Affiliations: Department of Industrial Engineering, University of Perugia, Perugia, Italy | Department of Mechanical Engineering, Swiss Federal Institute of Technology, Zürich, Switzerland | Department of Mechanics, Politecnico di Torino, Torino, Italy
Note: [] These authors contributed equally to this work.
Note: [] Address for correspondence: Alberto L. Audenino, Department of Mechanical Engineering, Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy. Fax: +39 11 090 6999; E-mail: [email protected].
Abstract: The fundamental passive mechanical properties of the bladder need to be known in order to design the most appropriate long-term surgical repair procedures and develop materials for bladder reconstruction. This study has focused on the bladder tissue viscoelastic behavior, providing a comprehensive analysis of the effects of fibers orientation, strain rate and loading history. Whole bladders harvested from one year old fat pigs (160 kg approximate weight) were dissected along the apex-to-base direction and samples were isolated from the lateral region of the wall, as well as along apex-to-base and transverse directions. Uniaxial monotonic (stress relaxation) and cyclic tests at different frequencies have been performed with the Bose Electroforce® 3200. Normalized stress relaxation functions have been interpolated using a second-order exponential series and loading and unloading stress–strain curves have been interpolated with a non-linear elastic model. The passive mechanical behavior of bladder tissue was shown to be heavily influenced by frequency and loading history, both in monotonic and cyclic tests. The anisotropy of the tissue was evident in monotonic and in cyclic tests as well, especially in tests performed on an exercised tissue and at high frequencies. In contrast, transverse and apex-to-base samples demonstrated an analogous relaxation behavior.
Keywords: Dynamic, viscoelastic, stiffness, damping, relaxation, cycle number
DOI: 10.3233/BIR-2012-0604
Journal: Biorheology, vol. 49, no. 1, pp. 49-63, 2012
