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Modelling with a Rubber component

Modelling with a Rubber component

Modelling with a Rubber component

(OP)
Hello Eng Tips.

I have a situation i'd like to model - it includes rubber as a cushion/ isolation between steel components. The application is a surface scraper: a blade connected to supporting steel via a rubber isolation cushion. I know the force at the blade, and want to check the supporting structure. The isolation cushion is a proprietary item (i'm not 'checking' that part of it), rather the supporting structure and the blade.

I'm having immense difficulty defining a hyperelastic material. I can find theory on the matter easily enough, but without performing my own testing, I cannot find any appropriate parameters for the material. The program I'm using can simulate the material, however i need a stress-strain/force-displacement curve for the material which i don't have (and cannot get).

Does any one have any stress-strain data resources (google isn't giving me much at all).

Anther related question: thought on if I assume that the cushion is a linear material (i.e. steel set to very low density) and use the simulation to . I'm not concerned with displacement of the blade, Would taking such an approach yield conservative results? Forgive the ignorance on this one please.

Thank you.

PS: Using either Strand 7 FEA or Nastran-in-CAD with Inventor.

RE: Modelling with a Rubber component

Check Matreality. They used to have some data on stuff they tested freely available on their website. Might still be there.

Rick Fischer
Principal Engineer
Argonne National Laboratory

RE: Modelling with a Rubber component

I've done some simple "proof of concept" modelling of rubber materials, and yes you can get an idea of what is going on using a linear modeller. For my device, I started with E = 3000 psi, and nu as close to 0.5 as I could get without the code bombing. I tweaked the E value to get the displacements closer to values supplied by the manufacturer of my parts, and once we had a design we were comfortable with, paid an outside company to do the testing and develop material model coefficients, and run non-linear models for us.

It sounds like you are planning to bond the rubber to other parts in your assembly. This gets tricky, you should be talking to a rubber molding shop, one with experience in bonding (hint: usually best done in the mold using bonding primers suited for your metals).

RE: Modelling with a Rubber component

(OP)
@rickfischer51

Thanks for the lead - can't find through a simple page 1 google search. If you have a link that'd be great.

RE: Modelling with a Rubber component

oops. Misspelled it. Matereality. cant spell to save my life. so I do FEA

Rick Fischer
Principal Engineer
Argonne National Laboratory

RE: Modelling with a Rubber component

"rubber Spring Design" by gobel has a plot youngs modulus vs IHRD, which is roughly the same as shore D.Might be useful for a first pass or if your deflections arent too high.

Rick Fischer
Principal Engineer
Argonne National Laboratory

RE: Modelling with a Rubber component

@WPM3022

Hello there,

I was in the same situations for few months until few days ago I came across with the following website.

There is a lot of material, lot of plotted stress-strain diagram and the best of it you can download its data for free too! :)

https://www.campusplastics.com

Good diving :)

regards,
mark

RE: Modelling with a Rubber component

Hello WMP3022,

As isolation cushion is a proprietary item as you said, could you get Force/Displacement curves from the supplier/manufacturer for it? Then you can use a 6 DOF beam material (Beam element) with curves representing stiffness in all 6DOFs. This will let you evaluate your structure,

PS: I am writing this from experience of working in LS-Dyna environment. No idea about how to go about this with Strand 7 FEA or Nastran-in-CAD with Inventor

RE: Modelling with a Rubber component

(OP)
Thanks A-Run

i have requested and will keep you posted.

the text 'Rubber Springs Desing" by Goebel is most helpful too. I obtained a 1974 copy from my library.

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