scholarly journals Stability Loss Analysis for Thin-Walled Shells with Elliptical Cross-Sectional Area

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5636
Author(s):  
Ján Kostka ◽  
Jozef Bocko ◽  
Peter Frankovský ◽  
Ingrid Delyová ◽  
Tomáš Kula ◽  
...  
Keyword(s):  
Stability Loss ◽  
Critical Force ◽  
The Finite Element Method ◽  
Cross Sectional ◽  
Elliptical Cross ◽  
Loss Analysis ◽  
Finite Strip ◽  
Finite Strip Method ◽  
Method Of Production ◽  
Sectional Shape

The aim of the scientific contribution is to point out the possibility of applicability of cylindrical shells with a constant elliptical cross-sectional shape for stability loss analysis. The solution to the problem consists of two approaches. The first approach is the experimental measurement of critical force levels, where the work also describes the method of production of the sample and jigs that cause the desired elliptical shape. The second approach is solving the problem in the use of numerical methods—the finite strip method together with the finite element method.

scholarly journals Hair Structures Affecting Hair Appearance

Cosmetics ◽  
2019 ◽  
Vol 6 (3) ◽  
pp. 43 ◽  
Author(s):  
Nagase
Keyword(s):  
Light Scattering ◽  
Total Reflection ◽  
Hair Length ◽  
Cross Sectional ◽  
Elliptical Cross ◽  
Factors Affecting ◽  
Hair Fiber ◽  
The Cross ◽  
Sectional Shape ◽  
Multiple Fibers

Optical factors affecting hair appearance are reviewed based on hair structures from macroscopic to microscopic viewpoints. Hair appearance is the result of optical events, such as reflection, refraction, scattering, and absorption. The effects of hair structures on such optical events are summarized and structural conditions for hair appearance are considered. Hair structures are classified into the following: the alignment of multiple hair fibers, the cross-sectional shape of the hair fiber, and the microstructures of hair fiber (cuticle, cortex, and medulla). The alignment of multiple hair fibers is easily affected by the existence of meandering fibers and their alignment along hair length becomes less-synchronized. The less-synchronized orientation of multiple fibers causes the broadening of the apparent reflection and luster-less dull impression. The cross-sectional shape of hair fiber affects light reflection behavior. Hair fibers with elliptical cross-section show glittering colored light based on total reflection in the hair. The scaly structures of cuticles at the surface of hair are often uplifted and cause light scattering, and then affect hair luster. The porous structure of the cortex and medulla in hair fiber can cause light scattering and affect hair luster and color. The above phenomena suggest that important factors for hair appearance are the alignment of multiple hair fibers, appropriate cross-sectional shape, ordered scaly structure, and pore-less internal structure.

The Structure and Function of the Basement Membrane Muscle System in Amphiporus lactifloreus (Nemertea)

1952 ◽  
Vol s3-93 (21) ◽  
pp. 1-15
Author(s):  
J. B. COWEY
Keyword(s):  
Basement Membrane ◽  
Cross Section ◽  
Circular Cross Section ◽  
The Body ◽  
Minimum Length ◽  
Muscle Fibres ◽  
Body Volume ◽  
Cross Sectional ◽  
Elliptical Cross ◽  
Sectional Shape

The body wall of A. lactifloreus has the following structure from the outside inwards. (i) A basement membrane of five to six layers immediately underlying the epithelium. Each layer consists of right-hand and left-hand geodesic fibres making a lattice, whose constituent parallelograms have a side length of from 5 to 6µ. The fibres are attached to one another where they cross; so there can be no slipping relative to one another. (ii) A layer of circular muscle-fibres running round the animal containing two systems of argyrophil fibres--one of fibres at intervals of 10µ. running parallel to the muscle-fibres and the other of fibres running radially through the layer from the basement membrane to the myoseptum. (iii) A myoseptum which is identical in structure with a single layer of the basement membrane (iv) A layer of longitudinal muscle, whose fibres are arranged in layers on each side of a series of longitudinal radial membranes. Membranes identical in structure with the basement membrane invest the nerve cords, the gut, the gonads, and the proboscis. The interrelations of argyrophil and muscle-fibres in the muscle layers is described and their functioning discussed. The system of inextensible geodesic fibres is analysed from a functional standpoint. The maximum volume enclosed by a cylindrical element (cross-section circular), of such a length that the geodesic makes one complete turn round it, varies with the value of the angle θ between the fibres and the longitudinal axis. When θ is 0° the volume is zero; it increases to a maximum when θ is 54° 44' and decreases again to zero when θ is 90°. The length of the element under these conditions varies from zero when θ is 90° to a maximum (the length of one turn of the geodesic) when θ is 0°. The body-volume of the worm is constant. Thus it has a maximum and minimum length when its cross-section is circular, and at any length between these values its cross-section becomes more or less elliptical. It is maximally elliptical when θ is 54° 44', i.e. when the volume the system could contain, at circular cross-section, is maximal. From measurements of the ratio of major to minor axes of this maximally elliptical cross-section, the maximum and minimum lengths of the worm relative to the relaxed length and values of θ at maximum and minimum length are calculated. The worm is actually unable to contract till its cross-section is circular; but measurements of its cross-sectional shape at the minimum length it can attain, permit calculation of the theoretical length and value of θ for this cross-sectional shape. Calculated values of length and the angle 6 agree well with the directly observed values.

