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How to set up a 1D element as P18_INT_BEAM? (in RadioSS - Quasi static)

A simple cantilever beam is considered with square cross section. Analytical tip displacement should be 0.108064. Attached is a model with P3_beam elements, this one works perfectly.

However when trying to use P18_INT_BEAM elements instead, it gives a displacement of 0.323… I suspect that the cause is somewhere in the material?

The material goes into plasticity (while it shouldn't). During debugging, the error messages lead me to believe it is incompatible with M1_elast? In order to still get elastic results I tried to elevate the yield point such that the analysis stays within the elastic regime but here I got stuck.

The question: how to configure the P18_INT_BEAM model to get some agreement with the linear elastic hand calculation?

36_PLAS_TAB_with_P18_INT_BEAM_0001.rad

36_PLAS_TAB_with_P18_INT_BEAM_0000.rad

M1_elast_with_P3_BEAM_0000.rad

M1_elast_with_P3_BEAM_0001.rad

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HarishT

Hi Wesley Peijnenburg,

I think the difference in the displacement may be due to material laws used in the model.

One is elastic and another elastic -plastic.

Let me check in detail and get back to soon.

Regards

Harish

HarishT

Also plz let me know which units you are following?

Wesley_Peijnenburg2

Thank you for the response!

The input is for validation of p18 beam only (quasi static) and does not yet represent a practical problem. If it matters, input can be considered as SI units (N-m-s).

Looking forward to your reply.

HarishT

Hi Wesley Peijnenburg,

Good Morning!

I looked into model and changed the few things as below.

1- Removed the damping which is not necessary.

2- Material units changed to ( N mm sec),

3- Load curve modified and applied gradually.

4- Cross section changed to ( 10 mm x 20 mm)

Please find the updated model, please review and let me know your comments

Regards

Harish

Beam_Type18_Mod01.zip

Beam_Type03_Mod01.zip

HarishT

Hi Wesley Peijnenburg,

Good Morning!

I looked into model and changed the few things as below.

1- Removed the damping which is not necessary.

2- Material units changed to ( N mm sec),

3- Load curve modified and applied gradually.

4- Cross section changed to ( 10 mm x 20 mm)

Please find the updated model, please review and let me know your comments

Regards

Harish

Beam_Type03_Mod01.zip

Beam_Type18_Mod01.zip

Wesley_Peijnenburg2

Hello Harish,

For point 1: running the provided "Beam_Type03_Mod01" gives below shown (highly dynamic) energy plot:

However, I'm interested in the stabilized end result (quasi-static). So the energy balance should level out as shown below (this is why damping was implemented):

For point 2-4: if units are changed, please note the cross section 0.1x0.2m equals 100x200mm. Length 6m becomes 6000mm and E modulus is 10.0 N/mm2 (this does not represent steel).

I have a question about the provided model "Beam_Type18_Mod01": Comparing the models, I find these differences: Property NITRS=2 (instead of 7), Ismstr=1 (instead of 4). However with these changes the tip displacement is still 0.323 instead of the expected 0.108. Do you have any idea why beam type 18 and 03 behave so different while the input for both is the same?

HarishT

Hi Wesley Peijnenburg,

Good Morning!

In Radioss help document we have verification on different elements, please refer using below link

https://2023.help.altair.com/2023.1/hwsolvers/rad/topics/solvers/rad/cantilever_beam_verification_intro_r.htm#reference_qzl_zwm_w3b

Hope its helpful.

Regards

Harish