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Posted: 1 decade ago 1 apr 2011, 17:18 GMT-4

You can set up a user defined hyperelastic property where you provide the equation for the strain energy density function. The easiest out of the 3 you mentioned is the Yeoh model as it depends on the I1 strain invariant which is directly provided by COMSOL. The Arruda-Boyce model has a more complex expression which also depends on I1 and the inverse of a Langevin function. That function is relatively difficult to evaluate directly, and you can find polynomial approximations that depend on I1^n with n varying from 1 to 5. The Odgen model is harder to implement because it depends on the principal stretches which COMSOL does not readily provide to the user-define hyperelastic property definition. Nagi Elabbasi Veryst Engineering

Posted: 1 decade ago 14 lug 2011, 05:50 GMT-4

Hi. I have a similar problem. I'm modelling a material with a foam type of behavior and would need a material model to characterize the compressibility. The problem is that foam models are in terms of the principal stretches which seems to be a little hard to get a hold of in COMSOL. Have anyone been able to implement a similar model and willing to share some tips i would be truly grateful. Thank you!

Attachments:

• StrainEnergyPotential.PNG

Posted: 1 decade ago 13 apr 2013, 21:44 GMT-4

Hi, I need to model a Hyper-elastic material. I have some strain-stress data from test. Is it possible that I give this set of data to COMSOL and it calculates "Lame constants" for "Neo-Hookean" material model? Or I have to calculate those constants by hand and give them to COMSOL through Material interface? I have searched the whole forum and couldn't find anything!!! That would be very helpful if COMSOL can calculate the constants by the given experimental data like ABAQUS . Regards,

Posted: 1 decade ago 14 apr 2013, 05:02 GMT-4

Hi there is an example in the model library about fitting experimental data, you can do the same for other and multiple parameters too (the optimisation modeule is handy as multi variable settings are pre-cooked for you) The principle you load the data, you define new dependentglobal variables of your unknown and have these driven by the fitting of your simulation to your data, it works nicely for most cases I have tested ;) -- Good luck Ivar

Posted: 1 decade ago 14 apr 2013, 08:48 GMT-4

HI Mohammad, There is no built-in tool in COMSOL for finding material constants that best fit experimental data (material calibration). We have a software tool called MCalibration that we developed for that purpose at Veryst. We are currently working on a version that interfaces with COMSOL and we will hopefully release it later this year. That way you can calibrate any material model from COMSOL’s library, such as the Neo-Hookean material in your case, to test data. In the Neo-Hookean material you only have 2 material constants so it’s also relatively easy to evaluate them manually. Nagi Elabbasi Veryst Engineering

Posted: 1 decade ago 7 giu 2013, 10:42 GMT-4

Hi, This is an old thread, but I still add some comments to it: [QUOTE] Are there any talks about COMSOL implementing other hyperelastic models like Yeoh, Ogen or Arruda-Boyce? [/QUOTE] Yeoh, Ogden and Arruda-Boyce materials are all available. [QUOTE] Hi. I have a similar problem. I'm modelling a material with a foam type of behavior and would need a material model to characterize the compressibility. The problem is that foam models are in terms of the principal stretches which seems to be a little hard to get a hold of in COMSOL. Have anyone been able to implement a similar model and willing to share some tips i would be truly grateful. Thank you! [/QUOTE] The model shown in the attachment to this question is now (from version 4.3b) available as the 'Storakers' model. Regards, Henrik