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truparel26
09-15-2009, 07:03 AM
Hello,

I, Tejas Ruparel, am a Graduate Student at the Mechanical Department at Worcester Polytechnic Institute, MA.
Currently, am working on a research titled "Development and Validation of a Knee-Thigh-Hip (KTH) LS-DYNA model of a 50th Percentile Male".
In this study, I am developing a Finite Element mode (using LS-Dyna) for the soft tissues/flesh in the lower extremities of human body (leg). We use this FE model in crash simulations to evaluate injury criteria.

I have been using the material model

*MAT_KELVIN-MAXWELL_VISCOELASTIC for modeling flesh in the thigh region of the leg.
following are the numbers:
Density: 2.8892E-09 tons/mm3
bulk modulus (elastic): 0.25
G0 (zero): 0.069 (Shear Modulus)
GI (Infinity): 0.155 (Shear Modulus)
Decay Constant: 1000
F0 (Formulation): Maxwell


This material model, somehow, fails with negative volumes during Crash Simulation and Dynamic Relaxation.

I am also using the *CONTACT_TIED_SURFACE_TO_SURFACE_OFFSET card to define contact between the Bone and the Flesh.
The bone (Femur) has a denser mesh than the Flesh.

I'd be thankful if someone could help me with this issue, recommend a different model, direct me to any papers that discuss FE modeling of Soft Tissues and their material properties.

I'd be glad to answer any questions and share any comments and suggestions with Biomch-L community.

Thank You,

Tejas Ruparel
Worcester Polytechnic Institute, MA.