Whenever an object moves or tends to move tangentially, with respect to the surface, on which it rests, the interlocking property of the projecting particle opposes the motion. This opposing force, which acts in the opposite direction of the movement of the upper block, is called the force of friction or friction.
Types of friction:
1. Static friction:
It is the friction, experienced by a body, when at rest.
2. Dynamic friction:
It is the friction, experienced by a body, when in motion. The dynamic friction is also called kinetic friction and is less than the static friction. It is of the following two types:
It is the friction, experienced by a body, when it slides over another body.
Rolling friction:
It is the friction, experienced between the surfaces, which have balls, or rollers interposed between them.
Pivot friction:
It is the friction, experienced by a body, due to the motion of rotation as in case of footstep bearings
Classification:
The friction may further be classified as:
The friction experienced between two dry and unlubricated surfaces in contact is known as dry or solid friction. It is due to the surface roughness. The dry or solid friction includes the sliding friction and rolling friction.
Friction between lubricated surfaces:
When the lubricant is applied between the two surfaces in contact, then the friction may be classified into
It is defined as the ratio of the limiting friction to the normal reaction between the two bodies. It is generally denoted by µ.
Angle of Repose:
If the angle of inclination α of the plane to the horizontal is such that the body begins to move down the plane, then the angle α is called the angle of repose.
Efficiency of inclined plane:
The ratio of the effort required neglecting friction to the effort required considering friction is known as efficiency of the inclined plane.
Bearing:
The fixed outer element of a turning pair is called a bearing.
Journal:
The portion of the inner element, which fits in the bearing, is called a journal. The journal is slightly less in diameter than the bearing, in order to permit the free movement of the journal in a bearing.
Point of Pressure or Seat:
When the bearing is not lubricated, then there is a line contact between the two elements. The load on the journal and normal reaction of the bearing acts through the center. The reaction acts vertically upwards at a point. This point is known as seat or point of pressure.
Types:
A friction clutch has its principal application in the transmission of power of shafts and machines, which must be started and stopped frequently. Its application is also found in cases in which power is to be delivered to machines partially or fully loaded.
Types:
- A ball or roller bearing consists, in general, two races separated by balls or rollers in a cage. One race is fixed in a housing and the other is secured to the moving part.
- The object of the cage is to prevent the balls or rollers rubbing each other. The two main types are journal and thrust bearings to carry radial and axial loads.
Types:
- Deep groove ball bearing.
- Double row self-aligning ball bearing.
- Double row spherical roller bearing.
- Cylindrical roller bearing.
- Tapered roller bearing.
Rolling Resistance:
- It is assumed that for a given pair of materials, the rolling resistance is directly proportional to the load and is independent of the relative curvature of the contact surfaces.
- The rolling resistance plays an important role in vehicles.
- It occurs between the wheel tyres and the surfaces of the track, at the bearing of the wheel axle.
Types of friction:
1. Static friction:
It is the friction, experienced by a body, when at rest.
2. Dynamic friction:
It is the friction, experienced by a body, when in motion. The dynamic friction is also called kinetic friction and is less than the static friction. It is of the following two types:
- Sliding friction
- Rolling friction
- Pivot friction
It is the friction, experienced by a body, when it slides over another body.
Rolling friction:
It is the friction, experienced between the surfaces, which have balls, or rollers interposed between them.
Pivot friction:
It is the friction, experienced by a body, due to the motion of rotation as in case of footstep bearings
Classification:
The friction may further be classified as:
- Friction between unlubricated surfaces
- Friction between lubricated surfaces
The friction experienced between two dry and unlubricated surfaces in contact is known as dry or solid friction. It is due to the surface roughness. The dry or solid friction includes the sliding friction and rolling friction.
Friction between lubricated surfaces:
When the lubricant is applied between the two surfaces in contact, then the friction may be classified into
- Boundary friction (or greasy friction or non-viscous friction): It is the friction, experienced between the rubbing surfaces, when the surfaces have a very thin layer of lubricant.
- Fluid friction (or film friction or viscous friction): It is the friction, experienced between the rubbing surfaces, when the surfaces have a thick layer of the lubricant.
It is defined as the ratio of the limiting friction to the normal reaction between the two bodies. It is generally denoted by µ.
Angle of Repose:
If the angle of inclination α of the plane to the horizontal is such that the body begins to move down the plane, then the angle α is called the angle of repose.
Efficiency of inclined plane:
The ratio of the effort required neglecting friction to the effort required considering friction is known as efficiency of the inclined plane.
Bearing:
The fixed outer element of a turning pair is called a bearing.
Journal:
The portion of the inner element, which fits in the bearing, is called a journal. The journal is slightly less in diameter than the bearing, in order to permit the free movement of the journal in a bearing.
Point of Pressure or Seat:
When the bearing is not lubricated, then there is a line contact between the two elements. The load on the journal and normal reaction of the bearing acts through the center. The reaction acts vertically upwards at a point. This point is known as seat or point of pressure.
Types:
- Flat pivot bearing
- Flat collar bearing
- Conical pivot bearing
- Trapezoidal or Truncated conical pivot bearing.
A friction clutch has its principal application in the transmission of power of shafts and machines, which must be started and stopped frequently. Its application is also found in cases in which power is to be delivered to machines partially or fully loaded.
Types:
- Disc or Plate clutches
- Single plate
- Multi plate
- Cone clutches – extensively used in automobiles because it consists of one pair of friction surface only.
- Centrifugal clutches – incorporated into motor pulleys.
- A ball or roller bearing consists, in general, two races separated by balls or rollers in a cage. One race is fixed in a housing and the other is secured to the moving part.
- The object of the cage is to prevent the balls or rollers rubbing each other. The two main types are journal and thrust bearings to carry radial and axial loads.
Types:
- Deep groove ball bearing.
- Double row self-aligning ball bearing.
- Double row spherical roller bearing.
- Cylindrical roller bearing.
- Tapered roller bearing.
Rolling Resistance:
- It is assumed that for a given pair of materials, the rolling resistance is directly proportional to the load and is independent of the relative curvature of the contact surfaces.
- The rolling resistance plays an important role in vehicles.
- It occurs between the wheel tyres and the surfaces of the track, at the bearing of the wheel axle.
2 comments:
Genial brief and this enter helped me alot in my college assignement. Gratefulness you as your information.
Very enlightening and beneficial to someone whose been out of the circuit for a long time.
- Kris
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