# Bolt connectors in PrePoMax? **URL:** \ **Category:** General Questions\ **Created:** [February 20, 2025, 7:16am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487 "2025-02-20T07:16:49Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![inquisitive\_engineer](https://avatars.discourse-cdn.com/v4/letter/i/f19dbf/32.png) [@inquisitive\_engineer](https://prepomax.discourse.group/u/inquisitive_engineer)\ **Post date:** [February 20, 2025, 7:16am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/1 "2025-02-20T07:16:49Z")
![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/8/8f369e62e96165c15bdc82134b051ecbf42e9a75.jpeg) Greetings! I want to simulate bolt connectors in a simple plate tension test. How to do this in prepomax? ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [February 20, 2025, 7:44am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/2 "2025-02-20T07:44:39Z")
There’s no such predefined feature but you could define a beam element (through keyword editor because beams are not supported in GUI yet) and connect it to the rest of the model via rigid body constraints: > [@Modeling bolt connection with preloaded beam element](https://prepomax.discourse.group/t/modeling-bolt-connection-with-preloaded-beam-element/1412): > > Hi everybody, it’s my first time here so i’d like, first, to say thank you to the people that are improving the software. I’m planning to test this software in some jobs where i’m using Ansys (some simple structures). The future objective is to use PrePoMax in the early stage of the design and Ansys only for the final checks. The software has almost all the needed features, the only thing that is missing is the design of bolt connections. I’m tryng to create the missing parts with the editor … > [@Connect rigid constraints with beam](https://prepomax.discourse.group/t/connect-rigid-constraints-with-beam/1798): > > Hello everyone. When I create rigid constraints and want to connect them to beam (via keywords). Bolt connection (similar to RBE2 with beams). Every rigid constraint has two control nodes, for translation and rotation. Do I need to create two beams? One beam between transformation control nodes and second between rotation nodes? \*Rigid body, Nset=Internal\_Selection-1\_Rigid\_Body-1, Ref node=2017, Rot node=2018 \*Rigid body, Nset=Internal\_Selection-1\_Rigid\_Body-2, Ref node=2019, Rot node=2020 \*… ---
**Author:** ![inquisitive\_engineer](https://avatars.discourse-cdn.com/v4/letter/i/f19dbf/32.png) [@inquisitive\_engineer](https://prepomax.discourse.group/u/inquisitive_engineer)\ **Post date:** [February 20, 2025, 9:10am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/3 "2025-02-20T09:10:43Z")
Thank you! i will check this out ---
**Author:** ![Paul18fr](https://avatars.discourse-cdn.com/v4/letter/p/35a633/32.png) [@Paul18fr](https://prepomax.discourse.group/u/Paul18fr)\ **Post date:** [February 20, 2025, 10:23am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/4 "2025-02-20T10:23:38Z")
Hi, I’m currently testing another way using DCOUP3D elements to mimic Rbe3 behavior. In the following screenshots, contact surfaces have been defined between the screw heads and the plate, but also between the plates themselves =\> in other words, the plates are only maintained by the contact. However i’m facing 2 issues when applying temperature: - I cannot impose a thermal scheme as i would like (see [this post)](https://calculix.discourse.group/t/thermomechanical-simulation-using-thermal-frd-results-bug/2601)) - error comes when using DCOUP3D elements with the temperature: i’ve to figure out if it’s a limitation, or something else ```auto *ERROR in envtemp: ***** number of network equations is not equal to number of active degrees of freedom ***** # of network equations = 18 # of active degrees of freedom= 679 ``` Anybody would have recognized the FEAnalyst model ([tutorial](https://www.youtube.com/watch?v=ZSDf1bNXo8g)) ![tightening_disp](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/e/edffa1c9fdeb5654c28ab15efc319163f68b19c6.png) ![tightening_stess_princ](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/7/74b54129381fe106decada127841d80f8756353c.png) ![tightening_stess_VM](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/9/942cba3440a9dc9c3c9cc7a3fa8ba391d7a883d4.png) Still investigating … ---
**Author:** ![ANYS](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/anys/32/7737_2.png) [@ANYS](https://prepomax.discourse.group/u/ANYS)\ **Post date:** [February 20, 2025, 10:58am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/5 "2025-02-20T10:58:24Z")
HI Paul18fr Is your model constrained in any way in the z direction? Regards EDITED: Try to define the DCOUP 3D element initial temperatures with custom cards. It might be a problem similar to the one with compresion only in thermal analisys. > [@Compresion Only Support + Initial Temperature Field](https://prepomax.discourse.group/t/compresion-only-support-initial-temperature-field/2360): > > Hi, When trying to define a Compression only support in presence of a Temperature Field ccx stops with the following message: \*ERROR in checktemp: no initial temperature defined in node 2089 Is it possible that the new gapuny nodes are waiting for the initial temperature to be assigned?. ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [February 20, 2025, 11:11am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/6 "2025-02-20T11:11:15Z")
