Viscoelastic Parameters for Dytran

[Elijah]

Hello!

I am a student working on a simulation which involves Neoprene Rubber. My question to all the experts out there is "How can I determine the input constants required by MSC Dytran? They are:
1) Bulk Modulus
2) Short-Time Shear Modulus
3) Long-Time Shear Modulus
4) Decay Constant
5) Shear Viscosity Constant"
The material model I have to implement is "Linear Viscoelastic". If somebody knows some test data that already exists, that will make my life a lot easier".

[Jorgen]

I am not too familiar with MSC Dytran, but I know about Neoprene rubber :wink:

:arrow: You can find data for a specific type of Neoprene rubber on the following web page (http://www.polymerfem.com/modules.php?name=Materials_Models&material=6). You should be able to extract the linear viscoelasticity parameters from that data.

:arrow: The bulk modulus is typically much higher than the shear modulus. The actual value of the bulk modulus is not important in most applications. Often you can assume that the bulk modulus is about 100 to 1000 times higher than the shear modulus.

Best of luck,
Jorgen

[Elijah]

Thanks for the reply!

Can you please tell me some reference for your comment about Bulk Modulus (100 to 1000 times shear modulus) as I shall have to qoute in my Project Report.

I have checked the web page you had referred, it shows two constitutive models combined together, 8-chain hyperelastic and Viscoelastc. In my application I dont have Large Deformations, so according to my understanding I can neglect the hyperelastic material model.

Also the material is in solid state so this "shear viscosity constant (must) = 0".

Can you refer me any ASTM or other standard which explains the recommended practices for Dynamic Testing. I wish I could find already existing curves for neoprene rubber.

Have a nice day.

[Elijah]

Ok,

I think last time I asked for too much so nobody replied.

May be anybody out there can just give me an idea, where to find the "Stress relaxation data" for neoprene rubber.

Thanx............

[Jorgen]

In additional to a general literature search I would check out the book: Effect of Creep and Other Time Related Factors on Plastics and Elastomers, by William Andrew Publishing/Plastics Design Library.

- Jorgen