scholarly journals Biomechanical Aspects of Closing Approaches in Postcarotid Endarterectomy

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Idit Avrahami ◽  
Dafna Raz ◽  
Oranit Bash
Keyword(s):  
Carotid Bifurcation ◽  
Stress And Strain ◽  
Surgery Complications ◽  
Artery Wall ◽  
Strain Fields ◽  
Structure Interaction ◽  
Cerebral Blood Supply ◽  
Patch Angioplasty ◽  
Alternative Approach ◽  
The Common

The carotid bifurcation tends to develop atherosclerotic stenoses which might interfere with cerebral blood supply. In cases of arterial blockage, the common clinical solution is to remove the plaque via carotid endarterectomy (CEA) surgery. Artery closure after surgery using primary closures along the cutting edge might lead to artery narrowing and restrict blood flow. An alternative approach is patch angioplasty which takes longer time and leads to more during-surgery complications. The present study uses numerical methods with fluid-structure interaction (FSI) to explore and compare the two solutions in terms of hemodynamics and stress and strain fields developed in the artery wall.

scholarly journals A mathematical evaluation of hemodynamic parameters after carotid eversion and conventional patch angioplasty

2013 ◽  
Vol 305 (5) ◽  
pp. H716-H724 ◽  
Author(s):  
Alexey V. Kamenskiy ◽  
Iraklis I. Pipinos ◽  
Yuris A. Dzenis ◽  
Prateek K. Gupta ◽  
Syed A. Jaffar Kazmi ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Fluid Structure Interaction ◽  
Vortical Flow ◽  
Intraluminal Pressure ◽  
Stress And Strain ◽  
Hemodynamic Parameters ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Patch Angioplasty ◽  
Eversion Endarterectomy

Carotid endarterectomy has a long history in stroke prevention, yet controversy remains concerning optimal techniques. Two methods frequently used are endarterectomy with patch angioplasty (CEAP) and eversion endarterectomy (CEE). The objective of this study was to compare hemodynamics-related stress and strain distributions between arteries repaired using CEAP and CEE. Mathematical models were based on in vivo three-dimensional arterial geometry, pulsatile velocity profiles, and intraluminal pressure inputs obtained from 16 patients with carotid artery disease. These data were combined with experimentally derived nonlinear, anisotropic carotid artery mechanical properties to create fluid-structure interaction models of CEAP and CEE. These models were then used to calculate hemodynamic parameters thought to promote recurrent disease and restenosis. Combining calculations of stress and strain into a composite risk index, called the integral abnormality factor, allowed for an overall comparison between CEAP and CEE. CEE demonstrated lower mechanical stresses in the arterial wall, whereas CEAP straightened the artery and caused high stress and strain concentrations at the suture-artery interface. CEAP produced a larger continuous region of oscillatory, low-shear, vortical flow in the carotid bulb. There was a more than two-fold difference in the integral abnormality factor, favoring CEE. In conclusion, in a realistically simulated carotid artery, fluid-structure interaction modeling demonstrated CEE to produce less mechanical wall stress and improved flow patterns compared with CEAP. Clinical validation with larger numbers of individual patients will ultimately be required to support modeling approaches to help predict arterial disease progression and comparative effectiveness of reconstruction methods and devices.

Mathematical Model of the Effective Properties of a Fiber Reinforced Composite with a Linearly Graded Transition Zone

2010 ◽  
Vol 38 (4) ◽  
pp. 286-307
Author(s):  
Carey F. Childers
Keyword(s):  
Mathematical Model ◽  
Transition Zone ◽  
Effective Properties ◽  
Local Stress ◽  
Stress And Strain ◽  
Fiber Reinforced ◽  
Strain Fields ◽  
Shear Moduli ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite

Abstract Tires are fabricated using single ply fiber reinforced composite materials, which consist of a set of aligned stiff fibers of steel material embedded in a softer matrix of rubber material. The main goal is to develop a mathematical model to determine the local stress and strain fields for this isotropic fiber and matrix separated by a linearly graded transition zone. This model will then yield expressions for the internal stress and strain fields surrounding a single fiber. The fields will be obtained when radial, axial, and shear loads are applied. The composite is then homogenized to determine its effective mechanical properties—elastic moduli, Poisson ratios, and shear moduli. The model allows for analysis of how composites interact in order to design composites which gain full advantage of their properties.