scholarly journals Effect of Groove Shape on Head Loss and Filtration Performance of Disc Filters

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1683
Author(s):  
Sang-ik Lee ◽  
Jin-Yong Choi ◽  
Won Choi
Keyword(s):  
Performance Test ◽  
Filter Design ◽  
Head Loss ◽  
Sectional Area ◽  
Cross Sectional ◽  
Loss Analysis ◽  
Groove Shape ◽  
Filtration Performance ◽  
Sectional Shape ◽  
The Relationship

To analyze the effect of a groove cross-sectional shape on disc filters, a head loss analysis and filtration performance test were conducted using disc filters with different groove shapes (semi-elliptical- and trapezoidal-shaped grooves). Furthermore, the groove shapes were analyzed using field emission scanning electron microscopy and the relationship between flow rate and head loss was derived from the head loss test. Even if the filters were designed with the same mesh standard, the sectional areas of the grooves were different depending on the shape. Therefore, the head loss was compared under the condition that the grooves have the same sectional area by applying the relationship between head loss and sectional area, and a smaller head loss was observed in the semi-elliptical-shaped groove. Additionally, the semi-elliptical-groove-shaped disc filter was evaluated to sufficiently filter the soil particles corresponding to the 120 mesh standard. Therefore, an optimum disc filter can be designed by considering the cross-sectional shape of the disc groove to reduce energy consumption and provide stable filtration. The elliptical groove shape, which is hydraulically advantageous, is preferred for the disc filter design.

Comparison of Methods for Modelling Vibrations of Collecting Electrodes in Dry Electrostatic Precipitators

2013 ◽  
Vol 60 (3) ◽  
pp. 431-449 ◽  
Author(s):  
Iwona Adamiec-Wójcik ◽  
Andrzej Nowak ◽  
Stanisław Wojciech
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
High Efficiency ◽  
Industrial Applications ◽  
The Finite Element Method ◽  
Hybrid Finite Element Method ◽  
Finite Strip ◽  
Finite Strip Method ◽  
Electrostatic Precipitators ◽  
Element Method

Abstract Dry electrostatic precipitators (ESPs) are widely used for purification of exhaust gases in industrial applications. Maintenance of their high efficiency depends primarily on periodical cleaning of the collecting electrodes (CEs). Dust removal (regeneration of CEs) is realized by inducing periodical vibrations of the electrodes. The paper presents results of vibration modelling of a system of CEs; the results were obtained by means of the finite element method, the hybrid finite element method, the finite strip method and a model formulated using Abaqus. Numerical results are compared with those obtained from experimental measurements. Conclusions concerning numerical effectiveness and exactness of the methods are formulated and reasons for differences are discussed.

Experimental and Numerical Analysis of Titanium Microtube Elliptical Flaring

2010 ◽  
Author(s):  
Weichao Wu ◽  
Ying Huang ◽  
Rajiv Malhotra ◽  
Yongjun Wang ◽  
Jian Cao
Keyword(s):  
Analytical Model ◽  
Cross Section ◽  
Fem Simulation ◽  
Circular Cross Section ◽  
Forming Process ◽  
Cross Sectional ◽  
Elliptical Cross ◽  
Tube Flaring ◽  
Sectional Shape ◽  
The Relationship

Traditional tube flaring processes focuses on expanding one end of the tube without changing its cross-sectional shape. This paper presents a new two-step tube flaring process for expanding one end of a titanium alloy microtube while simultaneously changing its cross-sectional shape from circular to elliptical. Experiments were performed to investigate and verify this process. Furthermore, an analytical model was developed to analyze the forming process and investigate the relationship between punch feed and maximum plastic strain during the flaring process. The analysis shows that the two-step flaring process used is effective in expanding the circular cross section to an elliptical cross section without failure. It is also shown that the developed analytical model can predict the fracture of the tube end during the flaring process approximately. Finally, a FEM simulation was performed to further investigate the two-step flaring process.

