Elimination of Pseudo Initial Stress for Proposed Invariants based Hyper elastic Strain Energy by
Abstract
Although fitting of experimental
data is important in selection of the best hyper elastic strain energy
function, the zero stress condition in the initial (unstressed) configuration
also should be taken into account. Therefore, in the current research a modification
for an invariants based model was developed to eliminate the pseudo initial
stress. To this goal, additional terms were added to hyper elastic strain
energy as a function of the right Cauchy-Green deformation tensor. To justify
the proposed algorithm, uniaxial loading of liver tissue and unfilled silicone
rubber were studied via constitutive modeling in VUMAT user subroutine of ABAQUS
software. Excellent agreement between the experimental and numerically
predicted stress-stretch curves showed that the modified strain energy function
enables to characterize the mechanical behavior of the liver tissue and
unfilled silicone rubber. As the deformed shapes of soft tissues are important
especially in the surgery operations, the effect of modification on the final deformed
geometry was investigated. Results were shown the deformed profile of the
modified and unmodified hyper elastic strain energy models were different.
