It is integral to such devices as gear-type speed reducers, belt or chain drives, conveyors, pumps, fans, agitators, and many types of automation equipment.
In the process of transmitting power at a given rotational speed, the shaft is inherently subjected to a torsion moment, or torque. Therefore, torsion shear stress is developed in the shaft.
Also, a shaft usually carries power-transmitting components such as gears, belt sheaves, or chain sprockets, which exert forces on the shaft in the transverse direction. These transverse forces cause bending moments to be developed in the shaft. requiring analysis of the stress due to bending
The equation used in Shaft Design
M.S.S. = maximum allowable shear stress
f1= maximum allowable stress
d = outside diameter of shaft
K = inside diameter / outside diameter
Km = combined shock and fatigue factor for bending
Kt = combined shock and fatigue factor for torsion
F = axial force
M = bending moment
T = torque
column action factor
use for L/k<115
use for L/k>115
L = length of shaft between bearings
k = radius of gyration of shaft cross section
Syc = yield strength in compression
E = modulus of elasticity
n = 1.6 for ends partly restrained (as in bearings)
n = 1 for hinged ends (as in self-aligning bearings)
| shaft | load applied | Km | Kt |
| stationary | gradually | 1.0 | 1.0 |
| ،@ | suddenly | 1.5-2.0 | 1.5-2.0 |
| rotating | gradually | 1.5 | 1.0 |
| ،@ | suddenly, minor shock | 1.5-2.0 | 1.0-1.5 |
| ،@ | suddenly, heavy shock | 2.0-3.0 | 1.5-3.0 |
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