scholarly journals A Mesoscale Finite Element Modelling Approach for Understanding Brain Morphology and Material Heterogeneity Effects in Chronic Traumatic Encephalopathy

2020 ◽  
Author(s):  
A. Bakhtairydavijani ◽  
G. Khalid ◽  
M.A. Murphy ◽  
K.L. Johnson ◽  
L. E. Peterson ◽  
...  
Keyword(s):  
Finite Element ◽  
Chronic Traumatic Encephalopathy ◽  
Complex Stress ◽  
Fe Analysis ◽  
Brain Morphology ◽  
Shear Stresses ◽  
List Type ◽  
Tissue Properties ◽  
Heterogeneity Effects ◽  
Modelling Approach

AbstractChronic Traumatic Encephalopathy (CTE) affects a significant portion of athletes in contact sports but is difficult to quantify using clinical examinations and modelling approaches. We use an in silico approach to quantify CTE biomechanics using mesoscale Finite Element (FE) analysis that bridges with macroscale whole head FE analysis. The sulci geometry produces complex stress waves that interact with each another to create increased shear stresses at the sulci depth that are significantly larger than in analyses without sulci (from 0.5 kPa to 18.0 kPa). Also, Peak sulci stresses are located where CTE has been experimentally observed in the literature.Highlights3 to 5 bullet points 85 characters maxSulci introduce stress localizations at their depth in the gray matterSulci stress fields interact to produce stress concentration sites in white matterDifferentiating brain tissue properties did not significantly affect peak stresses

Stresses and Strains in the Medial Meniscus of an ACL Deficient Knee under Anterior Loading: A Finite Element Analysis with Image-Based Experimental Validation

2005 ◽  
Vol 128 (1) ◽  
pp. 135-141 ◽  
Author(s):  
Jiang Yao ◽  
Jason Snibbe ◽  
Michael Maloney ◽  
Amy L. Lerner
Keyword(s):  
Finite Element ◽  
Ex Vivo ◽  
Element Model ◽  
Shear Stresses ◽  
Element Analysis ◽  
Knee Motion ◽  
Tissue Properties ◽  
Meniscal Tissue ◽  
Acl Deficient ◽  
Deficient Knee

The menisci are believed to play a stabilizing role in the ACL-deficient knee, and are known to be at risk for degradation in the chronically unstable knee. Much of our understanding of this behavior is based on ex vivo experiments or clinical studies in which we must infer the function of the menisci from external measures of knee motion. More recently, studies using magnetic resonance (MR) imaging have provided more clear visualization of the motion and deformation of the menisci within the tibio-femoral articulation. In this study, we used such images to generate a finite element model of the medial compartment of an ACL-deficient knee to reproduce the meniscal position under anterior loads of 45, 76, and 107N. Comparisons of the model predictions to boundaries digitized from images acquired in the loaded states demonstrated general agreement, with errors localized to the anterior and posterior regions of the meniscus, areas in which large shear stresses were present. Our model results suggest that further attention is needed to characterize material properties of the peripheral and horn attachments. Although overall translation of the meniscus was predicted well, the changes in curvature and distortion of the meniscus in the posterior region were not captured by the model, suggesting the need for refinement of meniscal tissue properties.

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.

scholarly journals A Practical Finite Element Modeling Strategy to Capture Cracking and Crushing Behavior of Reinforced Concrete Structures

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 506 ◽  
Author(s):  
Alexandre Mathern ◽  
Jincheng Yang
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Constitutive Relations ◽  
Fe Analysis ◽  
Rc Beams ◽  
Cracking Behavior ◽  
Concrete Cracking ◽  
Rc Structures ◽  
Nonlinear Fe Analysis ◽  
Modeling Strategy

