The Giant Magellan Telescope (GMT) primary mirror consists of seven 8.4 m light-weight honeycomb mirrors that are being manufactured at the Richard F. Caris Mirror Lab (RFCML), University of Arizona. In order to manufacture the largest and most aspheric astronomical mirrors various high precision fabrication technologies have been developed, researched and implemented at the RFCML. The unique 8.4 m (in mirror diameter) capacity fabrication facilities are fully equipped with large optical generator (LOG), large polishing machine (LPM), stressed lap, rigid conformal lap (RC lap) and their process simulation/optimization intelligence called MATRIX. While the core capability and key manufacturing technologies have been well demonstrated by completing the first GMT off-axis segment, there have been significant hardware and software level improvements in order to improve and enhance the GMT primary mirror manufacturing efficiency. The new and improved manufacturing technology plays a key role to realize GMT, the next generation extremely large telescope enabling new science and discoveries, with high fabrication efficiency and confidence.

Visitor activities in parks often have a heavy impact on the soil, vegetation, water and wildlife. In front country areas, the most extreme damage is concentrated on and adjacent to recreational trails. Aside from controlling the numbers, activities and behaviours of trail users, managers may choose to make trails more resistant to impact through surfacing. Unfortunately, surfacing may have negative influences on park visitors' enjoyment of trails by limiting access or detracting from the primitive setting. In addition, some surfaces may be ineffective in certain environmental conditions such as wet ground or steep slopes. Finally, the wide variety in construction and maintenance costs may make some surface types economically unfeasible. The goals of this research are to investigate the role of trail surfacing in the management of impacts from outdoor recreation; to develop better understanding of the social, economic and environmental aspects of trail surfacing decisions; and to explore a comprehensive framework for incorporating these three factors in trail management. It is hoped that this research can assist park managers in selecting surfacing options to reduce visitor impact without excessively compromising recreational experience or organizational limitations, such as financial resources. In addition to a comprehensive review of literature on visitor impact management on trails and surfacing techniques, this research employs three methods to further investigate the social, environmental and economic aspects of trail surfacing: a trail user survey, manager survey and trail condition assessment. The trail user survey was conducted at two well-used natural areas in southwestern Ontario, Canada: Presqu'ile Provincial Park and Belfountain Conservation Area. Surveys at each area explored trail users' perceptions and preferences of trail surfacing techniques in late summer 1999. The managers' survey provided insight into organizational approaches to surfacing, including construction cost and observations on recreational or environmental effectiveness. Finally, the trail condition assessment explored an approach to determining environmental effectiveness of trail surfacing techniques, but was limited by the physical and recreational variation between trails. Seven recommendations for trail managers are presented, tying in several conceptual frameworks of visitor impact management and trail surfacing decisions developed in the thesis. First, trail managers are recommended to develop a full understanding of trail design principles and alternative visitor impact management techniques. If surfacing is selected as the best impact management technique, trail managers should obtain as much information on user characteristics, environmental conditions and organizational limitations as possible. Despite the benefits and drawbacks for all surfaces, road base gravel (or angular screenings with fines) merits special attention as an excellent surface, while asphalt and concrete are not recommended for front country, semi-primitive recreation. Finally, trail managers are encouraged to share information on surfacing more freely and open surfacing decision processes to affected trail users. Overall, trail managers are provided with an approach to surfacing decisions that considers the social, environmental and economic aspects of trail surfacing, with the goal of working toward more enjoyable, environmentally responsible and cost-effective trail solutions.

