What are Governing Partial differential equations used in PDE ToolBox used to calculate Von Mises Stress by FEM

smodel = createpde('structural','static-solid');
importGeometry(smodel,'Blade.stl');
figure
pdegplot(smodel,'FaceLabels','on','FaceAlpha',0.5)
msh = generateMesh(smodel,'Hmax',0.01);
pdeplot3D(smodel);
structuralProperties(smodel,'YoungsModulus',E,'PoissonsRatio',nu,'CTE',CTE);
structuralBC(smodel,'Face',3,'Constraint','fixed');
structuralBoundaryLoad(smodel,'Face',11,'Pressure',p1);
structuralBoundaryLoad(smodel,'Face',10,'Pressure',p2);
Rs = solve(smodel);
max(Rs.VonMisesStress)

Here I have given fixed constraint by 'structuralBC' function, and gave load using 'structuralBoundaryLoad'. So in function Rs = solve(smodel) which basic governing equations are solved, I need that equations

[SALAH ALRABEEI]

Check this work here I remember that I compared some models bases on the Matlab solver and the solver I developed based on some the equtions