Ogden Material more with more than 3 coefficients

[duchoangnguyen]

Hello,

currently I am using FEAP 8.1. I am trying to modify the ogden material model, so that it is possible to include more than 3 coefficients. Therefore I am trying to make changes in nalp3f.f. I have seen that the stress and material tangent are only calculated from sums and wanted to extend these loops.
For this I wanted to use TINPUT and PINPUT to read in any number of input parameters after “OGDEn” (in the input file). However, the respective lines start here after “PROP” (in the input file), so that I cannot read in the parameters. Is it possible to jump to a previous point when reading in? What must be taken into account here?

I also wanted to ask whether this way or the creation of a user material would be better. I have turned away from the second variant because the input of umatl differs from that of nalp3f, which is why I thought that several changes would be necessary.

Best regards,
Duc Hoang Nguyen

[Prof. R.L. Taylor]

I am not able to access the files for ver8.1 -- it is very old and compiler changes make it risky to use.  You should consider an update.  So I am not sure if the following applies to your version.

The changes are made to "inmate.f" and "wder3f.f".

In 'inmate.f'

1. search for where 'ogde' is input and input the additional values you want to include into new local values.

2. search for where the Ogden is output and modify the output of the parameters to the file.  In my version this is done with format 2024.

3.  below the output the parameters are stored in d(21) to d(28).  I would move the number of parameters to d(22) and the place all the pairs after this in d(23) to the max.  There is a remote risk you may overlap some other use of the parameter but let's hope not!

In "wder3f.f" search for where the d(22) etc. are used and adjust to match what you reset in "inmate.f"

Good luck.

[duchoangnguyen]

For completeness:
d(31) seems to be occupied elsewhere. Accordingly, I have skipped this and continued with d(32). this must also be adapted in wder3f.
In the event that more than 10 inputs are given, I have read in another line via PINPUT (in the first block), as I have only seen reading in via TINPUT.
I do not know if that was nessesary but it seems to work.

Thank you very much!