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Following two previous nuclear reactor accidents involving light water reactors, there is a renewed interest in accident tolerant fuels. These accident tolerant fuels should not oxidise in a steam atmosphere during loss of coolant accidents. One such accident tolerant fuel that has been suggested is the use of ceramic composite cladding material as a replacement for the current zircaloy cladding. The high temperature stability of silicon carbide, together with its high resistance to corrosion may make it preferable to zircaloy during accident conditions. Furthermore, if the neutron absorption cross section of the cladding is less than the current zircaloy, extended life might be available when compared with current fuels. One of the main difficulties in using ceramic cladding materials as nuclear fuels is the lack of a reliable joining process to manufacture end caps for the cladding tubes. A manufacturing method would need to be developed to produce ceramic joint that is able to withstand a PWR environment. Two methods of ceramic joining have been proposed. Firstly, silicon carbide deposition process that is used to infill the gap between two ceramic components and secondly a ceramic soldering technique. A silicon carbide deposition process has been developed. The deposit was confirmed to be 3C silicon carbide which has preferable irradiation response to the other polytypes. The deposit was found to be carbon rich which was largely removed through the use of a thermal treatment step. The deposit was used to coat metallic surfaces for increased hardness, reduced sliding wear and corrosion resistance. Silicon carbide joints were produced using an oxide powder frit of silicon dioxide, yttrium oxide and aluminium oxide. Tubular samples were joined, however they contained circumferential cracking resulting in a join that was not hermetically sealed. The thermal conductivity of each joint varied from sample to sample. X-ray computed tomography showed there were large inconsistencies in the volume of joined material present in each sample giving rise to the large variation in thermal conductivity.

Magnesium alloys are being increasing considered for many automotive applications due their low density and high strength to weight ratio. However, joining of these materials by welding and especially to dissimilar materials such as aluminum or steel or mechanically by riveting at room temperature have faced many challenges. Research presented in thesis explores a new hot joining process referred to as Upset Protrusion Joining (or UPJ) as a means of mechanically joining cast magnesium alloy to other similar or dissimilar sheet materials. UPJ is being developed as a rapid and reliable joining method to be implemented in the automotive industry for weight and manufacturing cost reduction. It involves a cylindrical protrusion emanating perpendicular to the flat surface of a cast plate-like magnesium component that is fitted through a hole in another plate or sheet material. The two components are then clamped together, electrically heated and compressed perpendicular to the axis of the protrusion. During this process, the protrusion expands circumferentially to fill the hole as well as the region above the hole thus entrapping the sheet metal between the mushroomed head and the casting. The effect of different UPJ process parameters such as applied current, current duration, compression loading rate and compression distance were studied through experimentation that involved a newly developed computer-controlled experimental UPJ setup. The studies involved two cast magnesium alloys of interest to automotive industry, AM60 and AZ91, with protrusions of 11 mm diameter and 14 mm height on a 2 mm thick plate. Studies of the material properties and UPJ process parameters were performed to find optimal process parameters to achieve satisfactory quality of the joint in terms of post-UPJ joint strength with appearance. Also, microstructural studies, temperature measurements in the protrusion region, and electrical resistivity measurements were performed for the two alloys to fundamentally understand their roles in promoting temperature dependent material flow, strain localization, and fracture in the UPJ process. Lastly, materials specific process window for UPJ process was identified based on the experimental work for creation of robust UPJ joints with acceptable joint strengths in tensile shear mode of failure. This new hot joining method was shown as an industrially viable joining method for cast magnesium component. UPJ is a rapid joining method and provides good joint-strength depending upon joint specifications. This method can be implemented in automotive and other industrial manufacturing environment for joining cast component to a similar or dissimilar wrought sheet component. / Thesis / Master of Applied Science (MASc)

