Wulandana, Rachmadian
(2003)
A Nonlinear and Inelastic Constitutive Equation for Human Cerebral Arterial and Aneurysm Walls.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
The underlying motivation of this work is the desire to understand better the formation and development of cerebral saccular aneurysm, lesions frequently found at the apex of bifurcations in and near the Circle of Willis. Degradation of elastin, which is one important passive mechanical component of arterial walls, has been hypothesized to play a role in aneurysm formation. This hypothesis has been motivated by the aneurysm wall histology that always displays fragmented elastin.Currently there is no single appropriate constitutive equation for both cerebral arterial and aneurysm walls. Available constitutiveequations are directed at modeling the nonlinear behavior of cerebral arterial tissue that is hypothesized to arise from recruitment of collagen (another important passive biomechanicalcomponent of arterial wall) but not the inelastic behavior that is hypothesized to be due to elastin fragmentation.In this work, we propose a constitutive equation that is capable of handling both the nonlinearity and inelasticity. Thisconstitutive equation, unlike the classical single mechanism elastic constitutive relation, employs two mechanisms. The first and second mechanisms represent the mechanical response ofelastin and collagen, respectively. The collagen recruitment is modeled by introducing the second mechanism at a specified deformed state, while the elastin breakage is modeled by deactivating the first mechanism at a later deformed state.Moreover, we discuss applications of the new constitutive equation in some relevant problems. For example, we discuss the inflationof a cylindrical membrane and compare analytical results to existing experimental data that demonstrates both the nonlinear and inelastic behavior of cerebral arterial walls and use the data to obtain material constants for the new constitutive equation.The presentation of this work is intended to introduce a new approach that can be used to incorporate various biological mechanisms that have been hypothesized to be involved in aneurysmformation and development. Indeed the current work involves only two important mechanisms, but theoretically the current model can be generalized easily to include more mechanisms if necessary to represent gradual recruitment and breakage.
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| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
3 September 2003 |
| Date Type: |
Completion |
| Defense Date: |
18 June 2003 |
| Approval Date: |
3 September 2003 |
| Submission Date: |
6 August 2003 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Mechanical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
cerebral arteries; constitutive equations; inelastic; multi-mechanism; nonlinear; saccular aneurysms |
| Other ID: |
http://etd.library.pitt.edu:80/ETD/available/etd-08062003-005342/, etd-08062003-005342 |
| Date Deposited: |
10 Nov 2011 19:57 |
| Last Modified: |
15 Nov 2016 13:48 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/8925 |
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