Mechanical Engineering Design Notes

Design Contents

Preliminary Matters
Design Methodology
..brain storming
..evaluation matrix
Statistical Considerations
..variability in materials
..variability in dimensions
..variability in loading
..preferred sizes
Design Factor
Introduction to Failure
Failure Theories
Application of von Mises
..criterion in 2 D

Stress Concentration
..and notch sensitivity
Failure Under Combined Loading
..combined bending and torsion
Failure Under Cyclic Loading
..fracture mechanics
Instability - Buckling
Concentrically Loaded Strut
..slender columns
..Euler formula
..effective length
..short and intermediate columns
Eccentrically Loaded Strut
.. theory
Shock Loading


For the state of stress input, Mohr's circle is drawn and the design is marked with a + on a von Mises criterion plot. The von Mises failure criterion is applicable to most ductile metals.

Enter the values in the units indicated in the top boxes. Where the Design Factor is to be based on the yield strength rather than the ultimate tensile strength (UTS) enter the yield strength value in the 'UTS' box. Click on the 'Calculate' button, the principal stresses are printed in the boxes at the bottom of the cyan screen.

The 'Angle' is the rotation from the Sigma1 direction to the SigmaXX direction.

The Design Factor calculation assumes that the two principal stresses are changed by pro-rata amounts.

David J Grieve, Revised: 27th January 2010, Original: 23rd November 2006

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