Hello,
I have a hollow tube and I want to apply a pressure of -625.1 Pa on the outer nodes.
If I have a node set outer, then would the input deck have the following:
*DLOAD
outer, P6, -625
P6 means that P is applied in all 6 degrees of freedom, right? What exactly does it do?
Also, whenever I try to run the command send outer abq pres -625.1, I get a blank .dlo file with only a title.
I would appreciate any help
dload is for distributed load in element’s faces (normal to the face, inwards, I think but check it, please), so you have to select an element set with the appropriate faces. Prepomax is very good for that kind of selection.
Check the manual:
7.42 *DLOAD
Keyword type: step
This option allows the specification of distributed loads. These include con-
stant pressure loading on element faces, edge loading on shells and mass loading
(load per unit mass) either by gravity forces or by centrifugal forces.
For surface loading the faces of the elements are numbered as follows (for
the node numbering of the elements see Section 3.1):
for hexahedral elements:
• face 1: 1-2-3-4
• face 2: 5-8-7-6
• face 3: 1-5-6-2
• face 4: 2-6-7-3
• face 5: 3-7-8-4
• face 6: 4-8-5-1
Thank you for such a quick response!
Oh, I see. I had a node set instead of an element set.
I made an element set: Eouter and put the following in the .inp file:
*DLOAD
Eouter, P6, -625
However, it gives me zero for all result values.
Any clue on what could be the issue?
I can install PreProMax, but I do not have it as of yet, so I am working with the resources available.
try to display the faces in CGX to see if your selection is correct:
plus f Eouter t
Oh, it does not display.
So usually to make a .nam file for a nodeset I use the command:
send inlet abq nam where inlet is the nodeset
Is there such a command for making a .nam file for element sets?
I think is the same but you have to have elements faces (f) in the set…not a cgx expert…also you can load the .frd file (*NO ANALYSIS) and automatically cgx creates the set for the boundary condition so you can check them.
Oh I see; so since I have C3D4 elements means I have 4 faces.
Now how can I know the face I want the pressure to act on?
My elements point inwards, so it looks like it’s 1-2-3 but is there a way to confirm?
Is there a way that I could share my .inp file with you guys?
Isn’t plus f Eouter t to show the faces?
Beware that C3D4 is the worst element and that mesh looks too coarse for it. Use C3D10 or 20 if you can.
if your model is based on geometry use the geometric surfaces to create a surface set and the export to abq with cgx. Check out manual and/or M. Kraska examples at github.
Okay, will do.
Would this be easier to implement using shell?
I made a shell one (S3) as well but again, not sure how to apply the pressure. It says in the manual that no face needs to be described.
For shell elements no face number is needed since there is only one kind of
loading: pressure in the direction of the normal on the shell.
So, would it just be the element set and then pressure value? Or could I use node set?
I tried both and none worked
Would appreciate your guidance
I meant to use geometry in cgx to select the faces to which apply the pressure (assuming it is a single surface called A001, check your surfaces name using plot sa all):
seta pload A001
comp pload e
comp pload f
plot f pload
check the surface to be loaded is the right one, and the normal direction (pos/neg). then do send pload abq pres 0.05
assuming a pressure in all faces equal to 0.05 [pressure units]