This is the playback recording for the eSeminar held on December 11, 2014.
Much more material modeling information here: Material Modeling and Calibration - An Overview and Curriculum
Thank you for attending the eSeminar on “Modeling of Polymers and Plastics with Abaqus”. This eSeminar covers a variety of issues that arise when modeling elastomers, polymers and plastics. Much of elastomer modeling is already covered very well in our public class "Modeling Rubber and Viscoelasticity with Abaqus", so we have focused more on polymers and plastics in this eSeminar. Remember that with any material, there is not necessarily one best material model, but a material model that is appropriate for the use case, or application.
The topics that were discussed during the eSeminar are as below:
•Typical Behavior of Polymers and Plastics
•Where is the Yield Point?
•Strain Recovery Test
•Simulating Necking
•Advanced Material Models:
•Two-Layer Viscoplastic
•Parallel Rheological Framework
While elastomers are often thought of as nonlinearly elastic, and having viscoelasticity, plastics such nylon, polypropylene, polyethylene, etc. exhibit elasticity, plasticity and viscous behaviors. We start the eSeminar looking at a variety of real test data, and then dive into a discussion of determining the yield point in plastics. The challenge with plastics, as opposed to metals, is there is often viscous behavior early in the stress-strain response that masks the onset of plasticity. The "Strain Recovery Test" is shown to be a way to begin to delineate the viscous versus the plasticity behaviors. The final part of the eSeminar describes the use of two advanced material models that can be used when one wants/needs to model both the plasticity and viscous behavior of the polymer. For the Parallel Rheological Framework (aka PRF) model, we show an Isight calibration for a particular grade of polypropylene. We also attach to this blog post a document that describes the calibration process in more detail.
If you missed this eSeminar, please check out the recording of the presentation below. A pdf version of the presentation slides are also attached.
Video Recording of eSeminar (or Download here) :
PDF version of the eSeminar slides:
Document describing details of Isight calibration of polypropylene material:
A question came up after the eSeminar about use of *POTENTIAL, and my answer was more geared to the idea of pressure dependent yield - which does cause the yielding to be different in different modes of deformation. *POTENTIAL is really geared to capturing anisotropy of yielding - that is spatial dependence of yielding. My answer in the recording about *POTENTIAL was a bit misleading, because I was thinking more about pressure dependence. So *POTENTIAL is a sub-option for either *PLASTIC or *CREEP to capture the spatial dependence of yielding (non-isotropic yielding).
Questions also came in about plastics when their yielding is known to be a function of the hydrostatic pressure. There are many papers on this subject out in the public literature. The research shows that in general the yielding of plastics is pressure dependent. But equally important is the question - Is capturing the pressure dependent yielding important to your use case/application? Strive to model your use case with a simple model and if you get poor correlation, then improve/advance your material modeling. Many researchers advocate the use of the Drucker-Prager model to capture this hydrostatic pressure dependence of the yield stress. One particular paper that I can post here is from our SIMULIA Customer Conference:
Kim, et al, 2009 SCC ; (covers Drucker-Prager and DR creep for plastics):
We mentioned in the presentation that we could cite published paper references for the strain recovery test, Here are three references:
(shows testing for polypropylene, PP)
• Quinson, R., J. Perez, M. Rink, A. Pavan, Components of non-elastic deformation in amorphous glassy polymers, 1996
(shows testing for PMMA, PC, PS)
• Brusselle-Dupend, N., D. Lai, X. Feaugas, M. Guigon, M. Clavel, Experimental characterization and modeling of the uniaxial mechanical behavior of polypropylene before necking, 2002
(shows testing for polypropylene)
Back to: Material Modeling and Calibration - An Overview and Curriculum
Edit on 5-15-2015: I have added a D638 dogbone model (zipped .inp file)
