scholarly journals Numerical model development to predict the behaviour of infant/neonate crash dummy restrained inside of an incubator under deceleration

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
A. Rabiee ◽  
H. Ghasemnejad ◽  
N. Hitchins ◽  
J. Watson ◽  
J. Roberts ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Boundary Conditions ◽  
Model Development ◽  
Experimental Studies ◽  
Validation Process ◽  
British Standard ◽  
Negative Acceleration ◽  
Infant Incubator ◽  
Complex Boundary

AbstractIn this paper, advanced finite element (FE) methods are developed to investigate the effect of deceleration on the crash dummy test complied with British Standard Engineering (BS EN 1789). These techniques, which are related to material modelling, joints and contacts, offer an advanced numerical model representing an infant incubator with all complex boundary conditions and design contents. It is shown that the response of an infant incubator is a function of the ratchet straps, the tension on the belts, the belt type and the distance of the belts from the edges of the incubator, which can significantly affect the experienced acceleration, by the infant. The validation process is performed against experimental studies and various case parameters such as crash dummy mass and negative acceleration impulse are discussed in detail. The developed numerical model is capable to predict the behaviour of the crash dummy and the incubator in terms of acceleration, trajectory and kinematics by less than 8% error.

Physical statement of the problem for a numerical model of soil freezing and heaving taking into account heat and mass transfer

2021 ◽  
pp. 244-256
Author(s):  
Виктор Григорьевич Чеверев ◽  
Евгений Викторович Сафронов ◽  
Алексей Александрович Коротков ◽  
Александр Сергеевич Чернятин
Keyword(s):  
Finite Element Method ◽  
Mass Transfer ◽  
Finite Element ◽  
Numerical Model ◽  
Boundary Conditions ◽  
Heat And Mass Transfer ◽  
Soil Freezing ◽  
The Finite Element Method ◽  
Freezing Front ◽  
Element Method

Существуют два основных подхода решения задачи тепломассопереноса при численном моделировании промерзания грунтов: 1) решение методом конечных разностей с учетом граничных условий (границей, например, является фронт промерзания); 2) решение методом конечных элементов без учета границ модели. Оба подхода имеют существенные недостатки, что оставляет проблему решения задачи для численной модели промерзания грунтов острой и актуальной. В данной работе представлена физическая постановка промерзания, которая позволяет создать численную модель, базирующуюся на решении методом конечных элементов, но при этом отражающую ход фронта промерзания - то есть модель, в которой объединены оба подхода к решению задачи промерзания грунтов. Для подтверждения корректности модели был проделан ряд экспериментов по физическому моделированию промерзания модельного грунта и выполнен сравнительный анализ полученных экспериментальных данных и результатов расчетов на базе представленной численной модели с такими же граничными условиями, как в экспериментах. There are two basic approaches to solving the problem of heat and mass transfer in the numerical modeling of soil freezing: 1) using the finite difference method taking into account boundary conditions (the boundary, for example, is the freezing front); 2) using the finite element method without consideration of model boundaries. Both approaches have significant drawbacks, which leaves the issue of solving the problem for the numerical model of soil freezing acute and up-to-date. This article provides the physical setting of freezing that allows us to create a numerical model based on the solution by the finite element method, but at the same time reflecting the route of the freezing front, i.e. the model that combines both approaches to solving the problem of soil freezing. In order to confirm the correctness of the model, a number of experiments on physical modeling of model soil freezing have been performed, and a comparative analysis of the experimental data obtained and the calculation results based on the provided numerical model with the same boundary conditions as in the experiments was performed.

Effects of complex boundary conditions on natural convection of a viscoplastic fluid

2019 ◽  
Vol 29 (8) ◽  
pp. 2792-2808 ◽  
Author(s):  
Behnam Rafiei ◽  
Hamed Masoumi ◽  
Mohammad Saeid Aghighi ◽  
Amine Ammar
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Natural Convection ◽  
Boundary Conditions ◽  
Yield Stress ◽  
Heated Wall ◽  
Uniform Heating ◽  
Content Type ◽  
Yield Stress Fluids ◽  
Complex Boundary

