A Novel Finite Element Model to Assess the Effect of Solid Stress Inside Tumors on Elastographic Normal Strains and Fluid Pressure

2019 ◽  
Vol 2 (3) ◽  
Author(s):  
Md Tauhidul Islam ◽  
Raffaella Righetti
Keyword(s):  
Finite Element ◽  
Mechanical Behavior ◽  
Imaging Modality ◽  
Fluid Pressure ◽  
Element Model ◽  
Ultrasound Elastography ◽  
Fe Model ◽  
Solid Stress ◽  
Noninvasive Imaging Modality ◽  
Clinically Significant

Ultrasound elastography is a noninvasive imaging modality used to assess the mechanical behavior of tissues, including cancers. Analytical and finite element (FE) models are useful and effective tools to understand the mechanical behavior of cancers and predict elastographic parameters under different testing conditions. A number of analytical and FE models to describe the mechanical behavior of cancers in elastography have been reported in the literature. However, none of these models consider the presence of solid stress (SS) inside the cancer, a clinically significant mechanical parameter with an influential role in cancer initiation, progression, and metastasis. In this paper, we develop an FE model applicable to cancers, which include both SS and elevated interstitial fluid pressure (IFP). This model is then used to assess the effects of these mechanical parameters on the normal strains and the fluid pressure, estimated using ultrasound poroelastography. Our results indicate that SS creates space-dependent changes in the strains and fluid pressure inside the tumor. This is in contrast to the effects produced by IFP on the strains and fluid pressure, which are uniformly distributed across the cancer. The developed model can help elucidating the role of SS on elastographic parameters and images. It may also provide a means to indirectly obtain information about the SS from the observed changes in the experimental elastographic images.

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.

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.

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.

BLOOD FLOW IN CORONARY ARTERY BIFURCATION CALCULATED BY TURBULENT FINITE ELEMENT MODEL

2021 ◽  
Author(s):  
Aleksandar Nikolić ◽  
◽  
Marko Topalović ◽  
Milan Blagojević ◽  
Vladimir Simić
Keyword(s):  
Finite Element ◽  
Blood Flow ◽  
Kinetic Energy ◽  
Finite Element Model ◽  
Fluid Velocity ◽  
Fluid Pressure ◽  
Element Model ◽  
Viscous Sublayer ◽  
Flow Problems ◽  
Analysis Of Results

Simulation of blood flow in this paper is analyzed using two-equation turbulent finite element model that can calculate values in the viscous sublayer. Implicit integration of the equations is used for determining the fluid velocity, fluid pressure, turbulence, kinetic energy, and dissipation of turbulent kinetic energy. These values are calculated in the finite element nodes for each step of incremental- iterative procedure. Developed turbulent finite element model, with the customized generation of finite element meshes, is used for calculating complex blood flow problems. Analysis of results showed that a cardiologist can use proposed tools and methods for investigating the hemodynamic conditions inside bifurcation of arteries.

scholarly journals Development and analytical validation of a finite element model of fluid transport through osteochondral tissue

2020 ◽  
Author(s):  
Brady D. Hislop ◽  
Chelsea M. Heveran ◽  
Ronald K. June
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Fluid Transport ◽  
Fluid Pressure ◽  
Viscoelastic Model ◽  
Element Model ◽  
Pressure Gradients ◽  
Superficial Zone ◽  
Bone Interface ◽  
Osteochondral Tissue

AbstractFluid transport between cartilage and bone is critical to joint health. The objective of this study was to develop and analytically validate a finite element model of osteochondral tissue capable of modeling cartilage-bone fluid transport. A biphasic viscoelastic model using an ellipsoidal fiber distribution was created with three distinct layers of cartilage (superficial zone, middle zone, and deep zone) along with a layer of subchondral bone. For stress-relaxation in unconfined compression, our results for compressive stress, radial stress, effective fluid pressure, and elastic recoil were compared with established biphasic analytical solutions. Our model also shows the development of fluid pressure gradients at the cartilage-bone interface during loading. Fluid pressure gradients developed at the cartilage-bone interface with consistently higher pressures in cartilage following initial loading to 10% strain, followed by convergence towards equal pressures in cartilage and bone during the 400s relaxation period. These results provide additional evidence that fluid is transported between cartilage and bone during loading and improves upon estimates of the magnitude of this effect through incorporating a realistic distribution and estimate of the collagen ultrastructure. Understanding fluid transport between cartilage and bone may be key to new insights about the mechanical and biological environment of both tissues in health and disease.

