Trabecular Surface Remodeling Simulation for Cancellous Bone Using Microstructural Voxel Finite Element Models

2001 ◽  
Vol 123 (5) ◽  
pp. 403-409 ◽  
Author(s):  
Taiji Adachi ◽  
Ken-ichi Tsubota ◽  
Yoshihiro Tomita ◽  
Scott J. Hollister
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Cancellous Bone ◽  
Applied Load ◽  
Morphological Changes ◽  
Finite Element Models ◽  
Structural Level ◽  
Loading Direction ◽  
Surface Remodeling ◽  
Trabecular Surface

A computational simulation method for three-dimensional trabecular surface remodeling was proposed, using voxel finite element models of cancellous bone, and was applied to the experimental data. In the simulation, the trabecular microstructure was modeled based on digital images, and its morphological changes due to surface movement at the trabecular level were directly expressed by removing/adding the voxel elements from/to the trabecular surface. A remodeling simulation at the single trabecular level under uniaxial compressive loading demonstrated smooth morphological changes even though the trabeculae were modeled with discrete voxel elements. Moreover, the trabecular axis rotated toward the loading direction with increasing stiffness, simulating functional adaptation to the applied load. In the remodeling simulation at the trabecular structural level, a cancellous bone cube was modeled using a digital image obtained by microcomputed tomography (μCT), and was uniaxially compressed. As a result, the apparent stiffness against the applied load increased by remodeling, in which the trabeculae reoriented to the loading direction. In addition, changes in the structural indices of the trabecular architecture coincided qualitatively with previously published experimental observations. Through these studies, it was demonstrated that the newly proposed voxel simulation technique enables us to simulate the trabecular surface remodeling and to compare the results obtained using this technique with the in vivo experimental data in the investigation of the adaptive bone remodeling phenomenon.

Wing-Fuselage Lug Stress Prediction Using Finite Element Method

2013 ◽  
Vol 393 ◽  
pp. 317-322
Author(s):  
Abdul Malik Hussein Abdul Jalil ◽  
Wahyu Kuntjoro
Keyword(s):  
Finite Element ◽  
Load Distribution ◽  
Applied Load ◽  
Maximum Stress ◽  
Finite Element Models ◽  
Finite Element Analyses ◽  
Finite Element Software ◽  
Stress Prediction ◽  
Reaction Forces ◽  
The Individual

This paper describes the methodology to predict the stress level that occurs at the wing-fuselage lugs (joints). The finite element models of the wing, the wing lugs and the fuselage lugs were developed. Finite Element Analyses were performed using NASTRAN finite element software. CQUAD4 and BAR2 elements were used to represent the individual structures of the wing such as the ribs and stringers. The applied load was based on the symmetrical level flight condition. Once the load distribution acting at the wing had been calculated and applied, reaction forces at the nodes representing the wing lugs were obtained and these values applied to the lug models where the maximum stress value acting at the lugs was obtained.

Cemented Wellbore Experiments Reveals That Cement Interface Debonding Modeling Overestimate Potential Leakage Rates

2020 ◽  
Author(s):  
Zachary Speer ◽  
Jarrett Wise ◽  
Runar Nygaard ◽  
Geir Hareland ◽  
Eric Ford ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Models ◽  
Interface Debonding ◽  
Finite Element Models ◽  
Wellbore Integrity ◽  
Cement Interface ◽  
Abandoned Wells ◽  
Numerical Finite Element ◽  
Physical And Chemical

Abstract Leakage pathways may develop in wellbores during construction, production, or during and after plug and abandonment (P&A). These pathways are created due to events and conditions during cementing operations, or because of physical and chemical changes after cementing such as changes in temperature and wellbore pressures, and deterioration of the cement. Common leakage pathways develop inside the cement sheath, or as microannuli along the cement-tubing interface. Numerous evidence exists showing that wellbores leak, but there is no verified method to determine if a well will leak or not. To ensure long term wellbore integrity, leakage risks need to be evaluated for plugged and abandoned wells. To evaluate leakage risks from plugged and abandoned wells, numerical finite element models have been developed and used to investigate leakage scenarios during the life of the well. Currently, little work has been done to verify finite element numerical models with experimental data regarding flowpath size in cement sheaths. The aim of this paper is to model previously published experimental data to determine if the finite element models can accurately predict leakage potentials. Two lengths of cemented annuli were modeled, each with conventional and expanding cement to replicate the Aas et. al. [1] experiments. The numerical results show that the simulated microannuli overestimate flow rate compared to experimental data, indicating that flow path dimensions and/or fluid friction factor does not accurately represent the fluid flow in the experiments.

scholarly journals On the Biomechanics of Cardiac S-Looping in the Chick: Insights From Modeling and Perturbation Studies

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Ashok Ramasubramanian ◽  
Xavier Capaldi ◽  
Sarah A. Bradner ◽  
Lianna Gangi
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
The Body ◽  
Congenital Defects ◽  
Finite Element Models ◽  
Heart Tube ◽  
Dorsal Wall ◽  
Embryonic Developmental Stage ◽  
Cervical Flexure ◽  
Shape Changes

Cardiac looping is an important embryonic developmental stage where the primitive heart tube (HT) twists into a configuration that more closely resembles the mature heart. Improper looping leads to congenital defects. Using the chick embryo as the experimental model, we study cardiac s-looping wherein the primitive ventricle, which lay superior to the atrium, now assumes its definitive position inferior to it. This process results in a heart loop that is no longer planar with the inflow and outflow tracts now lying in adjacent planes. We investigate the biomechanics of s-looping and use modeling to understand the nonlinear and time-variant morphogenetic shape changes. We developed physical and finite element models and validated the models using perturbation studies. The results from experiments and models show how force actuators such as bending of the embryonic dorsal wall (cervical flexure), rotation around the body axis (embryo torsion), and HT growth interact to produce the heart loop. Using model-based and experimental data, we present an improved hypothesis for early cardiac s-looping.