Purpose The purpose of this paper is to analyze the effects of complex boundary conditions on natural convection of a yield stress fluid in a square enclosure heated from below (uniformly and non-uniformly) and symmetrically cooled from the sides. Design/methodology/approach The governing equations are solved numerically subject to continuous and discontinuous Dirichlet boundary conditions by Galerkin’s weighted residuals scheme of finite element method and using a non-uniform unstructured triangular grid. Findings Results show that the overall heat transfer from the heated wall decreases in the case of non-uniform heating for both Newtonian and yield stress fluids. It is found that the effect of yield stress on heat transfer is almost similar in both uniform and non-uniform heating cases. The yield stress has a stabilizing effect, reducing the convection intensity in both cases. Above a certain value of yield number Y, heat transfer is only due to conduction. It is found that a transition of different modes of stability may occur as Rayleigh number changes; this fact gives rise to a discontinuity in the variation of critical yield number. Originality/value Besides the new numerical method based on the finite element and using a non-uniform unstructured grid for analyzing natural convection of viscoplastic materials with complex boundary conditions, the originality of the present work concerns the treatment of the yield stress fluids under the influence of complex boundary conditions.

Experimental and numerical analysis of vibration frequency in sandwich composites with different radii of curvature

2017 ◽  
Vol 21 (8) ◽  
pp. 2870-2886
Author(s):  
Melis Yurddaskal ◽  
Buket Okutan Baba
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Boundary Conditions ◽  
Natural Frequencies ◽  
Experimental Studies ◽  
Sandwich Panels ◽  
Mode Shapes ◽  
Sandwich Composite ◽  
Radius Of Curvature ◽  
Finite Element Software

In this study, free vibration responses of sandwich composite panels with different radius of curvature were presented numerically. The studies were carried out on square flat and curved sandwich panels made of E-glass/epoxy face sheets and polyvinyl chloride foam with three different radii of curvature. Experimental studies were used to verify the numerical results. Vibration tests were performed on flat and curved sandwich panels under free–free boundary conditions. The experimental data were then compared with finite element simulation, which was conducted by ANSYS finite element software and it was shown that the numerical analysis results agree well with the experimental ones. Effect of the curvature on natural frequencies under different boundary conditions (all edge free, simply supported, and fully clamped) was investigated numerically. Results indicated that the natural frequencies and corresponding mode shapes were affected by boundary conditions and curvature of the panel. For all boundary conditions, the variation of curvature had smaller effect on the natural frequency of the first mode than those of the other modes.

scholarly journals Comparison of Experimentally Measured Deformation of the Plate on the Subsoil and the Results of 3D Numerical Model

2014 ◽  
Vol 14 (1) ◽  
pp. 57-66 ◽  
Author(s):  
Jana Labudková ◽  
Radim Čajka
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Boundary Conditions ◽  
Parametric Study ◽  
3D Model ◽  
3D Elements ◽  
Final Deformation ◽  
Measured Deformation ◽  
3D Numerical Model

Abstract The purpose of this paper is to compare the measured subsidence of the foundation in experiments and subsidence obtained from FEM calculations. When using 3D elements for creation of a 3D model, it is, in particular, essential to choose correctly the size of the modelled area which represents the subsoil, the boundary conditions and the size of the finite element network. The parametric study evaluates impacts of those parameters on final deformation. The parametric study is conducted of 168 variant models.

The Analysis on Effect of the Terrain to the Culverts Stress by the Finite Element Method

2012 ◽  
Vol 212-213 ◽  
pp. 643-646
Author(s):  
Qing Jiang ◽  
Huan Jun Lai ◽  
Zhi Zhong Su
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boundary Conditions ◽  
The Finite Element Method ◽  
Filling Height ◽  
Homogeneous Complex ◽  
Non Linear ◽  
Complex Boundary ◽  
The Difference ◽  
Element Method

Highlight advantages of the finite element method is suitable for non-linear, non-homogeneous, complex boundary conditions. The paper adopts the finite element method to analysis culvert stress in Valley terrain. Gain that when the filling height H=40 meters, considering the valley topography calculated Ks=1.19, otherwise the Ks=1.435, the difference is about 17%. Therefore, the effects of the valley terrain to the high embankment culvert can not be ignored.

Electro-Mechanical Impedance Assessment of a Bolted Circular Plate Element of a Space Structure

2017 ◽  
Author(s):  
David Hunter ◽  
Andrei Zagrai
Keyword(s):  
Boundary Conditions ◽  
Circular Plate ◽  
Structural Damage ◽  
Experimental Studies ◽  
Mechanical Impedance ◽  
Space Structure ◽  
Space Vehicles ◽  
Bolted Joint ◽  
Impedance Response ◽  
Complex Boundary

