Validation of Hydraulic Mechanism during Blowout Trauma of Human Orbit Depending on the Method of Load Application

The more we know about mechanisms of the human orbital blowout type of trauma, the better we will be able to prevent them in the future. As long as the buckling mechanism’s veracity is not in doubt, the hydraulic mechanism is not based on equally strong premises. To investigate the correctness of the hydraulic mechanism’s theory, two different methods of implementation of the hydraulic load to the finite element method (FEM) model of the orbit were performed. The intraorbital hydraulic pressure was introduced as a face load applied directly to the orbit in the first variant, while in the second one the load was applied to the orbit indirectly as a set of nodal forces transferred from the external surface of the eyeball via the intraorbital tissues to the orbital walls within the contact problem. Such an approach is aimed at a better understanding of the pattern for the formation of blowout fractures during the indirect load applied to the orbital bones. The nonlinear dynamic analysis of both numerical models showed that the potential fracture was observed in the second variant only, embracing a relatively large area: both medial and lower wall of the orbit. Interestingly, the pressure generated by the intraorbital entities transferred the energy of the impact to the orbital sidewalls mainly; thus, the nature of the mechanism known as the hydraulic was far from the expected hydraulic pressure. According to the eyeball’s deformation as well as the areas of the greatest Huber-Mises-Hencky (H-M-H) stress within the orbit, a new term of strut mechanism was proposed instead of the hydraulic mechanism as more realistic regarding the investigated phenomenon. The results of the current research may strongly influence the development of modern implantology as well as affect forensic medicine.

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Impact Damage Analysis and Experimental Test of Carbon/Epoxy Composite Laminate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1120-1121.590 ◽

2015 ◽

Vol 1120-1121 ◽

pp. 590-592

Author(s):

Hyoh Yun Choi ◽

Yeon Jun Lim ◽

Hyun Jun Cho ◽

Hyun Bum Park

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Composite Laminate ◽

Impact Analysis ◽

Impact Damage ◽

The Finite Element Method ◽

Fem Model ◽

The Impact ◽

Method Analysis ◽

Element Method

In this work, study on impact damage FEM model of composite structure was performed. From the finite element method analysis results of composite laminate, it was confirmed that the results of analysis was reasonable. The velocity of impactor to initiate damage was estimated, and in order to investigate the damage at the predicted velocity, impact analysis using finite element method was performed. According to the impact analysis results of composite laminate, it was confirmed that the damage was generated at the estimated impact velocity. Finally, the comparison of the numerical results with those measured by the experiment showed good agreement.

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Nonlinear Dynamic Analysis of Axisymmetric Solids by the Finite Element Method

Journal of Pressure Vessel Technology ◽

10.1115/1.3454148 ◽

1974 ◽

Vol 96 (2) ◽

pp. 103-112 ◽

Cited By ~ 4

Author(s):

M. Hartzman

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Numerical Technique ◽

Nonlinear Dynamic Analysis ◽

Plastic Behavior ◽

The Finite Element Method ◽

Lumped Mass ◽

Mass System ◽

The Impact ◽

Element Method

A method for calculating the dynamic response of deformable axisymmetric solids, subjected to time-dependent axisymmetric loads is described. The nonlinearities considered in this analysis include material nonlinearity (elastic-plastic behavior) and geometric nonlinearity, which includes finite deformation. The finite-element method is applied to approximate the continuum by a lumped-mass system connected by axisymmetric elements. The equations of motion are solved by applying a step-by-step numerical technique. The analysis is illustrated by application to the collapse of a built-in spherical dome with varying thickness and to the impact of a cylinder against a rigid wall. Close agreement is obtained between the results from the present technique and results obtained from the literature.

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Substructuring of a Petrol Engine: Dynamic Characterization and Experimental Validation

Applied Sciences ◽

10.3390/app9224969 ◽

2019 ◽

Vol 9 (22) ◽

pp. 4969 ◽

Cited By ~ 2

Author(s):

Enrico Armentani ◽

Venanzio Giannella ◽

Roberto Citarella ◽

Antonio Parente ◽

Mauro Pirelli

Keyword(s):

Forced Response ◽

Operating Conditions ◽

Petrol Engine ◽

The Finite Element Method ◽

Dynamic Characterization ◽

Fem Model ◽

Resonant Frequencies ◽

Engine Mounts ◽

Engine Dynamic ◽

The Impact

In this work, the vibration behavior of a 4-cylinder, 4-stroke, petrol engine was simulated by leveraging on the Finite Element Method (FEM). A reduced modelling strategy based on the component mode synthesis (CMS) was adopted to reduce the size of the full FEM model of the engine. Frequency response function (FRF) analyses were used to identify the resonant frequencies and corresponding modes of the different FEM models, and the obtained results were compared with experimental data to get the model validation. Subsequently, modal-based frequency forced response analyses were performed to consider the loads acting during the real operating conditions of the engine. Finally, the impact on vibrations at the mounts, produced by an additional bracket connecting the engine block and gearbox, was also investigated. Both the full and reduced FEM model demonstrated and reproduced with high accuracy the vibration response at the engine mounts, providing a satisfactory agreement with the vibrations measured experimentally. The reduced modelling strategy required significantly shorter runtimes, which decreased from 24 h for the full FEM model to nearly 2 h for the reduced model.

