Ultraprecision, single point diamond turning (SPDT) is a tool based machining technology that allows the ability to produce high quality surface finishes on the order of nanometers while meeting tight form tolerances on the order of micrometers. It is generally agreed that surface finish in SPDT is primarily affected by four factors: Tool edge quality, relative vibration between the tool and workpiece, material properties and microstructure, and tool geometry (nose radius and machining parameters) machining. To the author’s knowledge, no work has been done to combine all the factors to study their effect on surface generation in SPDT. This is important given that the factors are highly interdependent. Two diamond tools with nose radius of 12mm were used; however, one of them was chemically honed. Results suggest that the honed tool provides a much better surface finish with a significantly reduced amount of running-in stage tool wear. The cutting edge radius of the diamond tools was measured using a novel 3D confocal laser microscope to analyze the chemical honing process and to measure tool wear. The presence of built-up edge (BUE) is more prominent on the honed tool earlier in its life which results in unpredictable surface roughness to appear sooner than on the regular tool. To understand the dynamics of the machine, a redesign of the tool holder bracket was done to increase stiffness. Modal tests were then performed on it to verify performance improvement. With an understanding of the vibration and its effect on the cutting force, a 400Hz disturbance frequency was detected in the cutting forces. From a 3D scan of the surface, a total of 24 undulations on the surface of the part were observed when the spindle speed was set to 1000RPM The machine was instrumented and a rotordynamic investigation was carried out to determine the cause and nature of the vibration in an effort to reduce it and in so doing improve surface form accuracy. / Thesis / Master of Applied Science (MASc)

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Ultra precision single point diamond turning (SPDT) is a machining process used to produce optical grade surfaces in a wide range of materials. Aluminum is of primary interest as a workpiece material because it is easily diamond turnable, highly reflective and corrosion resistant. The cutting tool used is made from a single crystal diamond honed to a very sharp cutting edge. The machines used in this process are extremely precise and stiff. The nature of the cutting parameters used in SPDT changes the process physics substantially over conventional machining. The underlying reason relates to the relative size of the uncut chip thickness and the cutting edge radius of the tool in comparison to the grain size of the workpiece. When performing SPDT, there is a functional limit to the achievable surface finish. This is predominately due to material side flow and the opening up of material defects. Thus the machined surfaces have to undergo post processing operations like lapping or polishing, which increase cost and production time. Thus, the objective of this study was to improve the surface finish of the SPDT process to minimize the amount of post processing. The approach involved addressing the ratio between the tool cutting edge radius and the microstructure. Realizing the limitations associated with sharpening a diamond tool further, efforts have been made to mechanically or thermo-mechanically induce dislocations into the workpiece to refine the microstructure and in so doing enhance machinability. As dislocations act as a point of defect, it is observed that higher dislocation density offers less side flow and leads to better surface roughness. A special tool with a flat secondary edge was then developed to address the remaining side flow issue for planar surfaces. The combination of thermo-mechanically produced ultra fine grained material with the special tool provided a substantial reduction in surface roughness from values typically reported at 3nm [Roblee, 2007] Ra to 0.75nm R0 • In addition to this the use of the custom designed tool can improve the productivity associated with machining a flat face by a factor of one hundred times by allowing the feed rate to be increased while still achieving the desired surface finish. / Thesis / Doctor of Philosophy (PhD)

Over the past few years, White Americans have been exposed to moments of "racial reckonings" –where America was forced to realize racial injustice—often caused by police killings of Black Americans. The summer of 2020 sparked various discussions about White allies and their role in racial justice. Previous scholarship has explored White racial awakenings, also referred to as turning points, when White allies transition into allyship; however, little is known about how these narratives affect White allies' definitions and practices of White allyship. By interviewing self-identifying White allies in college, I examine types of turning point narratives and how they correspond to understandings of ally definitions and practices. I argue that experiencing turning points led White allies to similar definitions and practices of White allyship depending on whether these points occurred in routine or non-routine White experiences. Turning points that arise from typical White experiences (exposure to diversity and education) led White allies to common allyship failures and complicity with racialized structures. Alternatively, turning points resulting from uncommon White experiences (exposure to protests and diverse families) led allies to definitions and practices representing non-complicity with racialized structures. / Master of Science / Over the past few years, White Americans have been exposed to moments of race related dialogues, often caused by police killings of Black Americans. The summer of 2020 sparked various discussions about White allies and their role in racial justice. Previous scholarship has explored White racial awakenings, also referred to as turning points, when White allies transition into allyship; however, little is known about how these narratives affect White allies' definitions and practice of White allyship. By interviewing self-identifying White allies in college, I examine types of turning points and how they correspond ally definitions and practices. I argue that experiencing turning points led White allies to similar definitions and practices of White allyship depending on whether these points occurred in routine or non-routine White experiences. Turning points that arise from typical White experiences (exposure to diversity and education) led White allies to common allyship failures. Alternatively, turning points resulting from uncommon White experiences (exposure to protests and diverse families) led allies to beneficial definitions and practices of allyship.

Prediction of chip-breaking in machining is an important task for automated manufacturing. There are chip-breaking limits in maching chip-breaking processes, which determine the chip-breaking range. This paper presents a study of chip-breaking limits with grooved cutting tools, and a web-based machining chip-breaking prediction system. Based on the chip-breaking curve, the critical feed rate is modeled through an analysis of up-curl chip formation, and the critical depth of cut is formulated through a discussion of side-curl dominant chip-formation processes. Factors affecting chip-breaking limits are also discussed. In order to predict chip-breaking limits, semi-empirical models are established. Although the coefficients that occur in the model are estimated through machining tests, the models are applicable to a broad range of machining conditions. The model parameters include machining conditions, tool geometry, and workpiece material properties. A new web-based machining chip-breaking prediction system is introduced with examples of industrial applications.

