Analytical method to measure bending deformations in prismatic optical films

The aim of this work is to provide an analytical method based on experimental measurements in order to obtain the prismatic film deformation for different curvatures of Hollow Cylindrical Prismatic Light Guides (CPLG). To conform cylindrical guides is necessary bend the film to guide the light, changes induced by curving the film give rise to deformation shifts. Light losses affected by deformation has been experimentally evaluated and numerically analyzed. The effect of deformation in prism angle is specially increased for CPLG of curvatures higher than 20 m-1. An experimental method for accurate transmittance measurements related to bending is presented.

Influência da rigidez vertical no comportamento mecânico e dimensionamento da via permanente ferroviária.

A via permanente representa um elemento imprescindível na composição do transporte ferroviário e seu desempenho deve ser adequado, de forma a garantir tanto segurança quanto conforto. Assim, diversos aspectos devem ser analisados ainda na fase de projeto, através de dimensionamentos que confrontem diferentes parâmetros da resposta da via e os limites estabelecidos. Dessa forma, o conhecimento do comportamento mecânico da via, devido aos esforços impostos pela passagem do material rodante, passa a ser essencial no projeto de uma estrutura que garanta os requisitos necessários, sem ser inviável economicamente. Visto que esse comportamento mecânico é muito sensível à rigidez vertical da estrutura, o presente trabalho apresenta análises da influência desse parâmetro na resposta da via e, consequentemente, no seu dimensionamento. Nesse contexto, o trabalho abrange tanto o caso de vias em lastro solicitadas por trens de carga, quanto o caso de vias em laje solicitadas por trens de passageiros em meios urbanos. No primeiro caso são realizados estudos paramétricos, por meio de modelos clássicos e um modelo mecanicista, para a análise de momentos fletores e deflexões nos trilhos, bem como tensões verticais nas camadas de lastro, sub-lastro e subleito. Já no segundo caso, são realizados estudos paramétricos relativos à transmissibilidade e à atenuação de vibrações causadoras de ruído secundário. Também é feita uma análise da influência da rigidez vertical na amplificação dinâmica das cargas estáticas, que pode ser aplicada a ambos os casos citados e até extrapolada para casos de vias de alta velocidade. Os resultados mostraram que aumentos de rigidez vertical resultam em ganhos do ponto de vista de momentos fletores e deflexões nos trilhos, além de maior resistência e capacidade de dissipação de tensões verticais nas camadas de lastro, sub-lastro e subleito. Por outro lado, esses aumentos também levaram a maiores tensões nas camadas subjacentes à grade citadas, além de atenuações de vibrações em menores intervalos de frequência e maiores amplificações dinâmicas das cargas estáticas em vias de alta velocidade. Assim, é mostrado que a influência da rigidez vertical, tanto da via como um todo quanto de alguns elementos específicos, não deve ser analisada de forma genérica, pois, dependendo do parâmetro da resposta da via considerado no dimensionamento, seu aumento pode representar uma influência positiva ou negativa.

Coupled Biomechanical Response of the Cornea Assessed by Non-Contact Tonometry. A Simulation Study

The mechanical response of the cornea subjected to a non-contact air-jet tonometry diagnostic test represents an interplay between its geometry, the corneal material behavior and the loading. The objective is to study this interplay to better understand and interpret the results obtained with a non-contact tonometry test. A patient-specific finite element model of a healthy eye, accounting for the load free configuration, was used. The corneal tissue was modeled as an anisotropic hyperelastic material with two preferential directions. Three different sets of parameters within the human experimental range obtained from inflation tests were considered. The influence of the IOP was studied by considering four pressure levels (10–28 mmHg) whereas the influence of corneal thickness was studied by inducing a uniform variation (300–600 microns). A Computer Fluid Dynamics (CFD) air-jet simulation determined pressure loading exerted on the anterior corneal surface. The maximum apex displacement showed a linear variation with IOP for all materials examined. On the contrary, the maximum apex displacement followed a cubic relation with corneal thickness. In addition, a significant sensitivity of the apical displacement to the corneal stiffness was also obtained. Explanation to this behavior was found in the fact that the cornea experiences bending when subjected to an air-puff loading, causing the anterior surface to work in compression whereas the posterior surface works in tension. Hence, collagen fibers located at the anterior surface do not contribute to load bearing. Non-contact tonometry devices give useful information that could be misleading since the corneal deformation is the result of the interaction between the mechanical properties, IOP, and geometry. Therefore, a non-contact tonometry test is not sufficient to evaluate their individual contribution and a complete in-vivo characterization would require more than one test to independently determine the membrane and bending corneal behavior.

Numerical and experimental investigation of structural stiffness influence on ratcheting convection cell in granular soils under cyclic loading

Lateral cyclic loaded structures in granular soils can lead to an accumulation of irreversible strains by changing their mechanical response (densification) and forming a closed convective cell in the upper layer of the bedding. In the present thesis the convective cell dimension, formation and grain migration inside this closed volume have been studied and presented in relation to structural stiffness and different loads. This relation was experimentally investigated by applying a cyclic lateral force to a scaled flexible vertical element embedded in dry granular soil. The model was monitored with a camera in order to derive the displacement field by means of the PIV technique. Modelling large soil deformation turns out to be difficult, using mesh-based methods. Consequently, a mesh-free approach (DEM) was chosen in order to investigate the granular flow with the aim of extracting interesting micromechanical information. In both the numerical and experimental analyses the effect of different loading magnitudes and different dimensions of the vertical element were considered. The main results regarded the different development, shape and dimensions of the convection cell and the surface settlements. Moreover, the Discrete Element Method has proven to give satisfactory results in the modelling of large deformation phenomena such as the ratcheting convective cell.

Structure verification of bus passenger seats. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Structural design of roadway shoulders. Final report.

Federal Highway Administration, Office of Engineering and Highway Operations Research and Development, McLean, Va.

Vehicle component characterization. Volume I: project results. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

Vehicle component characterization. Volume II - data appendices. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

Hybrid materials substitution for Oldsmobile Omega X-body components. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

A pulsed bending magnet for the beam switchyard area of the Stanford two-mile linear electron accelerator /

"AEC Contract AT(04-3)-400."

A theory for the effect of mean stress on fatigue of metals under combined torsion and axial load or bending.

"Department of Army Project no. 5B99-01-004, Ordnance R and D Project no. TB2-0001, Office of Ordnance Research Project no. 1348, Contract no. DA-19-020-ORD-3250."

Axial tension and bending interaction curves for members loaded inelastically,

Mode of access: Internet.

A bending magnet with nonsaturating shimming /

"AEC Contract AT(04-3)-400."

A dietary factor essential for guinea pigs; a preliminary study of wrist stiffness, tissue calcification, and an upset phosphorus metabolism in guinea pigs on certain diets.

Special problem (M. N. S.)--Cornell Univ., Feb. 1948.