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Computer simulation study about the dependence of amorphous silicon photonic waveguides efficiency on the material quality

The European Physical Journal Applied Physics ◽

10.1051/epjap/2020190250 ◽

2020 ◽

Vol 90 (3) ◽

pp. 30502

Author(s):

Alessandro Fantoni ◽

João Costa ◽

Paulo Lourenço ◽

Manuela Vieira

Keyword(s):

Amorphous Silicon ◽

High Throughput Screening ◽

Simulation Analysis ◽

Low Cost ◽

Deposition Process ◽

Large Area ◽

Sidewall Roughness ◽

Sensing Applications ◽

Fabrication Defects ◽

The Impact

Amorphous silicon PECVD photonic integrated devices are promising candidates for low cost sensing applications. This manuscript reports a simulation analysis about the impact on the overall efficiency caused by the lithography imperfections in the deposition process. The tolerance to the fabrication defects of a photonic sensor based on surface plasmonic resonance is analysed. The simulations are performed with FDTD and BPM algorithms. The device is a plasmonic interferometer composed by an a-Si:H waveguide covered by a thin gold layer. The sensing analysis is performed by equally splitting the input light into two arms, allowing the sensor to be calibrated by its reference arm. Two different 1 × 2 power splitter configurations are presented: a directional coupler and a multimode interference splitter. The waveguide sidewall roughness is considered as the major negative effect caused by deposition imperfections. The simulation results show that plasmonic effects can be excited in the interferometric waveguide structure, allowing a sensing device with enough sensitivity to support the functioning of a bio sensor for high throughput screening. In addition, the good tolerance to the waveguide wall roughness, points out the PECVD deposition technique as reliable method for the overall sensor system to be produced in a low-cost system. The large area deposition of photonics structures, allowed by the PECVD method, can be explored to design a multiplexed system for analysis of multiple biomarkers to further increase the tolerance to fabrication defects.

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A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear

Applied Sciences ◽

10.3390/app11094136 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4136

Author(s):

Rosario Pecora

Keyword(s):

Numerical Method ◽

Initial Conditions ◽

Impact Load ◽

Numerical Models ◽

Landing Gear ◽

Design Stage ◽

Impact Dynamics ◽

State Variables ◽

Adopted Model ◽

The Impact

Oleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data.

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A Theoretical Analysis of Relations between Pressure Changes along Xylem Vessels and Propagation of Variation Potential in Higher Plants

Plants ◽

10.3390/plants10020372 ◽

2021 ◽

Vol 10 (2) ◽

pp. 372

Author(s):

Ekaterina Sukhova ◽

Elena Akinchits ◽

Sergey V. Gudkov ◽

Roman Y. Pishchalnikov ◽

Vladimir Vodeneev ◽

...

Keyword(s):

Higher Plants ◽

Initial Point ◽

Electrical Signal ◽

Terminal Point ◽

Hydraulic Pressure ◽

Long Distance ◽

Variation Potential ◽

Damaged Zone ◽

Pressure Dynamics ◽

The Impact

Variation potential (VP) is an important long-distance electrical signal in higher plants that is induced by local damages, influences numerous physiological processes, and participates in plant adaptation to stressors. The transmission of increased hydraulic pressure through xylem vessels is the probable mechanism of VP propagation in plants; however, the rates of the pressure transmission and VP propagation can strongly vary. We analyzed this problem on the basis of a simple mathematical model of the pressure distribution along a xylem vessel, which was approximated by a tube with a pressure gradient. It is assumed that the VP is initiated if the integral over pressure is more than a threshold one, taking into account that the pressure is transiently increased in the initial point of the tube and is kept constant in the terminal point. It was shown that this simple model can well describe the parameters of VP propagation in higher plants, including the increase in time before VP initiation and the decrease in the rate of VP propagation with an increase in the distance from the zone of damage. Considering three types of the pressure dynamics, our model predicts that the velocity of VP propagation can be stimulated by an increase in the length of a plant shoot and also depends on pressure dynamics in the damaged zone. Our results theoretically support the hypothesis about the impact of pressure variations in xylem vessels on VP propagation.

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Research on Hydroelastic Response of an FMRC Hexagon Enclosed Platform

Symmetry ◽

10.3390/sym13071110 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1110

Author(s):

Wei-Qin Liu ◽

Luo-Nan Xiong ◽

Guo-Wei Zhang ◽

Meng Yang ◽

Wei-Guo Wu ◽

...

