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Wyświetlanie 1-3 z 3
Tytuł:
Non-integer viscoelastic constitutive law to model soft biological tissues to in-vivo indentation
Autorzy:
Demirci, N.
Tönük, E.
Powiązania:
https://bibliotekanauki.pl/articles/307448.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
rachunek niecałkowitego rzędu
tkanka miękka
lepkosprężystość
fractional calculus
indentation tests
inverse finite element analysis
soft tissue constitutive relation
viscoelasticity
Opis:
Purpose: During the last decades, derivatives and integrals of non-integer orders are being more commonly used for the description of constitutive behavior of various viscoelastic materials including soft biological tissues. Compared to integer order constitutive relations, non-integer order viscoelastic material models of soft biological tissues are capable of capturing a wider range of viscoelastic behavior obtained from experiments. Although integer order models may yield comparably accurate results, non-integer order material models have less number of parameters to be identified in addition to description of an intermediate material that can monotonically and continuously be adjusted in between an ideal elastic solid and an ideal viscous fluid.Methods: In this work, starting with some preliminaries on non-integer (fractional) calculus, the “spring-pot”, (intermediate mechanical element between a solid and a fluid), non-integer order three element (Zener) solid model, finally a user-defined large strain non-integer order viscoelastic constitutive model was constructed to be used in finite element simulations. Using the constitutive equation developed, by utilizing inverse finite element method and in vivo indentation experiments, soft tissue material identification was performed. Results: The results indicate that material coefficients obtained from relaxation experiments, when optimized with creep experimental data could simulate relaxation, creep and cyclic loading and unloading experiments accurately.Conclusions: Non-integer calculus viscoelastic constitutive models, having physical interpretation and modeling experimental data accurately is a good alternative to classical phenomenological viscoelastic constitutive equations.
Źródło:
Acta of Bioengineering and Biomechanics; 2014, 16, 4; 13-21
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental testing and constitutive modeling of the mechanical properties of the swine skin tissue
Autorzy:
Łagan, S. D.
Liber-Kneć, A.
Powiązania:
https://bibliotekanauki.pl/articles/306666.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
materiał hipersprężysty
tkanka miękka
próba rozciągania
model konstytutywny
hyperelastic material
soft tissue
tensile test
pig’s skin
constitutive model
Opis:
The aim of the study was an estimation of the possibility of using hyperelastic material models to fit experimental data obtained in the tensile test for the swine skin tissue. Methods: The uniaxial tensile tests of samples taken from the abdomen and back of a pig was carried out. The mechanical properties of the skin such as the mean Young’s modulus, the mean maximum stress and the mean maximum elongation were calculated. The experimental data have been used to identify the parameters in specific strain-energy functions given in seven constitutive models of hyperelastic materials: neo-Hookean, Mooney–Rivlin, Ogden, Yeoh, Martins, Humphrey and Veronda–Westmann. An analysis of errors in fitting of theoretical and experimental data was done. Results: Comparison of load –displacement curves for the back and abdomen regions of skin taken showed a different scope of both the mean maximum loading forces and the mean maximum elongation. Samples which have been prepared from the abdominal area had lower values of the mean maximum load compared to samples from the spine area. The reverse trend was observed during the analysis of the values of elongation. An analysis of the accuracy of model fitting to the experimental data showed that, the least accurate were the model of neo- -Hookean, model of Mooney–Rivlin for the abdominal region and model of Veronda–Westmann for the spine region. Conclusions: An analysis of seven hyperelastic material models showed good correlations between the experimental and the theoretical data for five models.
Źródło:
Acta of Bioengineering and Biomechanics; 2017, 19, 2; 93-102
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Skinfold creep under load of caliper. Linear visco- and poroelastic model simulations
Autorzy:
Nowak, J.
Nowak, B.
Kaczmarek, M.
Powiązania:
https://bibliotekanauki.pl/articles/306928.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
symulacja komputerowa
tkanka miękka
lepkosprężystość
modelowanie
computer simulations
soft tissue
lymphoedema
viscoelasticity
poroelasticity
modeling
Opis:
Purpose: This paper addresses the diagnostic idea proposed in [11] to measure the parameter called rate of creep of axillary fold of tissue using modified Harpenden skinfold caliper in order to distinguish normal and edematous tissue. Our simulations are intended to help understanding the creep phenomenon and creep rate parameter as a sensitive indicator of edema existence. The parametric analysis shows the tissue behavior under the external load as well as its sensitivity to changes of crucial hydro-mechanical tissue parameters, e.g., permeability or stiffness. Methods: The linear viscoelastic and poroelastic models of normal (single phase) and oedematous tissue (twophase: swelled tissue with excess of interstitial fluid) implemented in COMSOL Multiphysics environment are used. Simulations are performed within the range of small strains for a simplified fold geometry, material characterization and boundary conditions. The predicted creep is the result of viscosity (viscoelastic model) or pore fluid displacement (poroelastic model) in tissue. Results: The tissue deformations, interstitial fluid pressure as well as interstitial fluid velocity are discussed in parametric analysis with respect to elasticity modulus, relaxation time or permeability of tissue. The creep rate determined within the models of tissue is compared and referred to the diagnostic idea in [11]. Conclusions: The results obtained from the two linear models of subcutaneous tissue indicate that the form of creep curve and the creep rate are sensitive to material parameters which characterize the tissue. However, the adopted modelling assumptions point to a limited applicability of the creep rate as the discriminant of oedema.
Źródło:
Acta of Bioengineering and Biomechanics; 2015, 17, 4; 39-48
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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