Analysis of laminated beams using the natural neighbour radial point interpolation method

Neste trabalho aplica‐se o método sem malha natural neighbour radial point interpolation method (NNRPIM) à análise unidimensional de vigas laminadas, considerando a teoria de Timoshenko. O NNRPIM combina o conceito matemático dos vizinhos naturais com a interpolação radial pontual. Os diagramas de Voronoï permitem impor a conectividade nodal e construir a malha de fundo para efeitos de integração, por intermédio das células de influência. É apresentada a construção das funções de interpolação NNRPIM, sendo, para estas, usada a função de base radial multiquadrática. As funções de interpolação geradas possuem continuidade infinita e a propriedade de delta Kronecker, o que facilita a imposição das condições de fronteira, uma vez que estas podem ser impostas com o método da imposição direta, tal como no método dos elementos finitos (FEM). De modo a obter o campo de deslocamentos e de deformações, a teoria de deformação de Timoshenko para vigas sujeitas a esforços transversos é considerada. Vários exemplos numéricos de vigas isotrópicas e vigas laminadas são apresentados de modo a demonstrar a convergência e a exatidão da aplicação proposta. Os resultados obtidos são comparados com soluções analíticas disponíveis na literatura.In this work, a meshless method, “natural neighbour radial point interpolation method” (NNRPIM), is applied to the one‐dimensional analysis of laminated beams, considering the theory of Timoshenko. The NNRPIM combines the mathematical concept of natural neighbours with the radial point interpolation. Voronoï diagrams allows to impose the nodal connectivity and the construction of a background mesh for integration purposes, via influence cells. The construction of the NNRPIM interpolation functions is shown, and, for this, it is used the multiquadratic radial basis function. The generated interpolation functions possess infinite continuity and the delta Kronecker property, which facilitates the enforcement of boundary conditions, since these can be directly imposed, as in the finite element method (FEM). In order to obtain the displacements and the deformation fields, it is considered the Timoshenko theory for beams under transverse efforts. Several numerical examples of isotropic beams and laminated beams are presented in order to demonstrate the convergence and accuracy of the proposed application. The results obtained are compared with analytical solutions available in the literature.Peer Reviewe

Cupula response to otoconia debris in the semicircular canal

The vertigo symptoms are commonly related with inner ear diseases and it affects 20%-30% of the world population, and its prevalence increases with age. In this work, a three-dimensional computational model of the semicircular canal of the vestibular system, containing the fluids which promote the body balance, was used. The smoothed-particle hydrodynamics method was the computational process used to simulate the fluid behaviour, in which the elements are represented by particles and have constant mass. The other vestibular components were discretized using the finite element method. The movement performed to endolymph/cupula interaction analysis was reproduced in the simulation through the acquisition of the displacement field based on image analysis. The results obtained with the frames of the video recorded during the process is the appropriate method to simulate the real moves, due to the analysis of the region of interest located near the inner ear. The data obtained from the video acquisition were the input in the simulation with the semicircular model. The principal stress cupular response allowed to understand the interaction of the vestibular structures during a vertigo episode, and the influence of the otoconia in the cupula displacement. This model is the first step to improve the vestibular rehabilitation and the quality of life of patients suffering from vertigo.info:eu-repo/semantics/publishedVersio

First in-beam studies of a Resistive-Plate WELL gaseous multiplier

We present the results of the first in-beam studies of a medium size (10$\times$10 cm$^2$) Resistive-Plate WELL (RPWELL): a single-sided THGEM coupled to a pad anode through a resistive layer of high bulk resistivity ($\sim$10$^9 \Omega$cm). The 6.2~mm thick (excluding readout electronics) single-stage detector was studied with 150~GeV muons and pions. Signals were recorded from 1$\times$1 cm$^2$ square copper pads with APV25-SRS readout electronics. The single-element detector was operated in Ne\(5% $\mathrm{CH_{4}}$) at a gas gain of a few times 10$^4$, reaching 99$\%$ detection efficiency at average pad multiplicity of $\sim$1.2. Operation at particle fluxes up to $\sim$10$^4$ Hz/cm$^2$ resulted in $\sim$23$\%$ gain drop leading to $\sim$5$\%$ efficiency loss. The striking feature was the discharge-free operation, also in intense pion beams. These results pave the way towards robust, efficient large-scale detectors for applications requiring economic solutions at moderate spatial and energy resolutions.Comment: Accepted by JINS

