# Bolt - plate contact **URL:** \ **Category:** General Questions\ **Tags:** results\ **Created:** [March 6, 2026, 10:02am UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315 "2026-03-06T10:02:35Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![fasanifrancesco](https://avatars.discourse-cdn.com/v4/letter/f/eb9ed0/32.png) [@fasanifrancesco](https://prepomax.discourse.group/u/fasanifrancesco)\ **Post date:** [March 6, 2026, 10:02am UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/1 "2026-03-06T10:02:35Z")
Good morning, I am trying to simulate two flanges connected by bolts. The flanges are a the tip of a square profile and they’re teared apart by a bending force. I can’t find a way to get a result. Do you have any tip? The errors span from Jacobian matrix errors ,when I try to simulate the contact between head bolts and plate with “Tie contact”, to non convergence when I simulate the contact with friction. Do you have any tips to try to get out of my condition? Please see the attached model “ ANALISI\_GIUNTO.pmx” Thak you in advance ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/f/fb13692b5529716f42d6c2ce780ef946ddca4f9b.jpeg) [ANALISI\_GIUNTO.pmx](https://prepomax.discourse.group/uploads/short-url/84S6F7VNogp9gldFzRQarDHfAyy.pmx) (6.2 MB) ---
**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:** [March 6, 2026, 10:21am UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/2 "2026-03-06T10:21:11Z")
> [@fasanifrancesco](#): > > The errors span from Jacobian matrix errors ,when I try to simulate the contact between head bolts and plate with “Tie contact”, to non convergence when I simulate the contact with friction. Do you have any tips to try to get out of my condition? Negative jacobian with tie constraints means that you should disable Adjust for them. Convergence is much more tricky and can have many causes (although it usually originates from contact). To find them, it’s best to simplify the model (reduce its size e.g. to segment with one bolt and gradually disable some advanced features such as the 3 nonlinearities). At the first glance, it seems that you could utilize symmetry in one plane. Also, you should improve the mesh - refine it for shells and use hexa or at least second-order tetra elements for the bolts. You will find many examples of similar models on the forum if you search for solid bolts. Such as this thread: [COMPRESSION ONLY for simulating bolts and nut faces](https://prepomax.discourse.group/t/compression-only-for-simulating-bolts-and-nut-faces/3110) Or this one: [Error during analysis of baseplate fixing](https://prepomax.discourse.group/t/error-during-analysis-of-baseplate-fixing/1471) Displacement-based preloading is much better for convergence. In the second step, where you apply the actual loading, you should freeze the preload (Displacement → Fixed). ---
**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:** [March 6, 2026, 10:44am UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/3 "2026-03-06T10:44:30Z")
According to last updates seems that preload direction is in the wrong direction. Bolts are opening. ---
**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:** [March 6, 2026, 11:02am UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/4 "2026-03-06T11:02:54Z")
The file was created in v2.4.0, but there were indeed changes in preload symbols in v2.5.0: [Diference between variable Displacements and Disp&Def for postprocessing deformed results? - #31 by Matej](https://prepomax.discourse.group/t/diference-between-variable-displacements-and-disp-def-for-postprocessing-deformed-results/3211/31) ---
**Author:** ![andrea.starnini](https://avatars.discourse-cdn.com/v4/letter/a/46a35a/32.png) [@andrea.starnini](https://prepomax.discourse.group/u/andrea.starnini)\ **Post date:** [March 6, 2026, 1:04pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/5 "2026-03-06T13:04:42Z")
Chek distance between hole center and plate edge. Seems to be too small (EN1993-1-8)-. For the stresses involved, 5 kN and about 1 kNm on the joint, the number of bolts seems to be exaggerated, as well as the thickness of the plates (15 mm) . Have you thought about the size of the washers? ---
**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:** [March 6, 2026, 2:02pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/6 "2026-03-06T14:02:21Z")
@Matej While testing this, I’ve noticed a small issue - deactivating steps with preload doesn’t deactivate the pretension section keyword (preloads within these steps have to be deactivated too): ![pret deact](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/f/f4b7c183f76916d9e55327d45cd80659b6ca0c44.png) [Deactivate preload.pmx](https://prepomax.discourse.group/uploads/short-url/6oeiMSYzUvrsZHJR2GjJV2oiQ29.pmx) (3.6 MB) ---