Nonlinear finite element (FE) analysis of reinforced concrete (RC) structures is characterized by numerous modeling options and input parameters. To accurately model the nonlinear RC behavior involving concrete cracking in tension and crushing in compression, practitioners make different choices regarding the critical modeling issues, e.g., defining the concrete constitutive relations, assigning the bond between the concrete and the steel reinforcement, and solving problems related to convergence difficulties and mesh sensitivities. Thus, it is imperative to review the common modeling choices critically and develop a robust modeling strategy with consistency, reliability, and comparability. This paper proposes a modeling strategy and practical recommendations for the nonlinear FE analysis of RC structures based on parametric studies of critical modeling choices. The proposed modeling strategy aims at providing reliable predictions of flexural responses of RC members with a focus on concrete cracking behavior and crushing failure, which serve as the foundation for more complex modeling cases, e.g., RC beams bonded with fiber reinforced polymer (FRP) laminates. Additionally, herein, the implementation procedure for the proposed modeling strategy is comprehensively described with a focus on the critical modeling issues for RC structures. The proposed strategy is demonstrated through FE analyses of RC beams tested in four-point bending—one RC beam as reference and one beam externally bonded with a carbon-FRP (CFRP) laminate in its soffit. The simulated results agree well with experimental measurements regarding load-deformation relationship, cracking, flexural failure due to concrete crushing, and CFRP debonding initiated by intermediate cracks. The modeling strategy and recommendations presented herein are applicable to the nonlinear FE analysis of RC structures in general.

scholarly journals Application of micro-computer tomography and inverse finite element analysis for characterizing the visco-hyperelastic response of bulk liver tissue using indentation

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Rajeswara R. Resapu ◽  
Roger D. Bradshaw
Keyword(s):  
Finite Element ◽  
Liver Tissue ◽  
Loading Rate ◽  
Time Dependent ◽  
Nonlinear Material ◽  
Computational Time ◽  
List Type ◽  
Prony Series ◽  
Time Dependent Behaviour ◽  
Dependent Behaviour

Abstract In-vitro mechanical indentation experimentation is performed on bulk liver tissue of lamb to characterize its nonlinear material behaviour. The material response is characterized by a visco-hyperelastic material model by the use of 2-dimensional inverse finite element (FE) analysis. The time-dependent behaviour is characterized by the viscoelastic model represented by a 4-parameter Prony series, whereas the large deformations are modelled using the hyperelastic Neo-Hookean model. The shear response described by the initial and final shear moduli and the corresponding Prony series parameters are optimized using ANSYS with the Root Mean Square (RMS) error being the objective function. Optimized material properties are validated using experimental results obtained under different loading histories. To study the efficacy of a 2D model, a three dimensional (3D) model of the specimen is developed using Micro-CT of the specimen. The initial elastic modulus of the lamb liver obtained was found to 13.5 kPa for 5% indentation depth at a loading rate of 1 mm/sec for 1-cycle. These properties are able to predict the response at 8.33% depth and a loading rate of 5 mm/sec at multiple cycles with reasonable accuracy. Article highlights The visco-hyperelastic model accurately models the large displacement as well as the time-dependent behaviour of the bulk liver tissue. Mapped meshing of the 3D FE model saves computational time and captures localized displacement in an accurate manner. The 2D axisymmetric model while predicting the force response of the bulk tissue, cannot predict the localized deformations.

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.

scholarly journals Fractographical Analysis and Biomechanical Considerations of a Tooth Restored With Intracanal Fiber Post: Report of the Fracture and Importance of the Fiber Arrangements

2016 ◽  
Vol 41 (5) ◽  
pp. E149-E158 ◽  
Author(s):  
VF Wandscher ◽  
CD Bergoli ◽  
IF Limberger ◽  
TP Cenci ◽  
P Baldissara ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Glass Fiber ◽  
Shear Stresses ◽  
Fiber Post ◽  
Element Analysis ◽  
Parallel Fibers ◽  
Tooth Structure ◽  
Anterior Teeth ◽  
Compressive Stresses

SUMMARY Objective: This article aims to present a fractographic analysis of an anterior tooth restored with a glass fiber post with parallel fiber arrangement, taking into account force vectors, finite element analysis, and scanning electron microscopy (SEM). Methods: A patient presented at the Faculty of Dentistry (Federal University of Santa Maria, Brazil) with an endodontically treated tooth (ETT), a lateral incisor that had a restorable fracture. The treatment was performed, and the fractured piece was analyzed using stereomicroscopy, SEM, and finite element analysis. Results: The absence of remaining coronal tooth structure might have been the main factor for the clinical failure. We observed different stresses actuating in an ETT restored with a fiber post as well as their relationship with the ultimate fracture. Tensile, compression, and shear stresses presented at different levels inside the restored tooth. Tensile and compressive stresses acted together and were at a maximum in the outer portions and a minimum in the inner portions. In contrast, shear stresses acted concomitantly with tensile and compressive stresses. Shear was higher in the inner portions (center of the post), and lower in the outer portions. This was confirmed by finite element analysis. The SEM analysis showed tensile and compression areas in the fiber post (exposed fibers=tensile areas=lingual surface; nonexposed fibers=compression areas=buccal surface) and shear areas inside the post (scallops and hackle lines). Stereomicroscopic analysis showed brown stains in the crown/root interface, indicating the presence of microleakage (tensile area=lingual surface). Conclusion: We concluded that glass fiber posts with parallel fibers (0°), when restoring anterior teeth, present a greater fracture potential by shear stress because parallel fibers are not mechanically resistant to support oblique occlusal loads. Factors such as the presence of remaining coronal tooth structure and occlusal stability assist in the biomechanical equilibrium of stresses that act upon anterior teeth.

