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## Efeitos mecânicos causados pela variação da inclinação do parafuso excêntrico no orifício da placa de autocompressão; Mechanical effects caused by the variation of the load screw inclination in the orifice of the dynamic compression plate

Fonte: Sociedade Brasileira de Ortopedia e Traumatologia
Publicador: Sociedade Brasileira de Ortopedia e Traumatologia

Tipo: Revisão de Livro

POR

Relevância na Pesquisa

35.6%

#Fixação interna de fraturas - métodos#Placas ósseas#Parafusos ósseos#Biomecânica#Fracture fixation, internal - methods#Bone plates#Bone screws#Biomechanics

OBJETIVO: Avaliar os efeitos mecânicos da inclinação do parafuso excêntrico sobre a compressão axial com placa. MÉTODOS: Corpos de prova artificiais simulando fragmentos de osso diafisário foram fixados com placa DCP® de 4,5mm de sete orifícios. Uma célula de carga registrou as forças de compressão axial no intervalo entre os fragmentos. Guias de perfuração excêntrica com inclinações em relação ao plano longitudinal e transversal da placa foram confeccionados para o experimento. A compressão foi medida em dois diferentes sítios do foco de fratura virtual. De acordo com a magnitude da inclinação e sua direção em relação ao orifício da placa, oito diferentes grupos foram constituídos. Os ensaios mecânicos registraram a força máxima e a força máxima efetiva. RESULTADOS: A inclinação do parafuso em direção contrária à da rampa de deslizamento do orifício da placa foi acompanhada de diminuição nos valores médios de força máxima e força máxima efetiva de compressão 0º > 10ºi (p < 0,001), 0º > 20ºi (p < 0,001), 0º > 25ºi (p < 0,001). CONCLUSÃO: Em modelo experimental, utilizando-se placas do tipo DCP® não pré-tensionadas, a inclinação na inserção de parafusos excêntricos promoveu alterações nos valores médios da força de compressão axial. Houve diferenças significativas (p < 0...

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## Thermo-mechanical vibration analysis of annular and circular graphene sheet embedded in an elastic medium

Fonte: Associação Brasileira de Ciências Mecânicas
Publicador: Associação Brasileira de Ciências Mecânicas

Tipo: Artigo de Revista Científica
Formato: text/html

Publicado em 01/08/2014
EN

Relevância na Pesquisa

95.89%

In this study, the vibration behavior of annular and circular graphene sheet coupled with temperature change and under in-plane pre-stressed is studied. Influence of the surrounding elastic medium 011 the fundamental frequencies of the single-layered graphene sheets (SLGSs) is investigated. Both Winkler-type and Pasternak- type models are employed to simulate the interaction of the graphene sheets with a surrounding elastic medium. By using the nonlocal elasticity theory the governing equation is derived for SLGSs. The closed-form solution for frequency vibration of circular graphene sheets lias been obtained and nonlocal parameter, inplane pre-stressed, the parameters of elastic medium and temperature change appears into arguments of Bessel functions. The results are subsequently compared with valid result reported in the literature and the molecular dynamics (MD) results. The effects of the small scale, pre-stressed, mode number, temperature change, elastic medium and boundary conditions on natural frequencies are investigated. The non-dimensional frequency decreases at high temperature case with increasing the temperature change for all boundary conditions. The effect of temperature change 011 the frequency vibration becomes the opposite at high temperature case in compression with the low temperature case. The present research work thus reveals that the nonlocal parameter...

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## Impact behaviour of preloaded glass/polyester woven plates

Fonte: Elsevier
Publicador: Elsevier

Tipo: Artigo de Revista Científica
Formato: application/pdf

Publicado em /05/2009
ENG

Relevância na Pesquisa

45.62%

#Glass fibres#Composite materials#Impact behaviour#Modelling#In-plane preloaded#Ingeniería Mecánica#Ingeniería Industrial

In this work, the effect of a biaxial preload in the behaviour of glass/polyester woven-laminate plates subjected to high-velocity transversal impact was studied. For this, an analytic model based on energy considerations that include the presence of an in-plane preload was used. The results of the analytic model for the biaxial preload state were compared with those found for a non-preload plate, the difference between them being minimal for the pre-stressed level reached in the tests (31% of the static UTS). Therefore, numerical simulations were made in order to study the effect of the preload in greater detail; furthermore, experimental tests were conducted, validating the analytic and numerical model. In general, the two methods revealed minimal differences between the values of the ballistic limit and those of the residual velocity.; The authors are indebted to the Spanish Comisión Interministerial de Ciencia y Tecnología (Project MAT2001-0735) for the financial support of this work.; 7 pages, 4 figures.-- Issue title: "16th International Conference on Composite Materials (ICCM-16) -- ONR (Office of Naval Research) sessions on Dynamic Failure and Durability" (Kyoto, Japan, Jul 6–11, 2007).

