Stress Strain Data for Rubber Modeling

[ME7]

Hi,

I was given the load vs displacement of a rubber dog bone sample off of an instrom tester. FEA SW such as Abaqusa and SoildWorks requires the stress strain data. My question is can I simple divide the original undeformed cross sectional area into the Load to obtain the stress. Similarly for the deflection, divide by the original length of the constant area of the dog bone sample.

Thank you for the help,
Rick

 

[eduardocamargo]

Dear ME7,

Just one thing. You're thinking in making a linear approach of the material data?

You've have to be careful with it, because as the dog bone is made from rubber you should use a hyperelastic approach.

Let's say, you have:
FORCE vs DISPLACEMENT
you can obtain
STRESS vs STRAIN (where STRESS is LOAD/AREA OF APPLICATION and STRAIN is DEFORMED LENGHT-UNDEFORMED LENGHT/UNDEFORMED LENGHT)

Having the STRESS vs STRAIN you're able to obtain the curve data for HYPERELASTIC approach:
STRESS vs STRETCH RATION where STRETCH RATIO is STRAIN+1

With this you're able to use it!

Hope this can help you!

Best regards,
Eduardo

 

[ME7]

Thank you for your reply. Yes I plan on using Mooney Rivlin provided no issues with this data.

Regards,
Rick

 

[mollam80]

hi

I am working on same kind of problem. I am a new abaqus user but as my understanding you can feed into nominal stress and engineering strains or you can select a model, like mooney rivlin and set the parameters.

the parameters can be obtained on excel by fitting. but be careful moneey rivlin uses cauchy stress vs stretch values.

so use this:
(assuming incompressibility, detF=1)

eng stress = (c1+c2/stretch)*(stretch-1/strecth^2)

strecth = 1+ eng strain

you can easily fit c1 and c2 if you have instron data on excel sheet. give d1=0 into abaqus then it will count as incompressible. for example for Q7-4850 silicone rubber c1 and c2 are around 0.48