Effect of Bone Tumor and Osteoporosis on Mechanical Properties of Bone and Bone Tissue Properties: A Finite Element Study

2007 ◽  
Author(s):  
Vipul P. Gohil ◽  
Paul K. Canavan ◽  
Hamid Nayeb-Hashemi
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Bone Density ◽  
Bone Tissue ◽  
Bone Tumor ◽  
Cellular Structure ◽  
Bone Tumors ◽  
World Health ◽  
Tissue Stiffness ◽  
Tissue Properties

This research is aimed to study the variations in the biomechanical behavior of bone and bone tissues with osteoporosis and bone tumors. Osteoporosis and bone tumors reduce the mechanical strength of bone, which creates a greater risk of fracture. In the United States alone, ten million individuals, eight million of whom are women, are estimated to already have osteoporosis, and almost 34 million more are estimated to have low bone mass (osteopenia) placing them at increased risk for osteoporosis. World Health Organization defines osteopenia, as a bone density between one and two and a half standard deviations (SD) below the bone density of a normal young adult. (Osteoporosis is defined as 2.5 SD or more below that reference point.). Together, osteoporosis and osteopenia are expected to affect an estimated 52 million women and men age 50 and older by 2010, and 61 million by 2020. The current medical cost of osteoporosis total is nearly about $18 billion in the U.S. each year. There is a dearth of literature that addresses the effects of osteoporosis on bone tissue properties. Furthermore, there are few studies published related to the effect of bone tumors such as Adamantinoma of long bones, Aneurysmal bone cyst, Hemangioma and others on overall behavior of bone. To understand the variations in bio-mechanical properties of internal tissues of bone with osteoporosis and bone tumor, a 2D finite element (FE) model of bone is developed using ANSYS 9.0 ® (ANSYS Inc., Canonsburg, PA). Trabecular bone is modeled using hexagonal and voronoi cellular structure. This finite element model is subjected to change in BVF (bone volume fraction) and bone architecture caused by osteoporosis. The bone tumor is modeled as finer multi-cellular structure and the effects of its size, location, and property variation of tumor on overall bone behavior are studied. Results from this analysis and comparative data are used to determine behavior of bone and its tissue over different stage of osteoporosis and bone tumor. Results indicate that both bone tumor and osteoporosis significantly change the mechanical properties of the bone. The results show that osteoporosis increases the bone tissue stiffness significantly as BVF reduces. Bone tissue stiffness is found to increase by 80 percent with nearly 55 percent reduction of BVF. The results and methods developed in this research can be implemented to monitor variation in bio-mechanical properties of bone up to tissue level during medication or to determine type and time for need of external support such as bracing.

Design and Analysis of Viscoelastic Seismic Dampers

2002 ◽  
Author(s):  
N. Shimizu ◽  
H. Nasuno ◽  
T. Yazaki ◽  
K. Sunakoda
Keyword(s):  
Finite Element ◽  
Constitutive Relation ◽  
Time Domain ◽  
Dynamic Properties ◽  
Design Procedure ◽  
Fe Analysis ◽  
Damping Capacity ◽  
Element Formulation ◽  
Element Analysis ◽  
Equivalent Viscous Damping

This paper describes a methodology of design and analysis of viscoelastic seismic dampers by means of the time domain finite element analysis. The viscoelastic constitutive relation of material incorporating with the fractional calculus has been derived and the finite element formulation based on the constitutive relation has been developed to analyze the dynamic property of seismic damper. A time domain computer program was developed by using the formulation. Dynamic properties of hysteresis loop, damping capacity, equivalent viscous damping coefficient, and equivalent spring constant are calculated and compared with the experimental results. Remarkable correlation between the FE analysis and the experiment is gained, and consequently the design procedure with the help of the FE analysis has been established.

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