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## Impact Behavior of In-plane Pre-stressed Pannels

Fonte: Universidade Carlos III de Madrid
Publicador: Universidade Carlos III de Madrid

Tipo: info:eu-repo/semantics/conferenceObject; info:eu-repo/semantics/article
Formato: application/pdf

Publicado em //2005
ENG

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95.86%

In this paper the behaviour of plates when they are subjected to normal impact under in-plane pre-stressed conditions was studied. Two kinds of lightweight materials were considered: aluminium alloy 7075 and quasi-isotropic glass fibre-reinforced vinylester resin. The residual velocity, the ballistic limit and, in the case of the composite material, the delaminated area, were measured in each test. Unstable cracks, that generate the catastrophic failure of the panel, were observed in the case of the aluminium at pre-stressed load levels lower than those inducing material yielding.; The authors are indebted to the Spanish Comisión Interministerial de Ciencia y Tecnología (Project MAT2001-0735) for the financial support of this work.; The 3rd International Conference on Structural Stability and Dynamics,, June 19-22, 2005, Kissimmee, Florida

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## Strain dependent elastic modulus of graphene

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 21/04/2015

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Indentation experiments on graphene membranes pre-stressed by hydrostatic
pressure show an increase in effective elastic modulus from 300 N/m in non
pressurized membranes to 700 N/m for pre-strains above 0.5 %. This pronounced
dependence of the stiffness of graphene with strain is attributed to its high
anharmonicity and the great influence of out of plane corrugations of this
atomic thick membrane in its mechanical properties. Our experimental findings
imply that graphene measured stiffness is highly influenced by the presence of
corrugations and that the in plane elastic modulus corresponding to atomic bond
stretching is more akin to 700 N/m, instead of the commonly accepted 340 N/m.; Comment: 17 pages and 4 figures

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## In-Plane Bistable Nanowire For Memory Devices

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 07/05/2008

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45.71%

We present a nanomechanical device design to be used in a non-volatile
mechanical memory point. The structure is composed of a suspended slender
nanowire (width : 100nm, thickness 430nm length : 8 to 30$\mu$m) clamped at its
both ends. Electrodes are placed on each sides of the nanowire and are used to
actuate the structure (writing, erasing) and to measure the position through a
capactive bridge (reading). The structure is patterned by electron beam
lithography on a pre-stressed thermally grown silicon dioxide layer. When later
released, the stressed material relaxes and the beam buckles in a position of
lower energy. Such symmetric beams, called Euler beams, show two stable
deformed positions thus form a bistable structure. This paper will present the
fabrication, simulation and mechanical and electrical actuation of an in plane
bistable nanowire. Final paper will include a section on FEM simulations.; Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838)

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## Initial stresses in elastic solids: Constitutive laws and acoustoelasticity

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 08/02/2013

Relevância na Pesquisa

25.64%

On the basis of the nonlinear theory of elasticity, the general constitutive
equation for an isotropic hyperelastic solid in the presence of initial stress
is derived. This derivation involves invariants that couple the deformation
with the initial stress and in general, for a compressible material, it
requires 10 invariants, reducing to 9 for an incompressible material.
Expressions for the Cauchy and nominal stress tensors in a finitely deformed
configuration are given along with the elasticity tensor and its specialization
to the initially stressed undeformed configuration. The equations governing
infinitesimal motions superimposed on a finite deformation are then used to
study the combined effects of initial stress and finite deformation on the
propagation of homogeneous plane waves in a homogeneously deformed and
initially stressed solid of infinite extent. This general framework allows for
various different specializations, which make contact with earlier works. In
particular, connections with results derived within Biot's classical theory are
highlighted. The general results are also specialized to the case of a small
initial stress and a small pre-deformation, i.e. to the evaluation of the
acoustoelastic effect. Here the formulas derived for the wave speeds cover the
case of a second-order elastic solid without initial stress and subject to a
uniaxial tension [Hughes and Kelly...

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## Buckling and wrinkling from geometric and energetic viewpoints

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 24/11/2015

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We discuss shape profiles emerging in inhomogeneous growth of squeezed
tissues. Two approaches are used simultaneously: i) conformal embedding of
two-dimensional domain with hyperbolic metrics into the plane, and ii) a pure
energetic consideration based on the minimization of the total energy
functional. In the latter case the non-uniformly pre-stressed plate, which
models the inhomogeneous two-dimensional growth, is analyzed in linear regime
under small stochastic perturbations. It is explicitly demonstrated that both
approaches give consistent results for buckling profiles and reveal
self-similar behavior. We speculate that fractal-like organization of growing
squeezed structure has a far-reaching impact on understanding cell
proliferation in various biological tissues.; Comment: 13 pages, 8 figures

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## On interface waves in misoriented pre-stressed incompressible elastic solids

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 23/04/2013

Relevância na Pesquisa

45.65%

Some relationships, fundamental to the resolution of interface wave problems,
are presented. These equations allow for the derivation of explicit secular
equations for problems involving waves localized near the plane boundary of
anisotropic elastic half-spaces, such as Rayleigh, Sholte, or Stoneley waves.
They are obtained rapidly, without recourse to the Stroh formalism. As an
application, the problems of Stoneley wave propagation and of interface
stability for misaligned predeformed incompressible half-spaces are treated.
The upper and lower half-spaces are made of the same material, subject to the
same prestress, and are rigidly bonded along a common principal plane. The
principal axes in this plane do not however coincide, and the wave propagation
is studied in the direction of the bisectrix of the angle between a principal
axis of the upper half-space and a principal axis of the lower half-space.

