A Feature-Based Morphing Methodology for Computationally Modeled Biological Structures Applied to Left Atrial Fiber Directions

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Alessandro Satriano ◽  
Chiara Bellini ◽  
Edward J. Vigmond ◽  
Elena S. Di Martino
Keyword(s):  
Finite Element ◽  
Left Atrium ◽  
3D Model ◽  
Material Model ◽  
Element Model ◽  
Dynamic Simulations ◽  
Tissue Properties ◽  
Biological Structures ◽  
Feature Based ◽  
Parameter Values

To properly simulate the behavior of biological structures through computer modeling, there exists a need to describe parameters that vary locally. These parameters can be obtained either from literature or from experimental data and they are often assigned to regions in the model as lumped values. Furthermore, parameter values may be obtained on a representative case and may not be available for each specific modeled organ. We describe a semiautomated technique to assign detailed maps of local tissue properties to a computational model of a biological structure. We applied the method to the left atrium of the heart. The orientation of myocytes in the tissue as obtained from histologic analysis was transferred to the 3D model of a porcine left atrium. Finite element method (FEM) dynamic simulations were performed by using an isotropic, neo-Hookean, constitutive model first, then adding an anisotropic, cardiomyocyte oriented, Fung-type component. Results showed higher stresses for the anisotropic material model corresponding to lower stretches in the cardiomyocyte directions. The same methodology can be applied to transfer any map of parameters onto a discretized finite element model.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

Prediction of Cutting Force in Bone Cutting Using Finite Element Analysis

2021 ◽  
Author(s):  
Varatharajan Prasannavenkadesan ◽  
Ponnusamy Pandithevan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cutting Force ◽  
Material Model ◽  
Tensile Tests ◽  
Bovine Bone ◽  
Element Analysis ◽  
Cutting Processes ◽  
Parameter Values ◽  
First Time

Abstract In orthopedic surgery, bone cutting is an indispensable procedure followed by the surgeons to treat the fractured and fragmented bones. Because of the unsuitable parameter values used in the cutting processes, micro crack, fragmentation, and thermal osteonecrosis of bone are observed. Therefore, prediction of suitable cutting force is essential to subtract the bone without any adverse effect. In this study, the Cowper-Symonds model for bovine bone was developed for the first time. Then the developed model was coupled with the finite element analysis to predict the cutting force. To determine the model constants, tensile tests with different strain rates (10−5/s, 10−4/s, 10−3/s, and 1/s) were conducted on the cortical bone specimens. The developed material model was implemented in the bone cutting simulation and validated with the experiments.

Using Features to Support Finite Element Idealizations

1994 ◽  
Author(s):  
Padmanabh Dabke ◽  
Vallury Prabhakar ◽  
Sheri Sheppard
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Spatial Reasoning ◽  
Element Model ◽  
Heuristic Knowledge ◽  
Knowledge Based System ◽  
Spatial Properties ◽  
Knowledge Based ◽  
Feature Based ◽  
The Finite Element Model

Abstract This paper describes how feature-based techniques can be used in a knowledge-based system to support finite element idealizations. Any system of this kind must have two important features. First, it must capture the experiential and heuristic knowledge used by expert analysts in making idealization decisions. Second, the system must be able to perform spatial reasoning about the finite element model being analyzed. The first requirement led us to incorporate knowledge-based reasoning in the idealization systems. We chose the formalism of “features” to capture the spatial reasoning because expert analysts often describe the idealization process in terms of removing / modifying features (such as holes, slots, notches, etc.) and their spatial properties.

Mechano-electric finite element model of the left atrium

2018 ◽  
Vol 96 ◽  
pp. 24-31 ◽  
Author(s):  
Alessandro Satriano ◽  
Edward J. Vigmond ◽  
David S. Schwartzman ◽  
Elena S. Di Martino
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Left Atrium ◽  
Element Model

scholarly journals Computer Simulation of Female Urinary Incontinence

2008 ◽  
Vol 2 (2) ◽  
Author(s):  
Yingchun Zhang ◽  
Gerald W. Timm ◽  
Arthur G. Erdman
Keyword(s):  
Finite Element ◽  
Urinary Incontinence ◽  
Finite Element Model ◽  
Element Model ◽  
Physical Activities ◽  
Sample Population ◽  
Force Level ◽  
Female Pelvis ◽  
Tissue Properties ◽  
Mechanical Tissue

Objectives: The purpose of this study is to establish pressure, distension and other parameters involved that produce tissue injury during vigorous physical activities in women, so that superior methods and devices for diagnosing and treating urinary incontinence (UI) can be created. Background: A higher prevalence of daily UI in a female athlete population was found compared to that of a randomly selected and age matched sample population, but the mechanism of UI is not clearly understood. Methods: Mechanical tissue properties of affected organ structures were determined by using specimens from cadavers. A realistic geometric model of the female pelvis was developed from patients’ specific CT images. The finite element model was built by combining the mechanical tissue properties and the geometry of organs involved, and the finite element analysis (FEA) was then performed using ABAQUS 6.7 to simulate the biomechanical response of the female pelvis during physical activities. Results: Tissue specimens from 11 cadavers were tested which included specimens of the bladder, uterus, pelvic muscle, vagina and urethra. A finite element model was built with approximately 500,000 tetrahedral elements. The force level and resulting organ displacements in the female pelvis during physical activities were investigated successfully by using the FEA method. Discussion: The knowledge of force level and organ displacements during physical activities helps to understand the mechanisms of UI occurring during physical activities.