Electro-mechanical impedance diagnostic is one of key structural health monitoring approaches in aerospace structures. Considerable number of studies have demonstrated its efficiency in monitoring bolted joints. This investigation focuses on effect of a bolted boundary on the electro-mechanical impedance response of the space structure. Many space vehicles incorporate cylindrical payloads featuring multiple plates connected with threaded rods. Position of nuts on the threaded rods determine layered structure of the payload. Because of the cylindrical configuration of the payload, internal layers are formed by circular plates bolted to the connection rods. The number of connection rods determines the number of bolted boundary conditions around plate’s circumference. In this case, the boundary of the plate is essentially a mix of bolted and free segments and is not associated with a classical boundary condition. It is suggested that this case may be represented by an elastic boundary conditions with boundary stiffnesses depending on torque applied to each bolted joint. Vibrations of a circular plate with indicated complex boundary conditions were studied in this contribution theoretically and experimentally. As a result of numerical studies, a range of stiffnesses was suggested to model the bolted boundary. An analytical expression for the electro-mechanical impedance of a circular plate was presented and was utilized in the calculation of the response of a circular plate with the complex boundary. Structural damage was modeled as deviation of the stiffness associated with the bolted joint. Experimental studies were carried out to validate results of theoretical investigations. Electro-mechanical impedance signatures of the circular plate with an attached piezoelectric active sensor were collected for different sets of boundary conditions representing theoretical scenarios. Effect of the compromised bolted joint on the electro-mechanical impedance response of the whole circular plate was explored and the analysis of changes due to different conditions of the bolted boundary was provided.

scholarly journals Numerical evaluation of systematic errors of a non-invasive intracranial pressure measurement

Energetika ◽  
2018 ◽  
Vol 64 (3) ◽  
Author(s):  
Edgaras Misiulis ◽  
Gediminas Skarbalius ◽  
Algis Džiugys
Keyword(s):  
Blood Flow ◽  
Intracranial Pressure ◽  
Numerical Model ◽  
Boundary Conditions ◽  
Systematic Error ◽  
Experimental Studies ◽  
Systematic Errors ◽  
Pressure Balance ◽  
Worst Case ◽  
Non Invasive

Intracranial pressure (ICP) monitoring procedure can be applied to aid in secondary brain damage prevention. A high invasiveness of commonly used ICP measuring methods poses a risk of complications, and therefore new non-invasive methods are currently being developed. A promising non-invasive ICP measurement method is based on the existence of pressure balance state, which is driven by the unique morphological property of ophthalmic artery (OA). The value of ICP can be obtained by evaluating blood flow or artery characteristics in different OA segments, intracranial OA segment (IOA) and extracranial OA segment (EOA). In order to increase measurement accuracy, the systematic errors must be evaluated, which requires an implementation of a numerical model encompassing various physical phenomena. In this paper, a developed numerical model is presented, which was used to solve a transient fluid–structure interaction (FSI) problem of the pulsatile blood flow in a straight, physically meaningful anisotropic, hyperelastic OA, with ICP and external pressure (Pe) loads. It was found that the systematic error based on mean cross-sectional area difference between IOA and EOA segments was {–1.48, –1.37, –1.17} mmHg with ICP = {10, 20, 30} mmHg, respectively. The systematic error based on mean blood flow velocity difference between IOA and EOA segments was {–1.84, –1.76, –1.625} mmHg with ICP = {10, 20, 30} mmHg, respectively. The presented numerical model examined the worst-case scenario in terms of boundary conditions, which were immovable, while lengths of OA segments were physiologically relevant statistical means; however, the obtained systematic errors still met the clinical standards of ANSI/AAMI, where it is stated that the error should not exceed the ± 2 mmHg in the range of 0–20 mmHg of ICP. Boundary conditions and compliance affects the systematic error in both ways (reduce or increase it); this may explain the low systematic errors obtained in experimental studies by other authors.

Numerical Solution for Weight Function of Electromagnetic Flowmeter Using Finite Element Method

2013 ◽  
Vol 444-445 ◽  
pp. 1360-1363
Author(s):  
Kai Xia Wei
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Analysis ◽  
Boundary Conditions ◽  
Weight Function ◽  
Numerical Solution ◽  
Electromagnetic Flowmeter ◽  
Analysis Method ◽  
Sensor Structure ◽  
Complex Boundary

Weight function is related with the sensor structure of electromagnetic flowmeter (EMF). Because of complex boundary conditions, it is difficult to solve the voltage differentiation equation of EMF directly to get weight function. The finite element numerical analysis method is tried to solve the weight function for the point and large-electrode EMF in this paper. The results prove it is feasible and efficient to obtain weight function of EMA by means of finite element numerical analysis.

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