This thesis is an exploration of method demonstrated in a series of mechanical drawings of the elements. An investigation of methods of drawing and of how different questions can be asked through drawing. Furthermore, this thesis asks the question of place in the elements of fire, earth, and sky in the formal relationship between walls, joints, trusses. These architectural elements protect against the natural ones, forming place focused around the hearth. This thesis traces the formal relationship between the elements of architecture stemming from the German thinker Gottfried Semper's treatise on architecture, but diverges from Semper's fixation with materiality and delves into questions of form, appearance, and construction through drawing. The drawings address questions about the elements; questions about form, tectonics, and the relation of part to whole. The whole becomes a building focused on forming a place and the relation of the elements to one another. / Master of Architecture / "Throughout all phases of society the hearth formed that sacred focus around which the whole took order and shape. It is the first and most important, the moral element of architecture. Around it were grouped the three other elements: the roof, the enclosure, and the mound, the protecting negations or defenders of the Hearth's flame against the three hostile elements of nature" (Semper 102) This reading, The Four Elements of Architecture by Gottfried Semper, and this quote were the origin of my thesis, which became a series of studies of these elements as parts and their relations to one another. Through mechanical investigative drawings I explored the traits and qualities assigned to these elements by Semper and developed my own understanding of them. Each element has a tectonic quality and architectural characteristic that defines it. The tectonic quality is "different technical skills of man used to construct the elements: ceramics and afterwards metal work around the hearth, water and masonry works around the mound, carpentry around the roof and its accessories… Wickerwork was the essence of the wall" (Semper 103-104). The mound forms the base of the building connecting it to the hearth, and also joins to the hearth and raises it. The roof as a dominant element protects from above. The wall is a spatial enclosure that forms the protected space. The hearth is the central and social element of the building, protected from nature by the other elements. In addition to an investigation of each of the elements, I also had an interest in constructing a building informed by these investigations, forming a place of gathering that focused around the hearth. How would the protective elements form and appear in space, and how would the hearth form the place around it. The wall, defined as woven and enclosing, led to a series of questions regarding its form, material, and connection to the other elements. Semper's understanding of woven extends to being a dressed wall or a wall of a pattern of parts, such as brick or wood. How can variation of size, depth, and material be used to form patterns in a wall? How do hierarchies of panels, verticality, and horizontality differ from one another? How can the wall connect to the mound and emphasize the existing character of the building? The roof, defined as dominant and of carpentry, led to a series of questions regarding frames and joints. My main interest in the roof was its structure, and the interior spatial quality it provided. How can the joint and the frame inform one another? What are the qualities of trusses? What are different types of joints and how do they display themselves? How do joints form a truss and the truss form a frame? The mound, defined as earthen and meeting, was investigated in conjunction with other elements. It forms the base that protects the hearth from the earth and acts as a base to the other elements. Its original use as a structural base for houses in marsh lands is no longer prevalent and its role lessened. Semper understood this evolution, "some elements [become] more developed while others [recede] into the background" (Semper 103). The hearth, defined as central and of worked metal, led to a series of questions regarding material, form, and relation to its surroundings. The hearth acts as a single focus that forms areas of repose protected by the other elements from nature. How should it connect to the roof and the floor? Benefits of a hanging hearth versus traditional? How can it act as more by storing wood and the other tools it needs to be worked? How can it relate to other elements through material and form? As Semper stated, "some elements [become] more developed" and I found some of these progressions through my studies. One of these developments is the hearth creating areas of transition in the interior and the need to connect this transitioning to the exterior. The frame of the hearth is repeated as a threshold, forming an area of transition between the exterior and the interior. Another development is the roof and the chimney belonging to the sky. As the mound recedes from importance, the sky and its connection to the roof develops further. These boards each developed from a series of questions, and led to further questions. They ask about the part and then about the part in relation to other parts. Each question can stand on its own, but it is only when you keep asking questions that you begin to find something. Each part is its own, but when formed together it creates something new. And that was my thesis, a series of questions and the joining of parts.

Recent work has described microwave applicators which produce localized spot heating of a workpiece with a Gaussian spatial distribution of microwave power. Applicators of this type provide a nearly ideal heating pattern for joining of ceramics and other applications requiring localized heating, and offer several advantages over conventional methods utilizing surface heat flux. A three-dimensional mathematical model of a circular volumetric heat source moving through a rectangular block was constructed to address some of the microwave heating concerns--electric field power requirements, uniform heating, and thermal runaway. The partial differential equation from the mathematical model was solved numerically with an implicit finite-difference method. Using experimentally measured dielectric loss properties for alumina, the required electric field strengths to raise the temperature of a localized spot in a rectangular block to 1500K are presented. With the block moving on an insulating support, the results also show that uniform temperature profiles through the depth of the alumina can be achieved, and thermal runaway can be prevented by choosing an appropriate block velocity and electric field strength. With the block on a highly conductive support, however, the high electric field power required to raise the temperature of the block makes thermal runaway and non-uniform temperature distributions likely. For the published dielectric loss coefficient data for glass, thermal runaway could not be avoided for a stationary block. Calculations suggest that maintaining a constant absorbed power in a moving workpiece could be a way of maintaining the desired maximum temperature within the blocks. From the preceding conclusions, a microwave spot heater appears to be an effective tool for the joining of ceramics. / Master of Science

No description available.

