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Article
Publication date: 9 November 2012

D. Balzani, D. Böse, D. Brands, R. Erbel, A. Klawonn, O. Rheinbach and J. Schröder

The purpose of this paper is to present a computational framework for the simulation of patient‐specific atherosclerotic arterial walls. Such simulations provide information…

421

Abstract

Purpose

The purpose of this paper is to present a computational framework for the simulation of patient‐specific atherosclerotic arterial walls. Such simulations provide information regarding the mechanical stress distribution inside the arterial wall and may therefore enable improved medical indications for or against medical treatment. In detail, the paper aims to provide a framework which takes into account patient‐specific geometric models obtained by in vivo measurements, as well as a fast solution strategy, giving realistic numerical results obtained in reasonable time.

Design/methodology/approach

A method is proposed for the construction of three‐dimensional geometrical models of atherosclerotic arteries based on intravascular ultrasound virtual histology data combined with angiographic X‐ray images, which are obtained on a routine basis in the diagnostics and medical treatment of cardiovascular diseases. These models serve as a basis for finite element simulations where a large number of unknowns need to be calculated in reasonable time. Therefore, the finite element tearing and interconnecting‐dual primal (FETI‐DP) domain decomposition method is applied, to achieve an efficient parallel solution strategy.

Findings

It is shown that three‐dimensional models of patient‐specific atherosclerotic arteries can be constructed from intravascular ultrasound virtual histology data. Furthermore, the application of the FETI‐DP domain decomposition method leads to a fast numerical framework. In a numerical example, the importance of three‐dimensional models and thereby fast solution algorithms is illustrated by showing that two‐dimensional approximations differ significantly from the 3D solution.

Originality/value

The decision for or against intravascular medical treatment of atherosclerotic arteries strongly depends on the mechanical situation of the arterial wall. The framework presented in this paper provides computer simulations of stress distributions, which therefore enable improved indications for medical methods of treatment.

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Article
Publication date: 16 April 2018

Stefan Prüger, Ashutosh Gandhi and Daniel Balzani

The purpose of this study is to quantify the impact of the variation of microstructural features on macroscopic and microscopic fields. The application of multi-scale methods in…

142

Abstract

Purpose

The purpose of this study is to quantify the impact of the variation of microstructural features on macroscopic and microscopic fields. The application of multi-scale methods in the context of constitutive modeling of microheterogeneous materials requires the choice of a representative volume element (RVE) of the considered microstructure, which may be based on some idealized assumptions and/or on experimental observations. In any case, a realistic microstructure within the RVE is either computationally too expensive or not fully accessible by experimental measurement techniques, which introduces some uncertainty regarding the microstructural features.

Design/methodology/approach

In this paper, a systematical variation of microstructural parameters controlling the morphology of an RVE with an idealized microstructure is conducted and the impact on macroscopic quantities of interest as well as microstructural fields and their statistics is investigated. The study is carried out under macroscopically homogeneous deformation states using the direct micro-macro scale transition approach.

Findings

The variation of microstructural parameters, such as inclusion volume fraction, aspect ratio and orientation of the inclusion with respect to the overall loading, influences the macroscopic behavior, especially the micromechanical fields significantly.

Originality/value

The systematic assessment of the impact of microstructural parameters on both macroscopic quantities and statistics of the micromechanical fields allows for a quantitative comparison of different microstructure morphologies and a reliable identification of microstructural parameters that promote failure initialization in microheterogeneous materials.

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Article
Publication date: 29 March 2022

Saeed Hatefi Ardakani, Peyman Fatemi Dehaghani, Hesam Moslemzadeh and Soheil Mohammadi

The purpose is to analyze the mechanical behavior of the arterial wall in the degraded region of the arterial wall and to determine the stress distribution, as an important factor…

137

Abstract

Purpose

The purpose is to analyze the mechanical behavior of the arterial wall in the degraded region of the arterial wall and to determine the stress distribution, as an important factor for predicting the potential failure mechanisms in the wall. In fact, while the collagen fiber degradation process itself is not modeled, zones with reduced collagen fiber content (corresponding to the degradation process) are assumed. To do so, a local weakness in the media layer is considered by defining representative volume elements (RVEs) with different fiber collagen contents in the degraded area to investigate the mechanical response of the arterial wall.

