scholarly journals Free and Forced Wave Motion in a Two-Dimensional Plate with Radial Periodicity

2021 ◽  
Vol 11 (22) ◽  
pp. 10948
Author(s):  
Elisabetta Manconi ◽  
Sergey V. Sorokin ◽  
Garziera Rinaldo ◽  
Matheus Mikael Quartaroli
Keyword(s):  
Wave Propagation ◽  
Forced Response ◽  
Polar Coordinates ◽  
Element Analysis ◽  
Forced Wave ◽  
Practical Engineering ◽  
Approaches To Study ◽  
Flow Through ◽  
Waves Propagation ◽  
Numerical Approaches

In many practical engineering situations, a source of vibrations may excite a large and flexible structure such as a ship’s deck, an aeroplane fuselage, a satellite antenna, a wall panel. To avoid transmission of the vibration and structure-borne sound, radial or polar periodicity may be used. In these cases, numerical approaches to study free and forced wave propagation close to the excitation source in polar coordinates are desirable. This is the paper’s aim, where a numerical method based on Floquet-theory and the FE discretision of a finite slice of the radial periodic structure is presented and verified. Only a small slice of the structure is analysed, which is approximated using piecewise Cartesian segments. Wave characteristics in each segment are obtained by the theory of wave propagation in periodic Cartesian structures and Finite Element analysis, while wave amplitude change due to the changes in the geometry of the slice is accommodated in the model assuming that the energy flow through the segments is the same. Forced response of the structure is then evaluated in the wave domain. Results are verified for an infinite isotropic thin plate excited by a point harmonic force. A plate with a periodic radial change of thickness is then studied. Free waves propagation are shown, and the forced response in the nearfield is evaluated, showing the validity of the method and the computational advantage compared to FE harmonic analysis for infinite structures.

CFD Simulation of Fluid Flow Through Porous Media: Application to Decomposed Gases Flow Through Foam Pattern in Lost Foam Casting

Materials ◽  
2003 ◽  
Author(s):  
Sayavur I. Bakhtiyarov ◽  
Ruel A. Overfelt
Keyword(s):  
Cfd Simulation ◽  
Reynolds Numbers ◽  
Phase Flow ◽  
Flow Through Porous Media ◽  
Foam Material ◽  
Element Analysis ◽  
Wide Range ◽  
Flow Through ◽  
Foam Pattern ◽  
Lost Foam

Numerical simulation of decomposed gases through foam pattern was conducted using finite element analysis. A new kinetic model is proposed for gaseos phase flow between molten metal and foam material. The computations were performed for a wide range of Reynolds numbers. The results of the simulations are compared with the experiemental data obtained in this study.

Axial Wave Propagation in Infinitely Long Periodic Curved Panels

2003 ◽  
Vol 125 (1) ◽  
pp. 24-30 ◽  
Author(s):  
C. Pany ◽  
S. Parthan
Keyword(s):  
Wave Propagation ◽  
Natural Frequencies ◽  
Propagation Constant ◽  
Infinite Length ◽  
Approximate Methods ◽  
Bending Vibration ◽  
Element Analysis ◽  
Curved Panel ◽  
Propagation Of Waves ◽  
Curved Panels

Propagation of waves along the axis of the cylindrically curved panels of infinite length, supported at regular intervals is considered in this paper to determine their natural frequencies in bending vibration. Two approximate methods of analysis are presented. In the first, bending deflections in the form of beam functions and sinusoidal modes are used to obtain the propagation constant curves. In the second method high precision triangular finite elements is used combined with a wave approach to determine the natural frequencies. It is shown that by this approach the order of the resulting matrices in the FEM is considerably reduced leading to a significant decrease in computational effect. Curves of propagation constant versus natural frequencies have been obtained for axial wave propagation of a multi supported curved panel of infinite length. From these curves, frequencies of a finite multi supported curved panel of k segments may be obtained by simply reading off the frequencies corresponding to jπ/kj=1,2…k. Bounding frequencies and bounding modes of the multi supported curved panels have been identified. It reveals that the bounding modes are similar to periodic flat panel case. Wherever possible the numerical results have been compared with those obtained independently from finite element analysis and/or results available in the literature.

