Import Newton-Raphson residuals

[lschuler1]

Hi all,

Is there a way to directly import Newton-Raphson residuals to Python ?
The command mapdl.nldiag('NRRE','ON') enables to write the residuals to a file but then how to import them? The command mapdl.nldpost only creates a summary of the file but does not import the residual forces.

Thank you,
Louis

[mikerife]

Hi @lschuler1 What do you want to do with the NR residuals? We can plot them but need to redirect to a png file as MAPDL will default to grph file. So:

mapdl.post1()
mapdl.set('last')
mapdl.show('png','rev')
mapdl.plnsol('nrre','fnrm',0,'',1)
mapdl.show('close')

Will create a png image of the NR residuals (for NR file nr0001). Did you want the values to manipulate? Mike

[lschuler1]

Hi @mikerife,

Thank you for your answer. Yes I wanted to import them as a numpy or MAPDL array to manipulate them.
In fact, I would like to solve a nonlinear problem in an unusual way using a global Newton method over time. So from a previous displacement solution known throughout the temporal domain, I would need to evaluate the residuals to compute a corrective solution.
But I'm not sure if that will be possible...

Louis

[mikerife]

Hi @lschuler1
Pandas can read in the data from the nr* files. And it has a function to create a numpy array from a dataframe. Let's say file.nr001 exists, try:

import pandas as pd
cols = ['Node', 'NR FX', 'NR FY', 'NR FZ']
file_nrr = pd.read_table('file.nr001', engine='python', delimiter='\s+',header=None, skiprows=4, names=cols)
file_nrr.to_numpy()

We could read in the data to a MAPDL array via some APDL...would you rather go that route?
Mike

[lschuler1]

Thank you @mikerife, your code with panda works fine.