Elastomer Tensile Tesing: strain rate

[fbmogal]

Hello,
I work on FEA of elastomer seals and we test the material in house for material data. For tensile testing, we use the cross head speed of 50 mm/min where as our colleagues in Germany use 1 mm/min. The reasoning behind 1mm/min is to get the relaxed behavior however the instantaneous response and high rate loading deformation is compromised. Since it really depends on the application as to which speed is more appropriate I was wondering if others have across similar problem. If we use 50 mm/min data along with the viscoelastic response, would the solution be more reasonable for any application or any loading rate?

Thanks
FM

[manfred]

If you would like to differntiate between hyperelasticity and viscoelasticity properties more or less precisely a more suitable procedure is recommented:

Make a “quasi-static” stress-strain experiment at sufficiantly high temperatures (50°C or 100°C for example) – and in addition perform a multi-frequency DMA in a broad temperature range: (Tg-30^°C)<T<150°C . Then both results combine in an appropriate way to fit your constitutive modelling. That works best!
But that is just an opinion of the community!

[Jorgen]

You may also want to simply test the elastomer material at a few different strain-rates and then calibrate a viscoelastic material model, such as the Bergstrom-Boyce (BB) model. The BB (http://polymerfem.com/content.php?5-Bergstrom-Boyce-Model-Info) model will be much more accurate than a simple hyperelastic material model for elastomers.

-Jorgen