Impellers are important components in the field of precision machine, energy technology, and aerospace industries. Due to their complex geometries and higher degrees of interference, to produce a impeller with high precision dimension is a challenging technology. In this study, flank milling is used to machine blade surfaces of impeller instead of point cutting. Flank milling can provide a surface better than point cutting without addition processes. When blades of an impeller are designed by ruled surfaces, the impeller can be machined by flank cutting technology. Based on the type of a five-axis CNC machine, the objective of this project is aimed to develop the technology of five-axis machining for impellers. The involved techniques are : the identification of undercutting in flank cutting for ruled surfaces, five-axis tool paths generation, coordinate transformations for five-axis machining, and determination of cutting parameters. In addition, a practical application example is provided to show the feasibility and effectiveness of the developed procedure.

Ocean-island flank collapses are amongst the most dangerous of all landslide related hazards in the world, as they have the potential to trigger ocean-wide tsunamis that can cause damage and loss of life to communities thousands of kilometres from their source of origin. The implications for landslide-induced tsunami originating from high volcanic islands in the Pacific are serious; and consequent hazards to life, infrastructure, and emergency management need to be constantly reviewed, monitored, and investigated. Ta’u, the easternmost inhabited island in the Samoa Islands volcanic chain, exhibits a series of down-faulted benches on its southern flank; believed to be the remnant of catastrophic collapse involving ~30km³. An historical map of Ta’u, charted during the first United States exploring expedition into the Pacific Ocean (Charles Wilkes Expedition), suggests that the event was recent; having occurred less than 170 years ago. A collapse event of this magnitude would have generated a locally devastating tsunami, with possible impacts experienced at the regional level. However, there exists no written or oral record of such an event. It appears that half the island, involving an estimated 30km³, disappeared off the map less than 170 years ago without anybody noticing it. A number of key questions thus emerged. Did this event actually happen within the last 170 years, and if so, how and why could it have gone unnoticed? Is the event much older than the impression obtained from the literature? More importantly, what is the likelihood of a future collapse and subsequent tsunami, and what would the hazard impacts be at the local and regional levels? These questions formed the research basis for this thesis. Specific aims were developed to address the issues identified, and a range of inter-disciplinary scientific techniques using innovative methods and new datasets were implemented to achieve them. The results demonstrate that the collapse most likely occurred more than 170 years ago, raising serious debate on the accuracy of observations made during the Charles Wilkes Expedition. The results also show that the eruptive-hazard at the site exists. Given that the nature and frequency of active volcanism in the area is uncertain, the risk of a future collapse and subsequent tsunami in the medium-term is considered high. The inter-disciplinary approach to landslide-tsunami hazard investigation on an oceanic island presented in this thesis, can be developed and applied by disaster managers to similar hazard investigations on other oceanic islands. Ultimately, the increase in knowledge-base can be used as a tool for developing safer and more resilient coastal communities.

