scholarly journals A new constitutive model for permanent deformation of blood clots with application to simulation of aspiration thrombectomy

2021 ◽  
pp. 110865
Author(s):  
Behrooz Fereidoonnezhad ◽  
Patrick McGarry
Keyword(s):  
Constitutive Model ◽  
Permanent Deformation ◽  
Aspiration Thrombectomy ◽  
Blood Clots

scholarly journals A new constitutive model for permanent deformation of blood clots with application to simulation of aspiration thrombectomy

2021 ◽  
Author(s):  
Behrooz Fereidoonnezhad ◽  
Patrick McGarry
Keyword(s):  
Plastic Deformation ◽  
Constitutive Model ◽  
Blood Clot ◽  
Permanent Deformation ◽  
Constitutive Law ◽  
Aspiration Thrombectomy ◽  
Key Factor ◽  
Cross Links ◽  
Improved Design ◽  
In Silico Models

Direct aspiration with large bore catheter as the first line option in treatment of acute Ischemic stroke (AIS) is a fast and effective technique with promising outcomes. In silico models are widely used for design and preclinical assessment of new developed devices and therapeutic methods. Accurate modelling of the mechanical behaviour of blood clot is a key factor in the design and simulation of aspiration devices. In this study we develop a new constitutive model which incorporates the unrecoverable plastic deformation of clots. The model is developed based on the deformation-induced microstructural changes in fibrin network, including the formation and dissociation of the cross-links between fibrin fibres. The model is calibrated using previously reported experimentally measured permanent clot deformation following uniaxial stretching. The calibrated plasticity model is then used to simulate aspiration thrombectomy. Results reveal that inclusion of permanent plastic deformation results in ~15 % increase in clot aspiration length at an applied aspiration pressure of 200 mmHg. The constitutive law developed in this study provides a basis for improved design and evaluation of novel aspiration catheters leading to increased first-pass revascularization rate.

Determination of Elastic and Plastic Subgrade Soil Parameters for Asphalt Cracking and Rutting Prediction

1996 ◽  
Vol 1540 (1) ◽  
pp. 97-104 ◽  
Author(s):  
G. Behzadi ◽  
W. O. Yandell
Keyword(s):  
Moisture Content ◽  
Constitutive Model ◽  
Permanent Deformation ◽  
Triaxial Tests ◽  
Deformation Analysis ◽  
Soil Parameters ◽  
Dry Density ◽  
Silty Clay ◽  
Exponential Relationship ◽  
Deviator Stress

A preliminary step in the prediction of rutting and cracking in a number of accelerated loading facility trials in Australia is presented. The results of laboratory repeated load triaxial tests were used to characterize the residual and resilient deformation of a silty clay subgrade material. The analysis of permanent deformation indicated that the well-known model ∈p = INS can be used to estimate the accumulated strain at any number of loading cycles. The parameter S (the slope of the line in a plot of log ∈p –log N) was found to be independent of stress and density, but very small increases were observed as moisture content increased. The parameter I (the intercept in a plot of log ∈p –log N) was found to be most sensitive to deviator stress. The test results also indicated that I increased with increasing moisture content and decreased as dry density increased. The analysis revealed that an exponential relationship existed between I and deviator stress. This relationship was used to develop a constitutive model for silty clay based on the previously mentioned well-known model. The constitutive model obtained would be able to predict the plastic strain under any number of loads at any specified stress level. Resilient deformation analysis has shown that resilient modulus initially decreased rapidly with increasing deviator stress and then increased slightly or was nearly constant. The elastic and plastic parameters will be used as input for performance predictors such as VESYS and Mechano-Lattice.

scholarly journals Influence of granular material characteristics in the behaviour of “Bouregreg Valley” soft ground improved with stone columns

2018 ◽  
Vol 149 ◽  
pp. 02020
Author(s):  
Noura Nehab ◽  
Khadija Baba ◽  
Latifa Ouadif ◽  
Lahcen Bahi
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Granular Material ◽  
Complex Geometry ◽  
Soft Soil ◽  
Permanent Deformation ◽  
Stone Columns ◽  
Soil Conditions ◽  
Natural Soil ◽  
Element Analysis

