A Computational Study of Fracture in the Calcaneus Under Variable Impact Conditions

2015 ◽  
Author(s):  
Sai Nithin Reddy Kantareddy ◽  
Rebecca A. Fielding ◽  
Michael J. Robinson ◽  
Reuben H. Kraft
Keyword(s):  
Failure Strain ◽  
Computational Study ◽  
Element Model ◽  
Fracture Patterns ◽  
Continuous Crack ◽  
Convergence Study ◽  
Preliminary Study ◽  
Element Erosion ◽  
Mesh Convergence ◽  
Variable Impact

This preliminary study aims to computationally model and study the fracture patterns in the human calcaneus during variable impact loading conditions. A finite element model of the foot and ankle is used to understand the effect of loading rates and orientation of the foot on fracture patterns. Simulations are carried out by applying varying impact velocities of steel plate to the foot & ankle model in accordance with data regarding underbody blasts. These impact velocities are applied to reach a peak in 1.5 ms. Fracture of bone is represented using the plastic kinematic constitutive model with element erosion method, where elements are removed from the simulation after an inelastic failure strain is exceeded. The simulations last for 5 ms to observe the extent of fracture in the calcaneus. Following simulations, the resulting fracture patterns are compared to available images from experimental impact tests to qualitatively assess the simufutions. A mesh convergence study is performed to determine the level of refinement of mesh necessary to represent this problem. The mesh appears to converge at the refinement level of the medium coarse mesh. The effect of impact velocities on fracture is studied on unjlexed and flexed foot models. At lower velocities, fracture is observed in the form of a single continuous crack, and a pronounced branched type of network is observed at higher velocities. Finally, variation in fracture networks due to variability in strength of the bone is studied. For lower values of failure strain, significantly larger and branched networks of fracture are observed.

Computational Study of Viscoelastic Flows in Microchannels

2021 ◽  
Author(s):  
Guanyang Xue ◽  
Xuanhong Cheng ◽  
Alparslan Oztekin
Keyword(s):  
Numerical Study ◽  
Computational Study ◽  
Viscoelastic Flows ◽  
Computational Domain ◽  
Cfd Simulations ◽  
First Normal Stress Difference ◽  
Computational Fluid Dynamics Cfd ◽  
Convergence Study ◽  
Cell Densities ◽  
Mesh Convergence

Abstract Computational Fluid Dynamics (CFD) simulations have been performed in a 2D cross-section of the microchannel to characterize the viscoelastic flow field using OpenFOAM with customized stabilizing methods. The continuity and momentum equations coupled with the Giesekus constitutive model are solved. The computational domain consists of a straight main channel that is 100 μm in width and a 1:4 square-shaped cavity in the middle of the channel. The mesh convergence study is performed with both structured and unstructured cells. Flow and stress fields are compared with different cell densities. The numerical study is carried out on various Deborah numbers (De). The first normal stress difference is computed to examine the elastic lift force for future studies for nanoparticle separations. The vortex on the expansion side shrinks while the contraction side expands as De is increased. A banded zone of stronger N1 in the bulk region of the cavity, observed at higher De, could be favorable in particle separation applications. As the simulation process being validated, this study can help with future improvements to achieve higher flow rates.

scholarly journals Analysis of Reinforced Concrete Structures for Accidental Blast during Launching of a Rocket

2021 ◽  
Vol 13 (3) ◽  
pp. 195-204
Author(s):  
Lovepreet SINGH ◽  
Nirmal Rakeshbhai RAVALIYA ◽  
M. Abdul AKBAR
Keyword(s):  
Blast Loading ◽  
Element Model ◽  
Civil Infrastructure ◽  
Parametric Studies ◽  
Convergence Study ◽  
Load Intensity ◽  
Mesh Convergence ◽  
The Impact ◽  
The Finite Element Model ◽  
Launching Site

