Learning Forum

[Sriparna Singh]

I have modeled a 3-D beam with dimensions: 100mm x 100 mm x 500mm in ANSYS workbench. ANSYS by default, is considering SOLID186 as an element type. The ANSYS modal results are based on Timoshenko beam theory, which does not match analytical results based on Euler theory. Can anyone suggest how I can force ANSYS to provide results based on Euler theory?

[peteroznewman]

Read some of these discussions.

[Sriparna Singh]

i tried changing element type to beam4 but I am getting an error as shown below

[Erik Kostson]

Beam4 is a beam (line element), so you can not use it on 3D solid bodies .

You need to define a line body.

See here how to define such a body (line) and how to analyse beams.

All the best

Erik

https://www.youtube.com/watch?v=5Ef5piegVh4

 

Erik

[Sriparna Singh]

thank you for your response. Sir can you please tell me which real constants I need to insert in commands. After going through several posts, I have found to use the follwing commands:

et, matid, beam4

r,2,.....................

after r,2, I am unable to understand what parameters do i need to enter

beam cross section : 100mm x 100mm x 500mm 

[Erik Kostson]

 

Hi

 

See this post for the real constants and help manual if needed:

/forum/forums/topic/euler-bernoulli-beam-theory/

use r,matid,AREA,IZZ,IYY,TKZ,TKY

and input the above (AREA=0.01*0.01 in your case I assume, etc).

I would suggest to learn the Mechanical (Getting started course),

https://innovationspace.ansys.com/product/get-started-with-ansys-mechanical/

and then also look into the APDL course as you need to learn what these commands mean when using them:

/courses/index.php/courses/intro-to-ansys-mechanical-apdl-scripting/lessons/overview-of-mapdl-lesson-1/

All the best

Erik

[Sriparna Singh]

http://mae.uta.edu/~lawrence/ansys/el_beam/el_beam.htm

Thank you for your response. In the above article, it shows that it can be used for 3D element. So, is it possible or not.

[Erik Kostson]

 

 

Hi

 

So beam4 is a 2 node beam element. 

In mechanical one then needs a line body ( see here how to define such a line body

https://www.youtube.com/watch?v=5Ef5piegVh4 )

You have a 3D solid body which is meshed with HEX8 or HEX20 3D solid elements so hence the error.

To sum up the geometry created needs to be a line body not a 3D solid like you have, in order to use a beam4 element – look at the video again to see how to define/create a line body.

All the best

Erik

 

 

[Sriparna Singh]

thank you for clarifying my doubt. I have serious doubts regarding Ixx, if you could help me with that, it would be of great help.

 

[Erik Kostson]

Hi

Please see the doc./help:

Search for beam4 (...the torsional moment of inertia (IXX)).

BEAM4 (ansys.com)

See here hwo to open the help link (/forum/forums/topic/how-to-access-the-ansys-online-help/#:~:text=Open%20Ansys%20Workbench%20(or%20any,A%20browser%20window%20will%20open.)

All the best

Erik

[Sriparna Singh]

thank you for your help. I will work on it

 

[Sriparna Singh]

My problem was that I was not able to match the numerical frequencies corresponding to the bending mode shapes with the ansys result. I read about BEAM4 element, but the results are still not accurate. I have attached the properties of the model and the natural frequencies corresponding to the 20 mode shapes have been shown in the table along with the ANSYS result. It would be very helpful if you can help me to identify that whether there is some limitation in the ANSYS software for this geometry or something else. Dimensions of 3D beam: 150mm x 150mm x 700mm

 

 

[Sriparna Singh]

just to clarify I have tried this problem in 3D model and also as line body for BEAM4 element

[Sriparna Singh]

The theoritical natural frequencies do no match with the frequencies obtained from ANSYS and the error between them keeps on increasing. Till 50th mode shape only the error is 50% and if I want even more higher mode shapes the error will be greater than 50%

[Sriparna Singh]

please reply if someone knows about this topic. It would really help a lot