**Maximum principal strain theory :**

This theory states that “ Yielding in a member subjected to complex/compound stress system commences when maximum principal strain of the system becomes equal to the strain corresponding to the yield point under simple tension test of the same material.”

**For a 3 – dimensional state of stress system **

**For a 2 – dimensional state of stress system**

Where

- є
_{1 }= maximum principal strain.

- υ = Poisson’s ratio.

- σ
_{1}= Major principal stress in x direction.

- σ
_{2 }= Minor principal stress in y direction.

- σ
_{3 }= Minor principal stress in z direction.

- σ
_{yt}= Maximum Tensile strength in yielding.

- σ
_{yc }=Maximum Compressive strength in yielding.

** Merits :**

- It computes the failure load based on all 3 values of principal stresses.

**De merits :**

- This theory gives unsatisfactory results for various materials.
- This theory is not much used for design purposes.
- This is not a very popular theory.

subha says

Please continue your service… Some terms is missing….please upload each topics….thank you

HARISHKUMAR says

What is the most applicable failure theory for aluminium