Página 1 dos resultados de 864 itens digitais encontrados em 0.010 segundos

Trigonometric function used to formulate a multi-nodal finite tubular element

Fonseca, E.M.M.; Melo, F.J.M.Q. de; Oliveira, C.A.M de
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.14%
It is presented an alternative formulation to solve the problem of the deformation analysis for tubular element under pinching loads. The solution is based on a new displacement field defined from a total set of trigonometric functions. The solution is developed in a multi-nodal finite tubular ring element with a total of eight degrees of freedom per section considered. The purpose of this paper is to provide an easy alternative formulation when compared with a complex finite shell element or beam element analysis for the same application. Several case studies presented have been compared and discussed with numerical analyses results reported by other authors and the results obtained with a shell element from a Cosmos/M® programme.

The modal analysis of a pipe elbow with realistic boundary conditions

Carneiro, J.O.; Melo, F.J.M.Q. de; Rodrigues, J.F.D.; Lopes, H.; Teixeira, Viriato
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.03%
A vibration analysis for the determination of the natural frequencies and the associated eigenmodes of a pipe elbow with end-flanges or tangent terminations was performed. A numerical investigation of this problem was achieved with a semi-analytic definition finite ring element and a commercial finite element code. To assess the accuracy of the numerical solution for the elbow vibration, an experimental modal analysis was performed on a curved and on a straight pipe. The responses were processed by a data acquisition system which performs a fast Fourier transform on the time histories to convert them from a time to frequency domain, these leading to the extraction of natural frequencies and mode shapes associated with the test-specimen. The results were compared with the corresponding ones from the numerical approach and discussion about the results completes the paper.

A multi-nodal ring finite element for analysis of pipe deflection

Fonseca, E.M.M.; Melo, F.J.M.Q. de; Madureira, M.L.R.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.07%
The main objective of this work is to present a numerical formulation to solve the problem of the deformation analysis ot thin-walled circular cylindrical pipes under concentred loads. The solutions is based on a displacement field entirely defined from a set of trigonometic functiobns where the amplitudes are assigned as a nodal paramenters in a multi-nodal finite element. With this formulation it is possible to provide an easy alternative tool when compared with a complex finite shell or solid element modelling for the same type of applications. The present work permits to examine the defection of pipe rings subjected to lateral (transverse) static loading conditions. Several case studies presented have been compared and discussed with numericalç analysisresults obtained with a shell element from Ansys programme.

Limiting the influence of friction on the split Hopkinson pressure bar tests by using a ring specimen

Alves, Marcilio; Karagiozova, D.; Micheli, G. B.; Calle, Miguel Angel Gonzales
Fonte: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD Publicador: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36%
The deformation of a ring under axial compression is analyzed in order to estimate a favorable ring specimen geometry capable of limiting the influence of friction on the stress-strain curve obtained from SHPB tests. The analysis shows that the use of a ring specimen with a large inner diameter and a small radial thickness offers some advantages comparing with the traditional disk sample. In particular, it can improve the reliability of the test results for ductile materials in the presence of friction. Based on the deformation analysis of a ductile ring under compression, a correction coefficient is proposed to relate the actual material stress strain curve with the reading from the SHPB. It is shown using finite element simulation that the proposed correction can be used for a wide range of conventional ductile materials. Experimental results with steel alloys indicate that the correction procedure is an effective technique for an accurate measurement of the dynamic material strength response. (C) 2012 Elsevier Ltd. All rights reserved.; FAPESP, Brazilian research funding agency; FINEP, Brazilian research funding agency

