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Finite element implementation of a generalized Fung-elastic constitutive model for planar soft tissues.
Biomech Model Mechanobiol. 2005 Nov; 4(2-3):190-9.BM

Abstract

Numerical simulations of the anisotropic mechanical properties of soft tissues and tissue-derived biomaterials using accurate constitutive models remain an important and challenging research area in biomechanics. While most constitutive modeling efforts have focused on the characterization of experimental data, only limited studies are available on the feasibility of utilizing those models in complex computational applications. An example is the widely utilized exponential constitutive model proposed by Fung. Although present in the biomechanics literature for several decades, implementation of this model into finite element (FE) simulations has been limited. A major reason for limited numerical implementations are problems associated with inherent numerical instability and convergence. To address this issue, we developed and applied two restrictions for a generalized Fung-elastic constitutive model necessary to achieve numerical stability. These are (1) convexity of the strain energy function, and (2) the condition number of material stiffness matrix set lower than a prescribed value. These constraints were implemented in the nonlinear regression used for constitutive model parameter estimation to the experimental biaxial mechanical data. We then implemented the generalized Fung-elastic model into a commercial FE code (ABAQUS, Pawtucket, RI, USA). Single element and multi-element planar biaxial test simulations were conducted to verify the accuracy and robustness of the implementation. Results indicated that numerical convergence and accurate FE implementation were consistently obtained. The present study thus presents an integrated framework for accurate and robust implementation of pseudo-elastic constitutive models for planar soft tissues. Moreover, since our approach is formulated within a general FE code, it can be straightforwardly adopted across multiple software platforms.

Authors+Show Affiliations

Department of Bioengineering, McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

16075264

Citation

Sun, Wei, and Michael S. Sacks. "Finite Element Implementation of a Generalized Fung-elastic Constitutive Model for Planar Soft Tissues." Biomechanics and Modeling in Mechanobiology, vol. 4, no. 2-3, 2005, pp. 190-9.
Sun W, Sacks MS. Finite element implementation of a generalized Fung-elastic constitutive model for planar soft tissues. Biomech Model Mechanobiol. 2005;4(2-3):190-9.
Sun, W., & Sacks, M. S. (2005). Finite element implementation of a generalized Fung-elastic constitutive model for planar soft tissues. Biomechanics and Modeling in Mechanobiology, 4(2-3), 190-9.
Sun W, Sacks MS. Finite Element Implementation of a Generalized Fung-elastic Constitutive Model for Planar Soft Tissues. Biomech Model Mechanobiol. 2005;4(2-3):190-9. PubMed PMID: 16075264.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Finite element implementation of a generalized Fung-elastic constitutive model for planar soft tissues. AU - Sun,Wei, AU - Sacks,Michael S, Y1 - 2005/08/02/ PY - 2004/01/09/received PY - 2005/05/10/accepted PY - 2005/8/3/pubmed PY - 2006/1/27/medline PY - 2005/8/3/entrez SP - 190 EP - 9 JF - Biomechanics and modeling in mechanobiology JO - Biomech Model Mechanobiol VL - 4 IS - 2-3 N2 - Numerical simulations of the anisotropic mechanical properties of soft tissues and tissue-derived biomaterials using accurate constitutive models remain an important and challenging research area in biomechanics. While most constitutive modeling efforts have focused on the characterization of experimental data, only limited studies are available on the feasibility of utilizing those models in complex computational applications. An example is the widely utilized exponential constitutive model proposed by Fung. Although present in the biomechanics literature for several decades, implementation of this model into finite element (FE) simulations has been limited. A major reason for limited numerical implementations are problems associated with inherent numerical instability and convergence. To address this issue, we developed and applied two restrictions for a generalized Fung-elastic constitutive model necessary to achieve numerical stability. These are (1) convexity of the strain energy function, and (2) the condition number of material stiffness matrix set lower than a prescribed value. These constraints were implemented in the nonlinear regression used for constitutive model parameter estimation to the experimental biaxial mechanical data. We then implemented the generalized Fung-elastic model into a commercial FE code (ABAQUS, Pawtucket, RI, USA). Single element and multi-element planar biaxial test simulations were conducted to verify the accuracy and robustness of the implementation. Results indicated that numerical convergence and accurate FE implementation were consistently obtained. The present study thus presents an integrated framework for accurate and robust implementation of pseudo-elastic constitutive models for planar soft tissues. Moreover, since our approach is formulated within a general FE code, it can be straightforwardly adopted across multiple software platforms. SN - 1617-7959 UR - https://www.unboundmedicine.com/medline/citation/16075264/Finite_element_implementation_of_a_generalized_Fung_elastic_constitutive_model_for_planar_soft_tissues_ L2 - https://www.lens.org/lens/search?q=citation_id:16075264 DB - PRIME DP - Unbound Medicine ER -