Maximum strain theory for the failure of a material at the elastic limit, is known as A. Guest’s or Trecas’ theory B. St. Venant’s theory C. Rankine’s theory D. Haig’s theory

The correct answer is: A. Guest’s or Trecas’ theory.

Guest’s or Trecas’ theory is a failure theory that states that a material will fail when the maximum strain reaches a certain value. This value is called the elastic limit, and it is the maximum strain that a material can withstand without permanently deforming.

St. Venant’s theory is a failure theory that states that a material will fail when the maximum stress reaches a certain value. This value is called the yield stress, and it is the maximum stress that a material can withstand without permanently deforming.

Rankine’s theory is a failure theory that states that a material will fail when the maximum shear stress reaches a certain value. This value is called the shear yield stress, and it is the maximum shear stress that a material can withstand without permanently deforming.

Haig’s theory is a failure theory that states that a material will fail when the maximum principal stress reaches a certain value. This value is called the ultimate tensile stress, and it is the maximum stress that a material can withstand before it fails.

Guest’s or Trecas’ theory is the only theory that is based on the strain, while the other three theories are based on the stress. This is because strain is a more accurate measure of the deformation of a material than stress.