Thank you for your reply, but when I print ElasticPlasticEq even for specific s11, s22 and t, I am getting this:
s11 = 0.01;
s22 = 0.01;
t = 0.00000001;
Print[ElasticPlasticEq];
{0. P[0.01,0.01,1.*10^-8]+(P^(0,0,1))[0.01,0.01,1.*10^-8]+2 (0. P[0.01,0.01,1.*10^-8]+4.88591...