Individual Trabecula Segmentation (ITS)-Based Plate-Rod Microstructural Finite Element Model Predicts Nonlinear Mechanical Properties of Human Trabecular Bone

2012 ◽  
Author(s):  
Bin Zhou ◽  
Ji Wang ◽  
Arnav Sanyal ◽  
Aaron J. Fields ◽  
Hong Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
High Resolution ◽  
Trabecular Bone ◽  
Element Model ◽  
Bone Fragility ◽  
Fe Model ◽  
Computationally Efficient ◽  
Human Trabecular Bone ◽  
Voxel Model

Osteoporosis is a major bone disease characterized by low bone mass and microarchitecture deterioration, which affects primarily trabecular sites and leads to increased bone fragility. Trabecular bone mechanical properties have direct relations with bone fragility. High-resolution image based-finite element (FE) models with the detailed 3D microstructure have been widely utilized to assess the mechanical properties of trabecular bone. Voxel-based FE model can be generated by converting individual voxels of high resolution bone images into 8-node brick elements. A number of studies have compared mechanical properties predicted by the voxel model with those by mechanical testing and have demonstrated that the voxel FE model can accurately predict the Young’s modulus and yield strength of human trabecular bone (1). However, the computational expense of the voxel-based technique, in general, limits its clinical applications, especially the nonlinear analysis for whole bone strength. Thus, it is not applicable to apply this technique to clinical use with the respect of current computer capability. There is apparent need for an alternative modeling approach that is more computationally efficient while preserving the accuracy of the predictions.

µCT/HR-pQCT Image Based Plate-Rod Microstructural Finite Element Model Efficiently Predicts the Elastic Moduli and Yield Strength of Human Trabecular Bone

2010 ◽  
Author(s):  
X. Sherry Liu ◽  
Aaron J. Fields ◽  
Tony M. Keaveny ◽  
Elizabeth Shane ◽  
X. Edward Guo
Keyword(s):  
Finite Element ◽  
Trabecular Bone ◽  
Shell Element ◽  
Element Model ◽  
Fe Model ◽  
Human Trabecular Bone ◽  
Age Related ◽  
The Individual ◽  
3D Volume

Osteoporosis is an age-related disease characterized by low bone mass and architectural deterioration, which affects primarily the trabecular sites and causes millions of fractures. High-resolution image voxel-based finite element (FE) models with the detailed 3D microstructure have been widely utilized to assess the mechanical properties of trabecular bone [1, 2]. However, the very large size of the voxel-based FE model, in general, limits its application to linear elastic cases. Despite the great potential it has shown in studying trabecular bone failure, iterative nonlinear analysis is still hard to be performed efficiently. Therefore, there is an apparent need for an alternative approach, which maintains the advantages of the voxel-based FE models in capturing details of trabecular microstructure, while allowing faster computation. Based on the individual trabeculae segmentation (ITS) technique [3], a specimen-specific plate-rod (P-R) microstructural FE model was developed by substituting the individual beam/shell element for 3D volume of trabecular plate/rod of μCT images of trabecular bone (21 μm resolution) (Fig. 1). The first goal of this study is to validate both linear and nonlinear predictions based on the P-R models for in vitro μCT images of human trabecular bone samples. The prediction accuracy and computational speed of the P-R model were examined by comparing with those of the voxel-based FE model.

scholarly journals Finite Element Modeling of the Pulse Wave propagation in the aorta for simulation of the Pulse Wave Imaging (PWI) method

2008 ◽  
Author(s):  
Jonathan Vappou
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Aortic Wall ◽  
Pulse Wave ◽  
Coupled Model ◽  
Element Model ◽  
Relative Difference ◽  
Imaging Method ◽  
Fe Model ◽  
Wave Imaging

