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A comparative analysis of coronary bypass implants: Experimental and fluid-structure interaction analysis

100%

Changizi S. , Afrasiabian N. , Rassoli A. , Fatouraee N. , Ahmadi Tafti S. H.

Biocybernetics and Biomedical Engineering

2024

tom Vol. 44, no. 2

393--401

Bypass surgery is a commonly employed method for treating coronary artery diseases, involving the use of grafts to bypass occluded arteries. However, graft occlusion remains a concern due to mechanical disparities between the grafts and native arteries. This study aims to compare the mechanical properties of three frequently used grafts in coronary bypass surgeries: human saphenous veins, mammary arteries, and radial arteries. Stress-relaxation tests were conducted on samples obtained from these vessels, and their mechanical properties were characterized. The stress-strain curves of each sample were fitted using the quasi-linear viscoelastic (QLV) model, with MATLAB software used to extract the model’s constants. Additionally, fluid-structure simulations were performed employing the extracted viscoelastic mechanical properties of the vessels. The analysis revealed that the saphenous vein exhibited the highest elastic coefficient (0.5247) and non-linearity coefficient (0.8135) among the studied grafts. The mammary artery demonstrated nearly seven times greater viscoelasticity compared to the other graft options. Furthermore, the examination of shear stress distribution indicated lower shear stress regions in the radial and mammary artery specimens compared to the saphenous specimens. Notably, the lower wall of the host artery exhibited the greatest oscillatory shear index (OSI), with the radial specimen displaying the highest oscillation in this region compared to the other two specimens. The mechanical characterization results presented in this study hold potential applications in pathogenic and clinical investigations of heart diseases, aiding in the development of appropriate treatment approaches.

Modelowanie właściwości mechanicznych materiałów w obliczeniach inżynierskich

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Bochnia J.

tom Z. 13

50--55

W artykule przedstawiono procedurę obliczania współczynników sprężystości i tłumienia w równaniu modelu ciała idealnego standardowy II, tak aby opisać relaksację wybranych materiałów poliuretanowych.

In the article one introduced the calculation procedure of the coefficients of elasticity and damping factors in the equation of ideal body – standard II, so to describe the relaxation of load in the select polyurethane materials.

Niektóre błędy wyznaczania parametrów modelu reologicznego na podstawie testu relaksacji naprężeń na przykładzie bulwy ziemniaka

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Stropek Z. , Gołacki K.

tom R. 9, nr 4

291--297

Artykuł prezentuje procedury oszacowania niektórych błędów wyznaczania parametrów modelu Maxwella opisującego zachowanie się walcowych próbek w teście relaksacji naprężeń na przykładzie tkanki ziemniaka odmiany Irga. Wyznaczono błędy zarówno toru pomiarowego jak i wynikające z niedokładności wykonania próbek. Uwzględniono także zmienny w funkcji siły reakcji próbki błąd systematyczny przy wyliczaniu współczynników sprężystości i lepkości dynamicznej modelu.

This paper presents the estimation procedures of Maxwell’s model parameters describing the behaviour of potato samples during stress relaxation test. Into consideration were taken errors resulting from an inaccuracy of sample preparation, as well as the used measurement device (defined, limited precision). Moreover systematic error depending on sample reaction force, at calculation of elastic and viscosity coefficients was taken into account.

Computer simulation of the Poisson's ratio of soft polydisperse discs at zero temperature

80%

Narojczyk J. , Wojciechowski K. W.

Materials Science Poland

2006

tom Vol. 24, No. 4

921--927

A simple algorithm is proposed to study structural and elastic properties of matter in the presence of structural disorder at zero temperature. The algorithm is used to determine the properties of the polydisperse soft disc system. It is shown that Poisson's ratio of the system essentially depends on the size polydispersity parameter; larger polydispersity implies larger Poisson's ratio. In the presence of any size polydispersity, Poisson's ratio increases also when the interactions between, the particles tend to the hard potential.

Numerical identification of elasticity coefficients for the bending problem

70%

Szablewski P.

2004

tom Vol. 4, no. 4

205--209

A test for identifying elasticity coefficients for the bending problem is discussed. Bending is a problem of flat textiles, and its existence is demonstrated by experimental material on the basis of coordinates of a bent sample. In this paper, we propose another usage of Peirce's cantilever test for determining the relationship between bending moment and curvature. Measuring error was taken into consideration during analysis. The results of calculation have been limited to the relationship between bending moment and curvature mainly of the second degree, but in this way the relationships of a higher degree can be examined. For the analysis a special computer program was developed, which can calculate the coordinates of a bent sample on the basis of an image saved as a .bmp file (bitmap).