Despite the greatest efforts, accidents continue to happen during the process of rocket launching, either in the form of generated blast wave or the debris that flies and hits random objects. In this paper, the impact of blast loading created by a rocket launch on the tie connection and the three-hinged arch is studied using the finite element model in ABAQUS. The impact of rocket launching was modelled using the physical characteristics/geometry of the launch pad, and a blast load intensity equivalent to 20,000lbs of TNT is applied using the CONWEP module. The tie connection and three-hinged arch after validation and mesh convergence study are applied with service loads in concurrence with the blast loading. The additional impact of blast loads on the static and dynamic response of the structure is studied. The distance of the structures from the point of blast (rocket launching site) is varied, and parametric studies are carried out to arrive at detailed guidelines on the minimum safety distance that stand-alone civil infrastructure should follow in order to minimize the rocket launching impact.

scholarly journals A Computational Study of the Shear Behavior of Reinforced Concrete Beams Affected from Alkali–Silica Reactivity Damage

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3346
Author(s):  
Bora Gencturk ◽  
Hadi Aryan ◽  
Mohammad Hanifehzadeh ◽  
Clotilde Chambreuil ◽  
Jianqiang Wei
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Parametric Study ◽  
Computational Study ◽  
Element Model ◽  
Shear Behavior ◽  
Shear Capacity ◽  
Reinforced Concrete Beams ◽  
Alkali Silica Reactivity ◽  
Concrete Mechanical Properties

In this study, an investigation of the shear behavior of full-scale reinforced concrete (RC) beams affected from alkali–silica reactivity damage is presented. A detailed finite element model (FEM) was developed and validated with data obtained from the experiments using several metrics, including a force–deformation curve, rebar strains, and crack maps and width. The validated FEM was used in a parametric study to investigate the potential impact of alkali–silica reactivity (ASR) degradation on the shear capacity of the beam. Degradations of concrete mechanical properties were correlated with ASR expansion using material test data and implemented in the FEM for different expansions. The finite element (FE) analysis provided a better understanding of the failure mechanism of ASR-affected RC beam and degradation in the capacity as a function of the ASR expansion. The parametric study using the FEM showed 6%, 19%, and 25% reduction in the shear capacity of the beam, respectively, affected from 0.2%, 0.4%, and 0.6% of ASR-induced expansion.

scholarly journals Imaging the Human Thyroid Using Three-Dimensional Diffuse Optical Tomography: A Preliminary Study

2021 ◽  
Vol 11 (4) ◽  
pp. 1670
Author(s):  
Tetsuya Mimura ◽  
Shinpei Okawa ◽  
Hiroshi Kawaguchi ◽  
Yukari Tanikawa ◽  
Yoko Hoshi
Keyword(s):  
Optical Tomography ◽  
Tumor Hypoxia ◽  
Three Dimensional ◽  
Diffuse Optical Tomography ◽  
Element Model ◽  
Needle Aspiration ◽  
Human Thyroid ◽  
Tissue Oxygen Saturation ◽  
Preliminary Study ◽  
First Time

Thyroid cancer is usually diagnosed by ultrasound imaging and fine-needle aspiration biopsy. However, diagnosis of follicular thyroid carcinomas (FTC) is difficult because FTC lacks nuclear atypia and a consensus on histological interpretation. Diffuse optical tomography (DOT) offers the potential to diagnose FTC because it can measure tumor hypoxia, while image reconstruction of the thyroid is still challenging mainly due to the complex anatomical features of the neck. In this study, we attempted to solve this issue by creating a finite element model of the human neck excluding the trachea (a void region). By reconstruction of the absorption coefficients at three wavelengths, 3D tissue oxygen saturation maps of the human thyroid are obtained for the first time by DOT.

