Calculation for the Diameter of a Circular Shaft Subject to Torsion and Bending 

This piece of Java Script uses two failure theories to determine the required shaft diameter to withstand the specified bending moment and torque for the material UTS and design factor (factor of safety) entered in the boxes below.

NB No account is taken of any stress concentration here, an appropriate design factor must be entered.

Theories used are:

The maximum shear stress theory (Trseca)
The maximum distortion energy theory (von Mises)
Bending moment, Nm:
Torque, Nm:
UTS MPa:
Design Factor:

Answer - Required shaft diameter (Tresca criterion), mm:

Answer - Required shaft diameter (von Mises criterion), mm:

David J Grieve, Revised: 27th January 2010, Original: 21st July 2004.