A plate with an elliptical hole in the centre, with semi-major axis (a) perpendicular to the direction of loading and semi-minor axis (b) along the direction of loading, is subjected to a pull P. The maximum stress induced at the edge of the hole is equal to (where $$\sigma $$ = Stress for a plate with no hole i.e. nominal stress)
A. $$\sigma \left( {1 + \frac{{\text{b}}}{{2{\text{a}}}}} \right)$$
B. $$\sigma \left( {1 + \frac{{2{\text{a}}}}{{\text{b}}}} \right)$$
C. $$\sigma \left( {1 + \frac{{\text{b}}}{{3{\text{a}}}}} \right)$$
D. $$\sigma \left( {1 + \frac{{3{\text{a}}}}{{\text{b}}}} \right)$$
Answer: Option B

(1+2a/b) is theoretical concentration factor and sigma is applied stress. So the correct expression is "B"