Finite Element Analysis of Drilling Frame on Down-the-Hole Drill Based on Mechanical Mechanics and Mechanical Properties

2014 ◽  
Vol 908 ◽  
pp. 282-286
Author(s):  
Wan Rong Wu ◽  
Lin Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Working Condition ◽  
Slenderness Ratio ◽  
Stress And Strain ◽  
Limit States ◽  
Element Analysis ◽  
Practical Engineering ◽  
Structure Strength ◽  
Strength And Stiffness

Drilling frame on TD165CH Down-The-Hole Drill that has large slenderness ratio and be longer than 10m is one component of Down-The-Hole drill which is mainly subjected to load.In the process of drilling, drilling frame is not only subjected to loads which are like tensile, compression and torsion and so on, and be under the influence of impacting and vibration of impactor,the situation of force is complicated.By analysing of working condition of Down-The-Hole drill,there get all kinds of limit states of typical working conditions, and then using Ansys doing finite element analysis, there get distribution of the stress and strain of drilling frame and the result of modal analysis to check whether drilling frame meets the requirements of strength and stiffness or not,and whether it is possible to resonate with the impactor or not.By analysis,Structure strength and stiffness of drilling Frame on TD165CH Down-The-Hole drill meet the requirements of practical engineering, and drilling Frame does not resonate with the impactor.

scholarly journals Design and Simulation of Nozzle for Pure Water Jet Portable Cutting Tool

2019 ◽  
Vol 8 (12S2) ◽  
pp. 703-706
Keyword(s):  
Pressure Drop ◽  
Cross Sections ◽  
Pure Water ◽  
Water Jet ◽  
Element Analysis ◽  
Cutting Machine ◽  
Water Jet Cutting ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
The Impact

A pure water jet at subsonic speed provides an opportunity for application in cutting soft material with the advantage of not contaminating the workpiece. Inside the nozzle, water is flowing through various cross sections, which lead to pressure drop and loss of energy. This requires a nozzle with a design that causes minimum pressure drop. In this work, Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) were used to analyse the flow through five different nozzles. For each nozzle, the pressures of 10 MPa, 20 MPa and 30 MPa were applies at the inlet. For the inlet pressure of 10 MPa, the highest outlet velocity us 136.12 m/s at the pressure of 9.261 MPa. The impact pressure at stand distance of 0.5 mm and 1.0 mm were 8.26 MPa and 8.02 MPa, respectively. For this nozzle, the Factor of Safety for 10 MPa, 20 MPa and 30 MPa were 6.4, 3.2 and 2.961, respectively. The findings are relevant to the development of pure water jet cutting machine

Research on the Prefabricated Prestressed Cylinder Foundation of Wind Turbines in the Soft Soil Region

2011 ◽  
Vol 368-373 ◽  
pp. 461-464
Author(s):  
Ren Le Ma ◽  
Ming Yi Zhang
Keyword(s):  
Large Scale ◽  
Wind Farm ◽  
Rapid Development ◽  
Soft Soil ◽  
Earth Pressure ◽  
Element Analysis ◽  
Inland Wetlands ◽  
Lateral Earth Pressure ◽  
Practical Engineering ◽  
Improved Design

With the rapid development of inland wind farm in China, the costal wind farm still has not got large-scale development as the result of the higher cost of fan foundation and the more difficulty of construction. The prefabricated prestressed cylinder foundation (PPC foundation), as a new type of wind turbine foundation designed for the soft soil region such as the inter-tidal coastal zone and inland wetlands, is introduced in this paper. The condition of lateral earth pressure distribution around the foundation which determines the flexural capacity of fan foundation in the soft soil is studied. Through theoretical analysis and mathematical derivation, the result shows that the lateral earth pressure around PPC foundation is changed with depth by 1.5th power curve which has good fitting to the finite element analysis result. The simplified and improved design process is applied into the practical engineering and the good economy of PPC foundation is proved.

