function[ES,vs]=fxx(stressx,E0,v0,fc,ft)
D=0.8;
stress(1,1)=stressx(1,1);
stress(1,2)=stressx(3,1);
stress(2,1)=stressx(3,1);
stress(2,2)=stressx(2,1);
I1=(stress(1,1)+stress(2,2))/2;
c1=I1+sqrt(((stress(1,1)-stress(2,2))/2)^2+stress(1,2)^2);
c2=I1-sqrt(((stress(1,1)-stress(2,2))/2)^2+stress(1,2)^2);
s(1,1)=stress(1,1)-I1;
s(2,2)=stress(2,2)-I1;
s(1,2)=stress(1,2);
s(2,1)=s(1,2);
J2=0;
for i=1:2
    for j=1:2
        J2=J2+s(i,j)*s(i,j)/2;
    end
end
GJ2=sqrt(J2);
if(c1>0)
    a=(fc/ft-1)/2;
    b=sqrt(3)*(1+fc/ft)/2;
else
    a=1+fc/(1.2*fc);
    b=sqrt(3)*(2-fc/(1.2*fc));
end
f=(1-a*I1/fc)/b;
x=f-1/(sqrt(3));
if(x<0)
    x=0;
end
EC=fc/0.002;
A=E0/EC;
Ef=EC/(1+4*(A-1)*x);
ds=sqrt((stress(1,1)+stress(2,2))^2+3*stress(1,2)^2);
if(c1>0)
B=c1/ft;
else
    B=-c1/fc;
end
if(B<=1)
    ES=E0/2-B*(E0/2-EC)+abs(sqrt((E0/2-B*(E0/2-Ef))^2+B*(EC^2)*(D*(1-B)-1)));
else
    ES=E0/2-B*(E0/2-EC)-abs(sqrt((E0/2-B*(E0/2-Ef))^2+B*(EC^2)*(D*(1-B)-1)));
end
Ba=0.8;vf=0.4;
if(B<Ba)
    vs=v0;
else
    vs=vf-(vf-v0)*abs(sqrt(1-((B-Ba)/(1-Ba))^2));
end