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Modeling of Passive Behavior of Soft Tissues Including Viscosity and Damage
Linköping University, Department of Management and Engineering, Mechanics . Linköping University, The Institute of Technology.
Departamento de Engenharia Civil e Arquitectura e I.C.I.S.T, Instituto Superior Técnico, Lisboa, Portugal.
2006 (English)In: III European Conference on Computational Mechanics, Lisbon, 5–9 June, 2006, 191-191 p.Conference paper (Refereed)
Abstract [en]

The mechanical properties of soft tissues depend strongly on the orientation of their fibers, and usually they have a highly nonlinear behavior: their stiffness increases as they are stretched. We are interested here in the passive behavior of soft tissues, when subjected to significant stretches, possibly leading to damage. In this paper we develop a model for a transversely isotropic material that has a damageable viscoelastic behavior. This model is then used to simulate the damage evolution of the tissue. The model is developed with the underlying framework of hyperelasticity, and the corresponding strain energy has different parts associated to different contributions to the material behavior: volumetric, isotropic, anisotropic and dissipative contributions. Since soft tissues are almost incompressible we use a multiplicative split of the deformation gradient into a volume preserving part and a part with (small) volume changes. The anisotropic behavior is characterized by the existence of a family of fiber directions within the tissue. The viscoelastic behavior associated with the non-equilibrium stress is treated as a standard solid material with M Maxwell elements simulating the fact that the response of soft tissues is almost independent of the loading frequency. The total damage is modeled by splitting the energy degradation into one isotropic part and one anisotropic part. That is, we can have fiber degradation independently of the damage of the surrounding matrix. The model is implemented in the commercial Finite element software ABAQUS and the tissue behavior is described by an user subroutine (UMAT). Qualitative features of the model are illustrated and discussed.

Place, publisher, year, edition, pages
2006. 191-191 p.
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-14333DOI: 10.1007/1-4020-5370-3_191ISBN: 978-1-4020-4994-1OAI: diva2:23260
Available from: 2007-03-16 Created: 2007-03-16
In thesis
1. Soft Tissue Mechanics with Emphasis on Residual Stress Modeling
Open this publication in new window or tab >>Soft Tissue Mechanics with Emphasis on Residual Stress Modeling
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns residual stress modeling in soft living tissues. The word living means that the tissue interacts with surrounding organs and that it can change its internal properties to optimize its function. From the first day all tissues are under pressure, due, for example, to gravity, other surrounding organs that utilize pressure on the specific tissue, and the pressure from the blood that circulates within the body. This means that all organs grow and change properties under load, and an unloaded configuration is never present within the body. When a tissue is removed from the body, the obtained unloaded state is not naturally stress free. This stress within an unloaded body is called residual stress. It is believed that the residual stress helps the tissue to optimize its function by homogenizing the transmural stress distribution.

The thesis is composed of two parts: in the first part an introduction to soft tissues and basic modeling is given and the second part consist of a collection of five manuscripts. The first four papers show how residual stress can be modeled. We also derive evolution equation for growth and remodeling and show how residual stress develops under constant pressure. The fifth paper deals with damage and viscosity in soft tissues.

Place, publisher, year, edition, pages
Institutionen för konstruktions- och produktionsteknik, 2007. 27 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1081
Mechanics, Residual Stress, Growth, Remodeling
National Category
Mechanical Engineering
urn:nbn:se:liu:diva-8490 (URN)978-91-85715-50-3 (ISBN)
Public defence
2007-04-13, Sal C3, Hus C, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2009-05-11

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