Rubber uniaxial testing for Ansys

[scarules2006]

Hello dear friends!
Today I was uniaxial testing in my lab some rubber specimens to introduce the data in Ansys Workbench. To do this I'm using a tensometer and "dog bone" shaped rubber samples. Is anyone here who has already done this? My results are affected by the way how hard I clamp the rubber specimen, if I clamp it harder the resulted force is larger than if i clamp it less, for the same deformation(about 15% larger). How can I know if my resulted force is the correct one? How hard should I clamp the rubber specimens? Thank you!

 

[rstupplebeen]

For testing I would follow the ASTM recommendations and only deviate if required. Clamping is a huge issue like you point out. This can be alleviated by measuring the strain in the necked down portion of the dog bone. This can be done with strain gauges, extensometers or optically by tracking speckles.

I typically model the test in FEA and tune the material properties using a tool such as Isight to optimize the properties by minimizing the error between the test and simulation data.

I hope this helps.

Rob Stupplebeen

http://www.optimaldevice.com

 

[scarules2006]

Hy Rob,
Thank you for your reply. Can you give me more details about modelling the test in FEA and tuning the material properties using a tool such as Isight?
Kind regards

 

[rstupplebeen]

Your welcome, I'm happy to help.

Basically model the test geometry in FEA using any symmetry is in the test. Pay careful attention to grip conditions. Start with an initial guess for the material model and properties. Run the simulation extract out the Load/Displacement or Load/Strain results that match your physical testing. Isight can automate the extraction of these results from FEA syncing with the test data. The error can be minimized by automating the modification of material properties and rerunning the analysis.

These methods were presented at the 2013 Simulia Customer Conference by my colleague Gary Richardson on our work at Bausch + Lomb

http://www.3ds.com/fileadmin/PRODUC...hanical-properties-in-situ-compression-13.pdf

I hope this helps.

Rob Stupplebeen

http://www.optimaldevice.com