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ANALYSIS OF IMPACT OF EXPERIMENT REALISATION ON MECHANICAL CHARACTERISTICS OF BIOMATERIALS
Slažanský, Martin ; Petruška, Jindřich (oponent) ; Horný,, Lukáš (oponent) ; Burša, Jiří (vedoucí práce)
The dissertation thesis focuses on the plausibility of mechanical testing of soft biological tissues and on the predictive capabilities of different material models, all assessed using finite element method. The first part of the thesis is dedicated to an introduction into the problem. Next soft biological tissues related to the problem and the ways of their mechanical testing are described according to the most recent knowledge. The second part of the thesis deals with finding the optimal experimental setup using computational modelling by virtual simulation of the mechanical testing. Results have confirmed that two narrow clamps per edge as well as commonly used hooks are applicable for biaxial tension testing of different soft tissues using square shape specimens. Use of clamps is therefore a time efficient, easy and reliable alternative not inferior to hooks. The analysis focused on recommendations for the choice of type, number and size of gripping elements for different specimen size was also carried out in the thesis. The third part of the thesis examines the predictive capabilities of material models of soft tissues and their dependencies. It can be concluded that the resulting mechanical behaviour of a fitted material model depends on starting parameters and there are no “ideal” starting parameters to be used when fitting experimental data. Despite the absence of “ideal” starting parameters, the most efficient way of achieving the best approximation of experimental data from many data sets is proposed. Furthermore, it is also concluded that a constraint of the fitted parameters results in unpredictable influence on the quality of the fit. Finally, the presumption of affine and non-affine deformation of material models was analysed in order to explain the large contradictions between the structure-based constitutive models and the results of biaxial tests under different testing protocols. Although certain differences between the analysed models were found out, they were not significant enough to explain those large contradictions. Further possible areas of investigation are mentioned as the last part of the thesis.
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ANALYSIS OF IMPACT OF EXPERIMENT REALISATION ON MECHANICAL CHARACTERISTICS OF BIOMATERIALS
Slažanský, Martin ; Petruška, Jindřich (oponent) ; Horný,, Lukáš (oponent) ; Burša, Jiří (vedoucí práce)
The dissertation thesis focuses on the plausibility of mechanical testing of soft biological tissues and on the predictive capabilities of different material models, all assessed using finite element method. The first part of the thesis is dedicated to an introduction into the problem. Next soft biological tissues related to the problem and the ways of their mechanical testing are described according to the most recent knowledge. The second part of the thesis deals with finding the optimal experimental setup using computational modelling by virtual simulation of the mechanical testing. Results have confirmed that two narrow clamps per edge as well as commonly used hooks are applicable for biaxial tension testing of different soft tissues using square shape specimens. Use of clamps is therefore a time efficient, easy and reliable alternative not inferior to hooks. The analysis focused on recommendations for the choice of type, number and size of gripping elements for different specimen size was also carried out in the thesis. The third part of the thesis examines the predictive capabilities of material models of soft tissues and their dependencies. It can be concluded that the resulting mechanical behaviour of a fitted material model depends on starting parameters and there are no “ideal” starting parameters to be used when fitting experimental data. Despite the absence of “ideal” starting parameters, the most efficient way of achieving the best approximation of experimental data from many data sets is proposed. Furthermore, it is also concluded that a constraint of the fitted parameters results in unpredictable influence on the quality of the fit. Finally, the presumption of affine and non-affine deformation of material models was analysed in order to explain the large contradictions between the structure-based constitutive models and the results of biaxial tests under different testing protocols. Although certain differences between the analysed models were found out, they were not significant enough to explain those large contradictions. Further possible areas of investigation are mentioned as the last part of the thesis.
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