GATE ME 2014 Set 3 — Question 20

Let's analyze each statement:(A) Intermediate principal stress is ignored when applying the maximum principal stress theory.
This statement is correct. The Maximum Principal Stress Theory (Rankine's theory) states that failure occurs when the maximum principal stress in a complex stress state reaches the yield strength in a simple tension test. It does not consider the intermediate principal stress.(B) The maximum shear stress theory gives the most accurate results amongst all the failure theories.
This statement is incorrect. The Maximum Shear Stress Theory (Tresca's theory) is generally considered more conservative than the Maximum Distortion Energy Theory (Von Mises theory) for ductile materials. The Von Mises theory often provides a better correlation with experimental results for ductile materials under complex loading conditions, making it generally considered more accurate.(C) As per the maximum strain energy theory, failure occurs when the strain energy per unit volume exceeds a critical value.
This statement is correct. The Maximum Strain Energy Theory (Haigh's theory) postulates that failure occurs when the total strain energy per unit volume at a point in a stressed body exceeds the strain energy per unit volume at the elastic limit in a simple tension test.(D) As per the maximum distortion energy theory, failure occurs when the distortion energy per unit volume exceeds a critical value.
This statement is correct. The Maximum Distortion Energy Theory (Von Mises theory) states that failure occurs when the distortion energy per unit volume in a stressed material reaches the distortion energy per unit volume at the elastic limit in a simple tension test.Therefore, the statement that is NOT correct is (B).The final answer is $\boxed{B}$