Thèse no 1266 sciences EPF Lausanne. / Literaturverz.

This bachelor thesis aims to present an overview of the performed steps to construct and program a prototype of a mechanical mirror. The idea of a mechanical mirror is that a camera captures an image that is translated into pixels of different brightness values. The brightness values are later displayed by metal plates, acting as pixels, rotated to different angles to reflect a corresponding light from a lamp. The pixels together shape grayscale images based on the frames captured by the camera. A prototype was constructed successfully. Tests showed that its purpose to move according to the captured image was fulfilled although adjustments could be made for the light to reach all the pixels to a greater extent. The angle span for the pixels turned out to be between 32°and 44°, which proved sufficient for their purpose. The reason for a difference in angle spans between the pixels was due to minor construction errors and was not an issue of functionality for the mirror. The refresh rate of the mirror, which could be described as the frequency at which the pixels rotate and shape an image, was set to 25 frames per second. This allowed the mirror to mimic movements in front of it without much delay while not exceeding the frame rate of the camera, which capture at a frame rate of 30 frames per second. The camera was therefore the vital limitation for the refresh rate of the mirror. / Detta kanidatexamensarbete har syftet att presentera en översikt av de steg som genomfördes för att konstruera och programmera en prototyp av en mekanisk spegel. Idén med en mekanisk spegel är att en kamera läser in en bild som sedan är översatt till pixlar med olika värden på ljusstyrka. Dessa ljusstyrkor visas sedan av metallplattor, vilka agerar som pixlar, som roterar till olika vinklar för att reflektera motsvarande ljus från en lampa. Pixlarna formar tillsammans gråskalebilder baserat på de bilder som kameran läser in. En prototyp konstruerades framgångsrikt. Test visade att dess syfte att röra sig i enlighet med den inlästa bilden uppfylldes, dock finns plats för justeringar för att ljuset från lampan ska nå pixlarna i större utsträckning. Pixlarnas vinkelomfång visade sig bli mellan 32°och 44°, vilket konstaterades vara tillräckligt för deras syfte. Skillnaden i vinkelomfång mellan pixlarna berodde på mindre konstruktionsfel och påverkade inte spegelns funktionalitet. Spegelns uppdateringsfrekvens, vilket kan beskrivas som frekvensen med vilken pixlarna roterar och formar en bild, sattes till 25 bilder per sekund. Detta tillät spegeln att härma rörelser framför den utan stor fördröjning utan att överstiga kamerans bildhastighet, som läser in med en bildhastighet på 30 bilder per sekund. Kameran var således den begränsade faktorn för pixlarnas uppdateringsfrekvens.

Η παρούσα διπλωματική εργασία εξετάζει τα φυσικά και μηχανικά χαρακτηριστικά του βραχώδους υλικού δύο διαφορετικών πετρωμάτων και συγκεκριμένα ψαμμιτών και γρανιτών. Οι ψαμμίτες προέρχονται από πέντε (5) επιλεγμένες θέσεις δειγματοληψίας σε αντίστοιχες θέσεις της Δ. Ελλάδας, από την ακολουθία του φλύσχη που ανήκει και στις τρεις αντιπροσωπευτικές γεωτεκτονικές ζώνες της ευρύτερης περιοχής. Η δειγματοληψία έγινε σε βραχώδη δείγματα μεγάλων διαστάσεων (block samples) και στη συνέχεια διαμορφώθηκαν κυλινδρικά δείγματα με εργαστηριακή καροταρία. Οι γρανίτες προέρχονται από δείγματα σημαντικού αριθμού δειγματοληπτικών γεωτρήσεων που εκτελέστηκαν στα πλαίσια της γεωτεχνικής έρευνας θεμελίωσης αιολικού πάρκου (ανεμογεννητριών) στην περιοχή Πισοδερίου Φλώρινας. Η εργαστηριακή έρευνα περιλάμβανε την προσέγγιση κυρίως της φυσικής συμπεριφοράς των ψαμμιτών με «μη καταστρεπτικές δοκιμές» σε 16 κυλινδρικά διαμορφωμένα δείγματα, ενώ για τους γρανίτες και συγκεκριμένα σε 120 κυλινδρικά δείγματα, έμφαση δόθηκε στις μηχανικές ιδιότητες η οποίες και απαιτούνται για τον ορθολογικό σχεδιασμό του συγκεκριμένου τεχνικού έργου. Οι ψαμμίτες ήταν κυρίως χαλαζιακοί, ασβεστιτικοί – χαλαζιακοί και αρκόζες. Τις χαμηλότερες τιμές ταχύτητας υπερήχων και σκληρότητας παρουσιάζουν οι αρκόζες, ενώ αντίθετα οι χαλαζιακοί ψαμμίτες εμφανίζονται σαν μέτρια σκληροί και με αρκετά χαμηλά πορώδη. Οι γρανίτες εμφανίζονται συνήθως σκληροί, υψηλής – πολύ υψηλής αντοχής με τιμές λόγου μέτρου (MR) να κυμαίνονται από περίπου 600 μέχρι <50. Ο σημαντικός αριθμός εργαστηριακών μετρήσεων κυρίως των παραμέτρων αντοχής επέτρεψε την στατιστική επεξεργασία τους και τη διατύπωση εμπειρικών σχέσεων γενικής εφαρμογής που χαρακτηρίζουν το συγκεκριμένο πέτρωμα. / This thesis examines the physical and mechanical characteristics of the rocky material of two different rocks and specifically sandstones and granites. The sandstones come from five (5) selected sampling sites in corresponding locations of Western Greece, from the sequence of flysch that belongs to all three representative geotectonic zones of the surrounding area. The sampling was done in large rock samples (block samples) and then formed cylindrical samples with laboratory karotaria. The granite samples come from a large number of sample drillings that carried out under the geotechnical research foundation of a wind farm (wind turbines) in Pissoderi Florina. The laboratory investigation included the main approach of the physical behavior of sandstones with "non-destructive testing" in 16 cylindrical shaped samples, while for the granite and specifically for 120 cylindrical samples, emphasis was placed on the mechanical characteristics which are necessary for the rational design of this specific technical project. The sandstones were mainly quartz, limestone - quartz and arkozes. The lowest ultrasound speed value and hardness show the arkozes, while the quartz sandstones appear as medium hard and relatively low porous. The granites usually appear tough, high - very high resistance to ratio value measure (MR) ranging from about 600 to <50. The large number of laboratory measurements of the parameters, mainly resistance’s, allowed the statistical processing and the formulation of empirical relationships of general application that characterize this rock.

No description available.

Techn. University, Inst. für Biomechanik, Diss.--Hamburg-Harburg, 2006. / Zusfassung in dt. Sprache.

Abstract High energy prices and new environmental policies have made geothermal energy increasingly popular. The EU, including Finland, aims to increase the use of renewable energy resources and reduce carbon emissions. Geothermal energy pile foundations, so-called energy piles, are considered a viable alternative technology for producing energy instead of traditional methods. Geothermal heat pump systems are economically efficient and renewable environmentally friendly energy production systems in which the ground acts as a heat source in winter and as a heat sink in summer. Energy piles are economical systems, as they act as dual-purpose structures in energy production and load transfer from buildings to the ground, avoiding extra expenses in ground boring solely for energy production. However, use of ground heat exchangers (GHE) for energy production in energy piles can result in temperature variations in the pile shaft and surrounding soil, in turn affecting the thermo-mechanical behaviour of pile shaft and soil in both structural and geotechnical terms. Despite large numbers of energy piles being installed, there is still a lack of reliable information and experience about the thermo-mechanical behaviour of these structures and their energy efficiency in cold climates. This thesis investigated the efficiency performance of energy pile foundations and their productivity in cold climates by considering different groundwater flow effects and short-term imbalanced seasonal thermal loadings. The structural and geotechnical bearing capacity of different types of energy piles fitted with GHEs were also evaluated, using numerical models, and the possibility of collapse due to use of thermal systems was examined. Use of the model to compare the performance of different GHEs in terms of their efficiency revealed that at a particular fluid flow rate, double U-tube systems had greater productivity than other systems tested. The results also indicated that using energy piles under medium groundwater flow can improve the productivity of systems by around 20% compared with saturated conditions with no groundwater flow. It was also concluded that in a design context, the structural bearing capacity of piles needs to be reduced due to the additional thermal stresses induced by heating/cooling pile operations. / Tiivistelmä Kasvaneet energiakustannukset ja kiristyneet ympäristösäädökset ovat lisänneet geotermisten energiaratkaisujen suosiota. EU, mukaan lukien Suomi, on asettanut tavoitteekseen lisätä uusiutuvien energialähteiden käyttöä ja vähentää hiilidioksidipäästöjä. Geotermistä energiaa hyödyntävä paaluperustukset, niin kutsutut energiapaalut, tarjoavat uudenlaisen teknologian vähäpäästöisen energian tuottamiseen. Geotermiset lämpöpumppujärjestelmät, maalämpöpumput, ovat taloudellisia ja ympäristöystävällisiä energiantuotantomenetelmiä, jotka talviaikaan siirtävät maaperään varastoitunutta energiaa rakennuksen lämmittämiseen ja vastaavasti jäähdyttävät rakennusta kesällä siirtämällä lämpöä maaperään. Energiapaalujen taloudellisuus syntyy siitä, että ne pystyvät palvelemaan rakennusta kahdessa roolissa. Ne ovat osa rakennuksen energiajärjestelmää ja toimivat samalla myös kantavana rakenteena, joka siirtää rakennuksen kuormia perustuksilta maaperään. Lämpöpumppujärjestelmän kytkeminen paaluihin voi johtaa lämpötilan vaihteluun paaluissa sekä niitä ympäröivässä maaperässä, mikä puolestaan vaikuttaa paalujen ja maaperän lämpömekaanisiin, rakenteellisiin sekä geoteknisiin ominaisuuksiin. Vaikka energiapaaluja on asennettu jo paljon, ei paalujen lämpömekaanisesta käyttäytymisestä tai energiatehokkuudesta kylmien ilmastojen alueilla ole vielä paljoa tutkittua tietoa. Tässä väitöstutkimuksessa selvitettiin numeerisesti energiapaalujen rakennuspaikan pohjaolosuhteista riippuvaa tuottopotentiaalia Skandinaavisissa olosuhteissa ja ilmastossa. Tarkastelut kohdistuivat erityisesti pohjavesivirtauksen sekä vuodenaikojen ja ilman lämpötilan vaihtelun vaikutuksiin. Tutkimuksessa arvioitiin myös paalujen lämpötilan vaihtelujen vaikutuksia paalujen geoteknisiin ja rakenteellisiin ominaisuuksia sekä kestävyyteen. Numeeristen simulaatiotulosten perusteella betonipaaluun asennetun U-putkirakenteen avulla saavutetaan paras tuottopotentiaali. Tulokset osoittivat, että kohtalainen pohjaveden virtaus parantaa systeemin tuottoa noin 20 % verrattuna tilanteeseen, jossa vedellä kyllästetyssä maassa ei tapahdu pohjaveden virtausta. Analyysitulokset osoittavat myös, että paalujen lämpötilavaihteluista aiheutuvat lisäjännitykset vähentävät paalujen kantokykyä, mikä tulee ottaa huomioon paalujen mitoituksessa.

Friction StirWelding (FSW) has been researched for a number of years since its inception in 1991. The work thus far has been based on understanding the material and thermal flow using the standard fixed pin tool. The keyhole resulting during tool extraction in a FSW weld, is a disadvantage and a current limiting factor. Eliminating this effect from a weld using a movable pin tools would make FSW more commercially viable. This dissertation focuses on the design of a novel retractable pin tool, and highlights the problems encountered during the welding of Aluminum plates, Al2024 and Al5083. Previously studied techniques of material and thermal flow were used, to investigate the effect of the tool during extraction in a FSW weld. A prototype retractable tool was designed using parametric and axiomatic design theory, and implementing a pneumatic muscle actuation system. The resulting problems in the calibration of the retractable pin tool and the resulting welds are presented, these results confirming previous studies. The movable pin produced discrepancies the heat generation around the shoulder during a FSW weld. The failure of this tool to produce a reasonable weld showed that previous ideas into the workings of a retractable pin tool requires further investigation, furthermore a fresh approach to the interpretation and understanding of the FSW weld process needs consideration.

