**Principal**Angle: The angle of orientation at which

**principal**stresses occur for a specific point.

**Principal Strain**: Maximum and minimum normal

**strain**possible for a specific point on a structural element. Shear

**strain**is 0 at the orientation where

**principal strain**occurs.

Then, what is principal stress theory?

Maximum

**principal stress theory**is useful for brittle materials. Maximum**principal stress theory**or maximum**principal stress**criterion states that failure will occur when maximum**principal stress**developed in a body exceeds uniaxial ultimate tensile/compressive strength (or yield strength) of the material.What is first principal stress?

The

**1st principal stress**helps you understand the maximum tensile**stress**induced in the part due to the loading conditions." "The 3rd**principal stress**acts normal to the plane in which**shear stress**is zero. It helps you understand the maximum compressive**stress**induced in the part due to the loading conditions."What is the state of stress?

The general

**state**of**stress**can be represented by a symmetric 3 x 3 matrix. It is always possible to choose a coordinate system such that all shear**stresses**are zero. The 3 x 3 matrix is then diagonalised, with the three principal**stresses**on the diagonal, and all other components equal to zero.