Keyword(s):

Time Domain ◽

Numerical Models ◽

Structural Response ◽

Deep Ocean ◽

Surface Model ◽

Large Area ◽

Floating Structure ◽

Small Depth ◽

Response Amplitude Operators ◽

Hydroelastic Response

The numerical hydroelastic method is used to study the structural response of a hexagon enclosed platform (HEP) of flexible module rigid connector (FMRC) structure that can provide life accommodation, ship berthing and marine supply for ships sailing in the deep ocean. Six trapezoidal floating structures constitute the HEP structure so that it is a symmetrical very large floating structure (VLFS). The HEP has the characteristics of large area and small depth, so its hydroelastic response is significant. Therefore, this paper studies the structural responses of a hexagon enclosed platform of FMRC structure in waves by means of a 3D potential-flow hydroelastic method based on modal superposition. Numerical models, including the hydrodynamic model, wet surface model and finite element method (FEM) model, are established, a rigid connection is simulated by many-point-contraction (MPC) and the number of wave cases is determined. The load and structural response of HEP are obtained and analyzed in all wave cases, and frequency-domain hydroelastic calculation and time-domain hydroelastic calculation are carried out. After obtaining a number of response amplitude operators (RAOs) for stress and time-domain stress histories, the mechanism of the HEP structure is compared and analyzed. This study is used to guide engineering design for enclosed-type ocean platforms.

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Assessment of the impact of gaseous ship emissions in ports using physical and numerical models: The case of Naples

Building and Environment ◽

10.1016/j.buildenv.2021.107812 ◽

2021 ◽

pp. 107812

Author(s):

Domenico Toscano ◽

Massimo Marro ◽

Benedetto Mele ◽

Fabio Murena ◽

Pietro Salizzoni

Keyword(s):

Numerical Models ◽

Ship Emissions ◽

The Impact

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Aluminium Alloy Foam Modelling and Prediction of Elastic Properties Using X-ray Microcomputed Tomography

Metals ◽

10.3390/met11060925 ◽

2021 ◽

Vol 11 (6) ◽

pp. 925

Author(s):

Diogo Heitor ◽

Isabel Duarte ◽

João Dias-de-Oliveira

Keyword(s):

Aluminium Alloy ◽

Finite Element Modelling ◽

Effective Properties ◽

Numerical Models ◽

Microcomputed Tomography ◽

Cellular Materials ◽

Metallic Foams ◽

X Ray ◽

The Impact ◽

Structural Imperfections

X-ray microcomputed tomography has been gaining relevance in the field of cellular materials to characterize materials and analyse their microstructure. So, here, it was used together with finite element modelling to develop numerical models to estimate the effective properties (Young’s modulus) of aluminium alloy foams and evaluate the effects of processing on the results. A manual global thresholding technique using the mass as a quality indicator was used. The models were reconstructed (Marching Cubes 33), then simplified and analysed in terms of mass and shape maintenance (Hausdorff distance algorithm) and face quality. Two simplification procedures were evaluated, with and without small structural imperfections, to evaluate the impact of the procedures on the results. Results demonstrate that the developed procedures are good at minimizing changes in mass and shape of the geometries while providing good face quality, i.e., face aspect ratio. The models are also shown to be able to predict the effective properties of metallic foams in accordance with the findings of other researchers. In addition, the process of obtaining the models and the presence of small structural imperfections were shown to have a great impact on the results.

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The effect of the outlet angle β2 on the thermomechanical behavior of a centrifugal compressor blade

Journal of the Mechanical Behavior of Materials ◽

10.1515/jmbm-2020-0001 ◽

2020 ◽

Vol 29 (1) ◽

pp. 1-8

Author(s):

Ahmed Allali ◽

Sadia Belbachir ◽

Ahmed Alami ◽

Belhadj Boucham ◽

Abdelkader Lousdad

Keyword(s):

Mechanical Behavior ◽

Centrifugal Compressor ◽

Three Dimensional ◽

Complex Form ◽

Compressor Blade ◽

Stress Fields ◽

The Finite Element Method ◽

Mechanical Fatigue ◽

Outlet Angle ◽

The Impact

AbstractThe objective of this work lies in the three-dimensional study of the thermo mechanical behavior of a blade of a centrifugal compressor. Numerical modeling is performed on the computational code "ABAQUS" based on the finite element method. The aim is to study the impact of the change of types of blades, which are defined as a function of wheel output angle β2, on the stress fields and displacements coupled with the variation of the temperature.This coupling defines in a realistic way the thermo mechanical behavior of the blade where one can note the important concentrations of stresses and displacements in the different zones of its complex form as well as the effects at the edges. It will then be possible to prevent damage and cracks in the blades of the centrifugal compressor leading to its failure which can be caused by the thermal or mechanical fatigue of the material with which the wheel is manufactured.

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