Hi,
I am having a problem solving a hyperelastic model that I have. I have been trying to figure out how to solve the problem for some time now but without any luck!
The material model contains user defined variables, a fixed constraint and a prescribed displacement. COMSOL is giving me the following error message when I try to solve the model:
"Undefined value found.
- Detail: Undefined value found in the equation residual vector."
There are 199 degrees of freedom giving NaN/Inf in the vector for the variable mod1.solid.pw.
at coordinates: (0,0), (0.000517625,0.000546197), (0.0008,0), (0,0.000807872), (0.0016,0), ...
- Feature: Stationary Solver 1 (sol1/s1)
I contacted the COMSOL Support Center where I got the explanation that something in my Volumetric strain energy density definition does not work with how COMSOL approaches the hyperelasticity. This is my volumetric strain energy definition:
k/2*(log((i5-i1*i4+i2)/(i4^(2*(m-v0))*exp((-4*m*(sqrt(i4)-1))))))^2
The COMSOL support suggested that somewhere in the model there was an expression containing the square root of something that is initially zero, and then when COMSOL tries to take the derivative of it, it ends up dividing by zero. When a small value (1e-8) is added inside the square roots of the variables in the model a division by zero error from one of the weak expressions in the hyperelastic model still appears.
I am currently unable to figure out what needs to be modified in the model in order for it to work and therefore I thought it might be a good idea to post my problem here. Do you see a possible solution to this problem? I have the COMSOL file attached if you would like to take a quick look at the model.
Best regards,
Brynjar
I am having a problem solving a hyperelastic model that I have. I have been trying to figure out how to solve the problem for some time now but without any luck!
The material model contains user defined variables, a fixed constraint and a prescribed displacement. COMSOL is giving me the following error message when I try to solve the model:
"Undefined value found.
- Detail: Undefined value found in the equation residual vector."
There are 199 degrees of freedom giving NaN/Inf in the vector for the variable mod1.solid.pw.
at coordinates: (0,0), (0.000517625,0.000546197), (0.0008,0), (0,0.000807872), (0.0016,0), ...
- Feature: Stationary Solver 1 (sol1/s1)
I contacted the COMSOL Support Center where I got the explanation that something in my Volumetric strain energy density definition does not work with how COMSOL approaches the hyperelasticity. This is my volumetric strain energy definition:
k/2*(log((i5-i1*i4+i2)/(i4^(2*(m-v0))*exp((-4*m*(sqrt(i4)-1))))))^2
The COMSOL support suggested that somewhere in the model there was an expression containing the square root of something that is initially zero, and then when COMSOL tries to take the derivative of it, it ends up dividing by zero. When a small value (1e-8) is added inside the square roots of the variables in the model a division by zero error from one of the weak expressions in the hyperelastic model still appears.
I am currently unable to figure out what needs to be modified in the model in order for it to work and therefore I thought it might be a good idea to post my problem here. Do you see a possible solution to this problem? I have the COMSOL file attached if you would like to take a quick look at the model.
Best regards,
Brynjar