**Author:** ![supreeth](https://avatars.discourse-cdn.com/v4/letter/s/dfb087/32.png) [@supreeth](https://prepomax.discourse.group/u/supreeth)\ **Post date:** [March 7, 2026, 12:04pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/7 "2026-03-07T12:04:59Z")
Have you tired the model without preloads in bolts.. @fasanifrancesco ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [March 7, 2026, 6:11pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/8 "2026-03-07T18:11:12Z")
I have fixed the problem. ---
**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:** [March 7, 2026, 6:41pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/9 "2026-03-07T18:41:09Z")
Preload is usually necessary, but using its displacement (BC) type can be really helpful for convergence issues. > [@Matej](#): > > I have fixed the problem. Nice, thanks for fixing it so quickly. ---
**Author:** ![supreeth](https://avatars.discourse-cdn.com/v4/letter/s/dfb087/32.png) [@supreeth](https://prepomax.discourse.group/u/supreeth)\ **Post date:** [March 10, 2026, 7:39am UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/10 "2026-03-10T07:39:05Z")
i made the model but not running how can i make the correct contact so that it runs. [KOKO3.pmx](https://prepomax.discourse.group/uploads/short-url/4TTq61UoQkZjzgfZ77j2t4DNH7X.pmx) (9.9 MB) ---
**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:** [March 10, 2026, 8:50am UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/11 "2026-03-10T08:50:28Z")
I see it’s without preload now. I would simplify the model a bit to see what’s wrong, use displacement-control and so on: [KOKO3 mod.pmx](https://prepomax.discourse.group/uploads/short-url/kpVaGqyuXehDSlGeNhLZJnOriZr.pmx) (9.9 MB) Basically, removing and then readding features gradually can help you debug the model. ---
**Author:** ![marcosprojetos](https://avatars.discourse-cdn.com/v4/letter/m/90ced4/32.png) [@marcosprojetos](https://prepomax.discourse.group/u/marcosprojetos)\ **Post date:** [March 10, 2026, 5:28pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/12 "2026-03-10T17:28:49Z")
Hello everyone, I am a Mechanical Engineer from Brazil and I am using a simple bolt-and-support assembly to learn how to properly set up contacts in PrePoMax. I’ve been trying to get this to converge for 3 days without success. As a new user, I cannot attach my .pmx file yet, but I am providing screenshots of my setup and the convergence monitor. **Model Setup:** - **Assembly:** A simple support plate with bolts. - **Contacts:** Surface-to-surface with friction (Hard contact). - **Solver:** CalculiX. - **Issue:** The simulation fails in the first increments with “No Convergence” or “Zero Pivot” errors. The residual forces in the monitor stay very high and never drop. **What I have tried so far:** - Swapping Master and Slave surfaces. - Enabling “Adjust: Yes” in the Contact Pair. - Reducing the initial time increment to 0.001. - Refining the mesh around the holes. **Could someone please provide a step-by-step guide on how to correctly set up contacts for this type of assembly?** I want to make sure I am following the best practices from the start. Please let me know if you need more details. Once I am allowed to attach files, I will upload the .pmx. Thank you in advance! Best regards, Marcos ---
**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:** [March 10, 2026, 5:30pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/13 "2026-03-10T17:30:40Z")
You should be able to attach files now. Please share the .pmx file. If it’s too large to fit directly on the forum, close the results before saving the file. If it’s still too large, you can use some hosting website. ---
**Author:** ![supreeth](https://avatars.discourse-cdn.com/v4/letter/s/dfb087/32.png) [@supreeth](https://prepomax.discourse.group/u/supreeth)\ **Post date:** [March 11, 2026, 12:35pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/14 "2026-03-11T12:35:16Z")
[https://we.tl/t-jA3pNprGAB](https://we.tl/t-jA3pNprGAB) i have made the model its running it took half an hour @FEAnalyst ![Screenshot 2026-03-11 180649](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/5/57a6db50ff074b3a28c1fdd44759859eb273cc05.jpeg) ---
**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:** [March 11, 2026, 12:53pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/15 "2026-03-11T12:53:57Z")
With some improvements (like in the previous models) for better convergence: [11.3.2026001 mod.pmx](https://prepomax.discourse.group/uploads/short-url/xfi9NHOH4YUi3slaWkGFH4o8jiW.pmx) (9.8 MB) ---
**Author:** ![supreeth](https://avatars.discourse-cdn.com/v4/letter/s/dfb087/32.png) [@supreeth](https://prepomax.discourse.group/u/supreeth)\ **Post date:** [March 11, 2026, 1:02pm UTC](https://prepomax.discourse.group/t/bolt-plate-contact/3315/16 "2026-03-11T13:02:22Z")
Ok I’ll check, just left office, tomorrow morning