Effects of Cartilage Constitutive Model on Specimen-Specific Validation and Predictions of Cartilage Mechanics in the Human Hip

2013 ◽  
Author(s):  
Corinne R. Henak ◽  
Ashley L. Kapron ◽  
Andrew E. Anderson ◽  
Gerard A. Ateshian ◽  
Benjamin J. Ellis ◽  
...  
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Articular Surface ◽  
Maximum Shear Stress ◽  
Hip Osteoarthritis ◽  
Experimental Measurements ◽  
Cartilage Mechanics ◽  
Model Predictions ◽  
Mechanical Factors

The initiation and progression of hip osteoarthritis (OA) may be predicted by mechanical factors [1]. Contact stress (CS), maximum shear stress (MSS) at the osteochondral interface and first principal strain (FPS) at the articular surface have been identified as parameters that alter the physical integrity and metabolism of cartilage [1]. Although these parameters are difficult to measure in-vivo, they can be predicted using finite element (FE) models. However, the reliability of model predictions and the effects of model assumptions are largely unknown. Direct validation of FE models against experimental measurements for a series of specimens shows the reliability of predictions across specimen geometry [1], although to date this has only been performed for a single hip [2].

scholarly journals Finite Element Prediction of Transchondral Stress and Strain in the Human Hip

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Corinne R. Henak ◽  
Gerard A. Ateshian ◽  
Jeffrey A. Weiss
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Tensile Strain ◽  
Maximum Shear Stress ◽  
Cartilage Damage ◽  
Constitutive Models ◽  
Hip Osteoarthritis ◽  
Principal Strain ◽  
Stress And Strain ◽  
Fiber Distribution

Cartilage fissures, surface fibrillation, and delamination represent early signs of hip osteoarthritis (OA). This damage may be caused by elevated first principal (most tensile) strain and maximum shear stress. The objectives of this study were to use a population of validated finite element (FE) models of normal human hips to evaluate the required mesh for converged predictions of cartilage tensile strain and shear stress, to assess the sensitivity to cartilage constitutive assumptions, and to determine the patterns of transchondral stress and strain that occur during activities of daily living. Five specimen-specific FE models were evaluated using three constitutive models for articular cartilage: quasilinear neo-Hookean, nonlinear Veronda Westmann, and tension-compression nonlinear ellipsoidal fiber distribution (EFD). Transchondral predictions of maximum shear stress and first principal strain were determined. Mesh convergence analysis demonstrated that five trilinear elements were adequate through the depth of the cartilage for precise predictions. The EFD model had the stiffest response with increasing strains, predicting the largest peak stresses and smallest peak strains. Conversely, the neo-Hookean model predicted the smallest peak stresses and largest peak strains. Models with neo-Hookean cartilage predicted smaller transchondral gradients of maximum shear stress than those with Veronda Westmann and EFD models. For FE models with EFD cartilage, the anterolateral region of the acetabulum had larger peak maximum shear stress and first principal strain than all other anatomical regions, consistent with observations of cartilage damage in disease. Results demonstrate that tension-compression nonlinearity of a continuous fiber distribution exhibiting strain induced anisotropy incorporates important features that have large effects on predictions of transchondral stress and strain. This population of normal hips provides baseline data for future comparisons to pathomorphologic hips. This approach can be used to evaluate these and other mechanical variables in the human hip and their potential role in the pathogenesis of osteoarthritis (OA).

scholarly journals Subject-Specific Finite Element Modeling of the Tibiofemoral Joint Based on CT, Magnetic Resonance Imaging and Dynamic Stereo-Radiography Data in Vivo

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Robert E. Carey ◽  
Liying Zheng ◽  
Ameet K. Aiyangar ◽  
Christopher D. Harner ◽  
Xudong Zhang
Keyword(s):  
Magnetic Resonance Imaging ◽  
Finite Element ◽  
Magnetic Resonance ◽  
Contact Area ◽  
Resonance Imaging ◽  
Model Predictions ◽  
Subject Specific ◽  
Skeletal Kinematics ◽  
Tibiofemoral Kinematics

