Good morning All,
I modeled, on my simple model, two bolt as SPRINGA element (as explained on this forum); but I’m not able to find the reaction force on the Springa element (on the node).
I saw that in one of the output files genereted by the solver there are this results, but I’m not able to find it.
Assieme_studio - rev02.pmx (6.5 MB)
I’ve attached the files from PrePoMax, so it could be easier to find my mistakes.
Thank you in advance for the help
WBR
Marco
You would have to add (history) output requests for that. For example:
*NSET, NSET=Spring_nodes
42737, 42735, 42737, 42739
...
*NODE PRINT, NSET=Spring_nodes
RF
Or simply:
It is also possible to get the forces from the springs themselves, but indirectly. See these threads on the CalculiX forum:
Thank you very much for your help 
If I want to change the Spring with a beam, how can I change the code?
Thank you in advance
WBR
Marco F.
In CalculiX, beams are not really the best choice for bolt modeling, but you can find an example here: Beam Element connections between Two plates (2D) and here: Why the top plate displacement is zero? and in many other threads on this forum such as: Simplified bolt connection with beam element and rigid constraints
In short words, you need at the very least (to avoid having to define second-order elements for circular profile):
*ELEMENT, TYPE=B31
element_number, node_1, node_2
...
*BEAM SECTION, MATERIAL=..., ELSET=..., SECTION=RECT
width, height
x, y, z
or with second-order elements:
*ELEMENT, TYPE=B32
element_number, node_1, node_2
...
*BEAM SECTION, MATERIAL=..., ELSET=..., SECTION=CIRC
diameter
All clear so, if I understood correctly, the best solution to model a screw (in a simple way - not using solid 3D element inside the assembly) is still the use of SPRINGA command.
WBR
Marco F.
Yes, I usually recommend simplified (cylindrical) solid bolt representations in CalculiX, but apart from that, you can use springs since they are easy to define (but they don’t support preload and you may need one in each direction to account for shear).
I’ve try to replace the SPRINGA with the beams, following your suggestion, but appear this message that I’m not able to understand how to solve it:
Assieme_studio - rev03.pmx (6.5 MB)
I’ve add the PrePoMax file to better understand.
Thank you in advance.
WBR
Marco F.
PrePoMax crashes for me when I try to make custom keywords active, but I see that you are trying to define a quadratic (3-node) beam element using only 2 nodes:
*ELEMENT, TYPE=B32, ELSET=beam_1
9000001, 42733, 42735
*ELEMENT, TYPE=B32, ELSET=beam_2
9000002, 42737, 42739
You need to add nodes in the middle with *NODE. See the syntax here: Simplified bolt connection with beam element and rigid constraints - #3 by qfontaine
Thank you for the suggestion I added the third node, but now appear this strange message:
Something releted to the allocation of the memory
Assieme_studio - rev03.pmx (6.5 MB)
This is a generic error message from CalculiX that may indicate a bug in the solver. Can you ask on their forum: https://calculix.discourse.group/ ? Perhaps they can fix it for the next release.
Meanwhile, try simplifying the model. Maybe some specific features trigger the bug. Keep in mind that using rigid body constraints with 1D (e.g. beam) and 2D (e.g. shell) elements is very risky in CalculiX. Especially in nonlinear analyses. CalculiX 2.23 (the newest release) doesn’t allow it at all, but the next version shouldn’t have so strict limitation.
Thank you very much for your help; I will try to simplify the model but I think that I will use SPRINGA element for the bolt (appling a concentrated force on one node to simulate the preload of the screw).
WBR
Marco F.
