In vivo indenter experiments on soft biological tissues for identification of material models and corresponding parameters

Petekkaya, Ali Tolga
Soft biological tissues, being live and due to their physiological structures, display considerably complex mechanical behaviors. For a better understanding and use in various applications, first study to be carried out is the tests made particularly as in vivo. An indenter test device developed for this purpose in the METU, Department of Mechanical Engineering, Biomechanics Laboratory is operational. In this study, in order to carry out precise and dependable tests, initially, various tests and improvements were conducted on the device and the software controlling the device. At the end of this study, displacement and load measurement accuracies and precisions were improved. Better algorithms for filtering the noisy data were prepared. Some test protocols within the software were improved and new protocols were annexed. To be able to conduct more dependable tests a new connection system was attached to the device. In order to study the anisotropic behavior of soft tissues ellipsoid tips were designed and produced. In the second phase of the study, tests on medial forearm were carried out. In these tests, hysteresis, relaxation and creep behaviors displaying the viscoelastic v properties of the soft biological tissues were observed. In addition to viscoelastic behaviors, preconditioning (Mullin’s) effect and anisotropic response were examined. By using the results of the relaxation and creep tests, parameters of the Prony series capable of modelling these data were determined. With this study, some important conclusions regarding the soft biological tissues were drawn and thus the behaviors of the soft biological tissues were better understood. Besides, the difficulties inherent to in-vivo tests were recognized and actions to reduce these difficulties were explained. Finally, clean experimental data, to be used in the computer simulations, were obtained.


In-vivo testing of biological bulk soft tissues by a non-axisymmetric tip indenter using displacement and force control
Ashrafi, Parinaz; Tönük, Ergin; Bozkurt, Murat; Department of Biomedical Engineering (2015)
Soft tissues of human body have complex structures and different mechanical behaviors than those of traditional engineering materials. There is a great urge to understand tissue behavior of human body. Experimental data is needed for improvement of soft tissue modeling and advancement in implants and prosthesis, as well as diagnosis of diseases. Mechanical behavior and responses change when tissue loses its liveliness and viability. One of the techniques for soft tissue testing is indentation, which is appl...
Petekkaya, Ali Tolga; Tönük, Ergin (2011-03-01)
Mechanical interaction of human body with surrounding is mostly via soft tissues because human body is nearly entirely covered with them. Finite element method, extensively used in various fields of engineering, could not reach to a similar success in simulating soft tissues (especially for modeling the interaction with exoskeletal prosteses and orthoses) mainly because soft tissue mechanical behavior is not known in detail in addition to relatively complex mechanical response of soft tissues.
Identification of soft tissue mechanical material model and corresponding parameters from in vivo experimental data by using inverse finite element method
Üsü, Kerem; Tönük, Ergin; Department of Mechanical Engineering (2008)
The purpose of this thesis is to search for the best material model for soft biological tissues in general. Different sections of human body exhibit different responses like stress relaxation, creep, hysteresis and preconditioning to external loading conditions. These body sections can be assumed as viscoelastic, poroelastic or pseudoelastic. After making the choice of the material model from one of these for the current study, the finite element model and the material code to be used with this model have b...
Three dimensional fracture analysis of FGM coatings
İnan, Özgür; Dağ, Serkan; Department of Mechanical Engineering (2004)
The main objective of this study is to model the three dimensional surface cracking problem in Functionally Graded Material (FGM) coatings bonded to homogeneous substrates. The FGM coating is assumed to be a (ZrO2) ا (Ti-6Al-4V) layer. Homogeneous ceramic, metal ا rich, ceramic ا rich and linear variation material compositions are considered in the analyses. The surface crack is assumed to have a semi ا circular crack front profile. The surface crack problem in the FGM coating ا substrate system is examined...
Three dimensional mixed mode fracture analysis of functionally graded materials
Köşker, Sadık; Dağ, Serkan; Department of Mechanical Engineering (2007)
The main objective of this study is to model and analyze a three dimensional inclined semi-elliptic surface crack in a Functionally Graded Material (FGM) coating bonded to a homogeneous substrate with a bond coat. The parametric analyses on FGMs are based upon zirconia-yttria (ZrO2-8wt%-Y2O3) FGM coating bonded to a substrate made of a nickel-based superalloy. It is assumed that there is a nickel-chromiumaluminumzirconium (NiCrAlY) bond coat between the FGM coating and substrate. Metal-rich, linear variatio...
Citation Formats
A. T. Petekkaya, “In vivo indenter experiments on soft biological tissues for identification of material models and corresponding parameters,” M.S. - Master of Science, Middle East Technical University, 2008.