> [@Paul18fr](#): > > - error comes when using DCOUP3D elements with the temperature: i’ve to figure out if it’s a limitation, or something else > > ```auto > *ERROR in envtemp: > ***** number of network equations is not equal to > number of active degrees of freedom ***** > # of network equations = 18 > # of active degrees of freedom= 679 > > ``` Strange, such errors should normally happen for 1D fluid elements: [Hydraulic analysis with split and joint - CalculiX (official versions are on www.calculix.de, the official GitHub repository is at https://github.com/Dhondtguido/CalculiX).](https://calculix.discourse.group/t/hydraulic-analysis-with-split-and-joint/2154) But I guess DCOUP3D elements are indeed the culprit here. ---
**Author:** ![Paul18fr](https://avatars.discourse-cdn.com/v4/letter/p/35a633/32.png) [@Paul18fr](https://prepomax.discourse.group/u/Paul18fr)\ **Post date:** [February 20, 2025, 11:25am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/7 "2025-02-20T11:25:05Z")
@ANYS: on the screw only, but not the plates. Hare the 2 slave nodes are free following Z ![tightening_BC](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/6/672b8a4ea04c04aafe2481fa7b8eae2de4e84924.png) Note the current model is a test : [model link](https://transfert.free.fr/xDFBsw9) (link available only 24 hours from now) ---
**Author:** ![ANYS](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/anys/32/7737_2.png) [@ANYS](https://prepomax.discourse.group/u/ANYS)\ **Post date:** [February 20, 2025, 12:07pm UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/8 "2025-02-20T12:07:11Z")
Thanks. I wasn’t able to preload without fixing at least one point in preload direction as you. Not big deal here. I have finished recently the performance check of a similar model. Not detailed stresses at threads or heads, just overall tensile at the bolt shank and Contact preload pressure. FEA result compared against analytical calculation (\*). Very good results. My goal is now to check the Bolt Preload Change Due to Temperature. I got a “simple” example with analitical solution and methodology if you are interested. It would be applicable to your model so you could check your aproach performance. I’m using the model described in here as reference: > **[Bolted Connections](https://calculix.discourse.group/t/bolted-connections/2548/8)** > > I have recently compared Pretension by means of load with Pretension by means of length adjustment using as reference a model that was hand calculated. The reference in case you are interested was suggested by Calc\_em user. My main interest... (\*) VDI 2230 methodology as described in the book “Introduction to the Design & Behavior of Bolted Joints” by John H. Bickford ---
**Author:** ![Paul18fr](https://avatars.discourse-cdn.com/v4/letter/p/35a633/32.png) [@Paul18fr](https://prepomax.discourse.group/u/Paul18fr)\ **Post date:** [February 20, 2025, 12:16pm UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/9 "2025-02-20T12:16:12Z")
> [@ANYS](#): > > the Bolt Preload Change Due to Temperature that’s i would like to do too, but i’m facing difficulties (see previous post); if you’ve a look to the thermal expansion of the materials, the one of the bolt is twice of the plates =\> the tightening should decrease accordingly. ---
**Author:** ![ANYS](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/anys/32/7737_2.png) [@ANYS](https://prepomax.discourse.group/u/ANYS)\ **Post date:** [February 20, 2025, 4:11pm UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/10 "2025-02-20T16:11:01Z")
> [@Paul18fr](#): > > the tightening should decrease accordingly Hi, ¿How do you Know? ---
**Author:** ![Paul18fr](https://avatars.discourse-cdn.com/v4/letter/p/35a633/32.png) [@Paul18fr](https://prepomax.discourse.group/u/Paul18fr)\ **Post date:** [February 21, 2025, 9:07am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/11 "2025-02-21T09:07:47Z")
> [@ANYS](#): > > ¿How do you Know? In the current model, with an uniform temperature and a screw that expands more than the plates =\> obviously the tightening (force) decreases … ---
**Author:** ![ANYS](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/anys/32/7737_2.png) [@ANYS](https://prepomax.discourse.group/u/ANYS)\ **Post date:** [February 21, 2025, 9:36am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/12 "2025-02-21T09:36:03Z")
> [@Paul18fr](#): > > =\> obviously the tightening (force) decreases That’s true if the system is free to expand. But,… you have fixed the bottom and the preload reference node. That space in beteeen is not expanding freely. ![imagen](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/e/e87b7ed89cf935d82009c6f1814fccf2fb1722cf.jpeg) ---
**Author:** ![Paul18fr](https://avatars.discourse-cdn.com/v4/letter/p/35a633/32.png) [@Paul18fr](https://prepomax.discourse.group/u/Paul18fr)\ **Post date:** [February 21, 2025, 10:26am UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/13 "2025-02-21T10:26:41Z")
you’re right for the current BCs 😅 ---
**Author:** ![ANYS](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/anys/32/7737_2.png) [@ANYS](https://prepomax.discourse.group/u/ANYS)\ **Post date:** [February 21, 2025, 11:10pm UTC](https://prepomax.discourse.group/t/bolt-connectors-in-prepomax/2487/14 "2025-02-21T23:10:40Z")
Not easy subject. I’m strugling too. So much parameters for a single bolt, ![imagen](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/b/ba3382a550a228b02f503cc47a4100bd67f4a8bd.png) 🤣 🤣 😂 😭. I think I now have them all. (Different book different names and letter) 😖. I need to simplify. 🤏. Tomorrow.