The modal analysis of a pipe elbow with realistic boundary conditions

Carneiro, J.O.; Melo, F.J.Q. de; Rodrigues, J.F.D.; Lopes, H.; Teixeira, V.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.03%
A vibration analysis for the determination of the natural frequencies and the associated eigenmodes of a pipe elbow with end-flanges or tangent terminations was performed. A numerical investigation of this problem was achieved with a semi-analytic definition finite ring element and a commercial finite element code. To assess the accuracy of the numerical solution for the elbow vibration, an experimental modal analysis was performed on a curved and on a straight pipe. The responses were processed by a data acquisition system which performs a fast Fourier transform on the time histories to convert them from a time to frequency domain, these leading to the extraction of natural frequencies and mode shapes associated with the test-specimen. The results were compared with the corresponding ones from the numerical approach and discussion about the results completes the paper.; (Not applicable)

The linear elastic stress analysis of curved pipes under generalized loads using a reduced integration finite ring element

Melo, F. J. M. Q.; Castro, P. M. S. T.
Fonte: SAGE Journals Publicador: SAGE Journals
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.21%
This paper consists of a linear elastic stress analysis of curved pipes having all the possible boundary conditions in structural engineering and submitted to a generalized in-plane or out-of-plane loading. A semi-analytic displacement formulation ring element was developed, where simple first-degree polynomials were used to interpolate the global shell displacements along the longitudinal direction, and Fourier series were used along the meridional direction. The deformed shape of the curved pipe results from the superposition of the beam-type displacement to that of a toroidal shell. For the first case, the curved pipe was considered as being a short thin-walled straight beam element joining two nodal sections. In this case, as the pipe element is not curved, it is natural to consider that the transverse section undergoes no ovalization or warping. A C0-continuity reduced integration beam element was adopted for this purpose, leading to a simple and economic definition for the stiffness terms. In the second case, the displacement field was assumed to result from a stressed toroidal shell, where the transverse section could ovalize and warp. The stiffness terms following these assumptions are combined with those of the straight beam to give the complete stiffness matrix. This element has the important advantage of generating a zero stress field along the curved centroidal line when submitted to pure in-plane bending and...

A reduced integration mindlin beam element for linear elastic stress analysis of curved pipes under generalized in-plane loading

Melo, F. J. M. Q. de; Castro, P. M. S. T. de
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.01%
This paper presents a ring element for the analysis of in-plane bending of curved pipes. The element is derived from the arch bending theory using short, straight elements as an approach to the curved structure. Each curved pipe element is considered as a straight thin-walled C0-continuity beam element for the purpose of the derivation of the beam stiffness matrix terms. The assumption of the straight elements does not involve ovalization and warping of the transverse section; for the stiffness terms concerning the distortion of the transverse section, the pipe element is assumed curved. This method leads to the important advantage of generating a zero stress field along the curved centroidal line of the element under pure in-plane bending and to the satisfaction of the ‘patch test’.

A semi-membrane ring element for the linear-elastic stress analysis of pipe elbows under in-plane bending

Melo, F. J. M. Q. de; Castro, P. M. S. T. de
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.19%
A semi-membrane deformation ring element is presented. The displacement field involves a combination of first degree interpolation polynomials for the longitudinal direction and Fourier series in the meridional or transverse section. The possible boundary conditions for these kind of shells, namely rigid or warping endflanges and tangent terminations, are readily inserted in this ring element. Results concerning transverse section stresses and flexibility factors are calculated and discussed.

The stress and flexibility analysis of thin-walled curved pipes under out-of-plane bending with the semi-membrane ring element

Melo, F. J. M. Q. de; Castro, P. M. S. T. de
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.1%
A semi-membrane curved ring element, described in a previous paper, is reformulated to take into account more general loading conditions, such as the out-of-plane bending. A new displacement field was defined so that the out-of-plane bending moment could be considered. Results concerning transverse section stresses and flexibility factors are presented and discussed.

Trigonometric function used to formulate a multi-nodal finite tubular element

Fonseca, E. M. M.; Melo, F. J. M. Q. de; Oliveira, C. A. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.14%
It is presented an alternative formulation to solve the problem of the deformation analysis for tubular element under pinching loads. The solution is based on a new displacement field defined from a total set of trigonometric functions. The solution is developed in a multi-nodal finite tubular ring element with a total of eight degrees of freedom per section considered. The purpose of this paper is to provide an easy alternative formulation when compared with a complex finite shell element or beam element analysis for the same application. Several case studies presented have been compared and discussed with numerical analyses results reported by other authors and the results obtained with a shell element from a Cosmos/M® programme.

