scholarly journals A Comparative Study of Continuum and Structural Modelling Approaches to Simulate Bone Adaptation in the Pelvic Construct

2019 ◽  
Vol 9 (16) ◽  
pp. 3320 ◽  
Author(s):  
Dan T. Zaharie ◽  
Andrew T.M. Phillips
Keyword(s):  
Structural Model ◽  
Bone Adaptation ◽  
Bone Architecture ◽  
Fe Model ◽  
Structural Modelling ◽  
Imaging Data ◽  
Modelling Framework ◽  
Sit To Stand ◽  
Iterative Adaptation ◽  
Modelling Approaches

This study presents the development of a number of finite element (FE) models of the pelvis using different continuum and structural modelling approaches. Four FE models were developed using different modelling approaches: continuum isotropic, continuum orthotropic, hybrid isotropic and hybrid orthotropic. The models were subjected to an iterative adaptation process based on the Mechanostat principle. Each model was adapted to a number of common daily living activities (walking, stair ascent, stair descent, sit-to-stand and stand-to-sit) by applying onto it joint and muscle loads derived using a musculoskeletal modelling framework. The resulting models, along with a structural model previously developed by the authors, were compared visually in terms of bone architecture, and their response to a single load case was compared to a continuum FE model derived from computed tomography (CT) imaging data. The main findings of this study were that the continuum orthotropic model was the closest to the CT derived model in terms of load response albeit having less total bone volume, suggesting that the role of material directionality in influencing the maximum orthotropic Young’s modulus should be included in continuum bone adaptation models. In addition, the hybrid models, where trabecular and cortical bone were distinguished, had similar outcomes, suggesting that the approach to modelling trabecular bone is less influential when the cortex is modelled separately.

scholarly journals A Comparative Study of Continuum and Structural Modelling Approaches to Simulate Bone Adaptation in the Pelvic Construct

2019 ◽  
Author(s):  
Dan Tudor Zaharie ◽  
Andrew T.M. Phillips
Keyword(s):  
Structural Model ◽  
Bone Adaptation ◽  
Bone Architecture ◽  
Fe Model ◽  
Structural Modelling ◽  
Imaging Data ◽  
Modelling Framework ◽  
Sit To Stand ◽  
Iterative Adaptation ◽  
Modelling Approaches

This study presents the development of a number of finite element (FE) models of the pelvis using different continuum and structural modelling approaches. Four FE models were developed using different modelling approaches: continuum isotropic, continuum orthotropic, hybrid isotropic and hybrid orthotropic. The models were subjected to an iterative adaptation process based on the Mechanostat principle. Each model was adapted to a number of common daily living activities (walking, stair ascent, stair descent, sit-to-stand and stand-to-sit) by applying onto it joint and muscle loads derived using a musculoskeletal modelling framework. The resulting models, along with a structural model previously developed by the authors, were compared visually in terms of bone architecture, and their response to a single load case was compared to a continuum FE model derived from CT imaging data. The main findings of this study were that the continuum orthotropic model was the closest to the CT derived model in terms of load response albeit having less total bone volume, suggesting that the role of material directionality in influencing the maximum orthotropic Young's modulus should be included in continuum bone adaptation models. In addition, the hybrid models, where trabecular and cortical bone were distinguished, had similar outcomes, suggesting that the approach to modelling trabecular bone is less influential when the cortex is modelled separately.

scholarly journals Pelvic Construct Prediction of Trabecular and Cortical Bone Structural Architecture

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Dan T. Zaharie ◽  
Andrew T. M. Phillips
Keyword(s):  
Cortical Bone ◽  
Structural Model ◽  
Thickness Distribution ◽  
Bone Adaptation ◽  
The Body ◽  
Lower Limbs ◽  
Fe Model ◽  
Adaptation Algorithm ◽  
Modeling Framework ◽  
Good Agreement