A Comparison Between Three- and Two-Dimensional Thermal Finite Element Analysis of the Gas Metal Arc Welding Process

2003 ◽  
Author(s):  
Mohammad S. Davoud ◽  
Xiaomin Deng
Keyword(s):  
Finite Element ◽  
3D Model ◽  
Gas Metal Arc Welding ◽  
Welding Process ◽  
Element Model ◽  
Transient Temperature ◽  
Two Dimensional ◽  
Element Analysis ◽  
Cross Sectional ◽  
2D Model

Predictions of transient temperature distributions in welding can help the selection of welding process parameters that minimize residual stresses. A three-dimensional (3D) thermal finite element model of bead-on-plate gas metal are welding (GMAW) is presented and is used to evaluate a cross-sectional, two-dimensional (2D) counterpart model. While the thermomechanical problem of welding is 3D in nature, it is shown that the 2D model can provide temperature field predictions comparable to those of the 3D model, even though the 2D model tends to predict peak temperatures higher than those of the 3D model. Both types of model predictions are compared to welding test measurements.

A Virtual Model for Aluminum Hot Forging Using an Artificial Neural Network Material Model Within Finite Element Analysis

2005 ◽  
Author(s):  
B. Scott Kessler ◽  
A. Sherif El-Gizawy
Keyword(s):  
Finite Element ◽  
Effective Means ◽  
Hot Forging ◽  
Material Model ◽  
Element Model ◽  
Operating Conditions ◽  
Element Analysis ◽  
Preliminary Model ◽  
Wide Range ◽  
Artificial Neural

The accuracy of a finite element model for design and analysis of a metal forging operation is limited by the incorporated material model’s ability to predict deformation behavior over a wide range of operating conditions. Current rheological models prove deficient in several respects due to the difficulty in establishing complicated relations between many parameters. More recently, artificial neural networks (ANN) have been suggested as an effective means to overcome these difficulties. In the present work, a previously developed ANN with the ability to determine flow stresses based on strain, strain rate, and temperature is incorporated with finite element code. Utilizing this linked approach, a preliminary model for forging an aluminum wheel is developed. This novel method, along with a conventional approach, is then measured against the forging process as it is currently performed in actual production.

Simulation of the Residual Stresses Generated Due to Cement Polymerization in a THA

2004 ◽  
Author(s):  
Pablo Vasquez ◽  
Natalia Nun˜o
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Total Hip Arthroplasty ◽  
Residual Stresses ◽  
Hip Arthroplasty ◽  
Proximal Femur ◽  
3D Model ◽  
Load Transfer ◽  
Element Model ◽  
Heel Strike

A personalized 3D model of the proximal femur is reconstructed from medical CT-scan images. The mechanical properties of the cortical and spongious bones are extracted from the medical images. A finite element model of a personalized total hip arthroplasty is developed to investigate the effect of residual stresses due to cement curing in the load transfer during simplified heel strike.

FE Modeling of the Three-Layer Human Carotid Artery Under Impact Loadings

2007 ◽  
Author(s):  
Aihong Zhao ◽  
Ken Digges ◽  
Mark Field ◽  
David Richens
Keyword(s):  
Finite Element ◽  
Carotid Artery ◽  
Model Simulation ◽  
Material Model ◽  
Element Model ◽  
Traumatic Rupture ◽  
Aortic Tissue ◽  
Fe Model ◽  
Arbitrary Lagrangian Eulerian ◽  
The Impact

Blunt traumatic rupture of the carotid artery is a rare but life threatening injury. The histology of the artery is key to understanding the aetiology of this injury. The carotid artery is composed of three layers known as the tunica intima, media, and adventitia, with distinct biomechanical properties. In order to examine the behaviour of the carotid artery under external load we have developed a three layer finite element model of this vessel. A rubber-like material model from LS-DYNA was selected for the FE model. The Arbitrary-Lagrangian Eulerian (ALE) approach was adopted to simulate the interaction between the fluid (blood) and the structure (carotid). To verify the FE model, the impact bending tests are simulated using this FE model. Simulation results agree with tests results well. Furthermore, the mechanical behaviour of carotid artery tissues under impact loading were revealed by the simulations. The results provide a basis for a more in-depth investigation of the carotid artery in vehicle crashes. In addition, it provides a basis for further work on aortic tissue finite element modeling.

A Feature-Based Morphing Methodology for Biological Structures Applied to the Spatial Organization of Cardiomyocytes in the Left Atrium

2011 ◽  
Author(s):  
Alessandro Satriano ◽  
Edward J. Vigmond ◽  
Elena S. Di Martino
Keyword(s):  
Spatial Organization ◽  
Experimental Tests ◽  
Smooth Transition ◽  
Patient Specific ◽  
Clinical Environment ◽  
Individual Values ◽  
Tissue Properties ◽  
Biological Structures ◽  
Critical Issues ◽  
Parameter Values

When complex biological structures are modeled, one of the most critical issues is the assignment of geometrical, mechanical and electrical properties to the meshed surfaces. Properties of interest are commonly obtained from diagnostic imaging, experimental tests or anatomical observation. These parameters are usually lumped into individual values assigned to a specific region after subdividing the structure in sub-regions. This practice simplifies the problem avoiding the cumbersome assignment of parameter values to each element. However, sub-regions may not adequately represent the smooth transition between regions thus resulting in artificial discontinuities. In addition, some parameters, such as for example the organization of cardiomyocytes, which is the objective of our research, may be obtained through destructive tests or through sophisticated methods that can only be performed on a limited number of samples. Or else, data structure obtained for one animal species could be applied on a different species. Furthermore, in a clinical environment the need for fast turnout of patient-specific models would benefit from the assignment of tissue properties in a semi-automatic manner.

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