Numerical investigations of 2-D planar magnetic nozzle effects on pulsed plasma plumes

2021 ◽  
pp. 1-20
Author(s):  
J. D. Burch ◽  
D. Han ◽  
S. N. Averkin
Keyword(s):  
Plasma Plume ◽  
Three Dimensional ◽  
Pulsed Plasma ◽  
Coil Current ◽  
Numerical Investigations ◽  
Magnetic Nozzle ◽  
Plasma Plumes ◽  
Discharge Parameters ◽  
Convergence Study ◽  
Mesh Convergence

Abstract This paper presents a study of a novel type of magnetic nozzle that allows for three-dimensional (3-D) steering of a plasma plume. Numerical simulations were performed using Tech-X’s USim® software to quantify the nozzle’s capabilities. A 2-D planar magnetic nozzle was applied to plumes of a nominal pulsed inductive plasma (PIP) source with discharge parameters similar to those of Missouri S&T’s Missouri Plasmoid Experiment (MPX). Argon and xenon plumes were considered. Simulations were verified and validated through a mesh convergence study as well as comparison with available experimental data. Periodicity was achieved over the simulation run time and phase angle samples were taken to examine plume evolution over pulse cycles. The resulting pressure, velocity, and density fields were analysed for nozzle angles from 0° to 14°. It was found that actual plume divergence was small compared to the nozzle angle. Even with an offset angle of 14° for the magnetic nozzle, the plume vector angle was only about 2° for argon and less than 1° for xenon. The parameters that had the most effect on the vectoring angle were found to be the coil current and inlet velocity.

Development of Parametric Kelvin Structures will Closed Cells

2016 ◽  
Vol 254 ◽  
pp. 49-54 ◽  
Author(s):  
Dan Andrei Şerban ◽  
Emanoil Linul ◽  
Sorin Sărăndan ◽  
Liviu Marşavina
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Relative Density ◽  
Material Properties ◽  
Cell Diameter ◽  
Rigid Polyurethane Foam ◽  
Loading Direction ◽  
Convergence Study ◽  
Simulation Results ◽  
Mesh Convergence

This work presents the design of a parametric Kelvin structure in which the relative density of the geometry can be varied by adjusting three parameters: cell diameter, cell wall thickness and cell chamfer radius, the structure consistsing of a tessellation of hollow truncated octahedral. The developed model was evaluated in terms of compressive stiffness for the case of a rigid polyurethane foam of 0.256 relative density. Three models were analyzed in order to determine the influence of geometric characteristics on mechanical properties: a model that presented no chamfer a model that presented a medium-sized chamfer and a model that presented a large chamfer. A mesh convergence study was performed which analyzed the results in terms of accuracy and time expenses for three element sizes for both linear and quadratic elements. Due to the orthotropic nature of the model, its response on both possible loading directions was investigated. Simulation results were compared with experimental results and yielded accurate results for one loading direction, when using the material properties for solid polyurethane described in literature.

scholarly journals Mesh convergence study for hydraulic turbine draft-tube

2016 ◽  
Vol 49 ◽  
pp. 082021
Author(s):  
C Devals ◽  
T C Vu ◽  
Y Zhang ◽  
J Dompierre ◽  
F Guibault
Keyword(s):  
Draft Tube ◽  
Hydraulic Turbine ◽  
Convergence Study ◽  
Mesh Convergence ◽  
Hydraulic Turbine Draft Tube

A COMPUTATIONAL STUDY ON THE DEFORMATION OF NANOCRYSTALLINE NICKEL

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1517-1522
Author(s):  
JIANQIU ZHOU ◽  
SHUN LI ◽  
NAN XU
Keyword(s):  
Finite Element ◽  
Grain Boundary ◽  
Finite Element Model ◽  
Computational Study ◽  
Equivalent Plastic Strain ◽  
Element Model ◽  
Boundary Phase ◽  
Nanocrystalline Nickel ◽  
Strain And Strain Rate ◽  
Log Normal

A phase mixture based finite element model was developed and the deformation of nanocrystalline nickel was studied in this paper. Monocrystalline grain interior phase and amorphous grain boundary phase were applied in the finite element model respectively. The digital topological model, which followed the Log-normal distribution, was generated by a systematic method. The experimental strain and strain rate hardening behaviors and severe nonlinearity phenomena of nanocrystalline nickel can be predicted very well by the numerical simulation. By presenting evolution process of Mises stress and equivalent plastic strain, we found shear localization phenomenon and much faster plastic deformation in grain boundary phase. These result in the relatively lower ductility of nanocrystalline nickel compared with that of coarse-grain counterparts.

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