Nodal precision
Nodal precision
(OP)
Hi everybody,
I do optimization using Matlab and combining it with Abaqus as the solver.My problem is implicit.
I need to increase the precision of the nodal displacements to 10 decimal digits. I get the nodal displacement in .dat file. Is there a way or KEYWORD I can define it in the input file?
I really appreciate your help.
Thank you
Maryam
I do optimization using Matlab and combining it with Abaqus as the solver.My problem is implicit.
I need to increase the precision of the nodal displacements to 10 decimal digits. I get the nodal displacement in .dat file. Is there a way or KEYWORD I can define it in the input file?
I really appreciate your help.
Thank you
Maryam





RE: Nodal precision
You can write translations and rotations to the *.odb. I create separate sets for the desired surfaces to ease the selection in CAE. From there you can export the data to the *.rpy. I hope this helps.
Rob Stupplebeen
https://sites.google.com/site/robertkstupplebeen/
RE: Nodal precision
Unfortunately, I can not do this because I can not use Abaqus interface.
I need to AUTOMATIZE obtaining results in high precision.
Actually, I am doing optimization combining Abaqus with Matlab.
In every Matlab loop I need to read the high precision nodal disp. calculate gradient and update the variable(Matlab Algorithm does it).
Any idea?
Thanks again
RE: Nodal precision
Tara
RE: Nodal precision
Brian
www.espcomposites.com
RE: Nodal precision
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RE: Nodal precision
Brian
www.espcomposites.com
RE: Nodal precision
Ok,
Here is my problem:
I am doing material optimization, combining Abaqus with Matlab.
I use Matlab intrinsic function to update my variable(E modulus).
Matlab uses Quasi-Newton method to update variable, for that reason it needs to calculate gradient at each iteration. For example, the initial guess for my variable is: E= 3.000 and
Matlab changes it to 3.0000008 and calculate gradient of the objective function, which in my case is displacement. So can you imagine how small the change would be!!!!
That's the reason why I need high precision output file.
I hate precision, in fact!
RE: Nodal precision
Do you realize that the ABAQUS (and any FEM solution) may not solve the displacements exactly per the system of equations? LU decomposition should give an exact solution (perhaps), but an iterative solution (common) only approximately solves the system of equations (i.e. inverse of stiffness matrix) to some threshold.
I don't think you can expect ABAQUS, or any FEM, to accurately adjust to those minute changes. In fact, it would not surprise me if the two solutions for E (3.000 and 3.00000008) gave a nonsensical trend (i.e. displacement goes in opposite direction of expected).
I think you are going to need to tell Matlab to change the value to something more meaningful. Besides this, how many iterations and how long would it take to optimize something based upon such minute changes?
Brian
www.espcomposites.com
RE: Nodal precision
HTH,
Dan
RE: Nodal precision
Tara