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The numerical implementation of invariant-based viscoelastic formulations at finite strains. An anisotropic model for the passive myocardium
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
2011 (English)In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 200, no 49-52, 3637-3645 p.Article in journal (Refereed) Published
Abstract [en]

The present study developed a conceptual framework for finite strain viscoelasticity thought to be suitable to capture the salient features of a class of passive soft biological tissues like the myocardium. A superposition of a Maxwell Body and an Elastic Body defines the viscoelastic continuum, and its deformation is related to two independent reference configurations. The reference configuration of the Maxwell Body moves in space as it is described (apart from rigid body rotation) by a rate equation in strain space, and stores the history of the deformation. At thermodynamic equilibrium the reference configuration of the Maxwell Body coincides with the current configuration of the continuum. The Helmholtz free energy is expressed as a function of two independent strain variables and entirely renders the constitution of the viscoelastic body. Although this view is to some extent different from reported viscoelastic concepts for finite strains, its linearization around the thermodynamic equilibrium coincides with earlier suggested viscoelastic models. The linearized viscoelastic model has been implemented for a particular anisotropic constitutive model for the passive myocardium. Non-negative dissipation of the model is guaranteed. Material parameters were estimated from in vitro testing of porcine myocardium and the response due to pushing a rigid punch into the myocardium was studied. Results between anisotropic and isotropic descriptions of the myocardium differed significantly, which justified the implementation of an anisotropic model for the myocardium.

Place, publisher, year, edition, pages
2011. Vol. 200, no 49-52, 3637-3645 p.
Keyword [en]
finite strains, anisotropy, viscoelastic, myocardium, soft biological tissue, pacemaker lead perforation, constitutive properties, FEM, nonlinear
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-31037DOI: 10.1016/j.cma.2011.08.022ISI: 000297494700011Scopus ID: 2-s2.0-80053501618OAI: oai:DiVA.org:kth-31037DiVA: diva2:402214
Funder
Swedish Research Council, 2007-4514
Note
QC 20110307Available from: 2011-03-07 Created: 2011-03-07 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Numerical simulation of failure response of vascular tissue due to deep penetration
Open this publication in new window or tab >>Numerical simulation of failure response of vascular tissue due to deep penetration
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xiv p.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0500
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-30875 (URN)
Presentation
2011-03-04, Sal E3, KTH, Osquars backe 14, Stockholm, 10:15
Opponent
Supervisors
Note

QC 20110307

Available from: 2011-03-07 Created: 2011-03-07 Last updated: 2013-01-15Bibliographically approved
2. Failure of vascular tissue with applications to the aneurysm wall, carotid plaque and myocardial tissue
Open this publication in new window or tab >>Failure of vascular tissue with applications to the aneurysm wall, carotid plaque and myocardial tissue
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cardiovascular disease is the leading cause of death in the modern world. Examples are thoracic aortic aneurysm (TAA), abdominal aortic aneurysm (AAA) and stroke due to plaque rupture. Failure in soft tissues caused by medical devices is also a medical challenge. In all these cardiovascular events a better prediction of failure of the tissue and a better understanding about the tissue properties will help in predicament and treatment. For example the diameter-based indication for surgical repair of AAA and TAAs is not sufficient and refined methods are needed. In this thesis failures of some soft vascular tissues, was studied. Experiments have been combined with numerical modeling to understand the elastic and failure properties of AAA, TAA and plaque tissue as well as the ventricular wall. Vascular tissue is anisotropic, time-dependent, nonlinear and shows large deformations. Among others this thesis showed the importance of viscoelasticity which motivates to develop a new continuum mechanical framework. In addition a large part of this thesis dealt with anisotropy of vascular tissue. For the first time the collagen orientation distribution in the AAA wall has been identified. Collagen and its distribution orientation is also an important feature of this tissue. There was a correlation between the strength and stiffness of the AAA samples with the decreasing wall thickness. Increased stiffness was found in the aortic wall of patients with chronic obstructive pulmonary disease (COPD) compared to patients that did not have COPD. As well as difference in stiffness of TAA tissue, in patients with non-pathologic and pathologic aortic valves. Some of the findings in this thesis could have a long-term consequence for management of risk of rupture in AAA, TAA and plaque.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. x, 30 p.
Series
Trita-HFL, ISSN 1104-6813 ; 0545
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-122840 (URN)978-91-7501-798-3 (ISBN)
Public defence
2013-06-07, Sal D2, Lindstedtsvägen 5, KTH, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

QC 20130528

Available from: 2013-05-28 Created: 2013-05-28 Last updated: 2013-05-29Bibliographically approved

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