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The assessment of the applicability of shear wave elastography in modelling of the mechanical parameters of the liver

Żmudzińska M., Inglot M., Zaleska-Dorobisz U., Jankowski L., Świątek-Najwer E.

Acta of Bioengineering and Biomechanics

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2018

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Vol. 20, no. 4

59--64

EN

The development of haptic technology in laparoscopic simulations indicates a demand of constant upgrade of tactile feedback, which is currently considered to be unsatisfactory. Presumably, one of its causes may be insufficiently examined and described mechanical parameters of soft tissues in vivo, including liver tissue. The aim of the following work was the attempt at assessing the applicability of data from shear wave elastography in organ modelling by correlating the mechanical parameters of the liver obtained by this noninvasive method, with the mechanical parameters obtained by indentation. Methods: Each one out of 12 porcine livers, was subjected to elastography and subsequently to the indentation test. The mean Young’s modulus for each liver lobe was obtained using elastography, while in indentation Young’s moduli in three different strain ranges and maximum load were calculated. Results: Differences between mechanical parameters of lobes were not found but the parameters were calculated for different methods and strain ranges. Conclusions: The limitations of both methods prevent the unambiguous assessment of the applicability of elastography in liver modelling for laparoscopic simulations, at the presented stage of research. Nevertheless, the presented study provides a valuable introduction to the development of a methodology for testing the mechanical parameters of liver tissue.

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Human cancellous bone mechanical properties and penetrator geometry in nanoindentation tests

Makuch A. M., Skalski K. R.

Acta of Bioengineering and Biomechanics

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2018

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Vol. 20, no. 3

153--164

EN

The goal of the study was to determine the influence of the penetrator geometry on the human cancellous bone mechanical properties in indentation tests. The aim of this research was also the assessment of the material properties of bone structures, having in mind the energy aspects of the curve obtained in the cycle: inelastic loading and elastic unloading. Methods: The samples were resected from a femoral heads of patients qualified for a hip replacement surgery. During the Depth Sensing Indentation tests, hardness and elastic modulus of the cancellous bone tissue were measured using the spherical and Vickers penetrators. Measurements were made in a node and in a trabecula for each sample. Results: The analysis of the measurement results and the calculations of total energy, i.e., elastic and inelastic, and those of the parameters of hardness and elasticity made it possible to assess the influence of the penetrator geometry on the mechanical properties of bone structures at a microscopic level. Conclusions: It was found, with respect to the methodology of indentation, that without determining the shape of the penetrator and the site of the indentation, an objective assessment of the micro mechanical properties of the tested material is not possible.

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A numerical study on indentation properties of cortical bone tissue : Influence of anisotropy

Demiral M., Abdel-Wahab A., Silberschmidt V.

Acta of Bioengineering and Biomechanics

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2015

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Vol. 17, no. 2

3--14

EN

Purpose: The purpose of this study is to investigate the effect of anisotropy of cortical bone tissue on measurement of properties such as direction-dependent moduli and hardness. Methods: An advanced three-dimensional finite element model of microindentation was developed. Different modelling schemes were considered to account for anisotropy of elastic or/and plastic regimes. The elastic anisotropic behaviour was modelled employing an elasticity tensor, and Hill’s criteria were used to represent the direction-dependent post-yield behaviour. The Oliver–Pharr method was used in the data analysis. Results: A decrease in the value of the transverse elasticity modulus resulted in the increased material’s indentation modulus measured in the longitudinal direction and a decreased one in the transverse direction, while they were insensitive to the anisotropy in post-elastic regime. On the other hand, an increase in plastic anisotropy led to a decrease in measured hardness for both directions, but by a larger amount in the transverse one. The size effect phenomenon was found to be also sensitive to anisotropy. Conclusions: The undertaken analysis suggests that the Oliver–Pharr method is a useful tool for first-order approximations in the analysis of mechanical properties of anisotropic materials similar to cortical bone, but not necessarily for the materials with low hardening reserves in the plastic regime.

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Właściwości tribologiczne metalowo--ceramicznych powłok kompozytowych

Ozimina D., Madej M., Pokorska I., Osuch-Słomka E.

Tribologia

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2007

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nr 3-4

59-69

PL

W pracy przedstawiono wyniki badań kompozytowych warstw powierzchniowych typu Ni-P i Ni-P-Al2O3. Warstwy te wytwarzano sposobem bezprądowym na podłożu ze stali 100Cr6. Badania obejmowały porównanie mikrotwardości, właściwości tribologicznych oraz adhezji powłok metalowych Ni-P oraz kompozytowych Ni-P- AI2O3. Testy tribologiczne realizowano w skojarzeniu kula-tarcza w warunkach tarcia technicznie suchego. Wyniki badań potwierdziły pozytywny wpływ korundu na mikrotwardość oraz właściwości tribologiczne warstw.

EN

The article discusses results of tests of the composite surface coatings type Ni-P and Ni-P-Al2O3 with a metallic matrix. The Ni-P-Al2O3 composite layers were superimposed on steel elements, 100Cr6, using the electroless plating technique. The investigations included the comparison of the microhardness, tribological properties and adhesion, for the Ni-P coatings and the composite material, i.e. Ni-P- AI2O3. The tribological tests were realized on a T-01M tribological ball-disc tester in technically dry friction. The results of the investigations confirmed the positive influence of corundum on the microhardness and tribological properties of the layers.