Question

Steel has proportionality limit of 300 MPa in simple tension. It is subjected to principal stresses of 120 MPa (tensile), 60 MPa (tensile) and 30 MPa (compressive). What is the factor of safety according to maximum shear stress theory?

• A. 1.5
• B. 1.75
• C. 1.8
• D. 2.0

Answer 1

The correct option is D 2.0

Maximum shear stress due to applied loading

${\tau }_{max}=\frac{{\sigma }_{max}-{\sigma }_{min}}{2}=\frac{120-(-30)}{2}$
75 MPa
Maximum shear stress in material at yield stress under uniaxial tension

${\tau }_y=\frac{\sigma y}{2}=\frac{300}{2}=150MPa$

$\therefore Factoryofsafety=\frac{{\tau }_y}{{\tau }_{max}}=\frac{150}{75}=2.0$