Stress analysis of structural material for the submarine gives the state of stress as shown in the figure. The yield strength of the material is 450 MPa. Using Von-mises yielding criteria determine whether yielding will occur or not? If not, what is the factor of safety?

Correct Answer: Yielding will occur, and the factor of safety is 1.28
criteria for yielding is R.H.S should be greater than 450MPa σo = 1/√2 1/2 σ1=300 MPa, σ2=50 MPa, σ3=-100MPa R.H.S = 1/√2 1/2 => 1/√2 1/2 => 350MPa yield stress (σo=450MPa) is more than stress deviator so yielding will not occur. The factor of safety = 450/350 = 1.285.