In a two dimensional stress system, the two principal stresses are σ1 of 180 N/mm2 (tensile) and σ2 (compressive). For the material, yield stress in simple tension and compression is 240 N/mm2 and Poisson's ratio is 0.25. According to maximum normal strain theory, the value of σ2 at which yielding will commence, is
∴From condition (i)σ2=240N/mm2
From condition (ii)σ2=195N/mm2
So the valueof σ2 at which yielding will start is 195 N/mm2