TORSIONAL STRESS CALCULATOR of SHAFTS

A shaft is a rotation member usually with cylindrical shape which is used to transmit torque, power and motion between various elements such as electric or combustion motors and gear sets, wheels, cams, flywheels, pulleys, or  turbines and electric generators. Shafts can be solid or hollow. During power transmission, shafts twist and stresses and deformations are taking place.

Torsion is twisting of an object due to an applied torque.  When a shaft twists, one end rotates relative to the other and shear stresses are produced on any cross section.

Shear stress is zero on the axis passing through the center of a shaft and maximum at the outside surface of a shaft. On an element where shear stress is maximum, normal stress is 0. This element where maximum shear stress occurs is oriented in such a way that its faces are either parallel or perpendicular to the axis of the shaft as shown in the figure. To obtain stress in other orientations, plane stress transformation is needed for shear stresses found with this calculator.

Torsional stress of shafts

The torsional stress calculator was developed to calculate shear stress, angle of twist and polar moment of inertia  parameters of a shaft. The calculator is only valid for solid/hollow circular shafts and can be used for sizing of the shafts. The formulas used for calculations are given in the List of Equations section.

Note: For more information on torsion of shaft, shaft materials, shaft layout, shaft design for stress and critical speeds for shafts, please refer to Chapter 3 (Load and Stress Analysis) and Chapter 7 (Shafts and Shaft Components) of Shigley's Mechanical Engineering Design.

Calculator:

Torsional stress of solid shaft Torsional stress of hollow shaft
Shaft style
 INPUT PARAMETERS
Parameter Symbol Value Unit
Torque T
Rotation speed w rpm
Shaft outer radius c2
Shaft inner radius c1
Shaft length L
Modulus of rigidity G

Note: Use dot "." as decimal separator.

 


 RESULTS
Parameter Symbol Value Unit
Maximum shear stress τmax ---
Angle of twist θ ---
Power requirement P ---
Polar moment of inertia J ---



Definitions:

Angle of Twist: The angle through which a part of an object such as a shaft is rotated from its normal position when a torque is applied.

Dynamometer: Dynamometer is a device to measure torque or power. There are different types of absorption unit in dynamometers such as Eddy current brake, magnetic powder brake, hysteresis brake.

Modulus of rigidity (modulus of elasticity in shear): The rate of change of unit shear stress with respect to unit shear strain for the condition of pure shear within the proportional limit. Typical values Aluminum 6061-T6: 24 GPa, Structural Steel: 79.3 GPa.

Notch Sensivity: A measure of how sensitive a material is to notches or geometric discontinuities.

Polar Moment of Inertia: A geometric property of cross section. Measure of ability how a beam resists torsion.

Stress Concentration Factor: Dimensional changes and discontinuities of a member in a loaded structure causes variations of stress and high stresses concentrate near these dimensional changes. This situation of high stresses near dimensional changes and discontinuities of a member (holes, sharp corners, cracks etc.) is called stress concentration. Ratio of peak stress near stress riser to average stress over a member is called stress concentration factor.

Torque meter: Torque meter is a device for measuring torque on a rotating system.

Supplements:

Link Usage
Stress concentration factors Stress concentration factor for different types of stress raisers can be calculated for tension, bending and torsional loading type.

List of Equations:

Step Parameter/Condition Symbol Equation
1 Shear stress τ Equation for shear stress for shaft torsion
2 Angle of twist θ Equation for angle of twist for shaft torsion
3 Maximum shear stress τmax Equation for maximum shear stress for shaft torsion
4 Polar moment of inertia of solid shaft Equation for polar moment of inertia of solid shaft
5 Polar moment of inertia of hollow shaft J Equation for polar moment of inertia of hollow shaft
6 Power P

Symbol Parameter
T Torque to be transmitted
J Polar moment of inertia
Radial distance to center of shaft
c1 Hollow shaft inner radius
c2 Shaft outer radius
L Length of the shaft
G Modulus of rigidity
w Rotation speed
P Power

Examples:

Link Usage
Torsion Of Solid Shaft An example about the calculation of torsional stress on stepped shaft. After calculation of torsional stress, principal stresses are calculated and evaluation of yield criteria of material is done with these stresses.

Reference: