scholarly journals Multiscale modelling of cerebrovascular injury reveals the role of vascular anatomy and parenchymal shear stresses

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Siamak Farajzadeh Khosroshahi ◽  
Xianzhen Yin ◽  
Cornelius K. Donat ◽  
Aisling McGarry ◽  
Maria Yanez Lopez ◽  
...  
Keyword(s):  
Strong Correlation ◽  
Principal Direction ◽  
Axial Stress ◽  
Axial Strain ◽  
Brain Area ◽  
Vascular Anatomy ◽  
Element Model ◽  
Shear Stresses ◽  
Complex Anatomy

AbstractNeurovascular injury is often observed in traumatic brain injury (TBI). However, the relationship between mechanical forces and vascular injury is still unclear. A key question is whether the complex anatomy of vasculature plays a role in increasing forces in cerebral vessels and producing damage. We developed a high-fidelity multiscale finite element model of the rat brain featuring a detailed definition of the angioarchitecture. Controlled cortical impacts were performed experimentally and in-silico. The model was able to predict the pattern of blood–brain barrier damage. We found strong correlation between the area of fibrinogen extravasation and the brain area where axial strain in vessels exceeds 0.14. Our results showed that adjacent vessels can sustain profoundly different axial stresses depending on their alignment with the principal direction of stress in parenchyma, with a better alignment leading to larger stresses in vessels. We also found a strong correlation between axial stress in vessels and the shearing component of the stress wave in parenchyma. Our multiscale computational approach explains the unrecognised role of the vascular anatomy and shear stresses in producing distinct distribution of large forces in vasculature. This new understanding can contribute to improving TBI diagnosis and prevention.

Finite Element Analysis of Tire/Rim Interface Forces Under Braking and Cornering Loads

1992 ◽  
Vol 20 (2) ◽  
pp. 83-105 ◽  
Author(s):  
J. P. Jeusette ◽  
M. Theves
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Contact Pressure ◽  
Element Model ◽  
Shear Stresses ◽  
Detailed Knowledge ◽  
Stress Distributions ◽  
Element Analysis ◽  
Plane Shear ◽  
Normal Contact

Abstract During vehicle braking and cornering, the tire's footprint region may see high normal contact pressures and in-plane shear stresses. The corresponding resultant forces and moments are transferred to the wheel. The optimal design of the tire bead area and the wheel requires a detailed knowledge of the contact pressure and shear stress distributions at the tire/rim interface. In this study, the forces and moments obtained from the simulation of a vehicle in stationary braking/cornering conditions are applied to a quasi-static braking/cornering tire finite element model. Detailed contact pressure and shear stress distributions at the tire/rim interface are computed for heavy braking and cornering maneuvers.

Reduction of Free-Edge Stress Concentration

1985 ◽  
Vol 52 (4) ◽  
pp. 801-805 ◽  
Author(s):  
P. R. Heyliger ◽  
J. N. Reddy
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Element Model ◽  
Free Edge ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Interlaminar Shear ◽  
Three Dimensional Elasticity

A quasi-three dimensional elasticity formulation and associated finite element model for the stress analysis of symmetric laminates with free-edge cap reinforcement are described. Numerical results are presented to show the effect of the reinforcement on the reduction of free-edge stresses. It is observed that the interlaminar normal stresses are reduced considerably more than the interlaminar shear stresses due to the free-edge reinforcement.

Stress Singularity of Edge Delamination in Angle-Ply and Cross-Ply Laminates

1997 ◽  
Vol 64 (3) ◽  
pp. 525-531 ◽  
Author(s):  
Wen-Hwa Chen ◽  
Tain-Fu Huang
Keyword(s):  
Transverse Shear ◽  
Axial Strain ◽  
Stress Singularity ◽  
Shear Stresses ◽  
Explicit Solutions ◽  
Real Constant ◽  
Stress Singularities ◽  
General Solutions ◽  
Transverse Shear Stresses ◽  
Edge Delamination

By utilizing the general solutions derived for the plies with arbitrary fiber orientations under uniform axial strain (Huang and Chen, 1994), the explicit solutions of the edge-delamination stress singularities for the angle-ply and cross-ply laminates are obtained. The dominant edge-delamination stress singularities for the angle-ply laminates are found to be a real constant, −1/2, and a pair of complex conjugates, −1/2±i/2πln{(b+b2−a2)/a}. For the cross-ply laminates, the significant effect of transverse shear stresses of the laminate is considered and the dominant edge-delamination stress singularities are shown as −1/2 and −1/2±i/2πln{(c2+c22−4c1c3)/2c1}. a, b, cl, c2, and c3 are the corresponding combined complex constants. In addition, two elementary forms of edge-delamination stress singularity, say, r−1/2 and rδr(lnr)n(δr=n−3/2,n=1,2...) exist for both the angle-ply and cross-ply laminates. Excellent correlations between the present results and available solutions show the validity of the approach. The deficiencies of the solutions available in the literature are compensated. New results for other angle-ply and cross-ply laminates are also provided.

Mechanical Simulation of Knee Movement in Basketball Shooting

2013 ◽  
Vol 336-338 ◽  
pp. 760-763
Author(s):  
Hui Yue
Keyword(s):  
Finite Element ◽  
Cruciate Ligament ◽  
Three Dimensional ◽  
Element Model ◽  
Basketball Player ◽  
Knee Movement ◽  
Dimensional Finite Element ◽  
Anterior Cruciate ◽  
Three Dimensional Finite Element

A short explanation of the finite element method as a powerful tool for mathematical modeling is provided, and an application using constitutive modeling of the behavior of ligaments is introduced. Few possible explanations of the role of water in ligament function are extracted from two dimensional finite element models of a classical ligament. The modeling is extended to a three dimensional finite element model for the human anterior cruciate ligament. Simulation of ligament force in pitching motion of basketball player is studied in this paper.