Visitor activities in parks often have a heavy impact on the soil, vegetation, water and wildlife. In front country areas, the most extreme damage is concentrated on and adjacent to recreational trails. Aside from controlling the numbers, activities and behaviours of trail users, managers may choose to make trails more resistant to impact through surfacing. Unfortunately, surfacing may have negative influences on park visitors' enjoyment of trails by limiting access or detracting from the primitive setting. In addition, some surfaces may be ineffective in certain environmental conditions such as wet ground or steep slopes. Finally, the wide variety in construction and maintenance costs may make some surface types economically unfeasible. The goals of this research are to investigate the role of trail surfacing in the management of impacts from outdoor recreation; to develop better understanding of the social, economic and environmental aspects of trail surfacing decisions; and to explore a comprehensive framework for incorporating these three factors in trail management. It is hoped that this research can assist park managers in selecting surfacing options to reduce visitor impact without excessively compromising recreational experience or organizational limitations, such as financial resources. In addition to a comprehensive review of literature on visitor impact management on trails and surfacing techniques, this research employs three methods to further investigate the social, environmental and economic aspects of trail surfacing: a trail user survey, manager survey and trail condition assessment. The trail user survey was conducted at two well-used natural areas in southwestern Ontario, Canada: Presqu'ile Provincial Park and Belfountain Conservation Area. Surveys at each area explored trail users' perceptions and preferences of trail surfacing techniques in late summer 1999. The managers' survey provided insight into organizational approaches to surfacing, including construction cost and observations on recreational or environmental effectiveness. Finally, the trail condition assessment explored an approach to determining environmental effectiveness of trail surfacing techniques, but was limited by the physical and recreational variation between trails. Seven recommendations for trail managers are presented, tying in several conceptual frameworks of visitor impact management and trail surfacing decisions developed in the thesis. First, trail managers are recommended to develop a full understanding of trail design principles and alternative visitor impact management techniques. If surfacing is selected as the best impact management technique, trail managers should obtain as much information on user characteristics, environmental conditions and organizational limitations as possible. Despite the benefits and drawbacks for all surfaces, road base gravel (or angular screenings with fines) merits special attention as an excellent surface, while asphalt and concrete are not recommended for front country, semi-primitive recreation. Finally, trail managers are encouraged to share information on surfacing more freely and open surfacing decision processes to affected trail users. Overall, trail managers are provided with an approach to surfacing decisions that considers the social, environmental and economic aspects of trail surfacing, with the goal of working toward more enjoyable, environmentally responsible and cost-effective trail solutions.

Precision optics can be accurately fabricated by computer controlled optical surfacing (CCOS) that uses well characterized polishing tools driven by numerically controlled machines. The CCOS process is optimized to vary the dwell time of the tool on the workpiece according to the desired removal and the calibrated tool influence function (TIF), which is the shape of the wear function by the tool. This study investigates four major topics to improve current CCOS processes, and provides new solutions and approaches for the next generation CCOS processes.The first topic is to develop a tool for highly aspheric optics fabrication. Both the TIF stability and surface finish rely on the tool maintaining intimate contact with the workpiece. Rigid tools smooth the surface, but do not maintain intimate contacts for aspheric surfaces. Flexible tools conform to the surface, but lack smoothing. A rigid conformal (RC) lap using a visco-elastic non-Newtonian medium was developed. It conforms to the aspheric shape, yet maintains stability to provide natural smoothing.The second topic is a smoothing model for the RC lap. The smoothing naturally removes mid-to-high frequency errors while a large tool runs over the workpiece to remove low frequency errors efficiently. The CCOS process convergence rate can be significantly improved by predicting the smoothing effects. A parametric smoothing model was introduced and verified.The third topic is establishing a TIF model to represent measured TIFs. While the linear Preston's model works for most cases, non-linear removal behavior as the tool overhangs the workpiece edge introduces a difficulty in modeling. A parametric model for the edge TIFs was introduced and demonstrated. Various TIFs based on the model are provided as a library.The last topic is an enhanced process optimization technique. A non-sequential optimization technique using multiple TIFs was developed. Operating a CCOS with a small and well characterized TIF achieves excellent performance, but takes a long time. Sequential polishing runs using large and small tools can reduce this polishing time. The non-sequential approach performs multiple dwell time optimizations for the entire CCOS runs simultaneously. The actual runs will be sequential, but the optimization is comprehensive.

No description available.

