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Modelling inflation of a sheet using Holzapfel (HGO) model

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slimjimmy

Nuclear
Apr 5, 2011
16
Hi Everyone,

I'm am preforming a simple analysis whereby I'm inflating a thin rectangular sheet of tissue using the built in Holzapfel (HGO) model. The sheet is constrained in 3 dof on three sides and unconstrained on the remaining side. A pressure load is applied to the inner face to inflate the surface. I am using Explicit to model this, as in future steps of the analysis I will need it for contact problems.

Using the same parameters for the model as that of arterial tissue (3.1.7 Anisotropic hyperelastic modelling of arterial layers in the Abaqus benchmarks manual), I get a concave deformation of the sheet as is expected, see attached figure (a). However when I use different parameters which make the model behaviour more compliant I do not get concave deformation, but rather the edges of the sheet deform only with the centre of the sheet not deforming in the concave direction (similar to a punch through a surface), see attached figure (b). I am assuming near incompressibility and using incompatible element type (C3D8I) to ensure no shear locking occurs during bending.

Anyone have any ideas as to why I am getting this unrealistic deformation? I am using the same mass scaling parameters in both analyses.

Thanks Everyone

 
 http://files.engineering.com/getfile.aspx?folder=d8bf184d-6de5-4b63-8a2b-88234acdc7a4&file=engtips.png
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