Display principal stresses

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bernd
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Re: Display principal stresses

Post by bernd »

Very value input Stefan. It is the way to go IMHO. The graphical output will even look better, similar to the picture in the first post.
EkaitzEsteban
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Re: Display principal stresses

Post by EkaitzEsteban »

Very interesting, I will need it sometime...

kudos. ;)
UR_
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Re: Display principal stresses

Post by UR_ »

AFAIK, Paraview offers three methods for reducing glyph density

ParaView 5.6.0-RC2 64-bit-000079.png
ParaView 5.6.0-RC2 64-bit-000079.png (6.77 KiB) Viewed 1642 times

Mode 2 and 3 are only dropping glyphs, there is no interpolation or other maths ;)

BTW, because of ordered mesh numbering, necessary for optimized solving, there is no major difference in visualization between mode 2 and mode 3.
Perhaps not worth the effort.
EkaitzEsteban
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Re: Display principal stresses

Post by EkaitzEsteban »

Hello,

I have a doubt regarding the stresses and their posterior calculation like principal stresses....

Taking a row vector from calculix .frd and .dat files...

Are the indexes of stress values sorted in the same manner?

I check that in the .dat file the stress for each element integration point is indexing in the following manner:

Code: Select all

stresses (elem, integ.pnt.,sxx,syy,szz,sxy,sxz,syz)
So if we include the values in the stress tensor, it is in the following way:

S=[sxx sxy sxz
sxy syy syz
sxz syz szz]

Using numbers as index...

S=[1 4 5
4 2 6
5 6 3]

However, the .frd file shows that:

Code: Select all

 -5  SXX         1    4    1    1
 -5  SYY         1    4    2    2
 -5  SZZ         1    4    3    3
 -5  SXY         1    4    1    2
 -5  SYZ         1    4    2    3
 -5  SZX         1    4    3    1
This means that the stress tensor values for nodes is:

S=[1 4 6
4 2 5
6 5 3]?

To sum up, are sxz and syz components exchanged?

Best regards,
fandaL
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Re: Display principal stresses

Post by fandaL »

EkaitzEsteban wrote: Sat Dec 22, 2018 8:56 am To sum up, are sxz and syz components exchanged?
I think you are right that components are written in a different order.
I don't exactly recall where it was discussed, if somewhere on this forum or on the ccx mailing list.
EkaitzEsteban
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Re: Display principal stresses

Post by EkaitzEsteban »

fandaL wrote: Sat Dec 22, 2018 9:27 pm
EkaitzEsteban wrote: Sat Dec 22, 2018 8:56 am To sum up, are sxz and syz components exchanged?
I think you are right that components are written in a different order.
I don't exactly recall where it was discussed, if somewhere on this forum or on the ccx mailing list.
Thank you FandaL!
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HarryvL
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Re: Display principal stresses

Post by HarryvL »

It was discussed in this topic, see a few posts back:

https://forum.freecadweb.org/viewtopic. ... 10#p240408
EkaitzEsteban
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Re: Display principal stresses

Post by EkaitzEsteban »

fandaL wrote: Sat Dec 22, 2018 9:27 pm
EkaitzEsteban wrote: Sat Dec 22, 2018 8:56 am To sum up, are sxz and syz components exchanged?
I think you are right that components are written in a different order.
I don't exactly recall where it was discussed, if somewhere on this forum or on the ccx mailing list.
Response from cxx mailing group https://groups.yahoo.com/neo/groups/cal ... ages/15199, I copy and paste it.

I don't know about .dat but I'll confirm that the .frd has the YZ component as the 5th component. I just ran a model with known shear stress and it appeared in the 5th position. It shouldn't matter though because you should use the ICIND1 and ICIND2 values to identify the component rather than the order.


Be careful when postprocessing .frd and .dat files...
EkaitzEsteban
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Re: Display principal stresses

Post by EkaitzEsteban »

HarryvL wrote: Sat Dec 22, 2018 9:44 pm It was discussed in this topic, see a few posts back:

https://forum.freecadweb.org/viewtopic. ... 10#p240408
Thumbs up!
EkaitzEsteban
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Re: Display principal stresses

Post by EkaitzEsteban »

Hello,

My last confirmation regarding stresses. I make a simple test: inital conditions pure stress (500 MPa - SXY direction) in element 51.

Code: Select all

#Element information
El=[46, 9, 3, 8, 6
    47, 5, 3, 6, 4
    48, 3, 4, 8, 6
    49, 7, 5, 6, 4
    50, 5, 3, 4, 2
    51, 3, 2, 1, 4]
# From FRD file:
NodeS=[[b]-5.53205E-01  7.20325E+00  7.61790E+01 -4.43743E+00 -2.79101E+02 -1.59312E+01[/b]
        1.45933E+01  1.11598E+01  8.20929E+01  9.95657E+00 -2.91087E+01 -2.00360E+01
        5.04025E+00 -9.63229E-01  1.54117E+00  1.13816E+00 -1.38002E+00 -3.10907E+00
       -2.67077E+00 -1.59571E-01 -1.99464E-02  2.53921E-01  5.64170E-02 -8.97747E-02
       -1.78328E-01 -1.56922E+00  1.64284E+00  2.19851E+00  8.63545E+01  4.65185E+00
       -7.29664E+00 -5.57991E+00 -4.10465E+01 -4.97829E+00  1.45544E+01  1.00180E+01
       -2.52012E+01  4.81615E+00 -7.70584E+00 -5.69080E+00  6.90009E+00  1.55453E+01;
        5.44095E-01 -1.24779E+00 -4.05538E+01 -1.07905E+00  1.00185E+01  9.87834E-01
        1.33538E+01  7.97857E-01  9.97321E-02 -1.26961E+00 -2.82085E-01  4.48874E-01]
# From DAT file:
ElementS=[1.335383E+01  7.978568E-01  9.973210E-02 -1.269606E+00  4.488735E-01 -2.820850E-01
         -5.073507E+00 -2.464022E+01 -7.537246E+01 -1.206424E+01  2.255105E+01  3.128036E+01
         -1.226564E+01 -3.293428E+00 -8.120725E+01 -8.885034E-01  1.526795E+00  2.031913E+01
         -2.520123E+01  4.816147E+00 -7.705843E+00 -5.690797E+00  1.554534E+01  6.900095E+00
          2.973975E+01  1.511639E+01  8.800681E+01  2.435058E+01 -2.414085E+01  2.208832E+02
         [b]-5.532049E-01  7.203245E+00  7.617900E+01 -4.437433E+00 -1.593121E+01 -2.791007E+02][/b]
I check the values in NODE 1 from element 51:

# Stress FRD file
-0.5532 7.2032 76.1790 -4.4374 -279.1010 -15.9312
# Stress DAT file
-0.5532 7.2032 76.1790 -4.4374 -15.9312 -279.1007

Sxy and Sxz are in different order.

Best regards,
Ekaitz.
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