Modeling Material-Degradation-Induced Elastic Property of Tissue Engineering Scaffolds

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
N. K. Bawolin ◽  
M. G. Li ◽  
X. B. Chen ◽  
W. J. Zhang
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Molecular Weight ◽  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Element Model ◽  
Time Dependent ◽  
Tissue Engineering Scaffolds ◽  
The Finite Element Model

The mechanical properties of tissue engineering scaffolds play a critical role in the success of repairing damaged tissues/organs. Determining the mechanical properties has proven to be a challenging task as these properties are not constant but depend upon time as the scaffold degrades. In this study, the modeling of the time-dependent mechanical properties of a scaffold is performed based on the concept of finite element model updating. This modeling approach contains three steps: (1) development of a finite element model for the effective mechanical properties of the scaffold, (2) parametrizing the finite element model by selecting parameters associated with the scaffold microstructure and/or material properties, which vary with scaffold degradation, and (3) identifying selected parameters as functions of time based on measurements from the tests on the scaffold mechanical properties as they degrade. To validate the developed model, scaffolds were made from the biocompatible polymer polycaprolactone (PCL) mixed with hydroxylapatite (HA) nanoparticles and their mechanical properties were examined in terms of the Young modulus. Based on the bulk degradation exhibited by the PCL/HA scaffold, the molecular weight was selected for model updating. With the identified molecular weight, the finite element model developed was effective for predicting the time-dependent mechanical properties of PCL/HA scaffolds during degradation.

scholarly journals Sensitivity Analysis of the Influence of Structural Parameters on Dynamic Behaviour of Highly Redundant Cable-Stayed Bridges

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
B. Asgari ◽  
S. A. Osman ◽  
A. Adnan
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Structural Parameters ◽  
Element Model ◽  
Structural Behavior ◽  
Model Tuning ◽  
The Finite Element Model ◽  
Cable Stayed Bridges

The model tuning through sensitivity analysis is a prominent procedure to assess the structural behavior and dynamic characteristics of cable-stayed bridges. Most of the previous sensitivity-based model tuning methods are automatic iterative processes; however, the results of recent studies show that the most reasonable results are achievable by applying the manual methods to update the analytical model of cable-stayed bridges. This paper presents a model updating algorithm for highly redundant cable-stayed bridges that can be used as an iterative manual procedure. The updating parameters are selected through the sensitivity analysis which helps to better understand the structural behavior of the bridge. The finite element model of Tatara Bridge is considered for the numerical studies. The results of the simulations indicate the efficiency and applicability of the presented manual tuning method for updating the finite element model of cable-stayed bridges. The new aspects regarding effective material and structural parameters and model tuning procedure presented in this paper will be useful for analyzing and model updating of cable-stayed bridges.

scholarly journals Vibration-based Bayesian model updating of civil engineering structures applying Gaussian process metamodel

2019 ◽  
Vol 22 (16) ◽  
pp. 3487-3502
Author(s):  
Hossein Moravej ◽  
Tommy HT Chan ◽  
Khac-Duy Nguyen ◽  
Andre Jesus
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Bayesian Approach ◽  
Model Updating ◽  
Numerical Models ◽  
Element Model ◽  
The Body ◽  
Structural Safety ◽  
Discrepancy Function ◽  
The Finite Element Model

Structural health monitoring plays a significant role in providing information regarding the performance of structures throughout their life spans. However, information that is directly extracted from monitored data is usually susceptible to uncertainties and not reliable enough to be used for structural investigations. Finite element model updating is an accredited framework that reliably identifies structural behavior. Recently, the modular Bayesian approach has emerged as a probabilistic technique in calibrating the finite element model of structures and comprehensively addressing uncertainties. However, few studies have investigated its performance on real structures. In this article, modular Bayesian approach is applied to calibrate the finite element model of a lab-scaled concrete box girder bridge. This study is the first to use the modular Bayesian approach to update the initial finite element model of a real structure for two states—undamaged and damaged conditions—in which the damaged state represents changes in structural parameters as a result of aging or overloading. The application of the modular Bayesian approach in the two states provides an opportunity to examine the performance of the approach with observed evidence. A discrepancy function is used to identify the deviation between the outputs of the experimental and numerical models. To alleviate computational burden, the numerical model and the model discrepancy function are replaced by Gaussian processes. Results indicate a significant reduction in the stiffness of concrete in the damaged state, which is identical to cracks observed on the body of the structure. The discrepancy function reaches satisfying ranges in both states, which implies that the properties of the structure are predicted accurately. Consequently, the proposed methodology contributes to a more reliable judgment about structural safety.

Correlating Finite Element Model of a Car Spot-welded Front-End Module in the Light of Modal Testing Data

2020 ◽  
Vol 17 (2) ◽  
pp. 7974-7984
Author(s):  
W.I.I. Wan Iskandar Mirza ◽  
M.N. Abdul Rani ◽  
M.A. Yunus ◽  
B. Athikary ◽  
M.S.M. Sani
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Element Model ◽  
Modal Testing ◽  
Front End ◽  
Welded Structure ◽  
Front End Module ◽  
The Finite Element Model ◽  
Spot Welded

Model updating methods can be adopted to improve the correlation level between the finite element model of a spot welded structure and its test model. However, in the presence of contact interfaces in the vicinity of the welded areas, improving the correlation level is problematic and challenging. An approach for correlating the finite element model of a welded structure with contact interfaces using finite element model updating and modal testing is proposed. The proposed approach was tested on a car front-end module structure that consisted of nine components and 76 resistance spot-welded joints used to assemble the components. CWELD and CELAS1 element connectors were used to represent the spot-welded joints and contact interfaces in the finite element modelling and updating. This approach was applied successfully to predict the modal parameters of the car spot-welded front-end module. The total error of the initial finite element model of the structure was reduced from 27.13% to 5.75%. The findings of this work suggest that the proposed approach has a great potential for use in investigating the dynamic behaviour of various spot-welded structures without a significant decline in accuracy.