The use of finite element analysis has become widespread in geotechnical practice as means of optimizing engineering tasks; it can be easily applied to the treated areas by stone columns, which are a method of improving the soil having low geotechnical properties and likely to deform significantly under load action, by incorporating granular material (commonly called ballast) compacted by remounting passes, so they act mainly as inclusions with a higher stiffness, shear strength than the natural soil. Moreover the stone columns are highly permeable and act as vertical drains facilitating consolidation of the soft soil improving the performance of the foundation. However the characteristics of this granular material influence the behavior of soft soils treated by the stone columns technique, especially: the friction angle, the cohesion, the modular ratio and the constitutive model. The choice of the constitutive model depends on many factors but, in general, it is related to the type of analysis that we intend to perform. Numerical modeling must consider the diversity of the materials nature, the complex geometry of structures-land and the behavior of materials generally nonlinear (permanent deformation). It is a simple and effective alternative to approach the real behavior of soils reinforced by stone columns and the influence of materials characteristics, it allows settlement analysis, lateral deformation, vertical and horizontal stresses in order to understand the behavior of columns and soil. It also has the advantage of integrating the settlements of the underlying layers. This paper aims to study the mechanisms of functioning and interactions of stone columns with the surrounding ground, and vis-à-vis the various parameters characterizing the granular material "ballast" and the surrounding soil, which influence the behavior of the improved soil, The paper presents, in the first part, soil conditions and the parameters associated with columns, is then presented 3D finite element analyses, so the parametric study was carried out varying several properties especially granular material properties.

scholarly journals Thrombectomy aspiration device geometry optimization for removal of blood clots in cerebral vessels

2020 ◽  
Vol 14 (1) ◽  
pp. 6229-6237
Author(s):  
C. Talayero ◽  
G. Romero ◽  
G. Pearce ◽  
J. Wong
Keyword(s):  
Robust Design ◽  
Blood Clot ◽  
Cerebral Vessels ◽  
Environment Change ◽  
Aspiration Thrombectomy ◽  
Catheter Design ◽  
Blood Clots ◽  
Potential Damage

A study involving the removal of blood clots in cerebral vessels by aspiration thrombectomy is presented. A robust design for the distal end geometry of a catheter is obtained that, together with adequate suction conditions, could avoid potential damage in the artery or fragmentation the thrombus. The optimization process of the parameters is undertaken by a Design of Experiments (DOE) that has been prepared based on Robust Design theories. In particular, 27 experiments are run for one factor at 9 levels (catheter geometry) and up to 9 factors at 3 levels. The experiments are formulated with virtual models that are solved with computing tools. Co-simulation between Computer Fluid Dynamics (CFD) and Finite Elements Method (FEM) structural analysis was used to obtain the suction conditions and the behavior of the blood clot during the intervention process. By comparing the results of the 27 experiments, the highest values of the suctioning force are obtained for a hole pattern based catheter design, that also gives the lowest risk for clot damage (based on the stress value obtained). Direct aspiration and designs based on conical catheter distal ends, give less robust solutions (results are not stable when the conditions of the environment change). Our study investigated the distance between the catheter and the clot, and it was noted that if the catheter was far from the clot, the suction generated a vessel narrowing and consequent potential damage. Up to 90 kPa could be applied when suctioning at a maximum distance equal to the diameter of the vessel between the distal end of the catheter and the proximal end of the clot. A maximum suctioning force of 0,514N was achieved without damage to the artery or the clot. This research enables us to determine and use the most representative parameters and geometries to be tested in in-vitro and in-vivo experiments. In this virtual study, hypothesizes are assumed with regard to the material properties, but the robustness of the design process allows to expect similar results in future in-vitro and in-vivo tests.

Thorough Investigation of Constitutive Model of Asphalt Pavement Permanent Deformation

2015 ◽  
Vol 744-746 ◽  
pp. 1331-1334
Author(s):  
Rui Zheng
Keyword(s):  
Constitutive Model ◽  
Asphalt Pavement ◽  
Permanent Deformation ◽  
Research Results ◽  
Nonlinear Viscoelastic ◽  
Elastoplastic Constitutive Model

In this paper, the constitutive model of the asphalt pavement permanent deformation is analyzed, which is based on the asphalt pavement permanent deformation. In order to reasonably predict the asphalt pavement permanent deformation, the domestic and foreign research results are thorough investigated. It shows that the nonlinear viscoelastic - elastoplastic constitutive model of Peng Miaojuan improves the defects of various models. This constitutive model comprehensively reflects the characteristics of permanent deformation of asphalt pavement.

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