mat_77 O_Ogden_model

[Emanuele Solfiti]

Hello,

I am working with mat_77 (O_Ogden_model).
I am struggling to understand how lsdyna is using the Poisson's ratio PR.

From the theory, I understand that the Ogden model is meant to model incompressible materials.

From the material remarks I read that actually there is a hydrostatic work term which is meant to include compressibility. This term vanishes when J = 1.

So I infer that if I set PR = 0.495, this work term is nonzero and the material is compressible.
Is this correct? Or maybe is PR only used for bulk modulus calculation as it happens in some other rubber material formulations? (And hence I am misunderstanding something...?)

Thanks a lot in advance,
regards,

Emanuele 

[James Kennedy]

Dear Emanuele,

 

See if this is of some help?

 

Naseri, H., :Calibration of Adipose Tissue Material Properties in LS-DYNA”,  Report 20222:03,

Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Gothenburg,

Sweden, April 2022.

 

https://research.chalmers.se/publication/523470/file/523470_Fulltext.pdf

 

Sincerely,

James M. Kennedy

KBS2 Inc.

August 27, 2025

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