General Mechanical

Topics relate to Mechanical Enterprise, Motion, Additive Print and more

degrees of freedom

• Massochy dos santos Ventura
Subscriber

I'm doing a modal analysis of a free-free steel plate and want to restrict the degrees of freedom in all nodes in the direction UX,UZ,ROTX,ROTY,ROTZ before excuting the solution. whether it's in workbench or APDL

• Akshay Maniyar
Ansys Employee

Hi,

Sorry, but I am not sure if I understood your question clearly. Do you want to do the free-free or modal analysis of the steel plate? Also, how do you want to constrain the model? If you can explain how the plate is constrained in reality, then I can help you with the correct boundary conditions in Ansys. I have attached some links to our AIC courses which might be helpful for you.

Intro to Modal Analysis | Ansys Innovation Courses

Modal Analysis in Ansys Mechanical | Ansys Courses

Thanks,

Akshay Maniyar

• Massochy dos santos Ventura
Subscriber

I'm doing a modal analysis on a free-free steel plate in order to extract stiffness matrix, mass matrix and the vectors corresponding to the vibration modes for each natural frequency. in order to reduce the values ​​of the matrices so I intend to restrict some degrees of freedom all nodes since the matrix is ​​formed by the multiplication between numbers of nodes and the degrees of freedom (in this case they are 6)..

• HuiLiu
Ansys Employee

Hi, if you are doing free-free modal, it means you don't have any boundary conditions and in this case you will get 6 zero modes like you did. If your question is about how to apply constraints, you can use "displacement" and "fixed rotation".

• Massochy dos santos Ventura
Subscriber
`how can i do this? can you share with me some command that allows you to do this?`
• HuiLiu
Ansys Employee

right click Modal from the tree  > insert > displacement (or fixed rotation)

• Massochy dos santos Ventura
Subscriber
`I intend to apply these conditions to all nodes`
• HuiLiu
Ansys Employee

You can scope to the entire surface(s) to apply the constraint to all nodes.

• Massochy dos santos Ventura
Subscriber
```please look in the image where I marked with the word "here"
I would like to extract the values ​​(vectors) of the vibration mode corresponding to each of the modes```
• Massochy dos santos Ventura
Subscriber
```please look in the image where I marked with the word "here"
I would like to extract the values ​​(vectors) of the vibration mode corresponding to each of the natural frequencies```
• HuiLiu
Ansys Employee

highlight all rows > right click > create mode shape results. once the mode shape results (deformation) is created and evaluated, right click on the deformation results > export, this will save the nodal results to a txt file.

If you need the x/y/z deformation instead of total, change the "total deformation" to directional.

• Massochy dos santos Ventura
Subscriber

thank you so much for everythink