scholarly journals Interaction Force between a Small Magnet and a Superconducting Sphere

2019 ◽  
Vol 30 (2) ◽  
pp. 3-7
Author(s):  
Ahmad Subahi Ahmad Subahi
Keyword(s):  
Boundary Conditions ◽  
Interaction Force ◽  
Method Of Images ◽  
Superconducting Sphere ◽  
Geometrical Dimensions

The interaction force between a small magnet and a superconducting sphere is calculated using the method of images. Our approach can be easily verified by applying boundary conditions. This work will possesses and clear the discrepancies found in the literature. For collinear dipoles case (small magnet and its image), we found the elevated force to be dependent on the geometrical dimensions of the problem

Buckling of Composite and Homogeneous Isotropic Cylindrical Shells Under Axial and Radial Loading

1969 ◽  
Vol 36 (4) ◽  
pp. 791-798 ◽  
Author(s):  
M. M. Lei ◽  
Shun Cheng
Keyword(s):  
Boundary Conditions ◽  
Axial Compression ◽  
Circular Cylindrical Shell ◽  
Radial Pressure ◽  
Buckling Load ◽  
Simply Supported ◽  
Classical Boundary ◽  
Axial Compressive Stress ◽  
Radial Loading ◽  
Geometrical Dimensions

A theoretical analysis of the buckling of a multilayered thin orthotropic composite circular cylindrical shell of finite length, subjected to (a) uniform axial compression, and (b) axial compression combined with radial pressure, is presented. At each end of the shell, four boundary conditions are satisfied. Four combinations of boundary conditions for simply supported shells, and four combinations of boundary conditions for clamped shells, are treated. These boundary conditions are reduced to the vanishing of a fourth-order determinant. Buckling loads for boron-epoxy composite shells are determined and the results are shown in a series of diagrams. The effect of boundary conditions on the buckling load for various geometrical dimensions of composite cylinders is investigated. Details of the boundary conditions are shown to have strong influence on the buckling load of the shell. The minimum critical axial compression for a simply supported shell with boundary conditions SS1 is as low as 79 percent of the minimum critical axial compression for a shell with classical boundary conditions SS3. As a special case of a composite shell, the minimum critical axial compressive stress for a homogeneous, isotropic, simply supported shell with end conditions SS1 is found to be 43.7 percent of the classical critical stress.

Qualification of Polymer Materials for Dynamic Riser Service

2021 ◽  
Author(s):  
Craig McCord ◽  
Colin Jones
Keyword(s):  
Boundary Conditions ◽  
Failure Modes ◽  
Fatigue Testing ◽  
Interaction Force ◽  
Full Scale ◽  
Steel Pipe ◽  
Vertical Orientation ◽  
Liner System ◽  
Potential Failure ◽  
Polymer Liner

Abstract Polymer liners have been used extensively in water injection flowlines for several years, however, have only recently gained traction as a corrosion protection solution for Steel Catenary Risers and other similar rigid pipe risers as the industry moves to more novel systems. In order to qualify a system for a dynamic service environment such as a riser, it is important to understand the system's fatigue response and characteristics to ensure that all potential failure modes are addressed. This is typically accomplished for rigid pipes via full scale resonance fatigue testing whereby a test specimen is subjected to a representative fatigue environment and point of failure determined. Rigid pipe specimens with polymer liner installed have been trialed and reported previously. In this programme, the full-scale test strings demonstrated that all the lined system components can withstand the standard fatigue performance test curves. However, it did not confirm the boundary conditions for failure of the polymer liner, as failure of the metallic host pipe always occurred first. A similar method can be used to test the polymer material in isolation, however given the strain levels involved and the material's inherent fatigue resistance, it was expected that the duration of testing would be impractical. It was therefore necessary to implement a test method that allowed for identification of the polymer boundary conditions within a reasonable time frame, whilst also allowing for comparison with existing fatigue testing. In order to achieve this, a small-scale fatigue testing programme was setup in line with ISO 18489, whereby pre-notched dumbbell samples would be prepared and tested, firstly at 23°C but also at 0°C and 60°C to not only allow comparison with existing full-scale data, but also allow determination of suitability across the full temperature range expected in service. Testing results have demonstrated that the polymer's fatigue resistance far exceeds that of the steel pipe, even with the inclusion of pre-initiated cracking in the samples. The testing was able to provide key data on parameters and their influence on the material's fatigue life such as temperature, stress and strain. Further to this, an additional test programme was setup to evaluate the influence that the vertical orientation of the riser has on the polymer liner system. In this test programme, the interaction force between the steel pipe and polymer liner was assessed to establish the necessary design criteria to ensure that the interaction force always exceeds the vertical self-weight of the liner. Testing results demonstrated that the steel pipe/liner interaction force exceeded the equivalent self-weight of the liner eliminating potential failure modes associated with creep. As a result, the vertical orientation of the riser does not present a risk to the integrity of the liner system.

