Orthotropic material setting CatiaV5

[LOFO]

Hello.
I am trying to run a FEA in CatiaV5R13 on a wood peice using the orthotropic material setting in the material properties. When running the analysis, I always get the "invalid material caracteristic" error message even thought the input values are well known and correct. Is there a secret Catia move that must be done so it works ? Even in the Help Files tutorial, there is no reference on orthotropic material setting. If I use the isothropic material setting it works but the values are way off from a wood ptototype I test benched.

Thanks in advance

Lofo

 

[SWComposites]

Please post the exact values that you are entering. Often this type of problem is due to an incorrect Poisson's ratio.

 

[LOFO]

Hello again SWComposite, here are the datas.
Young length/w 11200MPA
Young transv. 600MPA
Poisson: 0.45
Shear XY: 6MPA
Shear XZ: 6MPA
Shear YZ: 50MPA
Mass: 420kg m3
Tensile length/W 45MPA
Compres. length/W 30MPA
Tensile transv. 1,8MPA
Compres. transv. 3MPA
Thermal exp. lenght/W 0.00000002
Thermal exp. transv. 0.00000001

Thanks

Lofo

 

[SWComposites]

I have not used CATIA/FEA (thankfully) so I am not positive, but I suspect that it, like some other FE codes, expects the minor Poisson's ratio, nu21, to be entered for an orthotropic material rather than the major Poisson's ratio, nu12. The code then internally calculates nu12. You should try entering the following value for Poisson's ratio: nu21 = E2 * nu12 / E1 = 600 * 0.45 / 11200 = 0.024. If I am correct in my assumption, then the code is calculating with your current input values a value for nu12 = E1 * nu / E2 = 11200 * 0.45 / 600 = 8.4 ! which is physically impossible. I have run into this aggravating "problem" with other FE codes and if the Poisson's ratio convention is even documented at all, it is buried deep in some obscure place.