Study of the effect of friction between the ossicles of the middle ear

The human ear is a complex biomechanical system and is divided by three parts: outer, middle and inner ear. The middle ear is formed by three ossicles (malleus, incus and stapes), ligaments, muscles and tendons, that amplify the sound, sending the sound waves to the inner ear. In this work, a finite element modelling of the middle ear and ligaments was made. The connection between ossicles was achieved using contact formulation. The modelling of ligaments was based in a hyperelastic model. Studies based in the displacement field of the eardrum and footplate were made, as well as the rotation of the footplate. The stress field in the ligaments to the exterior of the ossicular chain was still analyzed. These studies were done for different friction rates, between the ossicles, and for different acoustic pressure values applied in the eardrum. We can conclude that the connection between the ossicles may be assigned by contact formulation including friction. For simulation proposes, we can assume a quasi-rigid connection between ossicles.Peer Reviewe

Study of the middle ear behavior considering the presence of fluid

O objetivo deste trabalho foi estudar a influência de diferentes fluidos dentro e fora da cavidade timpânica no comportamento biomecânico do ouvido médio. O modelo computacional 3 D da cadeia tímpano‐ossicular foi construído através de imagens de tomografia axial computorizada (TAC). Após a construção do modelo da cadeia tímpano‐ossicular, para a parte interna da membrana timpânica foi criada a caixa timpânica, que inclui toda a cadeia ossicular, e para a parte externa da membrana foi criada uma passagem, simulando o canal auditivo externo. A discretização do modelo foi feita utilizando o método dos elementos finitos, com base no software ABAQUS. As propriedades mecânicas foram extraídas de trabalhos anteriores. Foram obtidos os deslocamentos do umbo e de um ponto central da platina do estribo, para um nível de pressão sonora de 105 dB aplicada na membrana timpânica, comparando a cadeia tímpano‐ossicular e os diferentes níveis de pressão externa e interna do ouvido médio (fluido líquido e fluido gasoso). Os resultados demonstram que o comportamento biomecânico do ouvido médio é diferente para os diferentes níveis de pressões testadas neste modelo. Quando utilizada uma pressão de fluido líquido, os deslocamentos são de amplitude inferior quando comparados com os resultados obtidos com pressão de ar.The objective of this work is to study the influence of different fluids of the tympanic cavity into the biomechanical behavior of the middle ear. The 3 D computer model of the tympanic ossicular chain was built using images from computed tomography (CT). After construction of the tympanic ossicular chain model, it was adapted the simulation by placing the passage to the external auditory canal and to the tympanic cavity. The discretization of the model was made using the finite element method based on ABAQUS software. The mechanical properties were extracted from previous works. The umbo and the stapes footplate displacements, for a sound pressure level of 105 dB applied in tympanic membrane were obtained, comparing the tympanic ossicular chain and the different levels of external and internal pressure in the middle ear (liquid and air). The results demonstrate that the biomechanical behavior of the middle ear is different for different levels of pressure tested in this model. When using liquid, displacements are of lower amplitude when compared with the results obtained with air.Peer Reviewe

Micro-Hole and Strip Plate (MHSP) operation in CF4

The Micro-Hole and Strip Plate (MHSP) is a hybrid electron multiplier which combines the working principles of a Gas Electron Multiplier (GEM) and a Micro-Strip Gas Counter (MSGC). The compact double stage electron multiplication processes found in the MHSP enables the realisation of higher gas gain than the lone GEM operation. Thermal neutron detection using gas detectors involves the use of gas with another suitable stopping gas, operated at elevated pressure to confine the products of the neutron- reaction. It is, however, well known that the gain of GEMs drops too sharply with increasing chamber pressure.http://www.sciencedirect.com/science/article/B6TJM-4NS2G9V-D/1/497af6476b376b1c2f407a3fa7ff735

New enhanced strain elements for incompressible problems

A new enhanced strain element, based on the definition of extra compatibles modes of deformation added to the standard four-node finite element, is initially presented. The element is built with the objective of addressing incompressible problems and avoiding locking effects. By analysing at the element level the deformation modes which form a basis for the incompressible subspace the extra modes of deformation are proposed in order to provide the maximum possible dimension to that subspace. Subsequently another new element with more degrees of freedom is formulated using a mixed method. This is done by including an extra field of variables related to the derivatives of the displacement field of the extra compatible modes defined previously. The performance of the elements proposed is assessed in linear and non-linear situations. Copyright (C) 1999 John Wiley & Sons, Ltd