# Bolt Preload for Piping connection **URL:** \ **Category:** General Questions\ **Created:** [April 18, 2023, 6:25am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835 "2023-04-18T06:25:32Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [April 18, 2023, 6:25am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/1 "2023-04-18T06:25:32Z")
Hello awesome group. I have checked YouTube video for Bolt Pre-load and that gave me insights in trying it out for my reason. Problem I am trying to solve is that of a Flange pair separated with a gasket. There is a bolt (4 for the flange pair but only 1 modelled with symmetry constraints placed) 1. Flange, bolt, nut and shank material is standard Mild steel E=2.1e5 MPa with Poissons ratio = 0.3 2. Gasket material E=2.1e4 MPa with Poissons ratio = 0.2 (dummy values, I wanted to have softer gasket compared to flange) Flange has ID = 200mm, OD = 400mm. Thickness of flange is 20mm Internal pressure is 10MPa and 50kN is the preload on a M20 bolt which imparts 159.1549 MPa stress in the bolt ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/7/761ce5aa46e4addedadcef53b57bf224617b61c8.jpeg) I wanted to get contact pressure as given in this post [CalculiX-Examples/NonLinear/Bolt at master · calculix/CalculiX-Examples · GitHub](https://github.com/calculix/CalculiX-Examples/tree/master/NonLinear/Bolt) but I am not able to get it with my study. I try to hide top flange / bottom flange but how to get contact pressure. ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/e/ea685826100418b320a32057d3f4d75522b9becf.png) I have checked all posts in this discourse group but was not able to find it [Search results for 'bolt' - PrePoMax](https://prepomax.discourse.group/search?q=bolt) My files are heavy 69MB so I am not able to attach them here. But here is a screenshot. ![zqlq28SsnZf4k0Aq](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/8/8ec1eae3757c70519cb564a54d5487f399c7ac1d.png) Any help is appreciated. Kind regards Dharmit ---
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [April 18, 2023, 6:31am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/2 "2023-04-18T06:31:44Z")
I enabled contact but I am doing something wrong ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/0/050bb7497a7e37772aca1eba06834cf9fd39e2e0.png) ---
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [April 18, 2023, 6:40am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/3 "2023-04-18T06:40:17Z")
And I realized what wrong I did. I have not given friction in my input so how can I expect contact results 😄 Is there a path where this will be provided as a tutorial in future? ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [April 18, 2023, 6:42am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/4 "2023-04-18T06:42:11Z")
Contact pressure is only plotted for Surface-to-surface contact, as I remember. For Node-to-surface contact, the contact outputs do not work. Or am I wrong? You should get the pressure distribution even without friction. ---
**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:** [April 18, 2023, 7:07am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/5 "2023-04-18T07:07:29Z")
> [@Matej](#): > > Contact pressure is only plotted for Surface-to-surface contact, as I remember. For Node-to-surface contact, the contact outputs do not work. Or am I wrong? You are right: [Possible bug using \*Contact print - CalculiX (official versions are on www.calculix.de, the official GitHub repository is at https://github.com/Dhondtguido/CalculiX).](https://calculix.discourse.group/t/possible-bug-using-contact-print/927) ---
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [April 18, 2023, 11:42pm UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/6 "2023-04-18T23:42:37Z")
Thanks for replying. In my problem above, I still need to get my head around Node-to-surface contact vs surface-to-surface contact. I created gasket as a surface but does this mean that I have to specify gasket surface and flange surface pair as master-slave to get contact pressure? ---
**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:** [April 21, 2023, 4:52pm UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/7 "2023-04-21T16:52:04Z")
Only if _method_ is set to _node to surface_ in your contact pair settings window, you should change it to _surface to surface_. Anyway, does it work as expected now ? ---
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [May 3, 2023, 12:51am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/8 "2023-05-03T00:51:18Z")