Laser welding was investigated as a potential joining technology for alumina ceramic substrates. The objective of this study was to develop a method to preheat the ceramic using a single defocused laser beam prior to welding. Engineering ceramics are employed in a variety of systems and environments due to their unique properties. Joining technologies must be developed to facilitate the manufacture of complex or large ceramic components. Laser welding is advantageous as it forms joints rapidly, and does not introduce intermediate materials to form the bond, which can have deleterious effects. The Laser Machining System (LMS) at Queen’s University was adapted for this study. A defocused far-infrared (FIR) laser beam was positioned to overlay a focused near-infrared (NIR) laser beam; the defocused FIR beam preheated the ceramic substrate and the focused NIR beam formed the weld. A finite element model was developed in COMSOL MultiPhysics to simulate the preheating processes and to develop a preheating protocol. The protocol was implemented using the FIR beam and adjusted to achieve preheating temperatures of 1450, 1525, and 1600degC. Welds were performed on 1 mm thick alumina plates using the preheating protocols and NIR beam powers of 25, 50, and 75 W. Weld speed was held constant throughout the study at 0.5 mm/s. The preheating protocols were successful at achieving near-constant preheating temperatures, with standard deviations below 32 degrees. Partially penetrating welds were formed with the NIR beam at 25 W, and fully penetrating welds at 50 and 75 W. Large pores were present in the 25 W and 50 W welds. Minimal porosity was observed in the welds formed at 75 W. All of the welded plates experienced a transverse fracture that extended perpendicular to weld, and a longitudinal fracture extending parallel to the weld. This study shows that a fixed defocused laser beam can successfully preheat alumina substrates to the high temperatures required for welding; however, non-homogenous cooling results in fracture. Increasing the preheating beam diameter or introducing an auxiliary means to provide a controlled cool-down cycle may mitigate these effects. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-04-29 17:59:57.43

The ability to easily customize and produce specialized MW-components for research and industry is a real challenge and the need is identified, as standardized parts have limited use and can limit design freedom. This study aims at exploring if there are simple ways to manufacture rectangular X-band waveguides with operating frequency of 8-12GHz with novel polymer additive manufacturing and chemical metal deposition that can match Computer Numerical Control (CNC) manufactured rectangular metal waveguides in performance. X-band was chosen mostly because of it having a good size to start printing trials and x-band components being in heavy use where a lightweight would be beneficial. Also, to evaluate the manufacturing results by measuring and comparing s-parameters and weight between measuring standard and manufactured waveguides. Furthermore, to use the preexisting models for approximating the attenuation due to surface roughness. Different designs were tested with different polymers and electrodeposition techniques and approaches. Two of the benchmarked techniques gave better results; first, using a modular design with a combination of different polymers and an industrial copper plating technique; second, a single polymer one-piece design using an acrylic carbon paint and a small scale in-house electroless copper deposition. The performance of conventionally manufactured rectangular metal waveguides was not matched but the two investigated techniques show on results that the techniques could possibly be modified in the future to match the performance of conventionally manufactured waveguides.

Vi har valt att undersöka CNC-teknikens möjligheter i kombination medhantverkskunskap. Syftet med undersökningen är att ge oss själva större kunskap om CNC-tekniken och hur den kan användas för att produceraobjektmed ytor som känns intressanta. Vi har i enlighet mer vårt mål tagit fram ett antal olika produkter i form av fat som vi fann inspiration till i Japan. Vid tillverkningen har vi undersökt olika träslag och olika fräsriktningar för att få fram olika ytor på faten. Vi har också tittat på hur vi kan effektivisera bearbetningen av våra fat. Vi har sedan använt oss av en enkät där åtta personer med varierande förkunskaper har fått värdera faten utifrån personliga preferenser och uppfattningen av de olika ytorna. Det har vi gjort med avsikt för att få en uppfattning om vilka ytor som tilltalar människor.

<p>Cilj rada je bila izrada kvalitetnog zavarenog spoja pancirnog čelika.<br />Zavareni spoj poseduje dobre zatezne karakteristike, kao i visoku energiju<br />udara u metal šavu i ZUT-u, visoku otpornost na propagaciju prsline u<br />metal šavu i ZUT-u. Osnovni materijal ima najveću zateznu čvrstoću,<br />najnižu energiju udara, najmanju žilavost loma i otpornost na propagaciju<br />prsline. Nakon balističkih ispitivanja ustanovljeno je da ZUT i osnovni<br />materijal poseduju balističku otpornost, dok metal šava ne zadovoljava<br />standarde. Ispitivanjem gasne hromatografije ustanovljena je niska<br />količina difundovanog i zadržanog vodonika u zoni metal šava. U skladu<br />sa tim se zaključuje da su parameteri zavarivanja, kao i dodatni materijal<br />odgovarajuće izabrani. Na osnovu ispitivanja brzine rasta zamorne<br />prsline, određen je preostali vek oklopnih vozila koja se prave od<br />pancirnog čelika.</p> / <p>The aim of this paper was to produce a high-quality welded joint of armored steel.<br />The welded joint has good tensile properties, as well as a high impact energy in<br />the weld metal and HAZ, and high resistance to crack propagation in the weld<br />metal and HAZ. The base metal has the highest tensile strength, the lowest<br />impact energy and the smallest fracture toughness and crack propagation<br />resistance. After ballistic testing, the HAZ and basic metals have been found to<br />have ballistic resistance, while the weld metal does not meet the standards. Gas<br />chromatography analysis detected a low amount of diffused and retained<br />hydrogen in the metal seam zone. It may therefore be concluded that the welding<br />parameters and the additional material have been appropriately selected.<br />Based on the study of the fatigue crack growth rate, the fatigue life of armored<br />vehicles was predicted.</p>