Sound transmission between partitioned contiguous enclosures

2009 ◽  
Vol 223 (5) ◽  
pp. 1091-1101 ◽  
Author(s):  
H Hosseini-Toudeshky ◽  
M R Mofakhami ◽  
R Yarmohammadi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boundary Conditions ◽  
Sound Transmission ◽  
The Finite Element Method ◽  
Symmetric Configuration ◽  
New Buildings ◽  
Geometrical Dimensions ◽  
Party Wall ◽  
Transmission Level

By increasing the application of lightweight constructions, sound transmission between the adjacent enclosures becomes a more important consideration in designing new buildings. In this article, the parameters that may significantly affect the sound transmission level through a partition between two adjacent enclosures are investigated, i.e. geometrical dimensions, arrangement of enclosures, boundary conditions, multi-layered partitions, and framed (or reinforced) conditions of the partitions. For this purpose, sound transmission is modelled using the finite-element method. The obtained results from sound transmission using Perspex party walls with different width and boundary conditions are compared with those obtained from a double-layered wall with an air layer. The effects of an enclosure's arrangements and dimensions on sound transmission of the party walls are also studied. Using the cross-framed party wall causes more noise reduction than the double-layered party wall. The results also show that sound transmission between rooms with an asymmetric arrangement is less than that obtained from a symmetric configuration.

scholarly journals HYDRAULIC HEAVE – DESIGN CHARTS AND DESIGN FORMULA FOR THE REQUIRED EMBEDDED LENGTH

2014 ◽  
Vol 6 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Benjamin Aulbach ◽  
Martin Ziegler
Keyword(s):  
Boundary Conditions ◽  
Approximate Solutions ◽  
Unit Weight ◽  
Design Formula ◽  
Design Charts ◽  
Submerged Soil ◽  
The Difference ◽  
Geometrical Dimensions ◽  
Geometrical Boundary

For the determination of the required embedded length for the safety against hydraulic heave several approximate solutions exist. However, most of these solutions do not take into account the geometrical boundary conditions such as width B and length L of the excavation as well as the thickness of the aquifer S. Thus, values obtained by such simplified approximate solutions can easily lead to either uneconomical or unsafe design. For this reason investigations on the safety against hydraulic heave have been carried out at the Chair of Geotechnical Engineering at RWTH Aachen University. Based on the results of numerous calculations dimensionless design charts have been generated. With the help of these design charts the required embedded length T can be determined quite easily taking into account the difference of the ground water level H, the Thickness of the aquifer S, the geometrical dimensions B and L of the excavation and the unit weight of submerged soil γ′. In addition to these design charts a formula has been developed. By use of this design formula the required embedded length can directly be determined taking into account the before mentioned boundary conditions.

scholarly journals Demagnetization Effect on the Magnetoelectric Response of Composite Multiferroic Cylinders

2021 ◽  
Vol 5 (5) ◽  
pp. 139
Author(s):  
Somer Nacy ◽  
George Youssef
Keyword(s):  
Boundary Conditions ◽  
Composite Structures ◽  
Composite Cylinder ◽  
Concentric Cylinders ◽  
Inner Radius ◽  
Overall Performance ◽  
Multiferroic Composite ◽  
Magnetoelectric Response ◽  
Thin Elastic Layer ◽  
Geometrical Dimensions