scholarly journals THE FINITE STRIP METHOD FOR ACOUSTIC AND VIBROACOUSTIC PROBLEMS

2011 ◽  
Vol 19 (04) ◽  
pp. 353-378 ◽  
Author(s):  
J. POBLET-PUIG ◽  
A. RODRÍGUEZ-FERRAN
Keyword(s):  
Three Dimensional ◽  
The Finite Element Method ◽  
Frequency Range ◽  
Acoustic Boundary Conditions ◽  
Structure Interaction ◽  
Computational Costs ◽  
Finite Strip ◽  
Strip Method ◽  
Finite Strip Method ◽  
Dimensional Domain

The finite strip method, widely employed in structural mechanics, is extended to solve acoustic and vibroacoustic problems. The acoustic part of the formulation, including how to handle the most typical acoustic boundary conditions and the fluid structure interaction, is presented. Several realistic problems where the three-dimensional domain of interest has extrusion symmetry are solved. These examples illustrate the advantages of the method: it has smaller computational costs than the finite element method and consequently the analyzed frequency range can be increased.

GENERALIZED BEAM THEORY REVISITED: FROM THE KINEMATICAL ASSUMPTIONS TO THE DEFORMATION MODE DETERMINATION

2011 ◽  
Vol 11 (05) ◽  
pp. 969-997 ◽  
Author(s):  
N. SILVESTRE ◽  
D. CAMOTIM ◽  
N. F. SILVA
Keyword(s):  
Beam Theory ◽  
Deformation Mode ◽  
Cross Sectional ◽  
Finite Strip ◽  
Strip Method ◽  
Finite Strip Method ◽  
Buckling Behavior ◽  
Starting Point ◽  
Near Future ◽  
Generalized Beam Theory

This work is part of an ongoing investigation aimed at comparing the mechanics underlying the application of generalized beam theory (GBT) and the constrained finite strip method (cFSM), two alternative modal approaches to analyze the elastic buckling behavior of open-sectional unbranched thin-walled members. Previous work included an overall comparison between the numerical results yielded by the two approaches for lipped channel columns and beams, which were shown to be essentially identical — the few minor discrepancies were fully explained. The next step consists of revisiting the kinematical assumptions and procedures adopted by GBT to identify and characterize the cross-sectional deformations modes, presenting, explaining, and interpreting them from a novel perspective, deemed more suitable for a true comparison with the displacement field constraints employed in cFSM — the main objective of this paper. The starting point is the derivation of the conventional finite strip method (FSM), intended to show that some of the corresponding matrices also appear in GBT. Indeed, it is demonstrated that the determination of the GBT deformation modes involves a set of particular FSM matrices, termed "cross-sectional matrices." After a brief comparison between the GBT and cFSM assumptions and procedures, an illustrative example is presented and discussed, in order to provide a better grasp of the concepts and procedures involved in the new approach to the GBT deformation mode determination. Finally, the paper closes with a few concluding remarks that also address the work to be carried out in the near future.

scholarly journals Some aspects of consideration of initial imperfections in the calculations of stability of thin-walled elements of open profile

2021 ◽  
pp. 122-128
Author(s):  
Ivan Okhten ◽  
Olha Lukianchenko
Keyword(s):  
Middle Surface ◽  
Stability Loss ◽  
Critical Force ◽  
The Finite Element Method ◽  
Geometric Imperfections ◽  
Initial Imperfections ◽  
General Stability ◽  
Initial Geometric Imperfections ◽  
Linear And Nonlinear ◽  
The Stability

Performed analysis of the initial geometric imperfections influence on the stability of the open C-shaped bars. Test tasks were solved in MSC Nastran, which is based on the finite element method. Imperfections are given in different formulations: the general stability loss of an ideal bar, of wavy bulging of walls and shelves, of deplanation of a bar. To model imperfections, has been developed a program which for the formation of new coordinates of the nodes of the "deformed" model, the components of a vector similar to the form of stability loss are added to the corresponding coordinates of the middle surface of the bar. In this way, you can set initial imperfections in the forms of stability loss of the bar with different amplitude. Researches made with different values of the imperfection amplitude and eccentricity of applied efforts. All tasks are performed in linear and nonlinear staging. The conclusion is made regarding the influence of initial imperfections form and imperfection amplitude on the critical force in nonlinear calculations. It was found that the most affected are imperfections, which are given in the form of total loss of stability. It was revealed the influence of the imperfection amplitude on the magnitude of the critical force for such imperfections. The influence of imperfections amplitude given in the form of wavy bulging walls and in the form of deplanations is not affected on the value of the critical force.

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