A large number of pathological conditions result in significant changes of the mechanical properties of the aortic wall. Using the Pulse Wave Velocity (PWV) as an indicator of aortic stiffness has been proposed for several decades. Pulse Wave Imaging (PWI) is an ultrasonography-based imaging method that has been developed to map and quantify the pulse wave (PW) propagation along the abdominal aortic wall and measure its local properties. We present a finite-element-based approach that aims at improving our understanding of the complex PW patterns observed by PWI and their relationship to the underlying mechanical properties. A Fluid-Structure Interaction (FSI) coupled model was developed based on an idealized axisymmetric aorta geometry. The accuracy of the model as well as its ability to reproduce realistic PW propagation were evaluated by performing a parametric analysis on aortic elasticity, by varying the aortic Young�s modulus between 20 kPa and 2000 kPa. The Finite-Element model was able to predict with good accuracy the expected PWV values in different theoretical cases, with an averaged relative difference of 14% in the 20kPa-100kPa, which corresponds to a wide physiologic range for stiffness of the healthy aorta. This study allows to validate the proposed FE model as a tool that is capable of representing quantitatively the pulse wave patterns in the aorta.

Effects of Grain Orientations on Nanoindentation Behavior in Hexagonal Zirconium

2011 ◽  
Vol 702-703 ◽  
pp. 311-314 ◽  
Author(s):  
Arijit Lodh ◽  
Indradev Samajdar ◽  
Raghvendra Tewari ◽  
Dinesh Srivastava ◽  
Gautam Kumar Dey ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
High Resolution ◽  
Electron Diffraction ◽  
Crystal Orientation ◽  
Element Model ◽  
Orientation Dependence ◽  
Strain Hardening Exponent ◽  
Resolution Electron ◽  
Grain Orientations

The present study deals with nanoindentation behavior of commercial Zircaloy 2 and high purity (5N purity) crystal bar Zirconium. The effect of crystal orientation was studied through high resolution electron diffraction, while a finite element model was developed to extract yield strength and strain hardening exponent from nanoindentation data. The study brings in clear signatures of orientation dependence of mechanical properties in hexagonal Zirconium.

scholarly journals Effect of Intraspecimen Spatial Variation in Tissue Mineral Density on the Apparent Stiffness of Trabecular Bone

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Narges Kaynia ◽  
Elaine Soohoo ◽  
Tony M. Keaveny ◽  
Galateia J. Kazakia
Keyword(s):  
Finite Element ◽  
High Resolution ◽  
Spatial Variation ◽  
Trabecular Bone ◽  
Gold Standard ◽  
Mineral Density ◽  
Human Trabecular Bone ◽  
Apparent Stiffness ◽  
Tissue Mineral Density ◽  
Apparent Level

This study investigated the effects of intraspecimen variations in tissue mineral density (TMD) on the apparent-level stiffness of human trabecular bone. High-resolution finite element (FE) models were created for each of 12 human trabecular bone specimens, using both microcomputed tomography (μCT) and “gold-standard” synchrotron radiation μCT (SRμCT) data. Our results confirm that incorporating TMD spatial variation reduces the calculated apparent stiffness compared to homogeneous TMD models. This effect exists for both μCT- and SRμCT-based FE models, but is exaggerated in μCT-based models. This study provides a direct comparison of μCT to SRμCT data and is thereby able to conclude that the influence of including TMD heterogeneity is overestimated in μCT-based models.

A patient-specific finite element model of the smoker’s lung during breathing

2020 ◽  
pp. 095440892097481
Author(s):  
Mojtaba Hasani ◽  
Reza Razaghi ◽  
Kamran Hassani ◽  
Seyed Mohammadali Rahmati ◽  
Pedram Tehrani ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Lung Tissue ◽  
Element Model ◽  
Patient Specific ◽  
Chronic Obstructive ◽  
Fe Model ◽  
Obstructive Pulmonary Disease ◽  
Pressure Phase ◽  
Healthy Lung

