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Copy of bearing

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amirshayan behzadfar

on 25 December 2012

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Transcript of Copy of bearing

Ball Bearings A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearings inside and outside race. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. The bearing is made up of at least two races containing the balls, these are what the load is transmitted through . In most applications, one race is stationary and the other is attached to the rotating assembly (e.g., a hub or shaft).
As one of the bearing races rotates it causes the balls to rotate as well. Because the balls are rolling they have a much lower coefficient of friction than if two flat surfaces were sliding against each other. Ball bearings tend to have lower load capacity for their size and can handle higher speeds than other kinds of rolling bearings due to the smaller surface contact area between the balls and races. However they can tolerate some misalignment. Here's how a ball bearing works. Roller Bearings Quite a simple bearing, they have a single row of straight cylindrical rollers housed within a cage.
Can however have two rows of rollers housed inside a cage. Works at moderately high speeds.
Low torque.
Haven’t got quite a lot of tolerance to deal with misalignment.
The races can be separated meaning they are quite easy to install. The line contact enables them to carry heavy radial loads
They cannot however carry very heavy axial loads, usually around 10% of the radial load. Load Carrying Abilities Rolling Mills
Medium to heavy duty electric motors Applications Performance Faults
Groove surface metal peeling
Bearing burns
Plastic deformation
Housings cracking
Fractures
Metal adhesion in rolling body
Groove wear -Fluid bearings use a thin layer of liquid or gas fluid.

-They can be broadly classified as fluid dynamic bearings or hydrostatic bearings. Hydrostatic bearings are externally pressurised fluid bearings, where the fluid is usually oil, water or air, and the pressurisation is done by a pump. Hydrodynamic bearings rely on the high speed of the journal self-pressurising the fluid in a wedge between the faces.

-Fluid bearings are frequently used in high load, high speed or high precision applications where ordinary ball bearings have short life or high noise and vibration. They are also used increasingly to reduce cost. For example, hard disk drive motor fluid bearings are both quieter and cheaper than the ball bearings they replace. Fluid Bearings -Leaks are a common fault
-misalignment
-wear
-uneven wear
-Vibration
-excess noise Fluid Bearing Faults -Utilise a thin film of pressurised air to provide an exceedingly low friction load-bearing interface between
surfaces.

-The two surfaces don't touch. Being non-contact, air bearings avoid the traditional bearing-related
problems of friction, wear, particulates, and lubricant handling, and offer distinct advantages in precision
positioning, such as lacking backlash and stiction, as well as in high-speed applications.

-The fluid film of the bearing is air that flows through the bearing itself to the bearing surface. The design
of the air bearing is such that, although the air constantly escapes from the bearing gap, the pressure
between the faces of the bearing is enough to support the working loads. Air Bearings Tapered Roller Bearings The tapered roller bearing is essentially a roller bearing but with the rollers at an angle. What They Are Works best in moderate speeds
Generally used in heavy duty applications
Can support both radial and thrust loads
Generally used in pairs back to back so that thrust loads are dealt with from both sides Characteristics Car or other large vehicle wheels Applications The bearing can be forced in one direction if it is mounted alone.
Wear of the raceways
Fractures
Surface metal peeling Problems About Thrust Bearings:
There are different kinds of thrust bearings, these are ball, cylindrical, spherical and needle.
The purpose of thrust bearings is to withstand high axial forces as well as reducing friction and heat. Thrust Bearings A common problem with this type of bearing is that when it gets over 25 MW it starts vibration. This is because this type of bearing was not made to withstand fast speeds, it was made to withstand large axial forces.
Another few are:
Noise Thrust Bearings
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