Large volume artefact for calibration of multi-sensor projected fringe systems

Fringe projection is a commonly used optical technique for measuring the shapes of objects with dimensions of up to about 1 m across. There are however many instances in the aerospace and automotive industries where it would be desirable to extend the benefits of the technique (e.g., high temporal and spatial sampling rates, non-contacting measurements) to much larger measurement volumes. This thesis describes a process that has been developed to allow the creation of a large global measurement volume from two or more independent shape measurement systems. A new 3-D large volume calibration artefact, together with a hexapod positioning stage, have been designed and manufactured to allow calibration of volumes of up to 3 x 1 x 1 m3. The artefact was built from carbon fibre composite tubes, chrome steel spheres, and mild steel end caps with rare earth rod magnets. The major advantage over other commonly used artefacts is the dimensionally stable relationship between features spanning multiple individual measurement volumes, thereby allowing calibration of several scanners within a global coordinate system, even when they have non-overlapping fields of view. The calibration artefact is modular, providing the scalability needed to address still larger measurement volumes and volumes of different geometries. Both it and the translation stage are easy to transport and to assemble on site. The artefact also provides traceabitity for calibration through independent measurements on a mechanical CMM. The dimensions of the assembled artefact have been found to be consistent with those of the individual tube lengths, demonstrating that gravitational distortion corrections are not needed for the artefact size considered here. Deformations due to thermal and hygral effects have also been experimentally quantified. The thesis describes the complete calibration procedure: large volume calibration artefact design, manufacture and testing; initial estimation of the sensor geometry parameters; processing of the calibration data from manually selected regions-of-interest (ROI) of the artefact features; artefact pose estimation; automated control point selection, and finally bundle adjustment. An accuracy of one part in 17 000 of the global measurement volume diagonal was achieved and verified

Nuclear magnetic resonance measurements of velocity distributions in an ultrasonically vibrated granular bed

This paper was accepted for publication in the journal Philosophical Transactions of The Royal Society A-Mathematical Physical and Engineering Sciences and the definitive published version is available at http://dx.doi.org/10.1098/rsta.2013.0185We report the results of nuclear magnetic resonance (NMR) imaging experiments on granular beds of mustard grains fluidised by vertical vibration at ultrasonic frequencies. The variation of both granular temperature and packing fraction with height was measured within the three-dimensional cell for a range of vibration frequencies, amplitudes and numbers of grains. Small increases in vibration frequency were found – contrary to the predictions of classical ‘hard-sphere’ expressions for the energy flux through a vibrating boundary – to result in dramatic reductions in granular temperature. Numerical simulations of the grain-wall interactions, using experimentally-determined Hertzian contact stiffness coefficients, showed that energy flux drops significantly as the vibration period approaches the grain-wall contact time. The experiments thus demonstrate the need for new models for ‘soft-sphere’ boundary conditions at ultrasonic frequencies

Reducción y optimización de costos operativos en perforación y voladura Minera Yanaquihua S.A.C. E.E. Adgeminco S.A.C.

TesisEl presente trabajo tiene como objetivo exponer la factibilidad de la reducción de los costos operativos en una empresa minera, aplicando para ello estándares óptimos de trabajo en las principales operaciones unitarias de minado que son la perforación y voladura, asegurando de esta manera el éxito de todo el ciclo de minado. Éxito que se logra con un sistema de control y medición exhaustiva de las operaciones y que se sintetizan en la supervisión y capacitación continua en lo concerniente a la aplicación de estándares óptimos de trabajo en la operación. La implementación y aplicación continua de estos estándares de trabajo aseguran una operación económicamente más rentable, permiten tener un orden y estandarización de las operaciones e intensifica la seguridad en los trabajos. Sumándose a ello un "cambio" y compromiso del personal por mejorar el desempeño de su trabajo. El desarrollo de este trabajo expone inicialmente la situación de una mina ejemplo donde no existe un adecuado sistema de productividad, control y reducción de costos operativos mina y de optimización de las operaciones de minado en función a estándares objetivos de trabajo, obteniéndose un primer diagnóstico de la situación mediante la supervisión y control en campo de las operaciones y la revisión de los presupuestos existentes de las operaciones y proyectos. La segunda etapa consiste en la propuesta de estándares objetivos de trabajo en función a estudios y pruebas ingenieriles relacionados al método de explotación de minado, la perforación y voladura idónea, el análisis de costos, la mecánica de rocas y a la seguridad laboral, considerando a todas las etapas del trabajo en mina como procesos que integran un solo sistema en el cual las operaciones de perforación y voladura son el núcleo básicodel sistema. Finalmente se exponen los beneficios que se obtienen con la implementación y el control continuo de los estándares adecuados de trabajo, beneficios reflejados en una reducción de los costos directos operativos y en general de todos los costos de las diversas áreas que integran una mina, acotándose como una de las recomendaciones la vital importancia que representa la capacitación continua al personal en las técnicas de perforación y voladura y sobretodo el rol que juegan estas como el núcleo de todo el sistema, del mismo modo la importancia de la motivación y retroalimentación al personal que ejecutan este núcleo sobre los avances que se obtienen y lo importantede su desempeño

Nuclear magnetic resonance measurements of velocity distributions in an ultrasonically vibrated granular bed

We report the results of nuclear magnetic resonance (NMR) imaging experiments on granular beds of mustard grains fluidised by vertical vibration at ultrasonic frequencies. The variation of both granular temperature and packing fraction with height was measured within the three-dimensional cell for a range of vibration frequencies, amplitudes and numbers of grains. Small increases in vibration frequency were found – contrary to the predictions of classical ‘hard-sphere’ expressions for the energy flux through a vibrating boundary – to result in dramatic reductions in granular temperature. Numerical simulations of the grain-wall interactions, using experimentally-determined Hertzian contact stiffness coefficients, showed that energy flux drops significantly as the vibration period approaches the grain-wall contact time. The experiments thus demonstrate the need for new models for ‘soft-sphere’ boundary conditions at ultrasonic frequencies

Data for Figures 5, 9 and 10

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