A shaft is a
rotating machine element, usually circular in cross section, which is used to
transmit power from one part to another, or from a machine which produces power to a machine which absorbs power.
Types
They are mainly classified into two types.
* Transmission shafts are used to transmit power between the source and the machine absorbing power; e.g. counter shafts and
line shafts.
* Machine shafts are the integral part of the
machine itself; e.g.
crankshaft.
*Axle shaft.
*Spindle shaft.
Materials
The material used for ordinary shafts is
mild steel
Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:
* no minimum content is specified or required for chromium, cobal ...
. When high strength is required, an
alloy steel
Alloy steel is steel that is alloyed with a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups: low alloy steels and high alloy steels. The differ ...
such as
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
,
nickel-chromium or
chromium-vanadium steel is used. Shafts are generally formed by
hot rolling and finished to size by
cold drawing or
turning
Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helix toolpath by moving more or less linearly while the workpiece rotates.
Usually the term "turning" is reserved for the generation ...
and
grinding.
Standard sizes
Source:
[Mahadevan K and Reddy K.Balaveera, (2015), 'Design data hand book', CBS publishers and Distributors (P) ltd., New-Delhi, ]
Machine shafts
* Up to 25 mm steps of 0.5 mm
Transmission shafts
* 25 mm to 60 mm with 5 mm steps
* 60 mm to 110 mm with 10 mm steps
* 110 mm to 140 mm with 15 mm steps
* 140 mm to 500 mm with 20 mm steps
The
standard lengths of the shafts are 5 m, 6 m and 7 m.
Usually 1m to 5m is used.
Stresses
The following
stresses are induced in the shafts.
#
Shear stress
Shear stress, often denoted by (Greek: tau), is the component of stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. '' Normal stress'', on ...
es due to the transmission of
torque
In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of t ...
(due to torsional load).
# Bending stresses (
tensile or
compressive) due to the forces acting upon the machine elements like
gears
A gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth (called ''cogs''), which mesh with another (compatible) toothed part to transmit (convert) torque and speed. The basic ...
and
pulleys as well as the self weight of the shaft.
# Stresses due to combined
torsional and
bending
In applied mechanics, bending (also known as flexure) characterizes the behavior of a slender structural element subjected to an external load applied perpendicularly to a longitudinal axis of the element.
The structural element is assumed to ...
loads.
References
{{Reflist
External links
Online verification of shafts according standard
Machines
Mechanical engineering
Kinematics
Articles containing video clips
Shaft drives