The stress and strain fields in the neighbourhood of a notch in polyethylene

Polymer ◽  
1989 ◽  
Vol 30 (8) ◽  
pp. 1456-1461 ◽  
Author(s):  
Xue-qin Wang ◽  
Norman Brown
Keyword(s):  
Stress And Strain ◽  
Strain Fields

Endochronic Analysis of Cyclic Elastoplastic Strain Fields in a Notched Plate

1983 ◽  
Vol 50 (4a) ◽  
pp. 789-794 ◽  
Author(s):  
K. C. Valanis ◽  
J. Fan
Keyword(s):  
Residual Stress ◽  
Numerical Scheme ◽  
External Loading ◽  
Stress And Strain ◽  
Elastoplastic Strain ◽  
Residual Stress Field ◽  
Progressive Change ◽  
Strain Fields ◽  
Cyclic Tension ◽  
Cyclic Elastoplastic Strain

In this paper we present an analytical cum-numerical scheme, based on endochronic plasticity and the finite element formalism. The scheme is used to calculate the stress and elastoplastic strain fields in a plate loaded cyclically in its own plane along its outer edges and bearing two symmetrically disposed edge notches. One most important result that stands out is that while the external loading conditions are symmetric and periodic, the histories of stress and strain at the notch tip are neither symmetric nor periodic in character. In cyclic tension ratcheting phenomena at the tip of the notches prevail and a progressive change of the residual stress field at the notch line is shown to occur.

The influence of crack size on the ductile-brittle transition

1988 ◽  
Vol 415 (1848) ◽  
pp. 197-226 ◽  
Keyword(s):  
Boundary Layer ◽  
Fracture Toughness ◽  
Transition Temperature ◽  
Plane Strain ◽  
Crack Size ◽  
Specimen Geometry ◽  
External Loading ◽  
Stress And Strain ◽  
Strain Fields ◽  
Penny Shaped Crack

Simple criteria for brittle and ductile crack extension are applied to the stress and strain fields adjacent to the tip of a crack. They are applied at a specified distance from the crack tip, which should be related to the material’s microstructure. The basic approach is to examine each criterion and find which is satisfied first, as the external loading is increased; the predicted fracture is classified either brittle or ductile accordingly. The stress and strain fields depend upon temperature, principally through the variation of flow stress σ 0 with temperature and, to avoid excessive computation, a constitutive relation is constructed which allows stresses and strains both to be scaled in terms of σ 0 , so that major computations need to be done only at a reference temperature, for a range of applied loads. For any given crack configuration, the result of the calculation is a theoretical prediction of fracture toughness as a function of temperature. At low temperatures, the fracture toughness is low and rises rapidly with temperature, corresponding to satisfaction of the criterion for brittle failure. Above a transition temperature, T T , the ductile criterion is satisfied first, and the toughness variation thereafter falls slowly as temperature increases, corresponding to failure ‘on the upper shelf’. Both the absolute level of the toughness at a given temperature and the transition temperature T T are sensitive to crack size as well as specimen geometry. Although this is self-evident for cracks of microstructural dimensions, the striking feature of this work is the prediction that substantial sensitivity to size and geometry may well be displayed for cracks as large as 1 cm in materials of significance for major engineering structures. Generally, toughness increases and transition temperature decreases as crack size decreases, but these beneficial effects can be nullified by stress triaxiality. Detailed calculations are performed for a buried crack and an edge crack under conditions of plane strain and for a penny-shaped crack loaded axisymmetrically. The plane strain calculations are supplemented by ‘boundary layer’ calculations, in which the effect of specimen geometry appears through a single parameter. The close agreement of the ‘boundary layer’ calculations with the full specimen calculations offers the prospect of a simple characterization of specimen geometry and loading, without the need for geometry-specific computations. The calculations that are reported are, of course, based upon a particular model, chosen in part for com­putational convenience. Thus, their status is that they display possible trends which may be considered to merit further investigation, both theoretical and experimental.

Sign in / Sign up

Export Citation Format

Share Document