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.