Ocean-island flank collapses are amongst the most dangerous of all landslide related hazards in the world, as they have the potential to trigger ocean-wide tsunamis that can cause damage and loss of life to communities thousands of kilometres from their source of origin. The implications for landslide-induced tsunami originating from high volcanic islands in the Pacific are serious; and consequent hazards to life, infrastructure, and emergency management need to be constantly reviewed, monitored, and investigated. Ta’u, the easternmost inhabited island in the Samoa Islands volcanic chain, exhibits a series of down-faulted benches on its southern flank; believed to be the remnant of catastrophic collapse involving ~30km³. An historical map of Ta’u, charted during the first United States exploring expedition into the Pacific Ocean (Charles Wilkes Expedition), suggests that the event was recent; having occurred less than 170 years ago. A collapse event of this magnitude would have generated a locally devastating tsunami, with possible impacts experienced at the regional level. However, there exists no written or oral record of such an event. It appears that half the island, involving an estimated 30km³, disappeared off the map less than 170 years ago without anybody noticing it. A number of key questions thus emerged. Did this event actually happen within the last 170 years, and if so, how and why could it have gone unnoticed? Is the event much older than the impression obtained from the literature? More importantly, what is the likelihood of a future collapse and subsequent tsunami, and what would the hazard impacts be at the local and regional levels? These questions formed the research basis for this thesis. Specific aims were developed to address the issues identified, and a range of inter-disciplinary scientific techniques using innovative methods and new datasets were implemented to achieve them. The results demonstrate that the collapse most likely occurred more than 170 years ago, raising serious debate on the accuracy of observations made during the Charles Wilkes Expedition. The results also show that the eruptive-hazard at the site exists. Given that the nature and frequency of active volcanism in the area is uncertain, the risk of a future collapse and subsequent tsunami in the medium-term is considered high. The inter-disciplinary approach to landslide-tsunami hazard investigation on an oceanic island presented in this thesis, can be developed and applied by disaster managers to similar hazard investigations on other oceanic islands. Ultimately, the increase in knowledge-base can be used as a tool for developing safer and more resilient coastal communities.

Sinkhole collapse is a common karst land-use risk around the world. In the Bahamas cover-collapse sinkholes do not exist because soil cover is thin; almost all collapse is due to cave ceiling failure. The most common cave types in the Bahamas are flank margin caves and banana holes. Flank margin caves have three entrance types: dissolution pit, side breach, or ceiling collapse. Both side breach and ceiling collapse are the result of mass erosional forces; pits by focused dissolution. It was previously proposed that slope was a controlling factor in Bahamian cave collapse. This study demonstrated that 7.5 minute topographic maps cannot resolve slopes accurately enough to predict potential collapse locations. Field surveys with 1 m contours allowed for a more concise slope range in which each entrance type preferentially occurred; collapse breaches and pits were common on gentle slopes and side breaches on steep slopes.

This thesis presents models and algorithms necessary to simulate the five-axis flank milling of jet-engine impellers in a virtual environment. The impellers are used in the compression stage of the engine and are costly, difficult to machine, and time-consuming to manufacture. To improve the productivity of the flank milling operations, a procedure to predict and optimize the cutting process is proposed. The contributions of the thesis include a novel cutter-workpiece engagement calculation algorithm, a five-axis flank milling cutting mechanics model, two methods of optimizing feed rates for impeller machining tool paths and a new five-axis chatter stability algorithm. A semi-discrete, solid-modeling-based method of obtaining cutter-workpiece engagement (CWE) maps for five-axis flank milling with tapered ball-end mills is developed. It is compared against a benchmark z-buffer CWE calculation method, and is found to generate more accurate maps. A cutting force prediction model for five-axis flank milling is developed. This model is able to incorporate five-axis motion, serrated, variable-pitch, tapered, helical ball-end mills and irregular cutter-workpiece engagement maps. Simulated cutting forces are compared against experimental data collected with a rotating dynamometer. Predicted X and Y forces and cutting torque are found to have a reasonable agreement with the measured values. Two offline methods of optimizing the linear and angular feeds for the five-axis flank milling of impellers are developed. Both offer a systematic means of finding the highest feed possible, while respecting multiple constraints on the process outputs. In the thesis, application of these algorithms is shown to reduce the machining time for an impeller roughing tool path. Finally, a chatter stability algorithm is introduced that can be used to predict the stability of five-axis flank milling operations with general cutter geometry and irregular cutter-workpiece engagement maps. Currently, the new algorithm gives chatter stability predictions suitable for high speed five-axis flank milling. However, for low-speed impeller machining, these predictions are not accurate, due to the process damping that occurs in the physical system. At the time, this effect is difficult to model and is beyond the scope of the thesis.