Strain-mediated multiferroic composite structures are gaining scientific and technological attention because of the promise of low power consumption and greater flexibility in material and geometry choices. In this study, the direct magnetoelectric coupling coefficient (DME) of composite multiferroic cylinders, consisting of two mechanically bonded concentric cylinders, was analytically modeled under the influence of a radially emanating magnetic field. The analysis framework emphasized the effect of demagnetization on the overall performance. The demagnetization effect was thoroughly considered as a function of the imposed mechanical boundary conditions, the geometrical dimensions of the composite cylinder, and the introduction of a thin elastic layer at the interface between the inner piezomagnetic and outer piezoelectric cylinders. The results indicate that the demagnetization effect adversely impacted the DME coefficient. In a trial to compensate for the reduction in peak DME coefficient due to demagnetization, a non-dimensional geometrical analysis was carried out to identify the geometrical attributes corresponding to the maximum DME. It was observed that the peak DME coefficient was nearly unaffected by varying the inner radius of the composite cylinder, while it approached its maximum value when the thickness of the piezoelectric cylinder was almost 60% of the total thickness of the composite cylinder. The latter conclusion was true for all of the considered boundary conditions.

scholarly journals Method of Images for a Charge inside a Three-Layer Medium and Implementation of a Dirichlet Border Condition

2020 ◽  
Vol 44 (2) ◽  
pp. 7-14
Author(s):  
Fausto Valencia ◽  
Hugo Arcos
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Electric Field ◽  
Boundary Conditions ◽  
Electric Potential ◽  
Finite Element Simulations ◽  
Method Of Images ◽  
Layer Medium ◽  
A Charge ◽  
Good Agreement

A process to apply the method of images for a charge located in a three-layer medium is presented. The images are found according to the boundary conditions between the layers for the electric field. The characteristics of the electric potential are also considered, thus the number of unknown variables becomesa guide to set the image charges needed to solve the problem. The results are compared with finite element simulations through the use of the software FEMM 4.2, showing good agreement. The found limitations of the process are also noted, mainly in regards to the dependence of the images on the coordinates where the field is to be calculated. The model obtained was applied to different cases, where it was seen that it was not limited to three material media only. Finally, the null potential boundary condition was applied, showing how the method of images could be applied to this type of problems.

scholarly journals Finite element analysis of a composite piston for a diesel aircraft engine

2019 ◽  
Vol 179 (4) ◽  
pp. 107-111
Author(s):  
Konrad PIETRYKOWSKI ◽  
Paweł MAGRYTA ◽  
Krzysztof SKIBA
Keyword(s):  
Heat Flux ◽  
Boundary Conditions ◽  
Mechanical Load ◽  
Aircraft Engine ◽  
Element Analysis ◽  
Mechanical Loads ◽  
Thermal Boundary Conditions ◽  
Piston Crown ◽  
Geometrical Dimensions ◽  
Abaqus Software

The article presents calculations of thermal and mechanical loads of the piston, consisting of two parts: steel and aluminum. The calculations were made using FEM in the Abaqus software. The piston is characterized by a split construction and was equipped with a cooling oil channel. The piston will be used in an aircraft diesel engine characterized by opposite piston movement. The presented geometry of the piston is the next of the ones being developed earlier and contains preliminary assumptions as to the size and main geometrical dimensions. The thermal boundary conditions of the simulation tests assumed defined areas of heat reception surface and heating of the piston by defining a temperature map on its crown. The results of these studies were presented in the form of temperature distribution and heat flux on the surface of the tested element. The strength boundary conditions assumed a mechanical load in the form of pressure resulting from the pressure in the combustion chamber applied to the piston crown surface and the opposite pressure defined on the support at the surface of contact between the piston and the piston pin. The results of these tests were presented in the form of stress distribution on the surface of the tested element. As a result of the analyses carried out, the results constituting the basis for further modernization of the piston geometry were obtained.

Use of the Magnetostatic Analogue In Electromagnetic Lens Engineering

1970 ◽  
Vol 28 ◽  
pp. 360-361
Author(s):  
John W. Coleman
Keyword(s):  
Boundary Conditions ◽  
High Performance ◽  
Force Fields ◽  
Optical Design ◽  
Direct Conversion ◽  
Design Engineering ◽  
Design Data ◽  
Scalar Potentials ◽  
Geometric Elements ◽  
At Will

In the design engineering of high performance electromagnetic lenses, the direct conversion of electron optical design data into drawings for reliable hardware is oftentimes difficult, especially in terms of how to mount parts to each other, how to tolerance dimensions, and how to specify finishes. An answer to this is in the use of magnetostatic analytics, corresponding to boundary conditions for the optical design. With such models, the magnetostatic force on a test pole along the axis may be examined, and in this way one may obtain priority listings for holding dimensions, relieving stresses, etc..The development of magnetostatic models most easily proceeds from the derivation of scalar potentials of separate geometric elements. These potentials can then be conbined at will because of the superposition characteristic of conservative force fields.

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