scholarly journals Low Cost Frictional Seismic Base-Isolation of Residential New Masonry Buildings in Developing Countries: A Small Masonry House Case Study

2017 ◽  
Vol 11 (1) ◽  
pp. 1026-1035 ◽  
Author(s):  
Ahmad Basshofi Habieb ◽  
Gabriele Milani ◽  
Tavio Tavio ◽  
Federico Milani
Keyword(s):  
Finite Element ◽  
Seismic Vulnerability ◽  
Base Isolation ◽  
Low Cost ◽  
Element Model ◽  
Shaking Table ◽  
Fe Model ◽  
Isolation System ◽  
Finite Element Software ◽  
Non Linear

Introduction:An advanced Finite Element model is presented to examine the performance of a low-cost friction based-isolation system in reducing the seismic vulnerability of low-class rural housings. This study, which is mainly numerical, adopts as benchmark an experimental investigation on a single story masonry system eventually isolated at the base and tested on a shaking table in India.Methods:Four friction isolation interfaces, namely, marble-marble, marble-high-density polyethylene, marble-rubber sheet, and marble-geosynthetic were involved. Those interfaces differ for the friction coefficient, which was experimentally obtained through the aforementioned research. The FE model adopted here is based on a macroscopic approach for masonry, which is assumed as an isotropic material exhibiting damage and softening. The Concrete damage plasticity (CDP) model, that is available in standard package of ABAQUS finite element software, is used to determine the non-linear behavior of the house under non-linear dynamic excitation.Results and Conclusion:The results of FE analyses show that the utilization of friction isolation systems could much decrease the acceleration response at roof level, with a very good agreement with the experimental data. It is also found that systems with marble-marble and marble-geosynthetic interfaces reduce the roof acceleration up to 50% comparing to the system without isolation. Another interesting result is that there was little damage appearing in systems with frictional isolation during numerical simulations. Meanwhile, a severe state of damage was clearly visible for the system without isolation.

A Biomechanical Model of Lumbar Spine

2000 ◽  
Author(s):  
Subramanya Uppala ◽  
Robert X. Gao ◽  
Scott Cowan ◽  
K. Francis Lee
Keyword(s):  
Finite Element ◽  
Lumbar Spine ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Biomechanical Model ◽  
Element Model ◽  
Fe Model ◽  
Flexion Extension ◽  
Cortical Shell ◽  
Three Dimensional Finite Element

Abstract The strength and stability of the lumbar spine are determined not only by the bone and muscles, but also by the visco-elastic structures and the interplay between the different components of the spine, such as ligaments, capsules, annulus fibrosis, and articular cartilage. In this paper we present a non-linear three-dimensional Finite Element model of the lumbar spine. Specifically, a three-dimensional FE model of the L4-5 one-motion segment/2 vertebrae was developed. The cortical shell and the cancellous bone of the vertebral body were modeled as 3D isoparametric eight-nodal elements. Finite element models of spinal injuries with fixation devices are also developed. The deformations across the different sections of the spine are observed under the application of axial compression, flexion/extension, and lateral bending. The developed FE models provided input to both the fixture design and experimental studies.

scholarly journals A robust 3D finite element model for concrete columns confined by FRCM system