The pelvic construct is an important part of the body as it facilitates the transfer of upper body weight to the lower limbs and protects a number of organs and vessels in the lower abdomen. In addition, the importance of the pelvis is highlighted by the high mortality rates associated with pelvic trauma. This study presents a mesoscale structural model of the pelvic construct and the joints and ligaments associated with it. Shell elements were used to model cortical bone, while truss elements were used to model trabecular bone and the ligaments and joints. The finite element (FE) model was subjected to an iterative optimization process based on a strain-driven bone adaptation algorithm. The bone model was adapted to a number of common daily living activities (walking, stair ascent, stair descent, sit-to-stand, and stand-to-sit) by applying onto it joint and muscle loads derived using a musculoskeletal modeling framework. The cortical thickness distribution and the trabecular architecture of the adapted model were compared qualitatively with computed tomography (CT) scans and models developed in previous studies, showing good agreement. The sensitivity of the model to changes in material properties of the ligaments and joint cartilage and changes in parameters related to the adaptation algorithm was assessed. Changes to the target strain had the largest effect on predicted total bone volumes. The model showed low sensitivity to changes in all other parameters. The minimum and maximum principal strains predicted by the structural model compared to a continuum CT-derived model in response to a common test loading scenario showed good agreement with correlation coefficients of 0.813 and 0.809, respectively. The developed structural model enables a number of applications such as fracture modeling, design, and additive manufacturing of frangible surrogates.

scholarly journals Macro-Modelling of Laser Micro-Joints for Understanding Joint Strength in Electric Vehicle Battery Interconnects

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3552
Author(s):  
Abhishek Das ◽  
Richard Beaumont ◽  
Iain Masters ◽  
Paul Haney
Keyword(s):  
Joint Strength ◽  
Structural Model ◽  
Design Stage ◽  
Structural Modelling ◽  
Laser Weld ◽  
Computationally Efficient ◽  
Early Design Stage ◽  
Lap Shear ◽  
Battery Module ◽  
Modelling Approach

Laser micro-welding is increasingly being used to produce electrically conductive joints within a battery module of an automotive battery pack. To understand the joint strength of these laser welds at an early design stage, micro-joints are required to be modelled. Additionally, structural modelling of the battery module along with the electrical interconnects is important for understanding the crash safety of electric vehicles. Fusion zone based micro-modelling of laser welding is not a suitable approach for structural modelling due to the computational inefficiency and the difficulty of integrating with the module model. Instead, a macro-model which computationally efficient and easy to integrate with the structural model can be useful to replicate the behaviour of the laser weld. A macro-modelling approach was adopted in this paper to model the mechanical behaviour of laser micro-weld. The simulations were based on 5 mm diameter circular laser weld and developed from the experimental data for both the lap shear and T-peel tests. This modelling approach was extended to obtain the joint strengths for 3 mm diameter circular seams, 5 mm and 10 mm linear seams. The predicted load–displacement curves showed a close agreement with the test data.

A Sensitivity-Enhancing Control Approach for Structural Model Updating

2007 ◽  
Author(s):  
L. J. Jiang ◽  
K. W. Wang ◽  
J. Tang
Keyword(s):  
Closed Loop ◽  
Structural Model ◽  
Natural Frequencies ◽  
Model Updating ◽  
Measurement Data ◽  
Frequency Measurement ◽  
Physical Parameters ◽  
Fe Model ◽  
Initial Model ◽  
Closed Loop Systems

Model updating plays an important role in structural design and dynamic analysis. The process of model updating aims to produce an improved mathematical model by correlating the initial model with the experimentally measured data. There are a variety of techniques available for model updating using dynamic and static measurements of the structure’s behavior. This paper focuses on the model updating methods using the measured natural frequencies of the structure. The practice of model updating using only the natural frequencies encounters two well-known limitations: deficiency of frequency measurement data, and low sensitivity of measured natural frequencies with respect to the physical parameters that need to be updated. To overcome these limitations, a novel model updating method is presented in this paper. First, closed-loop control is applied to the structure to enhance the sensitivity of natural frequencies to the updating parameters. Second, by including the natural frequencies based on a series of sensitivity-enhanced closed-loop systems, we can significantly enrich the frequency measurement data available for model updating. Using the natural frequencies of these sensitivity-enhanced closed-loop systems, an iterative process is utilized to update the physical parameters in the initial model. To demonstrate and verify the proposed method, case studies are carried out using a cantilevered beam structure. The natural frequencies of a series of sensitivity-enhanced closed-loop systems are utilized to update the mass and stiffness parameters in the initial FE model. Results show that the modeling errors in the mass and stiffness parameters can be accurately identified by using the proposed model updating method.