The master´s diploma thesis elaborated as the master's degree M-STG Manufacturing Technology solves surfacing problems in the simulations of surfacing turbine rotors pinot pins. The work was seen as a preparatory work before the real surfacing. Topic commissioned by Siemens Industrial Turbomachinery Ltd. For welding plates test has been used the method of SAW and the base material was identical to turbine rotor material, X22CrMoV 12-1. Additional material was Fluxocord 42. Simulations were carried out in programs SYSWELD and Visual - WELD. The output of the simulation software are temperature and stress fields, material structures and creations of the CCT diagrams at the base material, filler material, and mixed area.

This project was elaborated under the graduate major program 2307 of masters engineering studies. It presents a proposal of anticorrosive protection of steam turbines rotors surface. Based on a literature recherché on automated welding and surfacing under flux, an optimized technology of surfacing of anticorrosive and antierosive layers at output parts of low-pressure sections of rotors will be presented. The optimization of the welding technology will be performed to minimize the possibility of hidden cracks due to application of anticorrosive protective surface and will be evaluated on test samples provided by the company SIEMENS.

Dans l’industrie de la verrerie, le laser cladding est une technique de rechargement très innovante permettant de déposer une couche très fine d’un alliage à base de nickel pour protéger les moules (utiles à la fabrication de bouteilles en verre) de la corrosion, de l’abrasion ainsi que de la fatigue thermique. La méthode utilisée ici (fusion de poudre projetée par laser) est très courante en fabrication additive. Cette étude s’intéresse à l’impact du rechargement sur le dépôt et les substrats en Cu-Ni-Al et en fonte GL. L’influence sur la microstructure ainsi que sur le comportement mécanique a pu être étudiée (MEB et microanalyses, dureté, contraintes résiduelles ...). Nous nous sommes focalisés sur l’apparition de défauts tels que le manque d’accroche lors du laser cladding sur du Cu-Ni-Al et sur la possible fissuration lors du rechargement sur de la fonte GL. Le but est bien sûr de s’affranchir de ces défauts. Il a notamment été mis en évidence que le manque d’accroche (cas du Cu-Ni-Al) est lié à la distribution gaussienne de la poudre qui atténue la puissance incidente du laser au niveau du pic de poudre. Le manque d'accroche n'est pas détecté sur le substrat en fonte en raison de sa forte absorptivité et de sa faible conductivité thermique. Néanmoins, des fissures peuvent être observées en raison de contraintes résiduelles thermiques et de la présence d'une zone affectée thermiquement. De plus, l’analyse statistique ANOVA a permis une optimisation des paramètres de rechargement de telle sorte à obtenir une accroche dans toute la section tout en respectant les préconisations géométriques données par les Établissements CHPOLANSKY pour le cordon. / In glass industry, the laser cladding is an innovative surfacing technique allowing to deposit a very thin layer of nickel to protect glass mold (useful for glass bottle production) against corrosion, abrasion and thermal fatigue. This method (powder fusion by projection) is well known in additive manufacturing. The aim of this work is to observe the impact of the laser cladding on the coating behavior but also on the Cu-Ni-Al and flake-graphite cast iron substrates. The microstructure and the mechanical properties were studied (SEM and microanalysis, microhardness, residual stress …) around the interface cladding/substrate. The work was also focused on the defects like lack of bonding but also on cracking behavior during surfacing on cast iron. The purpose was to prevent from those defects. This work showed that the lack of bonding to the Cu-Ni-Al substrate is due to the gaussian distribution of the powder which attenuates the input laser power at its peak. The lack of bonding is not detected on cast iron substrate thanks to its high absorptivity and low thermal conductivity. Nevertheless, cracks can be observed due to thermal residual stresses and the presence of a thermal affected zone. The ANOVA technique allowed us to optimize the processing parameters in order to obtain a perfect bonding and the geometry wanted by CHPOLANSKY Establishments.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18653号 / 工博第3962号 / 新制||工||1610(附属図書館) / 31567 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 白土 博通, 教授 河野 広隆 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.