Experimental and Modeling Studies for Understanding Shoe-Floor-Contaminant Friction and Designing for Slip-Resistance

2012 ◽  
Author(s):  
Kurt Beschorner
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Boundary Lubrication ◽  
Viscous Fluids ◽  
Finite Element Models ◽  
Sliding Speed ◽  
Friction Coefficients ◽  
Real Area Of Contact ◽  
Lubrication Regime ◽  
Real Area

Insufficient friction at the shoe-floor interface causes a large number of slip and falling accidents each year. Developing solutions for enhancing shoe-floor-contaminant friction requires understanding the mechanisms that contribute to slippery surfaces. Over the past several years, our research group has conducted several experimental and modeling studies to reveal the critical tribological mechanisms contributing to shoe-floor-contaminant friction. This extended abstract will discuss the findings of these studies to: 1) determine the lubrication regime(s) that is/are most relevant to under-shoe conditions during slipping; 2) quantify how under-shoe conditions, shoes and flooring affect the two main contributions to boundary lubrication: adhesion and hysteresis; and 3) describe how this information can be used to design slip-resistant shoes and flooring. To identify the lubrication regime, interfacial pressures at the shoe-floor-contaminant interface were measured and coefficient of friction was monitored. Low viscous fluids and shoes with at least 2mm of tread were found to have negligible interfacial pressures and moderate friction coefficients (0.07–0.40). Untreaded shoes combined with high viscous fluids led to high interfacial pressures that supported up to 40% of the normal load and low friction coefficients (<0.01). These results suggest that mixed/elasto-hydrodynamic lubrication is relevant in some untreaded conditions but that boundary lubrication is relevant for most other conditions. In boundary lubrication, the primary factors contributing to friction are adhesion and hysteresis. Experimental data and finite element models demonstrate that hysteresis friction increases with floor roughness and the ratio of shoe to floor hardness. Adhesion friction is dependent on real area of contact and the shear stress required to break junctions. Experimental data suggests that adhesion is dependent on the fluid lubricant, sliding speed, floor roughness and shoe material. Finite element models confirm that a reduction in the real area of contact occurs with increasing floor roughness and sliding speed, consistent with the experimental adhesion effects. Ensuring that the shoe-floor-fluid interface is operating in the boundary lubrication regime requires establishing minimum tread threshold for fluid lubricants that are likely to be found in a given environment. Designing a high hysteresis shoe-floor combination is preferred because it is relatively unaffected by fluid contaminants or under-shoe conditions (i.e. sliding speed). Therefore, ensuring a minimum tread depth is used along with increasing floor roughness and shoe to floor hardness may be effective in addition to minimum tread thresholds.

The Penn State Safety Floor: Part I—Design Parameters Associated With Walking Deflections

1998 ◽  
Vol 120 (4) ◽  
pp. 518-526 ◽  
Author(s):  
J. A. Casalena ◽  
T. C. Ovaert ◽  
P. R. Cavanagh ◽  
D. A. Streit
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Complex Dynamics ◽  
Impact Response ◽  
Design Parameters ◽  
Finite Element Models ◽  
Design Goal ◽  
Impact Forces ◽  
Penn State ◽  
Deformable Bodies

A new flooring system has been developed to reduce peak impact forces to the hips when humans fall. The new safety floor is designed to remain relatively rigid under normal walking conditions, but to deform elastically when impacted during a fall. Design objectives included minimizing peak force experienced by the femur during a fall-induced impact, while maintaining a maximum of 2 mm of floor deflection during walking. Finite Element Models (FEMs) were developed to capture the complex dynamics of impact response between two deformable bodies. Validation of the finite element models included analytical calculations of theoretical buckling column response, experimental quasi-static loading of full-scale flooring prototypes, and flooring response during walking trials. Finite Element Method results compared well with theoretical and experimental data. Both finite element and experimental data suggest that the proposed safety floor can effectively meet the design goal of 2 mm maximum deflection during walking, while effectively reducing impact forces during a fall.

scholarly journals Morphology based anisotropic finite element models of the proximal femur validated with experimental data

2016 ◽  
Vol 38 (11) ◽  
pp. 1339-1347 ◽  
Author(s):  
W.S. Enns-Bray ◽  
O. Ariza ◽  
S. Gilchrist ◽  
R.P. Widmer Soyka ◽  
P.J. Vogt ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Proximal Femur ◽  
Finite Element Models
Sign in / Sign up

Export Citation Format

Share Document