In this paper, we present a new methodology for subject-specific finite element modeling of the tibiofemoral joint based on in vivo computed tomography (CT), magnetic resonance imaging (MRI), and dynamic stereo-radiography (DSX) data. We implemented and compared two techniques to incorporate in vivo skeletal kinematics as boundary conditions: one used MRI-measured tibiofemoral kinematics in a nonweight-bearing supine position and allowed five degrees of freedom (excluding flexion-extension) at the joint in response to an axially applied force; the other used DSX-measured tibiofemoral kinematics in a weight-bearing standing position and permitted only axial translation in response to the same force. Verification and comparison of the model predictions employed data from a meniscus transplantation study subject with a meniscectomized and an intact knee. The model-predicted cartilage-cartilage contact areas were examined against “benchmarks” from a novel in situ contact area analysis (ISCAA) in which the intersection volume between nondeformed femoral and tibial cartilage was characterized to determine the contact. The results showed that the DSX-based model predicted contact areas in close alignment with the benchmarks, and outperformed the MRI-based model: the contact centroid predicted by the former was on average 85% closer to the benchmark location. The DSX-based FE model predictions also indicated that the (lateral) meniscectomy increased the contact area in the lateral compartment and increased the maximum contact pressure and maximum compressive stress in both compartments. We discuss the importance of accurate, task-specific skeletal kinematics in subject-specific FE modeling, along with the effects of simplifying assumptions and limitations.

Finite Element Aided Design Evolution of Composite Leaf Spring

2006 ◽  
Vol 3-4 ◽  
pp. 429-434 ◽  
Author(s):  
J. Hou ◽  
George Jeronimidis
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Maximum Shear Stress ◽  
Leaf Spring ◽  
Original Design ◽  
Virtual Production ◽  
Glass Fibre Reinforced ◽  
Spring System ◽  
Interlaminar Shear ◽  
Aided Design

This paper shows the process of the virtual production development of the mechanical connection between the top leaf of a dual composite leaf spring system to a shackle using finite element methods. The commercial FEA package MSC/MARC has been used for the analysis. In the original design the joint was based on a closed eye-end. Full scale testing results showed that this configuration achieved the vertical proof load of 150 kN and 1 million cycles of fatigue load. However, a problem with delamination occurred at the interface between the fibres going around the eye and the main leaf body. To overcome this problem, a second design was tried using transverse bandages of woven glass fibre reinforced tape to wrap the section that is prone to delaminate. In this case, the maximum interlaminar shear stress was reduced by a certain amount but it was still higher than the material’s shear strength. Based on the fact that, even with delamination, the top leaf spring still sustained the maximum static and fatigue loads required, the third design was proposed with an open eye-end, eliminating altogether the interface where the maximum shear stress occurs. The maximum shear stress predicted by FEA is reduced significantly and a safety factor of around 2 has been obtained. Thus, a successful and safe design has been achieved.

Pulsatile Flow in Fusiform Models of Abdominal Aortic Aneurysms: Flow Fields, Velocity Patterns and Flow-Induced Wall Stresses

2004 ◽  
Vol 126 (4) ◽  
pp. 438-446 ◽  
Author(s):  
Robert A. Peattie ◽  
Tiffany J. Riehle ◽  
Edward I. Bluth
Keyword(s):  
Shear Stress ◽  
Pulsatile Flow ◽  
Maximum Shear Stress ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Flow Fields ◽  
Aortic Aneurysms ◽  
Abdominal Aortic ◽  
Risk Of Rupture

As one important step in the investigation of the mechanical factors that lead to rupture of abdominal aortic aneurysms, flow fields and flow-induced wall stress distributions have been investigated in model aneurysms under pulsatile flow conditions simulating the in vivo aorta at rest. Vortex pattern emergence and evolution were evaluated, and conditions for flow stability were delineated. Systolic flow was found to be forward-directed throughout the bulge in all the models, regardless of size. Vortices appeared in the bulge initially during deceleration from systole, then expanded during the retrograde flow phase. The complexity of the vortex field depended strongly on bulge diameter. In every model, the maximum shear stress occurred at peak systole at the distal bulge end, with the greatest shear stress developing in a model corresponding to a 4.3 cm AAA in vivo. Although the smallest models exhibited stable flow throughout the cycle, flow in the larger models became increasingly unstable as bulge size increased, with strong amplification of instability in the distal half of the bulge. These data suggest that larger aneurysms in vivo may be subject to more frequent and intense turbulence than smaller aneurysms. Concomitantly, increased turbulence may contribute significantly to wall stress magnitude and thereby to risk of rupture.

