Prev Subsubsection 188.8.131.52: Mooney-Rivlin Up Subsection 4.1.2: Uncoupled Materials Subsubsection 184.108.40.206: Ogden Next
220.127.116.11 Muscle Material
This material model implements the constitutive model developed by Silvia S. Blemker . The material type for the muscle material is muscle material. The model is designed to simulate the passive and active material behavior of skeletal muscle. It defines the following parameters:
|<g1>||along fiber shear modulus||[P]|
|<g2>||cross fiber shear modulus||[P]|
|<p1>||exponential stress coefficients||[P]|
|<p2>||fiber uncrimping factor||[ ]|
|<Lofl>||optimal fiber length||[ ]|
|<smax>||maximum isometric stress||[P]|
|<lambda>||fiber stretch for straightened fibers||[ ]|
The main difference between this material formulation compared to other transversely hyperelastic materials is that it is formulated using a set of new invariants, originally due to Criscione , instead of the usual five invariants proposed by A.J.M. Spencer . For this particular material, only two of the five Criscione invariants are used. The strain energy function is defined as follows: The function is the strain energy contribution of the muscle fibers. It is defined as follows: where, and The values and are determined by requiring and continuity at .
The parameter is the activation level and can be specified using the active_contraction element. You can specify a loadcurve using the lc attribute. The value is interpreted as a scale factor when a loadcurve is defined or as the constant activation level when no loadcurve is defined.
The muscle fiber direction is specified similarly to the transversely isotropic Mooney-Rivlin model.
<material id="1" type="muscle material"> <g1>500</g1> <g2>500</g2> <p1>0.05</p1> <p2>6.6</p2> <smax>3e5</smax> <Lofl>1.07</Lofl> <lambda>1.4</lambda> <k>1e6</k> <fiber type="vector">1,0,0</fiber> </material>