The present work was conducted in Sandvik Coromant to enhance the knowledge and understanding of general flank wear growth and specifically in this case flank wear growth on the cutting edge of the coated (Ti(C, N)/ Al2O3/ TiN) tool inserts.   Reliable modeling of tool life is always a concern for machining processes. Numbers of wear models studies predicting the tool life length have been created throughout the metal-cutting history to better predict and thereby control the tool life span, which is a major portion of the total cost of machining.   A geometrical contact model defining the geometry of the flank wear growth on the cutting tool inserts was proposed and then compared with four suggested models, which estimates flank wear. The focus of this work is on the initial growth of flank wear process and thereby short cutting-time intervals are measured.   Wear tests on cutting tool inserts were performed after orthogonal turning of Ovako 825 B steel and were analysed by optical instrument, 3D optical imaging in Alicona InfiniteFocus and EDS in SEM. Force measurements for cutting speeds, Vc, 150, 200, and 250 m/min and feed rate, fn, 0.15 mm/rev were recorded as well.   Results show that initial flank wear land, VB, growth is dominated by sliding distance per cutting length for different cutting speeds. A good correlation between the geometrical contact model and estimation models is indentified. The cutting force measurements compared with the flank wear land show proportionality between two parameters. For the machining data in the present study the flank wear rate per sliding distance, dW/dL, is estimated to 2x103 (μ3/m).

This thesis presents models and algorithms necessary to simulate the five-axis flank milling of jet-engine impellers in a virtual environment. The impellers are used in the compression stage of the engine and are costly, difficult to machine, and time-consuming to manufacture. To improve the productivity of the flank milling operations, a procedure to predict and optimize the cutting process is proposed. The contributions of the thesis include a novel cutter-workpiece engagement calculation algorithm, a five-axis flank milling cutting mechanics model, two methods of optimizing feed rates for impeller machining tool paths and a new five-axis chatter stability algorithm. A semi-discrete, solid-modeling-based method of obtaining cutter-workpiece engagement (CWE) maps for five-axis flank milling with tapered ball-end mills is developed. It is compared against a benchmark z-buffer CWE calculation method, and is found to generate more accurate maps. A cutting force prediction model for five-axis flank milling is developed. This model is able to incorporate five-axis motion, serrated, variable-pitch, tapered, helical ball-end mills and irregular cutter-workpiece engagement maps. Simulated cutting forces are compared against experimental data collected with a rotating dynamometer. Predicted X and Y forces and cutting torque are found to have a reasonable agreement with the measured values. Two offline methods of optimizing the linear and angular feeds for the five-axis flank milling of impellers are developed. Both offer a systematic means of finding the highest feed possible, while respecting multiple constraints on the process outputs. In the thesis, application of these algorithms is shown to reduce the machining time for an impeller roughing tool path. Finally, a chatter stability algorithm is introduced that can be used to predict the stability of five-axis flank milling operations with general cutter geometry and irregular cutter-workpiece engagement maps. Currently, the new algorithm gives chatter stability predictions suitable for high speed five-axis flank milling. However, for low-speed impeller machining, these predictions are not accurate, due to the process damping that occurs in the physical system. At the time, this effect is difficult to model and is beyond the scope of the thesis.

