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)
Flange, bolt, nut and shank material is standard Mild steel E=2.1e5 MPa with Poissons ratio = 0.3
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
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.
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?
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.
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.
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.
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.
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.
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.
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
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
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?
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?
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?
