Search
Close this search box.
Notifications
Clear all

Shape of PNM-model prediction curves

2 Posts
2 Users
0 Likes
558 Views
Posts: 12
Topic starter
(@margonari)
Active Member
Joined: 16 years ago

Hi, I am currently trying to obtain parameters for a filled polybutadiene rubber for use in finite element analysis. I am using a PNM with eight-chain and Yeoh hyperelastic models and the Bergstrom-Boyce flow model. The general fit is pretty good and the peak force looks great but the problem lies with the initial gradient. Here is a picture to help you understand my point:

[IMG] [/IMG]

You can see that the loading curve shape, especially the initial section isnt quite right. Is this due to my selection of material models or is there a parameter which controls the loading shape??

Any help you be greatly appreciated. Thanks.

1 Reply
Posts: 3998
(@jorgen)
Member
Joined: 4 years ago

The experimental stress-strain curve seems to have very slow tangent stiffness at small strains, and then reach an almost constant slow around a strain of 1.5% (or so). My guess is that that behavior is caused by slack in the experimental setup and not a reflection of the true material behavior. Are you sure that the behavior is real?

My guess is that your material model (PNM) is just fine.

PS. The MCalibration software has a feature that can be used to compensate for initial slack, or you can eliminate it manually.

-Jorgen

1 Reply
Share: