Description and Validation of a Finite Element Model of Backflow During Infusion Into a Brain Tissue Phantom

2012 ◽  
Vol 8 (1) ◽  
Author(s):  
José J. García ◽  
Ana Belly Molano ◽  
Joshua H. Smith
Keyword(s):  
Finite Element ◽  
Hydraulic Conductivity ◽  
Finite Element Model ◽  
Brain Tissue ◽  
Nonlinear Boundary ◽  
Fluid Pressure ◽  
Element Model ◽  
Analytical Models ◽  
External Boundary ◽  
Forward Flow

An axisymmetric biphasic finite element model is proposed to simulate the backflow that develops around the external boundary of the catheter during flow-controlled infusions. The model includes both material and geometric nonlinearities and special treatments for the nonlinear boundary conditions used to represent the forward flow from the catheter tip and the axial backflow that occurs in the annular gap that develops as the porous medium detaches from the catheter. Specifically, a layer of elements with high hydraulic conductivity and low Young’s modulus was used to represent the nonlinear boundary condition for the forward flow, and another layer of elements with axial hydraulic conductivity consistent with Poiseuille flow was used to represent the backflow. Validation of the model was performed by modifying the elastic properties of the latter layer to fit published experimental values for the backflow length and maximum fluid pressure obtained during infusions into agarose gels undertaken with a 0.98-mm-radius catheter. Next, the finite element model predictions showed good agreement with independent experimental data obtained for 0.5-mm-radius and 0.33-mm-radius catheters. Compared to analytical models developed by others, this finite element model predicts a smaller backflow length, a larger fluid pressure, and a substantially larger percentage of forward flow. This latter difference can be explained by the important axial flow in the tissue that is not considered in the analytical models. These results may provide valuable guidelines to optimize protocols during future clinical studies. The model can be extended to describe infusions in brain tissue and in patient-specific geometries.

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.

Biomechanical Comparison of Real World Concussive Impacts in Children, Adolescents, and Adults

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Lauren Dawson ◽  
David Koncan ◽  
Andrew Post ◽  
Roger Zemek ◽  
Michael D. Gilchrist ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Brain Tissue ◽  
Dynamic Models ◽  
Element Model ◽  
Tissue Response ◽  
Model Simulations ◽  
Child Group ◽  
Adolescents And Adults ◽  
The Impact

Abstract Accidental falls occur to people of all ages, with some resulting in concussive injury. At present, it is unknown whether children and adolescents are at a comparable risk of sustaining a concussion compared to adults. This study reconstructed the impact kinematics of concussive falls for children, adolescents, and adults and simulated the associated brain tissue deformations. Patients included in this study were diagnosed with a concussion as defined by the Zurich Consensus guidelines. Eleven child, 10 adolescent, and 11 adult falls were simulated using mathematical dynamic models(MADYMO), with three ellipsoid pedestrian models sized to each age group. Laboratory impact reconstruction was conducted using Hybrid III head forms, with finite element model simulations of the brain tissue response using recorded impact kinematics from the reconstructions. The results of the child group showed lower responses than the adolescent group for impact variables of impact velocity, peak linear acceleration, and peak rotational acceleration but no statistical differences existed for any other groups. Finite element model simulations showed the child group to have lower strain values than both the adolescent and adult groups. There were no statistical differences between the adolescent and adult groups for any variables examined in this study. With the cases included in this study, young children sustained concussive injuries at lower modeled brain strains than adolescents and adults, supporting the theory that children may be more susceptible to concussive impacts than adolescents or adults.

A 3D Biphasic Finite Element Model of the Human Knee Joint for the Study of Tibiofemoral Contact and Fluid Pressurization

2013 ◽  
Author(s):  
Hongqiang Guo ◽  
Suzanne A. Maher ◽  
Robert L. Spilker
Keyword(s):  
Finite Element ◽  
Fluid Flow ◽  
Knee Joint ◽  
Contact Problem ◽  
Finite Element Model ◽  
Soft Tissues ◽  
Fluid Pressure ◽  
Element Model ◽  
Human Knee Joint ◽  
Biphasic Finite Element

Biphasic theory which considers soft tissue, such as articular cartilage and meniscus, as a combination of a solid and a fluid phase has been widely used to model their biomechanical behavior [1]. Though fluid flow plays an important role in the load-carrying ability of soft tissues, most finite element models of the knee joint consider cartilage and the meniscus as solid. This simplification is due to the fact that biphasic contact is complicated to model. Beside the continuity conditions for displacement and traction that a single-phase contact problem consists of, there are two additional continuity conditions in the biphasic contact problem for relative fluid flow and fluid pressure [2]. The problem becomes even more complex when a joint is being modeled. The knee joint, for example, has multiple contact pairs which make the biphasic finite element model of this joint far more complex. Several biphasic models of the knee have been developed [3–9], yet simplifications were included in these models: (1) the 3D geometry of the knee was represented by a 2D axisymmetric geometry [3, 5, 6, 9]; (2) no fluid flow was allowed between contact surfaces of the soft tissues [4, 8] which is inconsistent with the equation of mass conservation across the contact interface [10]; (3) zero fluid pressure boundary conditions were inaccurately applied around the contact area [7].

Minimum bending radius of Al-Li alloy extrusions in stretch bending

2016 ◽  
Vol 232 (2) ◽  
pp. 281-295 ◽  
Author(s):  
Tianjiao Liu ◽  
Yongjun Wang ◽  
Jianjun Wu ◽  
Xiaojiao Xia ◽  
Junbiao Wang ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Shear Failure ◽  
Element Model ◽  
Experimental Results ◽  
Analytical Models ◽  
Bending Test ◽  
Bending Tests ◽  
Stretch Bending ◽  
Bending Radius

In this investigation, the attention is focused on the minimum bending radii of 2196-T8511 and 2099-T83 Al-Li alloy extrusions. To predict the failure of Al-Li alloys, sheet and extrusion stretch bending tests are developed, carried out and simulated using finite element model. The theoretical minimum bending radius is introduced to derive a safe lower limit for the bending radius which can serve as a guideline for tool and product design. Stretch bending tests of Al-Li alloys are performed using the three-point bending test and displacement-controlled stretch bending test at room temperature. The finite element model incorporates three-dimensional solid elements and ductile damage modeling. The experimental results show that Al-Li alloy extrusions in stretch bending show three types of failures, occurring at the unbent region near the entrance of the jaws, at the region below the exit of the die and within the region in contact with the die, respectively. Comparison between predicted values and experimental results has been made, a consistent agreement being achieved, reflecting the reliability of the present model. The three types of failure mechanisms which compete with each other are tensile localization failure, die-corner failure and shear failure, respectively. Based on the analytical models, experiments and simulations, it appears that the three distinct failures need to be applied to predict the minimum bending radius and range of failures that can occur with 2196-T8511 and 2099-T83 Al-Li alloy extrusions in stretch bending.

Analysis on Oil Extraction Progressing Cavity Pump Three-Dimensional Finite Element Model

2014 ◽  
Vol 644-650 ◽  
pp. 670-673
Author(s):  
Guo You Han ◽  
Ming Qi Wang ◽  
Yu Hou ◽  
Qiang Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Fluid Pressure ◽  
Three Dimensional ◽  
Element Model ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Analysis Model ◽  
Element Analysis

The finite element analysis of PCP involves three nonlinear of geometry, material and contact, and the load of PCP is diversity, leading to it difficult to establish the finite element model and calculate by finite method. This article takes GLB120-27 as an example, to establish 3D solid model of PCP by using SolidWorks; to determine M-R model constant of stator rubber by using the data of uniaxial tensile test: to separate the seal band from the stator chamber by using Boolean operation and set up contact pairs, to achieve the correct simulation of stator chamber fluid pressure; to correctly simulate the interference fit between stator and rotor through setting correlation parameters; to establish 3D finite element analysis model and verify the correctness by using the experiment data of hydraulic characteristics of PCP.

Modeling Mismatch Strain Induced Self-Folding of Bilayer Gel Structures

2016 ◽  
Vol 08 (07) ◽  
pp. 1640004 ◽  
Author(s):  
Rui Xiao
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Explicit Expression ◽  
Analytical Model ◽  
Analytical Solutions ◽  
Element Model ◽  
Analytical Models ◽  
Swelling Ratio ◽  
Mismatch Strain ◽  
The Finite Element Model

When exposed to a solvent, a gel bilayer beam can bend due to different swelling abilities of the two layers. In this work, an analytical model is derived to obtain the curvature of the bilayer beam. The model is further linearized to obtain an explicit expression for the curvature. The finite element model is used to verify the above analytical solutions. The results show the curvature predicted by the analytical model is in excellent agreement with the finite element results. The linear model predicts a smaller curvature at large swelling ratio. These results suggest the analytical models can provide a design metric for self-folding 3D structures.