Forced Response and Random Vibration Analysis of Printed Circuit Boards

2000 ◽  
Author(s):  
James F. Tarter
Keyword(s):  
Random Vibration ◽  
Printed Circuit Boards ◽  
Random Excitation ◽  
Forced Response ◽  
Circuit Boards ◽  
Element Analysis ◽  
Design Data ◽  
Improve Design ◽  
Printed Circuit ◽  
Contour Plots

Abstract Finite element analysis has been used in conjunction with developed algorithms to analyze forced response and random vibration response of printed circuit boards. Analytical predictions have been compared to random vibration test data for model correlation and validation of the analysis methods. The described methods provide design data for predicting deflections and G levels as a function of frequency or predicting RMS levels for random excitation. These data are utilized for initiating design changes and guiding component placement. Deflection versus frequency contributions for random excitation are analyzed to identify critical design frequencies. Forced response contour plots include effects of modal coupling, modal participation factors, and system damping. These data provide a better description of the expected operating deflection shapes man a simple mode shape. All of these methods are used to improve design integrity and ensure specification compliance prior to hardware fabrication. The analyses utilize aggregate board properties, and do not currently provide data for individual components which are installed on the board.

scholarly journals Electrocution as an alternative euthanasia method to blunt force trauma to the head followed by exsanguination for non-viable piglets

2020 ◽  
Vol 62 (1) ◽  
Author(s):  
Johannes Husheer ◽  
Matthias Luepke ◽  
Peter Dziallas ◽  
Karl-Heinz Waldmann ◽  
Alexandra von Altrock
Keyword(s):  
Cardiac Arrest ◽  
Power Source ◽  
Public Perceptions ◽  
Constant Current ◽  
Element Analysis ◽  
Blunt Force ◽  
Blunt Force Trauma ◽  
Alternative Approach ◽  
Nociceptive Reflexes ◽  
Flow Through

Abstract Background On farms, the currently approved and most widely practised method of euthanising non-viable piglets is blunt force trauma to the head followed by exsanguination. However, the use of this method is criticised due to public perceptions and aversion to the methodology by caretakers. Therefore, electrocution after electrical stunning was examined as an alternative approach in 80 hybrid piglets. Initially, electrocution was simulated with finite element analysis using a computer piglet-model, where current density in the heart was visualised and size and position of the electrodes were defined. The following step investigated electrical parameters for electrocution in anaesthetised piglets; first, with a constant voltage power source and then with a constant current power source. The electrical stunning was examined using the constant current supply. Finally, the results of electrical stunning and electrocution were verified in 25 healthy piglets with a body weight between 1 and 2 kg. Unconsciousness was proven by testing palpebral, corneal and nociceptive reflexes. Time of death was confirmed by electroencephalography (EEG) and electrocardiography (ECG) records. Results Stunning succeeded with the preset of 1.3 A and 50 Hz, placing the electrodes on both sides of the head between the eyes and ears using different timespans between 8 and 20 s. Prolonged electrical flow resulted in reduced paddling movements after the epileptic seizure, and allowed undisturbed reflex tests and installation of electrodes for EEG and ECG recording during electrocution. Using 0.75 A and 400 Hz, pin-shaped electrodes were first positioned on both sides of the chest for 5 s, followed by a break of 20–30 s and a second current flow, whereby the electrodes were placed above the withers and the sternum for 5 s. Cardiac arrest and an isoelectric EEG were induced within 3 min after the onset of the electrical flow through the chest. The most obvious indicator of effective stunning and electrocution was termination of rhythmic breathing. Piglets with cardiac arrest showed only single gasps lasting up to 3 min after electrocution. Conclusions The evaluated stunning and electrocution protocol might ease concerns about timely piglet euthanasia. However, this should be verified in non-viable piglets to exclude influencing factors like dehydration and diseases.

Sign in / Sign up

Export Citation Format

Share Document