfaces due to the low speed, and it is easy to wear, so the sliding bearing material that can work under direct contact conditions must be selected for the manufacture of bearings or bearing linings. Hydrodynamic bearings require journal and pad surface geometry to be correct and smooth, with precise alignment during installation.

The minimum viscosity of the oil is limited by the minimum oil film thickness. When the microscopic convex peaks on the two surfaces come into contact at the minimum oil film thickness, the oil film is broken, and friction and wear increase. The frictional work heats up the oil and reduces the viscosity of the oil.

In order to make the viscosity of the oil relatively stable, a circulating oil supply system with a cooling device is generally used or additives are added to the oil to reduce the temperature sensitivity of the oil. The characteristic number of bearings reflects the relationship between the load, speed, viscosity and relative clearance of hydrodynamic lubrication: the lubricating oil with high viscosity and small relative clearance should be selected for bearings with large load and low speed; For bearings with small load and high speed, lubricating oil with low viscosity and large relative clearance should be selected.

3. How to adjust the parameter changes in the sliding bearing when the dynamic pressure principle of lubrication is applied?

The application of the dynamic pressure principle of lubrication in sliding bearings, how to adjust the parameter changes in sliding bearings? Hello dear <>

The oil film pressure of dynamic plain bearings is related to the following factors: lubricating oil viscosity, surface sliding speed and oil film thickness and their variations. A convergent wedge-shaped gap must be formed between the two surfaces that slide relative to each other; The two surfaces separated by the oil vertical film must have sufficient relative sliding speed, and the direction of its rolling motion must make the lubricating oil flow from the large mouth and out from the small mouth; The lubricating oil must have a certain viscosity.

Generally speaking, if the sliding bearing is used under the ideal condition of the correct residual key, its life can be said to be unlimited, but the reality is that the bearing is often burned out and worn, and it must be repaired. Often the repair of sliding bearings is a process with high difficulty, and sometimes it is necessary for professional sliding bearing manufacturers to repair, which brings more time losses and affects production efficiency.

CaidonmC20 High Temperature and High Speed Bearing Grease: High temperature thickener thickens synthetic oil, and adds multi-effect additives, it is a high-quality grease that maintains normal working condition in high temperature environment for a long time. Performance characteristics:

The structure is smooth, the fiber is delicate, it has a high degree of cleanliness, it can suppress the abnormal sound of the bearing during operation, and the long-term CaidonmC20 high-temperature high-speed bearing grease that meets the DN value of more than 500,000 high-speed bearings: high-temperature thickener thickens the synthetic oil, and adds multi-effect additives, which is a high-quality grease that maintains normal working conditions in a high-temperature environment for a long time. Performance characteristics:

The structure is smooth, the fiber is delicate, and it has a high cleanliness, which can suppress the abnormal sound of the bearing in the process of transporting potatoes and rotating the bearing, and meet the long-term operation requirements of high-speed bearings with a DN value of more than 500,000. Excellent high and low temperature resistance, lubricity, good colloidal stability and mechanical stability. It is highly waterproof, can withstand water washouts, and retains its hardness over a wide range of temperatures.

Excellent oxidation resistance and good wear resistance, so that the service life is extremely long, and the service life is 5-10 times that of lithium grease. Extremely high temperature tolerance and high-speed shear resistance make it easy to cope with high temperature and high speed environments. The operating temperature range is 40 230 °C, and the short time is up to 250 °C.

Recommended Applications: It is suitable for the lubrication of precision bearings, motor bearings and miniature bearings in high and low temperature environments. It is suitable for the lubrication of various high-speed bearings, high-speed and long-life gyro motors, high-speed grinding machines and other high-speed instruments and mechanical bearings.

It is suitable for machinery that requires noise reduction or the use environment is extremely bad, and it is also suitable for lubrication of high-temperature parts.

Motor bearing lubrication has an important impact on the fatigue life of rolling bearings and friction, wear, temperature dryness, vibration, etc., without normal lubrication, the bearing can not work. Analysis of the causes of bearing damage shows that about 40% of bearing damage is related to poor lubrication. Therefore, good motor bearing lubrication is an effective measure to reduce bearing friction and wear.

Motor bearings have the following requirements for grease:

1. Long service life, which can prolong the maintenance cycle and reduce bearing consumption.

2. Good fluidity, generally requires the use temperature of -25 °C-120 °C, small starting torque, low operating torque, less power consumption and low temperature rise.

3. Appropriate consistency, with good vibration damping, can reduce the noise of motor bearings, and is conducive to environmental protection.

4. The insulation grade is A, E and B grades, and it does not contain sulfur and chlorine extreme pressure additives.

6. Strong anti-rust and anti-salt spray ability, good water resistance, and can be applied to harsh working environments.

7. Good lubricity and anti-wear, no oil rejection, no drying, no emulsion cracking, no loss, and the grease itself should not contain solids.

8. Good adaptability, high and low temperature performance, can be used indoors and outdoors, north and south.

9. Good oxidation resistance, after long-term use, the appearance color and acidity of the grease change little, and there is no obvious oxidation.

The requirements of the motor bearing for grease are wear-resistant and high-temperature resistant, and it must have sufficient lubricating performance.

The most important indicator is high temperature resistance.

The choice of material for plain bearings depends on the failure mode. The main failure modes are wear and fatigue damage of bearings and shafts. Preventing wear and fatigue damage of bearings and bushings is the key to selecting bearings and bushing materials. The following aspects are mainly considered:

Abrasion resistance, friction reduction;

Run-in (run-in);

embeddedness; compliance;

strength, plasticity;

Good heat transfer and corrosion resistance;

Economy, manufacturability, etc.