Construction and Transposition of a 100-kilobase Extended P Element in Drosophila

Ring, Brian C.; Bass, Hank W.; Garza, Dan
Fonte: Cold Spring Harbor Laboratory Press Publicador: Cold Spring Harbor Laboratory Press
Tipo: Artigo de Revista Científica
Publicado em /10/2000 EN
Relevância na Pesquisa
35.96%
We have used P element deletion derivatives at defined locations in the Drosophila genome to construct a 100-kb extended P element more than twice the size of any previously available. We demonstrate that this prototypical extended P element is capable of transposition to new sites in the genome. The structural and functional integrity of a transposed extended P element was confirmed using molecular, genetic, and cytogenetic criteria. This is the first method shown to be capable of producing large, unlinked transpositional duplications in Drosophila. The ability to produce functional transposable elements from half-elements is novel and has many potential applications for the functional analysis of complex genomes.

20 MHz/40 MHz Dual Element Transducers for High Frequency Harmonic Imaging

Kim, Hyung Ham; Cannata, Jonathan M.; Liu, Ruibin; Chang, Jin Ho; Silverman, Ronald H.; Shung, K. Kirk
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/2008 EN
Relevância na Pesquisa
36.27%
Concentric annular type dual element transducers for second harmonic imaging at 20 MHz / 40 MHz were designed and fabricated to improve spatial resolution and depth of penetration for ophthalmic imaging applications. The outer ring element was designed to transmit the 20 MHz signal and the inner circular element was designed to receive the 40 MHz second harmonic signal. Lithium niobate (LiNbO3), with its low dielectric constant, was used as the piezoelectric material to achieve good electrical impedance matching. Double matching layers and conductive backing were used and optimized by KLM modeling to achieve high sensitivity and wide bandwidth for harmonic imaging and superior time-domain characteristics. Prototype transducers were fabricated and evaluated quantitatively and clinically. The average measured center frequency for the transmit ring element was 21 MHz and the one-way –3 dB bandwidth was greater than 50%. The 40 MHz receive element functioned at 31 MHz center frequency with acceptable bandwidth to receive attenuated and frequency downshifted harmonic signal. The lateral beam profile for the 20 MHz ring elements at the focus matched the Field II simulated results well, and the effect of outer ring diameter was also examined. Images of a posterior segment of an excised pig eye and a choroidal nevus of human eye were obtained both for single element and dual element transducers and compared to demonstrate the advantages of dual element harmonic imaging.

Essentiality of a non-RING element in priming donor ubiquitin for catalysis by a monomeric E3

Dou, Hao; Buetow, Lori; Sibbet, Gary J.; Cameron, Kenneth; Huang, Danny T.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.24%
RING E3 ligases catalyze the transfer of ubiquitin (Ub) from E2 ubiquitin-conjugating enzyme thioesterified with Ub (E2~Ub) to substrate. For RING E3 dimers, the RING domain of one subunit and tail of the second cooperate to prime Ub, but how this is accomplished by monomeric RING E3s in the absence of a tail-like component is unknown. Here, we present a crystal structure of a monomeric RING E3, Tyr363-phosphorylated human CBL-B, bound to a stabilized Ub-linked E2, revealing a similar mechanism in activating E2~Ub. Both pTyr363 and the pTyr363-induced element interact directly with Ub’s Ile36 surface, improving the catalytic efficiency of Ub transfer by ~200-fold. Hence, interactions outside the canonical RING domain are crucial for optimizing Ub transfer in both monomeric and dimeric RING E3s. We propose that an additional non-RING Ub-priming element may be a common RING E3 feature.