scholarly journals Vibration Tests and Structural Identification of the Bell Tower of Palermo Cathedral

2019 ◽  
Vol 13 (1) ◽  
pp. 319-330 ◽  
Author(s):  
Liborio Cavaleri ◽  
Marco Filippo Ferrotto ◽  
Fabio Di Trapani ◽  
Alessandro Vicentini
Keyword(s):  
Finite Element ◽  
Structural Model ◽  
High Sensitivity ◽  
Fe Model ◽  
Actual Behavior ◽  
Dynamic Identification ◽  
Safety Level ◽  
Bell Tower ◽  
Structural Capacity ◽  
Vibration Tests

Background: The recent seismic events in Italy have underlined once more the need for seismic prevention for historic constructions of architectural interest and in general, the building heritage. During the above-mentioned earthquakes, different masonry monumental buildings have been lost due to the intrinsic vulnerability and ageing that reduced the structural member strength. This has made the community understand more that prevention is a necessary choice for the protection of monuments. Objective: The paper aims at demonstrating a strategy of investigation providing the possibility of health judgment, identifying a computational model for the assessment of structural capacity under service and exceptional loading like/due to high-intensity earthquakes. Considering its cost, the proposed approach is applicable only for monumental buildings. In detail, activity regarding the Bell Tower of the Palermo Cathedral is described. This investigation is framed in a huge campaign aimed at assessing the health of monuments in Palermo and their capacity to resist expected seismic actions. Methods: The process of the dynamic identification of the Bell Tower of Palermo Cathedral is discussed starting from the measurement of the response by high sensitivity seismometers and the analysis of the response signals. Then, the formulation of a Finite Element (FE) model of the tower is proposed after the identification of the main modal shapes. Once the Finite Element (FE) model was assessed, it was possible to evaluate the Bell Tower safety level in service and faced with exceptional loads. Results: The structural signals recorded along the height of the tower were analyzed to recognize the variation of the frequency content varying the external environmental loads. The signals were processed to obtain the experimental modal shapes. An FE model was defined whose mechanical parameters were successfully calibrated to give the experimental modal shapes. Conclusion: The analysis of the response signals made it possible to identify the actual behavior of the structure and its compatibility with the service loads. Further, an effective structural model of the Bell Tower of Palermo Cathedral was possible for assessing its capacity level.

scholarly journals Continuum microhaemodynamics modelling using inverse rheology

2021 ◽  
Author(s):  
Joseph van Batenburg-Sherwood ◽  
Stavroula Balabani
Keyword(s):  
A Priori ◽  
Critical Role ◽  
Particle Image Velocimetry Data ◽  
Rheological Parameters ◽  
Complex Nature ◽  
Imaging Data ◽  
Concentration Data ◽  
Data Set ◽  
Measured Velocity ◽  
Modelling Framework

AbstractModelling blood flow in microvascular networks is challenging due to the complex nature of haemorheology. Zero- and one-dimensional approaches cannot reproduce local haemodynamics, and models that consider individual red blood cells (RBCs) are prohibitively computationally expensive. Continuum approaches could provide an efficient solution, but dependence on a large parameter space and scarcity of experimental data for validation has limited their application. We describe a method to assimilate experimental RBC velocity and concentration data into a continuum numerical modelling framework. Imaging data of RBCs were acquired in a sequentially bifurcating microchannel for various flow conditions. RBC concentration distributions were evaluated and mapped into computational fluid dynamics simulations with rheology prescribed by the Quemada model. Predicted velocities were compared to particle image velocimetry data. A subset of cases was used for parameter optimisation, and the resulting model was applied to a wider data set to evaluate model efficacy. The pre-optimised model reduced errors in predicted velocity by 60% compared to assuming a Newtonian fluid, and optimisation further reduced errors by 40%. Asymmetry of RBC velocity and concentration profiles was demonstrated to play a critical role. Excluding asymmetry in the RBC concentration doubled the error, but excluding spatial distributions of shear rate had little effect. This study demonstrates that a continuum model with optimised rheological parameters can reproduce measured velocity if RBC concentration distributions are known a priori. Developing this approach for RBC transport with more network configurations has the potential to provide an efficient approach for modelling network-scale haemodynamics.

