Encontrados 13 documentos, a visualizar página 1 de 2
Vibrações associadas à variação rápida da rigidez da via férrea por acção de ca...
Dimitrovová, Zuzana; Varandas, José N.; de Almeida, João R.; Silva, Manuel A.G.A variação rápida da rigidez das vias férreas, quer devido a mudança de solução estrutural, quer devido a alteração das condições geotécnicas pode induzir vibrações de amplitude excessiva à passagem de comboios de alta velocidade. Este comportamento causa desgaste da via. Nesta comunicação abordam-se aspectos de modelação e análise do problema. A contribuição consiste em desenvolvimento das soluções analíticas ...
TÉCNICAS DE PÓS-PROCESSAMENTO EM ESCOAMENTOS DE FRONTEIRA LIVRE NOS PROCESSOS D...
Dimitrovová, ZuzanaAs técnicas de pós-processamento da solução de MEF consistem em recálculo de modo que a taxa de convergência aumenta sem a necessidade de refinar a malha. São eficientes quando a maior precisão exige-se nas derivadas de variáveis nos nós na fronteira da condição de Dirichlet. Podem ser usadas na simulação de escoamento de Darcy de fronteira livre durante a infiltração de resina, porque apenas velocidades na fro...
MODELAÇÃO DE REFORÇO POR CFRP DE VIGAS DE BETÃO ARMADO
Marreiros, Rui; Dimitrovová, Zuzana; Silva, Manuel A.G.Provetes compostos por duas vigas de betão armado ligadas por rótula metálica na zona superior e por uma faixa compósita de CFRP colada na zona inferior foram ensaiados à flexão em quatro pontos, em programa dirigido à avaliação dos efeitos de envelhecimento acelerado, por ciclos de humidade e de nevoeiro salino, na aderência entre compósito e betão. Reportam-se resultados obtidos para vários patamares de carga...
POST-PROCESSING TECHNIQUES SUITABILITY FOR MESOLEVEL FREE BOUNDARY FLOWS
Dimitrovová, ZuzanaReliable flow simulation software is inevitable to determine an optimal injection strategy in Liquid Composite Molding processes. Several methodologies can be implemented into standard software in order to reduce CPU time. Post-processing techniques might be one of them. Post-processing a finite element solution is a well-known procedure, which consists in a recalculation of the originally obtained quantities s...
Design of New Materials for Passive Vibration Control
Lopes, Tiago; Dimitrovová, Zuzana; Faria, Luis; Rodrigues, Helder C.The objective of this contribution is to extend the models of cellular/composite material design to nonlinear material behaviour and apply them for design of materials for passive vibration control. As a first step a computational tool allowing determination of optimised one-dimensional isolator behaviour was developed. This model can serve as a representation for idealised macroscopic behaviour. Optimal isolat...
Ground Vibrations Induced by High-Speed Trains in Regions with Sudden Foundatio...
Dimitrovová, Zuzana; Varandas, José N.; Silva, Manuel A.G.In this paper analytical transient solutions of dynamic response of one-dimensional systems with sudden change of foundation stiffness are derived. In more details, cantilever dynamic response, expressed in terms of vertical displacement, is extended to account for elastic foundation and then two cantilever solutions, corresponding to beams clamped on left and right hand side, with different value of Winkler co...
SENSITIVITY ANALYSIS OF TRACK VIBRATIONS DUE TO VERTICAL STIFFNESS VARIATION IN...
Dimitrovová, Zuzana; Varandas, José N.; de Almeida, João R.; Silva, Manuel G.A.High speed trains, when crossing regions with abrupt changes in vertical stiffness of the track and/or subsoil, may generate excessive ground and track vibrations. There is an urgent need for specific analyses of this problem so as to allow reliable esimates of vibration amplitude. Full understanding of these phenomena will lead to new construction solutions and mitigation of undesirable features. In this paper...
The Influence of Damping on Vibration Induced by High-Speed Trains
Dimitrovová, Zuzana; Varandas, José N.Passage of high-speed trains may induce high ground and track vibrations, which, besides increasing wheel, rail and track deterioration, may have a negative impact on the vehicle stability and on the passengers comfort. In this paper two distinct analyses are presented. The first one is dedicated to efficient decoupling of rail and soil vibrations by suggesting new interface materials in rail-sleeper fixing sys...
Post-processing Techniques in Free Boundary Flows during Liquid Composite Mould...
Dimitrovová, ZuzanaPost-processing a finite element solution is a well-known technique, which consists in a recalculation of the originally obtained quantities such that the rate of convergence increases without the need for expensive remeshing techniques. Postprocessing is especially effective in problems where better accuracy is required for derivatives of nodal variables in regions where Dirichlet essential boundary condition ...
MASS CONSERVATION ENHANCEMENT OF FREE BOUNDARY FLOWS IN COMPOSITES MANUFACTURING
Dimitrovová, ZuzanaUndesirable void formation during the injection phase of the liquid composite molding process can be understood as a consequence of the non-uniformity of the flow front progression, caused by the dual porosity of the fiber perform. Therefore the best examination of the void formation physics can be provided by a mesolevel analysis, where the characteristic dimension is given by the fiber tow diameter. In mesole...
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