# Inverse engineering coefficients Ogden model

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 September 3, 2019, 19:35 Inverse engineering coefficients Ogden model #1 New Member   Join Date: Aug 2019 Posts: 10 Rep Power: 5 Hello I have a series of load and displacement values data from instron machine on a viscohyperelastic material (polyvinylchloride). I am going to use the 1st order Ogden model to simulate this material in ANSYS Finite Element. There is a way to use those data that I got from Instron Stress/Tensile machine (load,displacement) in order to inverse engineer the mu and alpha nonlinear coefficients of the ogden model (1st order) and predict the forces that cause the strain on the material along the width of its surfaces. I don't know the procedure of how to do this in ANSYS. Any kind of help would be appreciated. Thank you very much. Kind Regards

 September 9, 2019, 04:33 #2 Senior Member     Alexander Karachun Join Date: Nov 2015 Location: Mykolaiv, Ukraine Posts: 239 Rep Power: 10 This process is called Curve Fitting. https://www.youtube.com/watch?v=3bjCkvobbpY

 September 9, 2019, 10:16 #3 New Member   Join Date: Aug 2019 Posts: 10 Rep Power: 5 No, it's not about curve fitting. My excel values are not stress strain. We don't know the stress caused the strain but we know the strain. So the excel data are X,Y where X is the length of the material and Y its thickness. In excel if plotted it looks a deformed rubber material. So by importing the strain in ANSYS the material should look deformed.

 September 10, 2019, 02:10 #4 Senior Member     Alexander Karachun Join Date: Nov 2015 Location: Mykolaiv, Ukraine Posts: 239 Rep Power: 10 Hmm... Usualy stress is calculated from load, that you have. No one can measure stress directly in test sample. Anyway you can try to use design optimisation module to run many cases with dufferent material coefficients and compare deformed shape. But I`m not sure that optimisation module can compare deformed shapes authomaticaly, so this process may be long.

September 10, 2019, 03:22
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Alexander Kazantcev
Join Date: Sep 2019
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Quote:
 Originally Posted by SteFanI a series of load and displacement values data from instron machine on a viscohyperelastic material (polyvinylchloride).
I think there is a way to convert load-displacement curve to stress-strain. Our phd's have done so, but there were special experiments, one-dimensial and so on, than they have found constants for rubber and plastic materials considering hardening curve and plasticity theory.
Also curve fitting is used for such mat. constants generation.

 Tags ansys, finite element, finite element analysis, ogden, reverse engineering