2019 ◽  
Vol 281 ◽  
pp. 01006 ◽  
Author(s):  
Majid M.A. Kadhim ◽  
Mohammed J Altaee ◽  
Ali Hadi Adheem ◽  
Akram R. Jawdhari
Keyword(s):  
Finite Element ◽  
Cement Mortar ◽  
Three Dimensional ◽  
Concrete Columns ◽  
Element Model ◽  
Fe Model ◽  
3D Finite Element ◽  
Composite Failure ◽  
Global Buckling ◽  
Fibre Reinforced Polymer

Fibre reinforced cementitious matric (FRCM) is a recent application of fibre reinforced polymer (FRP) reinforcement, developed to overcome several limitations associated with the use of organic adhesive [e.g. epoxies] in FRPs. It consists of two dimensional FRP mesh saturated with a cement mortar, which is inorganic in nature and compatible with concrete and masonry substrates. In this study, a robust three-dimensional (3D) finite element (FE) model has been developed to study the behaviour of slender reinforced concrete columns confined by FRCM jackets, and loaded concentrically and eccentrically. The model accounts for material nonlinearities in column core and cement mortar, composite failure of FRP mesh, and global buckling. The model response was validated against several laboratory tests from literature, comparing the ultimate load, load-lateral deflection and failure mode. Maximum divergence between numerical and experimental results was 12%. Following the validation, the model will be used later in a comprehensive parametric analysis to gain a profound knowledge of the strengthening system, and examine the effects of several factors expected to influence the behaviour of confined member.

A finite element model to study the effect of porosity location on the elastic modulus of a cantilever beam

2019 ◽  
Vol 43 (4) ◽  
pp. 443-453
Author(s):  
Stephen M. Handrigan ◽  
Sam Nakhla
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Focused Ion Beam ◽  
Mechanical Response ◽  
Ion Beam ◽  
Three Dimensional ◽  
Beam Theory ◽  
Element Model ◽  
Fe Model ◽  
Three Dimensional Finite Element

An investigation to determine the effect of porosity concentration and location on elastic modulus is performed. Due to advancements in testing methods, the manufacturing and testing of microbeams to obtain mechanical response is possible through the use of focused ion beam technology. Meanwhile, rigorous analysis is required to enable accurate extraction of the elastic modulus from test data. First, a one-dimensional investigation with beam theory, Euler–Bernoulli and Timoshenko, was performed to estimate the modulus based on load-deflection curve. Second, a three-dimensional finite element (FE) model in Abaqus was developed to identify the effect of porosity concentration. Furthermore, the current work provided an accurate procedure to enable accurate extraction of the elastic modulus from load-deflection data. The use of macromodels such as beam theory and three-dimensional FE model enabled enhanced understanding of the effect of porosity on modulus.

Thermo-mechanical analysis of train wheel-rail contact using a novel finite-element model

2020 ◽  
Vol 72 (5) ◽  
pp. 687-693
Author(s):  
Liuqing Yang ◽  
Ming Hu ◽  
Deming Zhao ◽  
Jing Yang ◽  
Xun Zhou
Keyword(s):  
Finite Element ◽  
Peer Review ◽  
Frictional Heating ◽  
Element Model ◽  
Mechanical Analysis ◽  
Partial Slip ◽  
Computational Time ◽  
Fe Model ◽  
Content Type ◽  
Explicit Finite Element

Purpose The purpose of this paper is to develop a novel method for analyzing wheel-rail (W-R) contact using thermo-mechanical measurements and study the effects of heating on the characteristics of W-R contact under different creepages. Design/methodology/approach This study developed an implicit-explicit finite element (FE) model which could solve both partial slip and full sliding problems by setting different angular velocities on the wheels. Based on the model, four material types under six different creepages were simulated. Findings The results showed that frictional heating significantly affected the residual stress distribution under large creepage conditions. As creepage increased, the temperature of the wheel tread and rail head rose and the peak value was located at the trailing edge of the contact patch. Originality/value The proposed FE model could reduce computational time and thus cost to about one-third of the amount commonly found in previous literature. Compared to other studies, these results are in good agreement and offer a reasonable alternative method for analyzing W-R contact under various conditions. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2019-0298

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