Lungs expand during breathing through increasing the space in the chest cavity. The mechanical properties of the lung play a pivotal role for space, which provides during breathing. Smoking via chronic obstructive pulmonary disease (COPD) can affect this mechanical function through the alteration of the mechanical properties of the lung tissue. Recently our group performed an experimental study to measure the axial and transversal mechanical properties of the human healthy and smokers’ lung tissues (Karimi et al., Tech Health Care 2018). Our results revealed a higher stiffness for the smokers’ lung tissues compared to the healthy ones. Here, we aimed to calculate the stresses, pressures, deformations, and kinetic energies in the healthy and smokers’ lung tissues during breathing in interaction with the ribs and sternum. To do that, a patient-specific finite element (FE) model of the human lung was established and numerically subjected to an inhale-exhale pressure phase. The FE results revealed a higher pressure and a lower deformation in the smoking lung tissue compared to the healthy one. In addition, the stiffer smoking lung exerted a higher pressure and deformation in the sternum and ribs compared to the healthy lung. Furthermore, the smoking lung displayed a lower kinetic energy compared to the healthy lung and as a result, it transferred a higher amount of energy to the bones, which might increase the chance of bone remodeling and/or fracture during, e.g., coughing. These results have implications for not only understanding of the stresses and deformations induce in the lung tissues among the healthy and smokers during breathing but also for providing a preliminary information for the medical and biomechanical experts to have an assessment of the amount of injury occurs to the lung because of smoking.

Finite Element Analysis of the Distributed Vibration Absorbers for Structural Noise Control

2005 ◽  
Author(s):  
Ashwini Gautam ◽  
Chris Fuller ◽  
James Carneal
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Base Plate ◽  
Element Model ◽  
Fe Model ◽  
Vibration Absorbers ◽  
Element Analysis ◽  
Poroelastic Media ◽  
Hexahedral Elements ◽  
Component Models

This work presents an extensive analysis of the properties of distributed vibration absorbers (DVAs) and their effectiveness in controlling the sound radiation from the base structure. The DVA acts as a distributed mass absorber consisting of a thin metal sheet covering a layer of acoustic foam (porous media) that behaves like a distributed spring-mass-damper system. To assess the effectiveness of these DVAs in controlling the vibration of the base structures (plate) a detailed finite elements model has been developed for the DVA and base plate structure. The foam was modeled as a poroelastic media using 8 node hexahedral elements. The structural (plate) domain was modeled using 16 degree of freedom plate elements. Each of the finite element models have been validated by comparing the numerical results with the available analytical and experimental results. These component models were combined to model the DVA. Preliminary experiments conducted on the DVAs have shown an excellent agreement between the results obtained from the numerical model of the DVA and from the experiments. The component models and the DVA model were then combined into a larger FE model comprised of a base plate with the DVA treatment on its surface. The results from the simulation of this numerical model have shown that there has been a significant reduction in the vibration levels of the base plate due to DVA treatment on it. It has been shown from this work that the inclusion of the DVAs on the base plate reduces their vibration response and therefore the radiated noise. Moreover, the detailed development of the finite element model for the foam has provided us with the capability to analyze the physics behind the behavior of the distributed vibration absorbers (DVAs) and to develop more optimized designs for the same.

scholarly journals Applicability of a Three-Layer Model for the Dynamic Analysis of Ballasted Railway Tracks

Vibration ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 151-174
Author(s):  
André F. S. Rodrigues ◽  
Zuzana Dimitrovová
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Dynamic Analysis ◽  
Shear Stiffness ◽  
Shear Resistance ◽  
Railway Track ◽  
Fe Model ◽  
Inertial Effects ◽  
Layer Model ◽  
3D Finite Element

In this paper, the three-layer model of ballasted railway track with discrete supports is analyzed to access its applicability. The model is referred as the discrete support model and abbreviated by DSM. For calibration, a 3D finite element (FE) model is created and validated by experiments. Formulas available in the literature are analyzed and new formulas for identifying parameters of the DSM are derived and validated over the range of typical track properties. These formulas are determined by fitting the results of the DSM to the 3D FE model using metaheuristic optimization. In addition, the range of applicability of the DSM is established. The new formulas are presented as a simple computational engineering tool, allowing one to calculate all the data needed for the DSM by adopting the geometrical and basic mechanical properties of the track. It is demonstrated that the currently available formulas have to be adapted to include inertial effects of the dynamically activated part of the foundation and that the contribution of the shear stiffness, being determined by ballast and foundation properties, is essential. Based on this conclusion, all similar models that neglect the shear resistance of the model and inertial properties of the foundation are unable to reproduce the deflection shape of the rail in a general way.

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