Design Curves for Maximum Stresses in Blocks Containing Pressurized Bore Intersections

1991 ◽  
Vol 113 (4) ◽  
pp. 427-431 ◽  
Author(s):  
J. R. Sorem ◽  
J. R. Shadley ◽  
S. M. Tipton
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Approximation Method ◽  
Fluid Pressure ◽  
Element Model ◽  
Industrial Applications ◽  
Sound Design ◽  
The Finite Element Model ◽  
Maximum Stresses ◽  
Block Dimensions

Intersecting bore geometries are used in a number of industrial applications such as in fluid ends of reciprocating pumps. Maximum tensile stresses at stress concentration points in the block can be many times the fluid pressure in the bores. Obtaining good estimates of the maximum stresses in the structure is necessary for making sound design decisions on the block dimensions. Finite element models of the bore intersection geometry were analyzed for ranges of bore sizes and block dimensions. Results of the finite element model were compared with predictions provided by a popular approximation method based on mechanics of materials principles. The approximation method was found to underpredict the maximum stresses in the block in almost every case analyzed. For some conditions, the maximum stresses computed from the finite element model were more than two times the predictions provided by the approximation method. Design curves, based on the ratio of the sizes of the intersecting bores, are presented for selecting block dimensions to meet desired maximum stress criteria.

Optical Microscopy-Aided Indentation Tests

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
D. A. Doman ◽  
R. Bauer ◽  
A. Warkentin
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Optical Microscopy ◽  
High Speed ◽  
Material Model ◽  
Element Model ◽  
Rolling Contact ◽  
Analytical Models ◽  
Indentation Tests ◽  
The Finite Element Model

The contact characteristics of ceramic-metallic interactions are of critical importance in the design of high-speed ceramic rolling contact bearings. This type of interaction is not described well by traditional indentation tests since small displacements and barely discernable indentations are encountered. In this work, an optical microscopy system is described that is used to measure small indenter displacements accurately. Images of the indenter are taken throughout the test and processed using sophisticated edge detection algorithms to accurately determine the position of the center of the indenter. Thus, the indenter displacements on the order of 1μm can be measured independent of any structural flexibility present in the test apparatus. Experimental indentation tests using an alumina indenter mounted on a stainless steel post were performed and processed with the optical system. The results were compared to existing analytical models for fully elastic and elastoplastic cases as well as a finite element model developed using a Johnson–Cook plasticity material model. The comparison shows that the analytical models do not predict the experimental results well, whereas the finite element model agrees very well. Subsequent analysis of the finite element model shows that the size of the contact zone and pressure distributions, both very important in the design of bearings, can be more accurately described than the traditional analytical treatments.

Finite element analysis of CFRP-externally strengthened reinforced concrete beams subjected to three-point bending

2019 ◽  
Vol 17 (2) ◽  
pp. 183-202
Author(s):  
Sabiha Barour ◽  
Abdesselam Zergua ◽  
Farid Bouziadi ◽  
Waleed Abed Jasim
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Comparative Study ◽  
Finite Element Model ◽  
Element Model ◽  
Analytical Models ◽  
Element Analysis ◽  
Content Type ◽  
Linear Finite Element ◽  
Non Linear

Purpose This paper aims to develop a non-linear finite element model predicting the response of externally strengthened beams under a three-point flexure test. Design/methodology/approach The ANSYS software is used for modeling. SOILD65, LINK180, SHELL181 and SOLID185 elements are used, respectively, to model concrete, steel reinforcement, polymer and steel plate support. A parametric study was carried out. The effects of compressive strength, Young’s modulus, layers number and carbon fiber-reinforced polymer thickness on beam behavior are analyzed. A comparative study between the non-linear finite element and analytical models, including the ACI 440.2 R-08 model, and experimental data is also carried out. Findings A comparative study of the non-linear finite element results with analytical models, including the ACI 440.2 R-08 model and experimental data for different parameters, shows that the strengthened beams possessed better resistance to cracks. In general, the finite element model’s results are in good agreement with the experimental test data. Practical implications This model will predict the strengthened beams behavior and can describe the beams physical conditions, yielding the results that can be interpreted in the structural study context without using a laboratory testing. Originality/value On the basis of the results, a good match is found between the model results and experimental data at all stages of loading the tested samples. Crack models obtained in the non-linear finite element model in the beams are also presented. The submitted finite element model can be used to predict the behavior of the reinforced concrete beam. Also, the comparative study between an analytical model proposed by of current code of ACI 440.2 R-08 and finite element analysis is investigated.

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