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## Hyperelastic cloaking theory: Transformation elasticity with pre-stressed solids

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 20/04/2012

Relevância na Pesquisa

45.71%

Transformation elasticity, by analogy with transformation acoustics and
optics, converts material domains without altering wave properties, thereby
enabling cloaking and related effects. By noting the similarity between
transformation elasticity and the theory of incremental motion superimposed on
finite pre-strain it is shown that the constitutive parameters of
transformation elasticity correspond to the density and moduli of
small-on-large theory. The formal equivalence indicates that transformation
elasticity can be achieved by selecting a particular finite (hyperelastic)
strain energy function, which for isotropic elasticity is semilinear strain
energy. The associated elastic transformation is restricted by the requirement
of statically equilibrated pre-stress. This constraint can be cast as $\tr
{\mathbf F} =$ constant, where $\mathbf{F}$ is the deformation gradient,
subject to symmetry constraints, and its consequences are explored both
analytically and through numerical examples of cloaking of anti-plane and
in-plane wave motion.; Comment: 20 pages, 5 figures

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## Acoustic waves at the interface of a pre-stressed incompressible elastic solid and a viscous fluid

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 28/11/2007

Relevância na Pesquisa

35.6%

We analyse the influence of pre-stress on the propagation of interfacial
waves along the boundary of an incompressible hyperelastic half-space that is
in contact with a viscous fluid extending to infinity in the adjoining
half-space. One aim is to derive rigorously the incremental boundary conditions
at the interface; this derivation is delicate because of the interplay between
the Lagrangian and the Eulerian descriptions but is crucial for numerous
problems concerned with the interaction between a compliant wall and a viscous
fluid. A second aim of this work is to model the ultrasonic waves used in the
assessment of aortic aneurysms, and here we find that for this purpose the
half-space idealization is justified at high frequencies. A third goal is to
shed some light on the stability behaviour in compression of the solid
half-space, as compared with the situation in the absence of fluid; we find
that the usual technique of seeking standing waves solutions is not appropriate
when the half-space is in contact with a fluid; in fact, a correct analysis
reveals that the presence of a viscous fluid makes a compressed neo-Hookean
half-space slightly more stable. For a wave travelling in a direction of
principal strain, we obtain results for the case of a general (incompressible
isotropic) strain-energy function. For a wave travelling parallel to the
interface and in an arbitrary direction in a plane of principal strain...

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## Interface waves in pre-stressed incompressible solids

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 03/12/2007

Relevância na Pesquisa

35.65%

We study incremental wave propagation for what is seemingly the simplest
boundary value problem, namely that constitued by the plane interface of a
semi-infinite solid. With a view to model loaded elastomers and soft tissues,
we focus on incompressible solids, subjected to large homogeneous static
deformations. The resulting strain-induced anisotropy complicates matters for
the incremental boundary value problem, but we transpose and take advantage of
powerful techniques and results from the linear anisotropic elastodynamics
theory. In particular we cover several situations where fully explicit secular
equations can be derived, including Rayleigh and Stoneley waves in principal
directions, and Rayleigh waves polarized in a principal plane or propagating in
any direction in a principal plane. We also discuss the merits of polynomial
secular equations with respect to more robust, but less transparent, exact
secular equations.

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## Determination of source parameters by amplitude equalization of seismic surface waves: 2. Release of tectonic strain by underground nuclear explosions and mechanisms of earthquakes

Fonte: American Geophysical Union
Publicador: American Geophysical Union

Tipo: Article; PeerReviewed
Formato: application/pdf

Publicado em 15/02/1965

Relevância na Pesquisa

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The radiation patterns of Love and Rayleigh waves from three nuclear explosions (Hardhat, Haymaker, and Shoal) are studied to determine the nature of the asymmetry of radiation and the mechanism of Love wave generation. From a comparative study of different explosions it is reasoned that the Love waves are generated at the source of the explosion. The source function, represented as the superimposition of an isotropic dilatational component due to the explosion and a multipolar component due to the release of tectonic strain energy, is consistent with the observed radiation patterns and the amplitude spectrums. The amount of seismic energy due to the strain release is computed. In some cases (Haymaker and Shoal) it is found that this energy may be due to the relaxation of the pre-stressed medium by the explosion-formed cavity. In the case of Hardhat it is concluded that the explosion must have triggered some other strain release mechanism, such as an earthquake. The amplitude equalization method is applied to surface waves from an earthquake to determine the source parameters. From only the amplitude spectrums and radiation patterns of Love and Rayleigh waves, the source functions, source depth, strike and dip of the fault plane, and the rake of displacement are determined for the July 20...

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