Biomedical Engineering Reference
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(a)
(b)
(c)
(d)
20
30
40
50
60
70
(less aligned)
(well aligned)
Normalized Orientation Index (%)
Fig. 10.4
Mapping of the collagen fiber microstructural architecture onto the 3D finite element
mesh at the deformed (
fully loaded
) configuration
t
:
a
MVAL and
b
MVPL, and at the reference
(
stress-free
) configuration
0
:
c
MVAL and
d
MVPL
10.4.3 Finite Element Simulations of MV Closure
Simulations of the MV systolic closure were performed in the FE commercial soft-
ware ABAQUS 6.11 (SIMULIA, Providence, RI) by utilizing:
(i) the four-node shell elements for the MV leaflets and 3D tension-only truss
elements for the MV chordae tendineae,
(ii) user material subroutine
VUMAT
for implementation of the material models
for MV leaflets and chordae,
(iii)
QUASI-STATIC
option in the implicit dynamic analysis with automatic time
stepping,
(iv)
ORIENT
feature and user subroutine VUSDFLD for defining the element-
based local coordinate system with the preferred fiber direction and orientation
index obtained from the mapping technique,
(v)
THICKNESS TABLE
feature for assigning spatially varied MV leaflet thick-
nesses quantified based on the Micro-CT images,
(vi) general frictionless self-contact algorithm for handling the contact behavior
of the MV leaflets,
(vii) user subroutine
VDISP
for prescribing displacement boundary conditions
accounting for the MV annulus and papillary muscles dynamics due to left
ventricle contraction, and
(viii)
AMPLITUDE
feature for defining the transvalvular pressure loadings.
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