Investigation of Design Parameters and Failure Criteria of O-Ring Seal Structure

2005 ◽  
Author(s):  
Dianyin Hu ◽  
Rongqiao Wang ◽  
Quanbin Ren ◽  
Jie Hong
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Shear Stress ◽  
Normal Stress ◽  
Maximum Shear Stress ◽  
Design Parameters ◽  
Element Analysis ◽  
Axisymmetric Model ◽  
Sealing Performance ◽  
Maximum Contact

First, this paper established the seal structural 2D axisymmetric model of a certain Solid Rocket Booster (SRB) and calculated the deformation and stresses at ignition through a large displacement, incompressible, contact finite element analysis. The results show that the maximum contact stress appears at the contact area and the maximum shear stress at groove notch. Then, some typical parameters of the seal structure which might have the impact on the sealing performance, such as the gap breadth, initial compressibility, fillets of the groove notch and bottom, groove width, were analyzed. We can find that the gap breadth and initial compressibility do great contributions to the maximum contact normal stress, and the groove notch and bottom fillets act upon the maximum shear stress obviously. In order to verify the validity of the 2D axisymmetric model, 3D structural finite element analysis of the structure was conducted, and the results indicate that in service, the upper flange is inclined relative to the nether flange, which seems to mean that the gap breadth can not be considered as a constant during the 2D axisymmetric analysis. However further calculations say that if using the minimum gap breadth gotten in 3D analysis as its constant gap value, the above 2D axisymmetric model can rationally take the place of 3D model to analyze the sealing performance. Finally, the failure modes & criteria of the O-ring seals based on the maximum contact normal stress and shear stress were determined to ensure the reliability of this structure.

Mechanism Analysis of Rutting at Urban Intersections Based on Numerical Simulation of Moving Loads

2010 ◽  
Vol 152-153 ◽  
pp. 1192-1198 ◽  
Author(s):  
Ze Jiao Dong ◽  
Zong Jie Sun ◽  
Xiang Bing Gong ◽  
Hao Liu
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Asphalt Pavement ◽  
Moving Load ◽  
Maximum Shear Stress ◽  
Uniform Motion ◽  
Dynamic Mode ◽  
Mechanism Analysis ◽  
Horizontal Shear ◽  
Pavement Structure

Frequent starting and braking of vehicles causes rutting of asphalt pavement at urban intersection. As a result, dynamic response of pavement subjected to these kinds of vehicle loadings can be used to analyze rutting mechanism. At first, vehicle loading at urban intersection was described by a vertical and horizontal combined moving pressure with variable speeds. Then, three-dimensional finite element model in transient dynamic mode is developed based on the practical pavement structure. And the moving load, boundary conditions and material parameters were briefly introduced. Finally, through the comparison of time histories and spatial distribution among accelerating, decelerating and uniform motion, mechanism of rutting of asphalt pavement at urban intersections was illustrated according to the finite element simulation. It shows that frequent starting and braking of vehicle at urban intersections, obviously change the stress distribution within pavement structure compared with uniform motion case. The distribution and amplitude of maximum shear stress and horizontal shear stress was observed during the passage of the loading, which will result in shear flow deformation. Pavement structure subjected to moving load exhibits an alternative characteristic which will accelerate the rutting damage of pavement.

Research on the Shear Nails on the Arch Foot of an Oblique Cross Steel Box Arch Bridge

2013 ◽  
Vol 663 ◽  
pp. 49-54
Author(s):  
Xin Huang ◽  
Z.Z. Bai ◽  
De Wei Chen
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Finite Element Model ◽  
Mechanical Performance ◽  
Maximum Shear Stress ◽  
Element Model ◽  
Bottom Up ◽  
Arch Bridge ◽  
Distribution Rules

In order to find the distribution rules on the shear nails on the steel-concrete composite segment of arch foot of an oblique cross steel box arch bridge, it established a space finite element model through the engineering of Wenzhou Weiwulu oblique cross steel box arch bridge, analyzing the maximum shear stress of the shear nails under normal using stage. The result shows that the welding nails in different position have a great difference in their shear stress. The welding nails which welded in a place that has a greater stiffness bear a bigger shear stress. So their mechanical performance of steel-concrete segment is better. In addition, the maximum shear stress becomes bigger from the bottom up to the top of the steel box.