Combined-Stress Tests on 24S-T Aluminum-Alloy Tubes

1947 ◽  
Vol 14 (2) ◽  
pp. A147-A153
Author(s):  
W. R. Osgood
Keyword(s):  
Aluminum Alloy ◽  
Hoop Stress ◽  
Axial Stress ◽  
Axial Strain ◽  
Maximum Deviation ◽  
Shearing Stress ◽  
Stress Tests ◽  
Combined Stress ◽  
Stress Strain ◽  
Shearing Strain

Abstract Combined-stress tests were made on five 24S-T aluminum-alloy tubes, 1 3/4 in. ID × 0.05 in. thick. The ratios of circumferential (hoop) stress to axial stress were 0, 1/2, 1, 2, and ∞. The tubes were tested to failure and sufficient measurements of circumferential strain and axial strain were taken to plot stress-strain curves almost up to rupture. The results are presented in the form of two sets of stress-strain curves for each ratio of stresses, namely, maximum shearing stress plotted against maximum shearing strain, and octahedral shearing stress plotted against octahedral shearing strain. In each plot the maximum deviation of the curves is about ± 5 per cent. A method of evaluating small octahedral shearing strains from the data is given which does not assume Poisson’s ratio to be 1/2.

Finite element analysis of hydrogen effects on superelastic NiTi shape memory alloys: Orthodontic application

2018 ◽  
Vol 29 (16) ◽  
pp. 3188-3198 ◽  
Author(s):  
Wissem Elkhal Letaief ◽  
Aroua Fathallah ◽  
Tarek Hassine ◽  
Fehmi Gamaoun
Keyword(s):  
Finite Element ◽  
Coupled Model ◽  
Element Model ◽  
Orthodontic Wires ◽  
Niti Wire ◽  
Element Analysis ◽  
Finite Element Software ◽  
Orthodontic Wire ◽  
Niti Shape Memory Alloys

Thanks to its greater flexibility and biocompatibility with human tissue, superelastic NiTi alloys have taken an important part in the market of orthodontic wires. However, wire fractures and superelasticity losses are notified after a few months from being fixed in the teeth. This behavior is due to the hydrogen presence in the oral cavity, which brittles the NiTi arch wire. In this article, a diffusion-mechanical coupled model is presented while considering the hydrogen influences on the NiTi superelasticity. The model is integrated in ABAQUS finite element software via a UMAT subroutine. Additionally, a finite element model of a deflected orthodontic NiTi wire within three teeth brackets is simulated in the presence of hydrogen. The numerical results demonstrate that the force applied to the tooth drops with respect to the increase in the hydrogen amount. This behavior is attributed to the expansion of the NiTi structure after absorbing hydrogen. In addition, it is shown that hydrogen induces a loss of superelasticity. Hence, it attenuates the role of the orthodontic wire on the correction tooth malposition.

scholarly journals The role of school activities in reducing school dropout phenomenon from the point of view of the principals of public schools in the Deir Ala district in Jordan: دور الأنشطة المدرسية في الحد من ظاهرة التسرب المدرسي من وجهة نظر مديري المدارس الحكومية في لواء دير علا بالأردن

2020 ◽  
Vol 4 (4) ◽  
Author(s):  
Raida Hussein Mohammed Sous
Keyword(s):  
Public Schools ◽  
Strong Correlation ◽  
School Dropout ◽  
Point Of View ◽  
Department Heads ◽  
School Dropouts ◽  
School Activities ◽  
Descriptive Approach ◽  
Educational Field

The study aimed at uncovering the role of school activities in reducing school dropout phenomenon from the point of view of the principals of public schools in the Deir Ala district. The researcher used the descriptive approach. In order to achieve the goal of the study, The results showed that the role of school activities in reducing the phenomenon of school dropout with an average of (3.66). The order of the fields ranked in descending order according to the level of fields: Educational field, reached (3.92) (3.40), all of which are rated (high) That the administrative level of creativity of the department heads are high average (3.94), also showed a strong correlation by (0.82). In the light of the results, a number of recommendations and proposals were presented to raise the level of school activities to reduce school dropouts.

Identification Scheme to Assess the Role of Interfacial Damage in a Hemp-Starch Biocomposite

2014 ◽  
Vol 875-877 ◽  
pp. 524-528
Author(s):  
Sofiane Guessasma ◽  
Mohameden Hbib ◽  
David Bassir
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Precise Determination ◽  
Mechanical Parameters ◽  
Interfacial Damage ◽  
Failure Properties ◽  
Experimental Response

This paper aims at studying the effect of interfacial damage on the mechanical behavior of starch - hemp composite. The procedure encompasses an experimental investigation towards the determination of microstructural features and mechanical testing of the material. A finite element model is developed to account for a particular damage kinetics that triggers failure properties. Our results show that the experimental evidence of interfacial damage driven failure is achieved. Finite element model is able to capture this feature using an abrupt damage criterion. But in order to identify the observed behavior, the experimental response is matched with the numerical one. This process tunes the mechanical parameters to fit the experimental response. The optimization process conducted in this way leads to a precise determination of the mechanical parameters that quantifies the observed ultimate properties.

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