Rubber FEA
Rubber FEA
(OP)
Two questions about archived thread727-53543:
1. GSC ended the thread by saying, "Setting linear or piecewise linear elastic properties with poisson ratio > 0.495 could give fairly good results at small deformations only." I would think that using a Poisson's ratio >= 0.49, even for small strains, leads to serious numerical errors (www.mscsoftware.com-assets-103_elast_paper.pdf, p. 42). Has anyone besides GSC obtained reasonable FEA results for nearly incompressible materials by using a Poisson's ratio and bulk modulus (instead of Young's modulus) from small-strain linear elasticity theory?
2. Earlier in the thread (5 jun 03) jgough said, "In this case his uniaxial tension test should suffice to provide a value for C10. Theoretically it shouldn't matter what deformation mode he uses (as long as his material is isotropic, which it should be)...." Since rubber's stress-strain curve is very different for compression than tension, why shouldn't the deformation mode of the uniaxial test matter when determining constants for a hyperelastic material model?
1. GSC ended the thread by saying, "Setting linear or piecewise linear elastic properties with poisson ratio > 0.495 could give fairly good results at small deformations only." I would think that using a Poisson's ratio >= 0.49, even for small strains, leads to serious numerical errors (www.mscsoftware.com-assets-103_elast_paper.pdf, p. 42). Has anyone besides GSC obtained reasonable FEA results for nearly incompressible materials by using a Poisson's ratio and bulk modulus (instead of Young's modulus) from small-strain linear elasticity theory?
2. Earlier in the thread (5 jun 03) jgough said, "In this case his uniaxial tension test should suffice to provide a value for C10. Theoretically it shouldn't matter what deformation mode he uses (as long as his material is isotropic, which it should be)...." Since rubber's stress-strain curve is very different for compression than tension, why shouldn't the deformation mode of the uniaxial test matter when determining constants for a hyperelastic material model?





RE: Rubber FEA
Re. 1: I would suggest using bulk modulus and young's modulus.
Re. 2: I couldn't agree more with your question, and think that jgough was seriously oversimplifying things...
Ron
RE: Rubber FEA
FEA without material nonlinearity (and anisotropy) requires a single modulus--not bulk modulus AND Young's modulus.
I didn't mean to imply that jgough was oversimplifying things. I'm just trying to understand.