The development of a CNC-based technology FSW machine to accurately produce friction stir weld samples that can be analyzed for research purposes is implemented and discussed. A process diagnosis and control scheme to improve the process monitoring and weld evaluation capabilities of an FSW machine are proposed and implemented. Basic CNC-based hardware implementation such as optical encoders and inverters for process control are explained and verified. The control scheme and framework of interfaces to the digital I/O cards for PC user interface are explained. An advanced monitoring system which senses process performance parameters such as tool temperature, 3-axis tool forces, torque and spindle speed are explained. Mechanical designs and manufacturing techniques such as tool, clamp and backing plate designs are explained and verified. The process parameters for quality optimization are investigated and optimized by making use of Correlation and Regression Analysis. The statistical data and analytical relationships between welding parameters (independent) and each of the performance parameters (dependent) are obtained and used to simulate the machining process. The weld research samples are tested for strength and integrity making use of various scientific testing techniques. The reliability of the samples are also evaluated and compared to that of other institutions. Process variables and the optimum operating range of the Friction Stir Welding machine is determined and a framework for further research into weld quality optimization is set.

The refrigerant circuits of car air-conditioning systems are fitted with so-called open type compressors, because there is only a lip seal preventing the refrigerant from leaking from the compressor housing to the atmosphere. In addition, the cycle uses damping elements between the compressor and the other components on the suction and pressure lines to reduce vibration and noise transfer from the engine to the car body. Both the lip seal and damping elements result in loss of refrigerant as they are made from elastomers and leak with age, and, under high temperature conditions inside the engine room, these elements also allow a relatively high permeation of the refrigerant gas to the atmosphere. With very high refrigerant losses in the older R12 -cooling cycles and the damage caused by this gas to the ozone layer in the stratosphere, the Montreal protocol phased out this refrigerant and the car industry was forced to revert completely to R134a until 1994/95. R134a has no ozone depletion potential, but it has a direct global warming potential, and, therefore, leakages also have to be minimised. R134a has, because of its molecular size, a high permeation potential and, hence, all the refrigerant hoses are lined internally. Unfortunately, these hoses also leak with age and significant refrigerant loss will occur [1] R134a can therefore only be viewed as a solution until an alternative refrigerant with no direct global warming potential has been developed. Candidates for new refrigerants are natural substances such as hydrocarbons or carbon dioxide [2]. Unfortunately, both substances have disadvantages and their use is restricted to special cases, for e.g. hydrocarbons are flammable and are not used in car air-conditioners, but in Germany it is used as a refrigerant in household refrigerators with hermetic cycles. What makes the implementation of carbon dioxide (CO2) difficult are the high system pressures and the low critical point [3].

Vehicle suspension optimisation is a complex and difficult task, as there are a variety of factors influencing the dynamic performance of a vehicle. During suspension development, the optimisation of a selected few of these factors is often to the detriment of others, as they are all inter-related. In addition, expertise in vehicle setup and suspension tuning is scarce, and is limited to experienced racing teams and large automotive manufacturers with extensive research and development capabilities. The motivation for this research was therefore to provide objective and user-friendly methodologies for vehicle suspension optimisation, in order to support student projects like Formula Student, while having relevance to the needs of the South African automotive industry and racing community. With the onset of digital data acquisition, it has become feasible to take real-time measurements of tyre temperatures, to provide information on how a tyre is performing at a specific point on the track. Measuring the tyre surface temperature can provide a useful indication on whether the tyre is loaded equally or not, and what suspension adjustments should be made to improve tyre load distribution.