Finite Element Modeling of Knee Joint Contact Pressures and Comparison to Magnetic Resonance Imaging of the Loaded Knee

2003 ◽  
Author(s):  
Jiang Yao ◽  
Art D. Salo ◽  
Monica Barbu-McInnis ◽  
Amy L. Lerner
Keyword(s):  
Magnetic Resonance Imaging ◽  
Finite Element ◽  
Magnetic Resonance ◽  
Knee Joint ◽  
Material Properties ◽  
Three Dimensional ◽  
Resonance Imaging ◽  
Three Dimensional Model ◽  
Model Predictions

A finite element model of the knee joint could be helpful in providing insight on mechanisms of injury, effects of treatment, and the role of mechanical factors in degenerative conditions. However, preparation of such a model involves many geometric simplifications and input of material properties, some of which are poorly understood. Therefore, a method to compare model predictions to actual behaviors under controlled conditions could provide confidence in the model before exploration of other loading scenarios. Our laboratory has developed a method to apply axial loads to the in vivo human knee during magnetic resonance imaging, resembling weightbearing conditions. Image processing algorithms may then be used to assess the three-dimensional kinematics of the tibia and femur during loading. A three-dimensional model of the tibio-menisco-femoral contact has been generated and the image-based kinematic boundary conditions were applied to investigate the distribution of stresses and strains in the articular cartilage and menisci throughout the loading period. In this study, our goal is to investigate the contact patterns during long term loading of up to twenty minutes in the healthy knee. Specifically, we assess the use of both elastic and poroelastic material properties in the cartilage, and compare model predictions to known loading conditions and images of tissue deformations.

Research on Anti-Rutting Performance of Reconstruct Pavement

2012 ◽  
Vol 178-181 ◽  
pp. 1601-1604
Author(s):  
Lian Yu Wei ◽  
Fei Gao ◽  
Shi Bin Ma ◽  
Qing Zhou Wang
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Finite Element Model ◽  
Asphalt Pavement ◽  
Maximum Shear Stress ◽  
Element Model ◽  
The State ◽  
Longitudinal Slope ◽  
The Finite Element Model

Based on the overhaul structure of actual asphalt pavement, establishes the finite element model and analyses the shear stress in the state of overload, longitudinal slope and contact coefficient. The result is that the load and the gradient of longitudinal slope larger, the influence of rutting more seriously. The growth of shear stress is larger which brought by adding load on steep longitudinal slope than that of adding on longitudinal slope. The contact coefficient of interlayer α larger the maximum shear stress larger, on the contrary, the contact coefficient of interlayer α smaller the maximum shear stress smaller.

Plaque Growth Functions Combining Wall Stress, Flow Shear Stress and Morphology May Provide Better Prediction for Atherosclerosis Progression: 3D FSI Studies Based on In Vivo Serial MRI

2011 ◽  
Author(s):  
Chun Yang ◽  
Gador Canton ◽  
Chun Yuan ◽  
Tom Hatsukami ◽  
Dalin Tang
Keyword(s):  
Shear Stress ◽  
Atherosclerotic Plaque ◽  
Maximum Shear Stress ◽  
Patient Specific ◽  
Plaque Morphology ◽  
Shear Stresses ◽  
Plaque Progression ◽  
Growth Functions ◽  
Plaque Growth

Atherosclerotic plaque progression involves biological, structural and mechanical factors. Previous work has shown that initiation and early progression of atherosclerotic plaque correlate negatively with flow wall shear stresses [1–2]. However, plaque growth functions based on patient-specific data to predict future plaque growth are lacking in the current literature. Six plaque growth functions based on fluid-structure-interaction (FSI) models and in vivo serial magnetic resonance image (MRI) data were proposed for progression prediction. This is to test the hypothesis that combining plaque morphology, plaque wall maximum principal stress (WS), strain (WSN) and flow maximum shear stress (FSS) could better predict plaque progression.

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