Extracting sigmayy and sigmazz

[Mirialex]

hi all,

im trying to get inspiration from this topic published before

Incompressible Humphrey hyperelastic material in Fencis

I found the solution. There were a few issues with the variation formulation. Here is the complete code for uniaxial testing of incompressible NeoHookean hyperelastic material. > > from dolfin import * > import matplotlib.pyplot as plt > import os > import dolfin as dlf > import numpy as np > import math > > parameters["form_compiler"]["cpp_optimize"] = True > parameters["form_compiler"]["representation"] = "uflacs" > > > # traction > class Traction(UserExpression): > def __init__(sel…

and i wondering if changing the number of 0 to 1 or 2 will give me the stretch and stress on y and z accorinatly “stretch_vec.append(defGrad(point)[1])”

if not, is there a suggestion on how to do it? to get the stress in yy and zz?

i refer to those lines in the code those lines

>     
>     # get stretch at a point for plotting
>     point = (0.5,0.5,0)
>     DF = I + grad(u_plot)
>     defGrad.assign(project(DF, W_DFnStress))
>     stretch_vec.append(defGrad(point)[0])
> 
>     # get stress at a point for plotting
>     PK1_s,thydpress = pk1Stress(u_plot,p_plot,E,nu)
>     PK1_stress.assign(project(PK1_s, W_DFnStress))
>     stress_vec.append(PK1_stress(point)[0])
>     

thanks in advance

[Mirialex]

hi all, maybe someone had a chance to take a look on it and might help me?

[mpierre]

If I understand your question correctly, you have the 1st Piola-Kirchhoff stress tensor (PK1_stress) and you want to get its components at a given point.
PK1_stress(point) will return a vector (9 components in 3D) of the components of the tensor value at that point. If you are looking for values yy and zz they should lie on the diagonal of the tensor (index 4 and 8).