I’m just try to understand the resultant of
diff operator. It is a good way to get differentiation with automated way but is it possible to represent the resultant explicitly by UFL representation ?
An example from hyperelasticity:
F = Identity(len(u)) + grad(u) F = variable(F) . . .
#Free Energy Form:
psi= (mu/2)*((Ic - 3))- mu*ln(J) + (lmbda/2)*(ln(J))**2
#Exact PK Sress: S_exact = lambda F: mu * F - mu * inv(F).T + lmbda * ln(det(F)) * inv(F).T #Alternative PK Stress: S_alter = diff(psi, F)
For simple problems as above, it is simple to take difference between S_exact and S_alter but for complicated energy functions, I cannot be sure about the resultant of
diff operator. Is there any way to print the result of S_Alter explicitly as we write S_exact ?