Computational Analysis of Microstructure of Ultra High Molecular Weight Polyethylene for Total Joint Replacement

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Kelly M. Seymour ◽  
Sara A. Atwood
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Finite Element ◽  
Finite Element Model ◽  
High Molecular Weight ◽  
Element Model ◽  
Experimental Results ◽  
Linear Elastic ◽  
Ultra High Molecular Weight ◽  
Scanning Electron

Ultra high molecular weight polyethylene (UHMWPE, or ultra high), a frequently used material in orthopedic joint replacements, is often the cause of joint failure due to wear, fatigue, or fracture. These mechanical failures have been related to ultra high's strength and stiffness, and ultimately to the underlying microstructure, in previous experimental studies. Ultra high's semicrystalline microstructure consists of about 50% crystalline lamellae and 50% amorphous regions. Through common processing treatments, lamellar percentage and size can be altered, producing a range of mechanical responses. However, in the orthopedic field the basic material properties of the two microstructural phases are not typically studied independently, and their manipulation is not computationally optimized to produce desired mechanical properties. Therefore, the purpose of this study is to: (1) develop a 2D linear elastic finite element model of actual ultra high microstructure and fit the mechanical properties of the microstructural phases to experimental data and (2) systematically alter the dimensions of lamellae in the model to begin to explore optimizing the bulk stiffness while decreasing localized stress. The results show that a 2D finite element model can be built from a scanning electron micrograph of real ultra high lamellar microstructure, and that linear elastic constants can be fit to experimental results from those same ultra high formulations. Upon altering idealized lamellae dimensions, we found that bulk stiffness decreases as the width and length of lamellae increase. We also found that maximum localized Von Mises stress increases as the width of the lamellae decrease and as the length and aspect ratio of the lamellae increase. Our approach of combining finite element modeling based on scanning electron micrographs with experimental results from those same ultra high formulations and then using the models to computationally alter microstructural dimensions and properties could advance our understanding of how microstructure affects bulk mechanical properties. This advanced understanding could allow for the engineering of next-generation ultra high microstructures to optimize mechanical behavior and increase device longevity.

Simulating the Mechanical Properties of a Yarn Based on the Properties and Arrangement of its Fibers Part I: The Finite Element Model

1997 ◽  
Vol 67 (4) ◽  
pp. 263-268 ◽  
Author(s):  
Lieva Van Langenhove
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Theoretical Model ◽  
Finite Elements ◽  
Finite Element Model ◽  
Tensile Strain ◽  
Virtual Work ◽  
Element Model ◽  
Dynamic Relaxation ◽  
The Finite Element Model

A theoretical model is established to predict stress-strain and torque-tensile strain curves of a yarn. The yarn is described by its properties and the arrangement of its fibers, which have a finite length. The yarn is transformed into finite elements. Equilibrium is expressed by virtual work, and is calculated iteratively using the dynamic relaxation technique. The principles of the model, its potential, limitations, and possible improvements are discussed.

Investigation of the Mechanical Properties of a Stitched Triaxial Fabric

2014 ◽  
Vol 611-612 ◽  
pp. 332-338 ◽  
Author(s):  
Cynthia J. Mitchell ◽  
James A. Sherwood ◽  
Lisa M. Dangora ◽  
Jennifer L. Gorczyca
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Material Behavior ◽  
Composite Forming ◽  
Experimental Deformation ◽  
Shear Frame ◽  
The Finite Element Model ◽  
The Ideal

A traxial fabric was investigated for use in composite forming applications. Three stitched layers of fibers, originally oriented at [-60o/0o/60o], comprise the fabric architecture. The mechanical properties of the material are characterized by testing the tensile, shear, and frictional behavior. Conventional shear frame testing methodology assumes that the yarns are originally oriented perpendicular to one another; however, such an assumption is not valid for this particular fabric geometry and must be adjusted. The material behavior is implemented into a discrete mesoscopic finite element model that can predict the response of the material during deformation. Different element types will be investigated to represent the fabric and used to determine the ideal mesh configuration that best captures the fabric behavior. Different modes of deformation will also be studied, and the observed experimental deformation will be compared to the deformation predicted by the finite element model.

Dynamic Test and Analysis of Concrete Filled Steel Tube Arch Bridge

2010 ◽  
Vol 163-167 ◽  
pp. 2843-2847
Author(s):  
Li Xian Wang ◽  
Sheng Kui Di
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Yellow River ◽  
Dynamic Properties ◽  
Dynamic Test ◽  
Element Model ◽  
Steel Tube ◽  
Acceleration Signal ◽  
The Finite Element Model

Based on random vibration theory, virtual response is obtained from the measured acceleration signal of Yantan Yellow River Bridge of Lanzhou under ambient excitation, Yantan Yellow River bridge's modal parameters were identified by using the peak picking and stochastic subspace identification, analyzed from theoretical and experimental aspects, compared with the finite element model results and verified the reliability of recognition results. The identified dynamic properties can be served as the basis in the finite element model updating, damage detection, condition assessment and health monitoring of the bridge.

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