Application of Taguchi method in optimization of cervical ring cage

Yang, K.; Teo, E.; Fuss, F.
Fonte: Elsevier Sci Ltd Publicador: Elsevier Sci Ltd
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
36.08%
The Taguchi method is a statistical approach to overcome the limitation of the factorial and fractional factorial experiments by simplifying and standardizing the fractional factorial design. The objective of the current study is to illustrate the procedures and strengths of the Taguchi method in biomechanical analysis by using a case study of a cervical ring cage optimization. A three-dimensional finite element (FE) model of C5–C6 with a generic cervical ring cage inserted was modelled. Taguchi method was applied in the optimization of the cervical ring cage in material property and dimensions for producing the lowest stress on the endplate to reduce the risk of cage subsidence, as in the following steps: (1) establishment of objective function; (2) determination of controllable factors and their levels; (3) identification of uncontrollable factors and test conditions; (4) design of Taguchi crossed array layout; (5) execution of experiments according to trial conditions; (6) analysis of results; (7) determination of optimal run; (8) confirmation of optimum run. The results showed that a cage with larger width, depth and wall thickness can produce the lower von Mises stress under various conditions. The contribution of implant materials is found trivial. The current case study illustrates that the strengths of the Taguchi method lie in (1) consistency in experimental design and analysis; (2) reduction of time and cost of experiments; (3) robustness of performance with removing the noise factors. The Taguchi method will have a great potential application in biomechanical field when factors of the issues are at discrete level.; http://www.jbiomech.com/home; Kai Yang...

Compact wideband filter element based on complementary split-ring resonators

Karami Horestani, A.; Shaterian, Z.; Withayachumnankul, W.; Fumeaux, C.; Al-Sarawi, S.; Abbott, D.
Fonte: SPIE; USA Publicador: SPIE; USA
Tipo: Conference paper
Publicado em //2011 EN
Relevância na Pesquisa
36.04%
A double resonance defected ground structure is proposed as a filter element. The structure involves a transmission line loaded with complementary split ring resonators embedded in a dumbbell shape defected ground structure. By using a parametric study, it is demonstrated that the two resonance frequencies can be independently tuned. Therefore the structure can be used for different applications such as dual bandstop filters and wide bandstop filters.; Ali K. Horestani, Zahra Shaterian, Withawat Withayachumnankul, Christophe Fumeaux, Said Al-Sarawi and Derek Abbott

Modelling of surface PM machine using soft magnetic composites and a bonded magnet ring

Tang, C.; Soong, W.; Liew, G.; Ertugrul, N.
Fonte: IEEE; USA Publicador: IEEE; USA
Tipo: Conference paper
Publicado em //2012 EN
Relevância na Pesquisa
36.1%
This paper examines the modelling of a 1.6 kW, 3,000 rpm surface permanent magnet machine which was constructed using soft magnetic composites (SMC) stator tooth segments and a bonded rare-earth magnet ring. It was designed for high torque density and efficiency, and low cogging torque. Both 2D and 3D finite-element model results are provided and compared to the experimental measurements of the flux densities, back-EMF, cogging torque, inductance and power losses. Challenges were found in modelling the magnetization of the bonded-ring magnet. The rated efficiency and field-weakening performance are examined by using both measured and finite-element calculated parameters.; Chun Tang, Wen L. Soong, Gene S. Liew and Nesimi Ertugrul

Finite element simulation of steel ring fragmentation under radial expansion

Rusinek, Alexis; Zaera, Ramón
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em /04/2007 ENG
Relevância na Pesquisa
36.13%
This paper presents a numerical analysis of the expansion of a mild steel ring with of 50 mm diameter, 1 mm thickness and a cross section of 1 mm2. A hardening relation which takes into account strain, strain rate and temperature is proposed to define precisely the thermoviscoplastic behaviour of the material considered in the study. As a second step, an algorithm to integrate the thermoviscoplastic constitutive equations, including the hardening law, is implemented in the commercial finite element code ABAQUS/Explicit via a user subroutine. Finally, this tool is used to simulate the problem of a ring expanding radially in a broad range of strain rates, covering both low and high initial velocities (from 1 to 370 m/s). The aim is to analyse the effect of loading velocity on the number of fragments resulting from the multiple failure of the ring and also the influence of the hardening behaviour of the material on the number of fragments and on the failure mode of the ring, considering different values of the plastic strain hardening exponent n0. A simple failure criterion was used, based on a critical value of the equivalent strain which depends on the hardening exponent. The numerical predictions, in perfect agreement with the experimental observations...

