modeling the pelvic floor using shell elements
DESCRIPTION
Modeling the Pelvic Floor using Shell Elements. D. d'Aulignac (1) , J.A.C. Martins (1) , T. Mascarenhas ( 2 ) , R.M. Natal Jorge ( 3 ) and E.B. Pires (1). 3 IDMEC Faculty of Engineering University of Porto Portugal. - PowerPoint PPT PresentationTRANSCRIPT
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Modeling the Pelvic Floor using Shell Elements
1Departamento de Engenharia Civil Instituto Superior Técnico Av. Rovisco Pais 1049-001 Lisboa Portugal
2S. João HospitalPortoPortugal
3IDMECFaculty of EngineeringUniversity of Porto Portugal
D. d'Aulignac(1), J.A.C. Martins(1), T. Mascarenhas(2), R.M. Natal Jorge(3) and E.B. Pires(1)
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Plan
AnatomyFinite Element
Simulation
Data Geometry
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Why? Understand working of the pelvic
floor Support of organs
Predict damages during childbirth Stress incontinence Prolapse
Uterine Vaginal Rectal
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Pelvic Floor
Illust. From Netter
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MRI Images Sao Joao Hospital, Porto
axial sagittal
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Visualisation
Rasmussen et al (University of Illinois at Chicago)
Segmented manually from MRI data. Julia R. Fielding et al. (Harvard medical school)
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Cadaver Measurements
Janda et al 2003
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Geometry
Point SetNURB
Surfaces(Rhino 3d)
PolygonMesh
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Mesh Geometry
top
side
Frontal view of the mesh:
3068 triangles
1620 nodes
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3D Muscle Model
1
1[2 ' ' ] '
''
''
''
I f f J
II C
ff
f
JJ
dev U B U n n U IJU
UI
UU
UU
J
isotropic
fibers
volume
Martins et al. 98
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Muscle Model
11 12
21 22p
F FF
F F
Tp p pB F F
Tp p pC F F
Deformation gradient
Left Cauchy-Green tensor
Right Cauchy-Green tensor
233 33 33B C F
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Muscle Model
1 33( )CpI tr C C
Tf p pN CN
p pp
f
F Nn
Fibre strain
Direction of fibres (deformed)
First Invariant
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Plane Stress
33
33
33
1
1
det( )
0
2 ' ( ) '
p
p I p f f p p
J
FF
U B B I U n n
Since incompressibility is assumed
Since normal stresses are zero the plane stress is given as
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Passive Behaviour
}1])1({exp[
}1)]3({exp[
)()(
2
1
1
ff
CI
ffC
I
aAU
IbcU
UIUU
Humphrey’s model for
cardiac tissue
isotropic fibres
2
2
3.87 /
23.46
5.84 /
12.43
c g cm
b
A g cm
a
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Passive Tests
lambda
)/( 2cmgstress
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Muscle Fibres
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Active Behaviour
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Muscle Activation
( ) ( , )f pas f act fU U U
20
1
1 4( 1)
for 0.5 1.5
Mact f
f
U T
Sum of passive and active contributions
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Total Stress
active
total isotropic
fibers
2( / )g cm
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Discussion Large quantitative differences between
different models Oomens Martins Bosboom Gielen Kojic Humphrey
Comparison with other models and experimental results is essential
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Simulation
3068 triangular shell elements
Non-linear simulation performed with ABAQUS
UMAT routine decribing the material
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Muscle Activation
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The Future Deformation of pelvic floor during
childbirth Damage, fracture of soft tissues Prolapse of internal organs Geometric models from MRI data 8-node solid FE (de Sousa et al. 03)
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Muscle Model
11 12
21 2233
33
00
00
0 0
p
F FF
F F FF
F
233 33
0 0
0 0
TpT p pB F F
B FFB F
233 33
0 0
0 0
TpT p pC F F
C F FC F
Deformation gradient
Left Cauchy-Green tensor
Right Cauchy-Green tensor