Multi-Level Design of Tubular Joints

2018 ◽  
Author(s):  
Søren F. Ø. Jensen ◽  
Lars Vabbersgaard Andersen ◽  
Ronnie R. Pedersen ◽  
Martin Bjerre Nielsen
Keyword(s):  
Structural Model ◽  
Three Dimensional ◽  
Alternative Methods ◽  
Fe Model ◽  
Solid Models ◽  
Interpolation Procedure ◽  
Actual Geometry ◽  
External Loads ◽  
Consistent Application ◽  
General Method

In offshore jacket design, it has long been recognized that an accurate global structural model requires implementation of the effects of local joint flexibility (LJF). However, there is still no general method for implementing these effects accurately and efficiently without complicating the application of loads. The literature describes several techniques for determining LJFs using parametric formulas and implementing these in global models of a jacket structure. These techniques are simple but associated with uncertainties and a risk of compromising the accuracy of the global model. Alternative methods, such as the use of superelements, provide very accurate results but complicate the consistent application of external loads as well as postprocessing. This paper introduces a new methodology which is called the Correction Matrix Methodology. This allows the effects of LJF from detailed three-dimensional (3D) finite-element (FE) shell or solid models to be incorporated in a global beam FE model via a simple correction matrix. The effectiveness of the methodology is improved by using interpolation between a limited number of correction matrices. The new methodology provides exact results when correction matrices associated with the actual geometry are applied. When using the interpolation procedure, the methodology provides accurate results and computational efficiency when the database has been established. The Correction Matrix Methodology is a significant improvement of the conventional methods for modelling LJF and is currently being implemented in a general form for arbitrary joints in Rambolls Offshore Structural Analysis Program (ROSAP).

A Novel Mechanical Bioreactor System Allowing Simultaneous Strain and Fluid Shear Stress on Cell Monolayers

2011 ◽  
Author(s):  
W. Scott Van Dyke ◽  
Eric Nauman ◽  
Ozan Akkus
Keyword(s):  
Shear Stress ◽  
Fluid Flow ◽  
Fluid Shear Stress ◽  
Compressive Strain ◽  
Bone Adaptation ◽  
Bone Architecture ◽  
Mechanical Stimuli ◽  
Interstitial Fluid Flow ◽  
Loading Mode

The causes, mechanisms, and biology of bone adaptation have been under intense investigation ever since Julius Wolff proposed that bone architecture is determined by mathematical laws as a result of mechanical loading. How bone responds to mechanical loads by converting the mechanical signals into chemical signals is known as mechanotransduction. The in vivo environment of bone is complex, and most studies of cell-level phenomena have relied on the use of in vitro experiments using mechanical bioreactors. The main types of bioreactors are fluid flow shear stress, tensile and/or compressive strain, and hydrostatic pressure [1–2]. Of these bioreactors, the most intuitive mechanical stimulus for bone would be the tensile and compressive strain bioreactors. However, many researchers now claim that shear stress via interstitial fluid flow in the lacunar-canalicular porosity is the primary mechanosensory stimulus [3]. A handful of studies have attempted to compare the effects of both of these mechanical stimuli on osteoblasts, but these studies are lacking in two respects [4–6]. First, if both fluid flow and strain are performed in the same bioreactor, the magnitude of one loading mode is explicitly determined through constitutive equations, while the other is only estimated. Second, if the magnitudes of the loading modes are able to be explicitly determined they are performed in different bioreactors, providing the cells different extracellular environments. Therefore, a highly controllable dual-loading mode mechanical bioreactor, as described and characterized in this study, is a necessary tool to further understand the mechanotransduction of bone.

scholarly journals Causality in the Social Sciences: a structural modelling framework

2019 ◽  
Vol 53 (5) ◽  
pp. 2575-2588
Author(s):  
Federica Russo ◽  
Guillaume Wunsch ◽  
Michel Mouchart
Keyword(s):  
Social Sciences ◽  
Structural Modelling ◽  
Modelling Framework ◽  
The Social
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