Adjoining a universal inner inverse to a ring element

Bergman, George M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.03%
Let $R$ be an associative unital algebra over a field $k,$ let $p$ be an element of $R,$ and let $R'=R\langle q\mid pqp= p\rangle.$ We obtain normal forms for elements of $R',$ and for elements of $R'$-modules arising by extension of scalars from $R$-modules. The details depend on where in the chain $pR\cap Rp \subseteq pR\cup Rp \subseteq pR + Rp \subseteq R$ the unit $1$ of $R$ first appears. This investigation is motivated by a hoped-for application to the study of the possible forms of the monoid of isomorphism classes of finitely generated projective modules over a von Neumann regular ring; but that goal remains distant. We end with a normal form result for the algebra obtained by tying together a $k$-algebra $R$ given with a nonzero element $p$ satisfying $1\notin pR+Rp$ and a $k$-algebra $S$ given with a nonzero $q$ satisfying $1\notin qS+Sq,$ via the pair of relations $p=pqp,$ $q=qpq.$; Comment: 28 pages. Results on mutual inner inverses added at end of earlier version, and much clarification of wording etc.. After publication, any updates, errata, related references etc. found will be recorded at http://math.berkeley.edu/~gbergman/papers

The CQDRNG8 - a quadratic, isoparametric, axisymmetric finite element for the NASTRAN computer program

Gray, John
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
36.01%
The development of an axisymmetric ring finite element is presented and FORTRAN subroutines for implementing the capability into the MSC/NASTRAN finite element program are given. The element is an eightnoded isoparametric quadrilateral of quadratic order. The following matrices and capabilities are developed: 1. stiffness matrix for homogeneous isotropic materials, 2. thermal conductance matrix for homogeneous isotropic materials, 3. calculation of equivalent nodal forces due to temperature loads, 4. calculation of stresses, and 5. plotting of undeformed and deformed structures. Several classical thermal and structural problems are solved to demonstrate these capabilities. In all cases, the element results compare well with theory. Comparisons are made to existing MSC/NASTRAN axisymmetric finite elements. The new element shows increased accuracy compared to the existing elements. Convergence of the element is shown.

Numerical Modeling of the Thomson Ring in Stationary Levitation Using FEM-Electrical Network and Newton-Raphson

Guzmán,Juan; González-Montañez,Felipe de Jesús; Escarela-Pérez,Rafael; Olivares-Galván,Juan Carlos; Jiménez-Mondragon,Victor Manuel
Fonte: Facultad de Ingeniería, UNAM Publicador: Facultad de Ingeniería, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2015 EN
Relevância na Pesquisa
36.05%
There are a lot of applications of the Thomson ring: levitation of superconductor materials, power interrupters (used as actuator) and elimination of electric arcs. Therefore, it is important the numerical modeling of Thomson ring. The aim of this work is to model the stationary levitation of the Thomson ring. This Thomson ring consists of a copper coil with ferromagnetic core and an aluminum ring threaded in the core. The coil is fed by a cosine voltage to ensure that the aluminum ring is in a stationary levitated position. In this situation, the state of the electromagnetic field is stable and can be used the phasor equations of the electromagnetic field. These equations are discretized using the Galerkin method in the Lagrange base space (finite element method, FEM). These equations are solved using the COMSOL software. A methodology is also described (which uses the Newton-Raphson method) that obtains the separation between coil and aluminum ring. The numerical solutions of this separation are compared with experimental data. The conclusion is that the magnetic coupling of the aluminum ring on the coil can be neglected if the source voltage is high.