abstract: Olympus Mons is the largest volcano on Mars. Previous studies have focused on large scale features on Olympus Mons, such as the basal escarpment, summit caldera complex and aureole deposits. My objective was to identify and characterize previously unrecognized and unmapped small scale features to understand the volcanotectonic evolution of this enormous volcano. For this study I investigated flank vents and arcuate graben. Flank vents are a common feature on composite volcanoes on Earth. They provide information on the volatile content of magmas, the propagation of magma in the subsurface and the tectonic stresses acting on the volcano. Graben are found at a variety of scales in close proximity to Martian volcanoes. They can indicate flexure of the lithosphere in response to the load of the volcano or gravitation spreading of the edifice. Using Context Camera (CTX), High Resolution Imaging Science Experiment (HiRISE), Thermal Emission Imaging System (THEMIS), High Resolution Stereo Camera Digital Terrain Model (HRSC DTM) and Mars Orbiter Laser Altimeter (MOLA) data, I have identified and characterized the morphology and distribution of 60 flank vents and 84 arcuate graben on Olympus Mons. Based on the observed vent morphologies, I conclude that effusive eruptions have dominated on Olympus Mons in the Late Amazonian, with flank vents playing a limited role. The spatial distribution of flank vents suggests shallow source depths and radial dike propagation. Arcuate graben, not previously observed in lower resolution datasets, occur on the lower flanks of Olympus Mons and indicate a recent extensional state of stress. Based on spatial and superposition relationships, I have constructed a developmental sequence for the construction of Olympus Mons: 1) Construction of the shield via effusive lava flows.; 2) Formation of the near summit thrust faults (flank terraces); 3) Flank failure leading to scarp formation and aureole deposition; 4) Late Amazonian effusive resurfacing and formation of flank vents; 5) Subsidence of the caldera, waning volcanism and graben formation. This volcanotectonic evolution closely resembles that proposed on Ascraeus Mons. Extensional tectonism may continue to affect the lower flanks of Olympus Mons today. / Dissertation/Thesis / Masters Thesis Geological Sciences 2015

This thesis presents models and algorithms necessary to simulate the five-axis flank milling of jet-engine impellers in a virtual environment. The impellers are used in the compression stage of the engine and are costly, difficult to machine, and time-consuming to manufacture. To improve the productivity of the flank milling operations, a procedure to predict and optimize the cutting process is proposed. The contributions of the thesis include a novel cutter-workpiece engagement calculation algorithm, a five-axis flank milling cutting mechanics model, two methods of optimizing feed rates for impeller machining tool paths and a new five-axis chatter stability algorithm. A semi-discrete, solid-modeling-based method of obtaining cutter-workpiece engagement (CWE) maps for five-axis flank milling with tapered ball-end mills is developed. It is compared against a benchmark z-buffer CWE calculation method, and is found to generate more accurate maps. A cutting force prediction model for five-axis flank milling is developed. This model is able to incorporate five-axis motion, serrated, variable-pitch, tapered, helical ball-end mills and irregular cutter-workpiece engagement maps. Simulated cutting forces are compared against experimental data collected with a rotating dynamometer. Predicted X and Y forces and cutting torque are found to have a reasonable agreement with the measured values. Two offline methods of optimizing the linear and angular feeds for the five-axis flank milling of impellers are developed. Both offer a systematic means of finding the highest feed possible, while respecting multiple constraints on the process outputs. In the thesis, application of these algorithms is shown to reduce the machining time for an impeller roughing tool path. Finally, a chatter stability algorithm is introduced that can be used to predict the stability of five-axis flank milling operations with general cutter geometry and irregular cutter-workpiece engagement maps. Currently, the new algorithm gives chatter stability predictions suitable for high speed five-axis flank milling. However, for low-speed impeller machining, these predictions are not accurate, due to the process damping that occurs in the physical system. At the time, this effect is difficult to model and is beyond the scope of the thesis. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Flank margin caves are karst features that develop in the freshwater/saline mixing zone within the carbonate islands of the Bahamas. The flank margin caves that are currently exposed developed during the last interglacial sea level highstand (+6 m; ~125 ka). Initially small ovid chambers, the caves increase in size to about 100 m2, then interconnect with adjacent chambers to form medium-sized caves. At about 1000 m2, these medium-size caves interlink forming large caves that are laterally extensive, vertically restricted, do not penetrate the fresh-water lens a significant amount, and run parallel to the axis of the ridge in which they formed. Small caves have a much smaller area to perimeter ratio than do large caves. As cave chambers grow and interconnect, perimeters become much more complex, and the number of bedrock columns in the cave increases. These results have implications for water resource management, and porosity modeling.