Design/methodology/approach

A three-dimensional (3D) large strain hierarchical multiscale technique, based on the homogenization and genetic algorithm (GA), is utilized to numerically model collagen fiber degradation in a typical artery. Determination of material constants for the ground matrix and collagen fibers in the microscale level is performed by the GA. In order to investigate the mechanical degradation, two types of RVEs with different collagen contents in fibers are considered. Each RVE is divided into two parts of noncollagenous matrix and collagen fiber, and the part of collagen fiber is further divided into matrix and collagen fibrils.

Findings

The von Mises stress distributions on the inner and outer surfaces of the artery and the influence of collagen fiber degradation on thinning of the arterial wall in the degraded area are thoroughly studied. Comparing the maximum stress values on outer and inner surfaces in the degraded region shows that the inner surface is under higher stress states, which makes it more prone to failure. Furthermore, due to the weakness of the artery in the degraded area, it is concluded that the collagen fiber degradation considerably reduces the wall thickness in the degraded area, leading to an observable local inflation across the degraded artery.

Originality/value

Considering that little attention has been paid to multiscale numerical modeling of collagen fiber degradation, in this paper a 3D large strain hierarchical multiscale technique based on homogenization and GA methods is presented. Therefore, while the collagen fiber degradation process itself is not modeled in this study, zones with reduced collagen fiber content (corresponding to the degradation process) are assumed.

Details

Engineering Computations, vol. 39 no. 6
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 15 November 2011

Jarraya Abdessalem, Imen Kammoun Kallel and Dammak Fakhreddine

The purpose of this paper is to describe a general theoretical and finite element implementation framework for the constitutive modelling of biological soft tissues.

970

Abstract

Purpose

The purpose of this paper is to describe a general theoretical and finite element implementation framework for the constitutive modelling of biological soft tissues.

Design/methodology/approach

The model is based on continuum fibers reinforced composites in finite strains. As an extension of the isotropic hyperelasticity, it is assumed that the strain energy function is decomposed into a fully isotropic component and an anisotropic component. Closed form expressions of the stress tensor and elasticity tensor are first established in the general case of fully incompressible plane stress which orthotropic and transversely isotropic hyperelasticity. The incompressibility is satisfied exactly.

Findings

Numerical examples are presented to illustrate the model's performance.

Originality/value

The paper presents a constitutive model for incompressible plane stress transversely isotropic and orthotropic hyperelastic materials.

Details

Multidiscipline Modeling in Materials and Structures, vol. 7 no. 4
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 30 September 2019

Dan Zhao, Cun Xin, Tao Jin, Xiaopeng Yan, Shenggguo Ma and Zhihua Wang

The purpose of this study to analyze the plastic anisotropy of 6061 aluminum alloy with finite deformation using crystal plasticity finite element method.

146

Abstract

Purpose

The purpose of this study to analyze the plastic anisotropy of 6061 aluminum alloy with finite deformation using crystal plasticity finite element method.

Design/methodology/approach

A representative volume element (RVE) model was constructed by Voronoi tessellation. In this model, grain shapes, grain orientations and distribution of grains were involved. The mechanical response of the component under composite loading was tested using specify cruciform specimen. Moreover, different stress and strain states in the specific central region were analyzed to reveal the effects of complex loading.

Findings

We calculated the influence of misorientation of adjacent grains as well as the evolution of the micro structure’s plastic deformation on the macroscopic deformation of the structure. Geometry design for the cruciform specimen helps obtain a homogenous distribution of the stress and strain at the specimen center. In this process, the initial grain orientation is also an important factor, and the larger misorientations between special grains may cause greater stress concentration.

Originality/value

The influence of micro-scale factors on macro-scale plastic anisotropy of AA6061 is analyzed using RVE model and cruciform specimen, and they offer a reference for related research.