It is working but the results I am getting are vague as the material properties I used for gasket are vague. Garbage In Garbage Out I guess. I am doing more research on the Young’s Modulus and Poissons ratio of different types of gaskets and how to use them in FEA. If you have any information on material properties of gaskets, please point me in the right direction. Kind regards, Dharmit ---
**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:** [May 3, 2023, 7:00am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/9 "2023-05-03T07:00:41Z")
Gaskets are tricky when it comes to FEA. Abaqus even offers special element type for their accurate modeling. But, regardless of the software, if it’s rubber gasket, hyperelastic material model should be used in most cases. ---
**Author:** ![jbr](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jbr](https://prepomax.discourse.group/u/jbr)\ **Post date:** [May 9, 2023, 4:12pm UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/10 "2023-05-09T16:12:47Z")
> [@FEAnalyst](#): > > Gaskets are tricky when it comes to FEA Indeed. Very tricky some times. > [@FEAnalyst](#): > > if it’s rubber gasket, hyperelastic material model should be used in most cases. I agree unless you are getting convergence problems. Using linear elastic properties based on the bulk/shear modulus values for the hyperelastic model may be okay. ---
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [May 12, 2023, 4:32am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/11 "2023-05-12T04:32:15Z")
True, gaskets are tricky. For the time being I am just using Metallic gaskets so it is fine, but when I will start using Compressed Non Asbestos fiber gaskets and/or Rubber gaskets, it will be different. ---
**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:** [May 12, 2023, 6:40am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/12 "2023-05-12T06:40:52Z")
I have recently found that Layered shells could mix all kind of material models including Hyperplastic, plastic, Linear isotropic and orthotropic. Haven’t verified the results yet. Maybe you could look at this possibility as gaskets are typically a layered mix of Graphite or Carbon Fiber (Orthotropic) , rubber (hyperplastic) and metallic inserts (Plastic , Linear elastic). I can try to set up one of this with Prepomax but I gess it will have to be custom cards. I would like to ask if someone knew about this possibility and has some experience or warnings about it. I suppose it can be hard to validate or even verify one of this mixing components so any comment regarding this approach is appreciated. Maybe if we try to reproduce the behaviour of a well documented product.?¿?. This are the two best suppliers with mixed components products gasskets. > **[Products](https://flexitallic.com/products/)** > > Flexitallic is the market leader in the manufacture and supply of static sealing solutions, delivering high quality industrial gaskets on a global scale. > **[KLINGER Maxiprofile Kammprofile Gasket](https://www.klinger.co.uk/products/metallic-gaskets/maxiprofile-kammprofile-gasket)** > > The Maxiprofile style gasket is mainly used in vessel applications where often the gasket width is limited. ---
**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:** [May 12, 2023, 7:39am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/13 "2023-05-12T07:39:39Z")
This is an axample of a completely invented material made of: 0.05,OGDEN\_Intima (Hyperelastic Ogden Material model) 0.01,Gelcoat (isotropic elastic material model) 0.01,Carbon\_UD (ortothropic user material model) 0.01,S235\_DNV\_HARD (Plastic KINEMATIC Hardening) 0.01,S235\_DNV\_HARD (Plastic KINEMATIC Hardening) 0.01,S235\_DNV (Plastic) 0.01,S235\_DNV (Plastic) 0.01,S235\_DNV (Plastic) 0.02,medium\_density\_foam (isotropic elastic material model) 0.01,Glass\_biax (ortothropic user material model) 0.01,Gelcoat (isotropic elastic material model) 0.05,OGDEN\_Intima (Hyperelastic Ogden Material model) ![imagen](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/1/145f9ceb966dbc966660b1a0a16cbeef711b499d.png) > **[Mixed material model Composite.inp](https://wetransfer.com/downloads/5df276c41d28339da8e1be89d1dc9e9d20230512073849/181bc9)** > > 1 file sent via WeTransfer, the simplest way to send your files around the world ---
