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.

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.

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.

Finite Element Model Updating of Machine-Tool Spindle Systems

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Hongrui Cao ◽  
Bing Li ◽  
Zhengjia He
Keyword(s):  
Finite Element ◽  
Machine Tool ◽  
Model Updating ◽  
Joint Stiffness ◽  
Coupled Model ◽  
Iteration Process ◽  
Element Model ◽  
Fe Model ◽  
Machine Tool Spindle ◽  
Fe Model Updating

The unknown joint dynamics are the main obstacle that limits the accuracy of the finite element (FE) model of a machine-tool spindle assembly. In this paper, an FE model updating method is proposed to assist industrial engineers in achieving a reliable model that can accurately represent the dynamic characteristics of machine-tool spindle systems. In the proposed FE model updating procedure, the iterative algorithm based on frequency response functions (FRFs) is applied. The joint stiffness parameters are identified through the iteration process, while the FE model is updated simultaneously. The proposed method was applied to update an existing coupled model of a machine-tool spindle system. The experimental results show that the identified joint stiffness parameters are acceptable and the dynamic behavior of the spindle mounted in the machine tool column is predicted reliably.

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.

Finite Element Model of Human Cochlea Considering of the Helicotrema Size

2013 ◽  
Vol 456 ◽  
pp. 576-581 ◽  
Author(s):  
Li Fu Xu ◽  
Na Ta ◽  
Zhu Shi Rao ◽  
Jia Bin Tian
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Basilar Membrane ◽  
Round Window ◽  
Element Model ◽  
Oval Window ◽  
Fe Model ◽  
Cochlear Duct ◽  
Human Cochlea ◽  
Set Up

A 2-D finite element model of human cochlea is established in this paper. This model includes the structure of oval window, round window, basilar membrane and cochlear duct which is filled with fluid. The basilar membrane responses are calculated with sound input on the oval window membrane. In order to study the effects of helicotrema on basilar membrane response, three different helicotrema dimensions are set up in the FE model. A two-way fluid-structure interaction numerical method is used to compute the responses in the cochlea. The influence of the helicotrema is acquired and the frequency selectivity of the basilar membrane motion along the cochlear duct is predicted. These results agree with the experiments and indicate much better results are obtained with appropriate helicotrema size.

A Novel Noninvasive Technique for Pulse-Wave Imaging and Characterization of Clinically-Significant Vascular Mechanical Properties In Vivo

2007 ◽  
Vol 29 (3) ◽  
pp. 137-154 ◽  
Author(s):  
Kana Fujikura ◽  
Jianwen Luo ◽  
Viktor Gamarnik ◽  
Mathieu Pernot ◽  
Royd Fukumoto ◽  
...  
Keyword(s):  
Aortic Wall ◽  
Pulse Wave ◽  
Distal Region ◽  
Noninvasive Technique ◽  
Abdominal Aortic ◽  
Wave Imaging ◽  
Risk Patients ◽  
Noninvasive Mapping ◽  
Clinically Significant

The pulse-wave velocity (PWV) has been used as an indicator of vascular stiffness, which can be an early predictor of cardiovascular mortality. A noninvasive, easily applicable method for detecting the regional pulse wave (PW) may contribute as a future modality for risk assessment. The purpose of this study was to demonstrate the feasibility and reproducibility of PW imaging (PWI) during propagation along the abdominal aortic wall by acquiring electrocardiography-gated (ECG-gated) radiofrequency (rf) signals noninvasively. An abdominal aortic aneurysm (AAA) was induced using a CaCl2 model in order to investigate the utility of this novel method for detecting disease. The abdominal aortas of twelve normal and five CaCl2, mice were scanned at 30 MHz and electrocardiography (ECG) was acquired simultaneously. The radial wall velocities were mapped with 8000 frames/s. Propagation of the PW was demonstrated in a color-coded ciné-loop format in all cases. In the normal mice, the wave propagated in linear fashion from a proximal to a distal region. However, in CaCl2 mice, multiple waves were initiated from several regions (i.e., most likely initiated from various calcified regions within the aortic wall). The regional PWV in normal aortas was 2.70 ± 0.54 m/s ( r2 = 0.85 ± 0.06, n = 12), which was in agreement with previous reports using conventional techniques. Although there was no statistical difference in the regional PWV between the normal and CaCl2-treated aortas (2.95 ± 0.90 m/s ( r2 = 0.51 ± 0.22, n = 5)), the correlation coefficient was found to be significantly lower in the CaCl2-treated aortas ( p<0.01). This state-of-the-art technique allows noninvasive mapping of vascular disease in vivo. In future clinical applications, it may contribute to the detection of early stages of cardiovascular disease, which may decrease mortality among high-risk patients.

Finite Element Mesh Generator Applying Constraints’ Propagation and Isoparametric Mapping

1991 ◽  
Author(s):  
J. Rodriguez ◽  
M. Him
Keyword(s):  
Finite Element ◽  
Mesh Generation ◽  
Element Model ◽  
Finite Element Mesh ◽  
Fe Model ◽  
Element Analysis ◽  
Element Mesh ◽  
Mesh Generator ◽  
Generation Algorithm ◽  
Essential Input

Abstract This paper presents a finite element mesh generation algorithm (PREPAT) designed to automatically discretize two-dimensional domains. The mesh generation algorithm is a mapping scheme which creates a uniform isoparametric FE model based on a pre-partitioned domain of the component. The proposed algorithm provides a faster and more accurate tool in the pre-processing phase of a Finite Element Analysis (FEA). A primary goal of the developed mesh generator is to create a finite element model requiring only essential input from the analyst. As a result, the generator code utilizes only a sketch, based on geometric primitives, and information relating to loading/boundary conditions. These conditions represents the constraints that are propagated throughout the model and the available finite elements are uniformly mapped in the resulting sub-domains. Relative advantages and limitations of the mesh generator are discussed. Examples are presented to illustrate the accuracy, efficiency and applicability of PREPAT.

Calculating Mechanics Characteristics of Single-Walled Carbon Nanotube Materials by Finite Element Method

2017 ◽  
Vol 730 ◽  
pp. 548-553
Author(s):  
Jing Ge ◽  
Hao Jiang ◽  
Zhen Yu Sun ◽  
Guo Jun Yu ◽  
Bo Su ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Radial Direction ◽  
Element Model ◽  
Beam Element ◽  
Beam Position ◽  
Single Walled Carbon ◽  
Finite Element Software ◽  
Calculation Results ◽  
The Moment

In this paper, we establish the mechanical property analysis of Single-walled Carbon Nanotubes (SWCNTs) modified beam element model based on the molecular structural mechanics method. Then we study the mechanical properties of their radial direction characteristics using the finite element software Abaqus. The model simulated the different bending stiffness with rectangular section beam elements C-C chemical force field. When the graphene curled into arbitrary chirality of SWCNTs spatial structure, the adjacent beam position will change the moment of inertia of the section of the beam. Compared with the original beam element model and the calculation results, we found that the established model largely reduced the overestimate of the original model of mechanical properties on the radial direction of the SWCNTs. At the same time, compared with other methods available in the literature results and the experimental data, the results can be in good agreement.

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