{"title":"Constitutive Equations for Human Saphenous Vein Coronary Artery Bypass Graft","authors":"Hynek Chlup, Lukas Horny, Rudolf Zitny, Svatava Konvickova, Tomas Adamek","country":null,"institution":"","volume":20,"journal":"International Journal of Biomedical and Biological Engineering","pagesStart":272,"pagesEnd":276,"ISSN":"1307-6892","URL":"https:\/\/publications.waset.org\/pdf\/5594","abstract":"Coronary artery bypass grafts (CABG) are widely\r\nstudied with respect to hemodynamic conditions which play\r\nimportant role in presence of a restenosis. However, papers which\r\nconcern with constitutive modeling of CABG are lacking in the\r\nliterature. The purpose of this study is to find a constitutive model for\r\nCABG tissue. A sample of the CABG obtained within an autopsy\r\nunderwent an inflation\u2013extension test. Displacements were\r\nrecoredered by CCD cameras and subsequently evaluated by digital\r\nimage correlation. Pressure \u2013 radius and axial force \u2013 elongation\r\ndata were used to fit material model. The tissue was modeled as onelayered\r\ncomposite reinforced by two families of helical fibers. The\r\nmaterial is assumed to be locally orthotropic, nonlinear,\r\nincompressible and hyperelastic. Material parameters are estimated\r\nfor two strain energy functions (SEF). The first is classical\r\nexponential. The second SEF is logarithmic which allows\r\ninterpretation by means of limiting (finite) strain extensibility.\r\nPresented material parameters are estimated by optimization based\r\non radial and axial equilibrium equation in a thick-walled tube. Both\r\nmaterial models fit experimental data successfully. The exponential\r\nmodel fits significantly better relationship between axial force and\r\naxial strain than logarithmic one.","references":null,"publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 20, 2008"}