**Author:** ![synt](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/synt/32/4658_2.png) [@synt](https://prepomax.discourse.group/u/synt)\ **Post date:** [May 12, 2023, 12:30pm UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/14 "2023-05-12T12:30:51Z")
> [@ANYS](#): > > I have recently found that Layered shells could mix all kind of material models including Hyperplastic, plastic, Linear isotropic and orthotropic. Probably, this is called uniformity of the solver were notified in documentation. The advantages of CalculiX beam and shell element being expanded to solid . Some consideration still required in definition of boundary condition, constraint and coupling which may different compared to classical element. ---
**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:** [May 12, 2023, 12:48pm UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/15 "2023-05-12T12:48:33Z")
@Matej By the way. Really nice tool to split /separate the layers. ¿Why don’t they open uniformly? Looks like the center ones keep together.? EDITED: Seems some of them don’t move. ![imagen](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/b/bf9bbab3b2b0ba39505aae43c7d1b4ed43a3e2f8.jpeg) ---
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [May 15, 2023, 1:44am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/16 "2023-05-15T01:44:53Z")
One more attempt. Input file is here [P5701178-02-214\_BoltedConnectionFEA.zip](https://prepomax.discourse.group/uploads/short-url/rcNdAXlqfFEX2kIgjFJ4HRgOzMb.zip) (1.5 MB) Metal to metal contact, no gaskets involved. There are 4 bolts in L pattern. First assumption is that they are M10 Class 4.6 bolts with Proof strength of 225MPa and for Pre-Load we go upto 90% of proof strength thus Pre-Load = 15.9kN Contact pressure I get for this is shown below. Pressure = 1.094 Pascals ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/8/8ae27fb093ec89279f3755e159569c419594a629.jpeg) For second assumption bolts are M10 Class 8.8 with Proof strength of 600MPa and Pre-Load = 42.4kN Contact pressure I get for this is shown below. Pressure = 3 Pascals ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/a/a50f2f661c89a25ab651bad75ff1148e0af531a9.png) Pressure increased from around 1 Pascals to 3 Pascals as the Pre-Load increased from ~15kN to ~42kN My question is, why is the contact pressure so small? What can I do to get realistic results? Thanking in advance. ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [May 16, 2023, 7:06pm UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/17 "2023-05-16T19:06:44Z")
It seems to me that your mesh is merged in the contact area. In this case, the load is transversed via nodes and not via contact. Can you share the pmx file? ---
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [May 16, 2023, 11:19pm UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/18 "2023-05-16T23:19:25Z")
Here you go. This file is heavy so it is stored on my private server. > **[P5701178-02-214\_BoltedConnectionFEA.pmx](https://drive.dlmtech.xyz/d/s/tbFtJ4eIFsKX8uV1uGjQ7cmVzEN5gaVM/yEpxWMFaDLYs4mZs1K28rbMahGkLEHW7-JbDgz1UJcgo)** ---
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [May 17, 2023, 1:25am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/19 "2023-05-17T01:25:03Z")
Hello @FEAnalyst, Your YouTube video provides more help but there are some questions I had after watching it. YouTube video link is here [PrePoMax (CalculiX FEA) - Tutorial 34 - Bolted joint with preload - YouTube](https://www.youtube.com/watch?v=ZSDf1bNXo8g) I am confused as to why did you make displacement 0mm in Step 2 for the surface that joins bolt with shank. Will this not make force applied on the bolt head to go in the top part of the bolt only? I have a question regarding Contact surface pressure on the faces of the members that the bolt is joining. Can you please show in your video how to show Contact Surface Pressure. My understanding is that when you apply PreLoad, contact Pressure should be a certain value, and then when you apply other loads on the members that the bolt is joining (e.g. two flanges or two plates) then this pressure will increase or decrease depending on the direction of force/pressure. Am I correct in making this assumption? ---
**Author:** ![datsnl](https://avatars.discourse-cdn.com/v4/letter/d/8e7dd6/32.png) [@datsnl](https://prepomax.discourse.group/u/datsnl)\ **Post date:** [May 17, 2023, 1:27am UTC](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835/20 "2023-05-17T01:27:58Z")
Also, I downloaded your file in step format and wanted to check if I am getting same results. By mistake I made compound of all 4 parts but the compound shows 5 parts in it. Why did it take 5th surface as part? Is there any importance of this surface? ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/2/215230e66ed4a8927fa76892c625d5becc7e5c3e.png) [Next page](https://prepomax.discourse.group/t/bolt-preload-for-piping-connection/835.md?page=2)