A hybrid approach to determining cornea mechanical properties in vivo using a combination of nano-indentation and inverse finite element analysis

Abyaneh, M. H.; Wildman, Ricky D.; Ashcroft, Ian; Ruiz, Pablo D.

doi:10.1016/j.jmbbm.2013.05.016

Cited by 23 publications

(21 citation statements)

References 28 publications

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“…[17][18][19][20][21][22] This method is particularly useful when combined with nanoindentation as the test enables the spatial distribution of properties to be investigated whilst the IFEM enables access to material models not available in the standard forward analysis of nanoindentation data. [23][24][25][26][27][28] This technique has been described previously by the authors in the analysis of 3D ink jet based printed objects to identify spatial variation in properties. 28 All methods and applications using the IFEM technique require selection of the right material constitutive model since without it, it is not possible to describe the mechanical behavior of the material in question.…”

Section: Introductionmentioning

confidence: 99%

An investigation into the depth and time dependent behavior of UV cured 3D ink jet printed objects

et al. 2017

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An ultra-violet (UV) curable ink jet 3D printed material was characterized by an inverse finite element modeling (IFEM) technique employing a nonlinear viscoelastic-viscoplastic (NVEVP) material constitutive model; this methodology was compared directly with nanoindentation tests. The printed UV cured ink jet material properties were found to be z-depth dependent owing to the sequential layer-by-layer deposition approach. With further post-UV curing, the z-depth dependence was weakened but properties at all depths were influenced by the duration of UV exposure, indicating that none of the materials within the samples had reached full cure during the 3D printing process. Effects due to the proximity of an indentation to the 3D printed material material-sample fixing interface, and the different mounting material, in a test sample were examined by direct 3D finite element simulation and shown to be insignificant for experiments performed at a distance greater than 20 lm from the interface.

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Section: Introductionmentioning

confidence: 99%

An investigation into the depth and time dependent behavior of UV cured 3D ink jet printed objects

et al. 2017

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“…Além do MEF, outros métodos são aplicados para análise do comportamento biomecânico de córneas, como por exemplo, a técnica por enxame de partículas [6], métodos híbridos utilizando nanoindentação [19] e a técnica de microscopia de força atômica [20].…”

Section: Referencial Teóricounclassified

Estudo do tempo de processamento para análises do comportamento mecânico de córneas via simulações numéricas

Almeida¹,

Magalhães

2017

RBCA

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Resumo: A córnea e a esclera formam a superfície externa do globo ocular, proporcionando proteção aos componentes internos e mantendo o formato de refração do olho. A estrutura da córnea é composta de epitélio, endotélio e estroma, sendo este último o principal responsável pelas características mecânicas da córnea. Estudos biomecânicos envolvendo o Método dos Elementos Finitos (MEF) podem revelar características mecânicas importantes da córnea, porém estes estudos normalmente requerem alto custo computacional. Este trabalho propõe um estudo do tempo de processamento para análises do comportamento mecânico de córneas humanas via MEF, levando-se em consideração modelos computacionais com baixa complexidade. As simulações foram realizadas utilizando um software comercial de análise de elementos finitos para medir o deslocamento no ponto central da córnea, em que variou-se a quantidade de elementos e nós dos modelos, com o objetivo de comparar os resultados.Palavras-chave: Biomecânica. Córnea. Método dos Elementos Finitos.Abstract: Cornea and sclera are parts of the ocular globe external surface, providing protection to the internal components and keeping the shape of eye refractive. The corneal structure is composed by epithelium, endotheliumn and stroma, being this last one the main responsible for the mechanical properties of the cornea. Biomechanical studies involving the Finite Element Method (FEM) can reveal important mechanical characteristics of the cornea, however these studies usually require high computational cost. This work proposes a study of the processing time for mechanical behavior analysis of human corneas by using FEM, taking into consideration computational models with low complexity. Simulations were performed using a commercial software finite element analysis to measure the displacement at the central point of the cornea in which the amount of elements and nodes of the model was changed in order to compare the results.Keywords: Biomechanics. Cornea. Finite Element Method. IntroduçãoUma das partes mais importantes do globo ocular é a córnea a qual possui características mecânicas que podem ser analisadas no intuito de aprimorar métodos para prevenção de doenças e o surgimento de equipamentos mais eficientes na área médica [1]. Ter uma compreensão do comportamento mecânico de córneas é importante para constatar aplicações clínicas, como exemplos: a tonometria, diagnósticos de ceratocone e estudos relacionados às cirurgias refrativas [2].As propriedades biomecânicas da córnea humana estão relacionadas à sua estrutura, em especial ao comportamento do estroma [3]. A elasticidade da córnea depende da forma como as fibras de colágeno estão agrupadas, variando conforme a direção das fibras [4]. Estudos realizados sobre o comportamento da córnea humana demonstram comportamento elástico não-linear, tendo seu módulo de elasticidade (módulo de Young), crescente, à medida em que a tensão aplicada é aumentada [5].

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“…In this work, 3 load cases are considered for describing the formulation. In each experiment, the displacement at some boundary points is measured and restored in vectors Y (1) , Y (2) and Y (3) . If they are N 1 , N 2 and N 3 measured data in load cases 1, 2 and 3, respectively, Y (i) (i = 1, 2, 3) are defined as follows…”

Section: Inverse Analysismentioning

confidence: 99%

“…Then, by using a function in ABAQUS finite element software, he determined the constants of Mooney-Rivlin model for the materials. Abyaneh et al (2013) used an inverse method to obtain viscoelastic material properties of porcine cornea by performing tension and indentation tests. They used a sample with possible maximum length for the tension test.…”

Section: Introductionmentioning

confidence: 99%

Determination of material parameters of isotropic and anisotropic hyper-elastic materials using boundary measured data

Hajhashemkhani

Hematiyan

2015

jtam

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Identification of mechanical properties of isotropic and anisotropic materials that demonstrate non-linear elastic behavior, such as rubbers and soft tissues of human body, is critical for many industrial and medical purposes. In this paper, a method is presented to obtain the mechanical constants of Mooney-Rivlin and Holzapfel hyper-elastic material models which are employed to describe the behavior of isotropic and anisotropic hyper-elastic materials, respectively. By using boundary measured data from a sample with non-standard geometry, and by using an iterative inverse analysis technique, the material constants are obtained. The method uses the results of different experiments simultaneously to obtain the material parameters more accurately. The effectiveness of the proposed method is demonstrated through three examples. In the two first examples, the simulated measured data are used, while in the third example, the experimental data obtained from a polyvinyl alcohol sample are used.

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A hybrid approach to determining cornea mechanical properties in vivo using a combination of nano-indentation and inverse finite element analysis

Cited by 23 publications

References 28 publications

An investigation into the depth and time dependent behavior of UV cured 3D ink jet printed objects

An investigation into the depth and time dependent behavior of UV cured 3D ink jet printed objects

Estudo do tempo de processamento para análises do comportamento mecânico de córneas via simulações numéricas

Determination of material parameters of isotropic and anisotropic hyper-elastic materials using boundary measured data

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