APDL Node selection on a meshed line

[anlblk]

Dear all,

I have a question about APDL, I hope someone can help me out with this.
I have a line which is created with 2 keypoints. After meshing, I would like select a specific location on this line and add a nodal mass (mass21).
This location is dynamic, so that it is calculated each time.
My problem is I cannot figure out how to select that.
Is there any way to define another keypoint in advance and make it a part of that line, or directly, to select the nodes that are created on this defined location and apply the element type?
I will be glad to hear also if someone has another idea.
Thank in advance.
Regards

Anl

 

[petb]

Hi!

You are talking about 2 things here, the geometry model and the finite element mesh. What's the underlying element type, if the line is already meshed (is it a beam, shell edge, solid edge). You can't just add a node, the node must be part of the mesh or otherwise connected to the original mesh. Can you elaborate a little more on your question so we don't have to guess what you want.

 

[anlblk]

Hi,

I am sorry for the lack of information. Please let me explain in a better way.
I am creating a BEAM188 element for a line that is created with 2 key points. Let's consider as K1(0,0,0), K2(100,100,0)
Then i use LMESH to mesh this line. After that I want to apply a nodal mass by Mass21 command on a location (70,70,0).
In order to do that I use NSEL with LOC item type, but due to the number of mesh elements it selects several nodes on that location so that I cannot use E command to link them. For instance, if I have a rough mesh, then it selects one node and it completes the simulation.
What I would like to do select all the nodes on that specific location, merge them an apply a nodal force.
In addition, I am not using GUI, I cant select something on that interface as manually.
I hope it is clear now.
Thank in advance.
Regards.

 

[petb]

If you know the location beforehand, then just create a kp there and define the lines between that kp and the other ones. Or, put a workplane at the location and divide the line with that. There are numerous ways.

How can you get a lot of elements selected with NSEL? The standard tolerance is really small. Is there a specific reason that you are meshing a line with a lot of beam elements? That's normally not required to capture the physics.

Otherwise just create a node at your location with N,loxc,locy,locz and tie that to you mesh with either RBE2 or RBE3, whatever is appropriate for your problem.

/PB

 

[anlblk]

Thanks a lot for your concern.

I am trying to perform a modal analysis for a 2 link structure that will have different orientations.
When I create 2 lines with 3 keypoints as you mentioned, then I need to add a joint element which will cause an additional dof. Because otherwise, they move separately.
I don't know what causes this, but the output of NSEL says multiple nodes are selected. For instance, when I enter 300 for sizing, it selects 17 nodes.
Basically, what I was looking for is creating a connectivity with those nodes.
I haven't used RBE3 before, I will look for it.
Thank you!
Regards.

 

[petb]

Sorry, I don't really follow you here, can you draw a sketch of what you are modelling. Also if it is true links or struts, with only axial capacity, Link180 should be your element of choice, not a beam element with bending capacity.
/PB

 

[anlblk]

This is my model. The joint on the left hand, has a connector,and that is what I am trying to simply model with Mass21 element.
I hope it is more clear now.
Regards

 

[petb]

This looks like a planar linkage, maybe better to try textbook solutions for the kinematics or multi body dynamics? What's your load case here?

 

[anlblk]

It is an impact test for eigen frequencies, so on APDL model, there is no load.
I am able to perform the simulation, just this C shape connector's weight is missing. That's why I am trying to find a way to add it as a nodal mass.
Thank you for you suggestion.
Regards