He also contributed significantly to the theory surrounding strength of materials and structures.

Mohr started his career as an engineer on the railroads in Germany, designing bridges. At the age of 32 he became a professor at Stuttgart Polytechnic and later moved to Dresden Polytechnic.

Mohr’s Circle

Also known as the point stress distribution diagram or stress circle, which studies the lines of influence in structures allowing engineers to pinpoint the maximum stress.

Mohr cannot take all the credit, it was Cauchy who defined the concept of stress on a material, defined as force per unit area. Then Culmann who introduced the concept of graphically representing this. But Mohr developed their concepts further to represent both two and three dimensional stresses.

Equation:

Stress transformation equations:

Practical Applications Using Mohr’s Circle

• Define principle Second Moments of Area using Mohr’s Circle with the Unsymmetrical Cantilever Apparatus (SM1003)
• Calculate the Shear Strain at any position in a cylinder with Mohr’s Circle using the Thin Cylinder Apparatus (SM1007)

Useful Reading

• Using Mohrs circle to find principle stresses and angles – Dummies.com
• Mohr’s circle calculator – Engineeringcalculator.net