Details

Engineering Computations, vol. 37 no. 3
Type: Research Article
ISSN: 0264-4401

Keywords

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Abstract

Details

The Aging Workforce Handbook
Type: Book
ISBN: 978-1-78635-448-8

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Book part
Publication date: 21 June 2022

Nicola Sharp-Jeffs

Abstract

Details

Understanding and Responding to Economic Abuse
Type: Book
ISBN: 978-1-80117-418-3

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Article
Publication date: 1 December 1902

AT Oxford, on October 8th and 9th, was celebrated the tercentenary of the founding of the Bodleian Library by Sir Thomas Bodley, an Exeter man, who early realised the value of…

28

Abstract

AT Oxford, on October 8th and 9th, was celebrated the tercentenary of the founding of the Bodleian Library by Sir Thomas Bodley, an Exeter man, who early realised the value of books in the work of education. The occasion was made one of great importance, and there were gathered together distinguished representatives of literature and librarianship from all parts of the world. The list of delegates given below will show how extensive this representation was, although it will occur to some, as a somewhat remarkable circumstance, that not a single municipal library in London was represented, while many of the more important English towns were also ignored. Considering that such libraries are doing so much in the cause of popular education, compared to which the work of many of the colleges and institutions represented is microscopical, it does strike the outsider that the gathering would have been much more impressive and representative had there been more “Town” and less “Gown” in the celebration. The following is a full list of all but the Oxford representatives, who included practically every head of a college, professor, or college librarian, together with various local celebrities:—

Details

New Library World, vol. 5 no. 5
Type: Research Article
ISSN: 0307-4803

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Book part
Publication date: 4 July 2024

Karoly Bodnar

The author presents the meat of the most common species consumed in Europe and their role in nutrition. The work focuses on the meat of mammals and birds; it does not deal with…

Abstract

The author presents the meat of the most common species consumed in Europe and their role in nutrition. The work focuses on the meat of mammals and birds; it does not deal with the importance of protein sources from other taxonomic categories. European meat consumption habits and consumer preferences are presented, taking into account religious, cultural and geographical differences. It examines the possibility of influencing and changing consumer behavior based on consumer opinions. It separately examines the reasons for the less preference of meat or the complete rejection of meat consumption among consumers. This chapter also points out the demographic effects, lifestyle changes and the economic effects of income conditions. It presents examples of the role of government propaganda and the marketing activities of producers or processors in encouraging consumption.

Details

Entrepreneurship and Development for a Green Resilient Economy
Type: Book
ISBN: 978-1-83797-089-6

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Article
Publication date: 8 August 2016

Sunil Bhat and S. Narayanan

Since failure of laminated composites by delaminations is common, the purpose of this paper is to present a numerical procedure to check the stability of delaminations in fiber…

115

Abstract

Purpose

Since failure of laminated composites by delaminations is common, the purpose of this paper is to present a numerical procedure to check the stability of delaminations in fiber metal laminate (Glare), with different possible damage configurations, under uni-axial tension. Deformation behavior of the laminate is also examined. Influence of the type and the extent of damage, represented by varying sizes and number of delaminations, on delamination driving force and laminate deformation is found.

Design/methodology/approach

Delaminated Glare is modeled by finite element method. Interface cohesive elements are used to model the delaminations. Finite element results provide the deflection/deformation characteristics of the laminate. Driving forces of delaminations are estimated by J integrals that are numerically obtained over cyclic paths near delamination tips. Laminates with different types of delaminations are also fabricated and externally delaminated for measurement of their interlaminar fracture toughness. The delamination is considered to be stable if its driving force is less than corresponding interlaminar fracture toughness of the laminate.

Findings

Delaminations are found to be stable in laminates with lower number of delaminations and unstable in laminates with higher number of delaminations. Increase in size of delaminations increases the deformations but reduces the delamination driving force whereas increase in number of delaminations increases both deformations and driving forces. The trends change in case of laminates with symmetrical damage. Shape of delamination is also found to influence the deformations and driving forces. The finite element model is validated.

Research limitations/implications

There is scope for validating the numerical results reported in the paper by theoretical models.

Practical implications

Checking the stability of delaminations and their effect on deformation behavior of the laminate helps is assessment of safety and remaining life of the laminate. If failure is predicted, preemptive action is taken by using repair patch ups at identified critical locations in order to avoid failures in service conditions.

Originality/value

The paper offers the following benefits: use of cohesive zone method that is readily possible in finite element procedures and is relatively simple, fast and reasonably accurate is demonstrated; suitability of using J integrals over paths crossing non-homogeneous and property mismatched material layers is tested; and influence of the type and the extent of damage in the laminate on its deformation behavior and delamination driving forces is found. This type of work has not been reported so far.

Details

International Journal of Structural Integrity, vol. 7 no. 4
Type: Research Article
ISSN: 1757-9864

Keywords

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