Finish machining of hardened steel is receiving increasing attention as an alternative to the grinding process, because it offers comparable part finish, lower production cost, shorter cycle time, fewer process steps, higher flexibility and the elimination of environmentally hazardous cutting fluids. In order to demonstrate its economic viability, it is of particular importance to enable critical hard turning processes to run in optimal conditions based on specified objectives and practical constraints. In this dissertation, a scientific and systematic methodology to design the optimal tool geometry and cutting conditions is developed. First, a systematic evolutionary algorithm is elaborated as its optimization block in the areas of: problem representation; selection scheme; genetic operators for integer, discrete and continuous design variables; constraint handling and population initialization. Secondly, models to predict process thermal, forces/stresses, tool wear and surface integrity are addressed. And then hard turning process planning and optimization are implemented and experimentally validated. Finally, an intelligent advisory system for hard turning technology by integrating experimental, numerical and analytical knowledge into one system with user friendly interface is presented. The work of this dissertation improves the state of the art in making tooling solution and process planning decisions for hard turning processes.

Unlike straight turning, the effective cutting conditions and tool geometry in contour turning operations are changing with changing workpiece profile. This causes a wide variation in machining performance such as chip flow and chip breakability during the operation. This thesis presents a new methodology for optimizing the machining performance, namely, chip breakability and surface roughness in contour finish turning operations. First, a computer program to calculate the effective cutting conditions and tool geometry along the contour workpiece profile is developed. Second, a methodology to predict the chip side-flow for complex grooved tool inserts is formulated and integrated in the current predictive model for contour turning operations. Third, experimental databases are established and numerical data interpolation is applied to predict the cutting forces, chip shape and size, and surface roughness for 1045 steel work material. Finally, based on the machining performance predictions, a new optimization program is developed to determine the optimum cutting conditions in contour finish turning operations.

Titanium alloys have outstanding mechanical properties such as high hardness, a good strength-to-weight ratio, excellent fatigue properties and high corrosion resistance. However, several inherent properties including their low thermal conductivity and high chemical affinity to tool materials impairs severely their machinability with conventional machining techniques. Conventional machining of Ti-based alloys is typically characterized by low depths of cuts and relatively low feed rates, thus adversely affecting the material removal rates during the machining process. Recently, a non-conventional machining technique known as ultrasonically assisted turning (UAT) was introduced to machine modern alloys, in which low-energy, high-frequency vibration is superimposed on the movement of a cutting tool during a conventional cutting process. This novel machining technique results in a multi-fold decrease in the level of cutting forces with a concomitant improvement in surface finish of machined modern alloys. Also, since the late 20th century, machining of wear resistant materials that soften when heated has been carried out with hot machining techniques. In this work, a new hybrid machining technique called Hot Ultrasonically Assisted Turning (HUAT) is introduced for processing of a Ti-based alloy Ti-15V3Al3Cr3Sn. In this technique, UAT is combined with a traditional hot machining technique to gain combined advantages of both schemes for machining of intractable alloys. HUAT of the studied alloy was analysed experimentally and numerically to demonstrate its benefits in terms of reduction in cutting forces over a wide range of industrially relevant speed-feed combinations. Thermal evolution in the cutting process was assessed, and the obtained results were compared with FE simulations to gain knowledge of temperatures reached in the cutting zone. The developed novel turning process appeared to improve dry turning of the Ti alloy with significant reduction of average cutting forces without any substantial metallurgical changes in the workpiece material. Nano-indentation, light microscopy and SEM studies were performed to get an insight into the development of hardness in a zone near the machined surface in the workpiece. Backscatter electron microscopy was also used to evaluate the formation of α-Ti during the novel HUAT. No grain changes or α-precipitation were observed in machined workpieces in conventional and hybrid turning processes. 3D elasto-plastic thermomechanically coupled finite-element models for the orthogonal turning process were developed for conventional turning (CT), hot conventional turning (HCT), UAT and HUAT, followed by a more realistic novel 3D finite-element model for the oblique turning process. These 3D models were used to study the effects of cutting parameters (cutting speed, feed rate and depth of cut, ultrasonic vibration, ultrasonic frequency, rake angle and tool nose radius) on cutting forces, temperature in the process zone and stresses. The later model was used to analyse the effect of vibration and heat on the radial and axial components of cutting forces in HUAT, which was not possible with the developed 3D orthogonal-turning model. Comparative studies were performed with the developed CT, HCT, UAT and HUAT finite-element models and were validated by results from experiments conducted on the in-house prototype and in literature. The HUAT for the Ti-15333 was analysed experimentally and numerically to demonstrate the benefits in terms of a significant reduction in the cutting forces and improvement in surface roughness over a wide range of industrially relevant speed-feed combinations.

Vibration in metal cutting is a common problem in the manufacturing industry, especially when long and slender tool holders or boring bars are involved in the manufacturing process. Vibration has a detrimental effect on machining. In particular the surface finish is likely to suffer, but tool life is also most likely to be reduced. Tool vibration also results in loud noise that may disturb the working environment. The first part of this thesis describes the development of a robust and manually adjustable analog controller capable of actively controlling boring bar vibrations related to internal turning. This controller is compared with an adaptive digital feedback filtered-x LMS controller and it displays similar performance with a vibration attenuation of up to 50 dB. A thorough experimental investigation of the influence of the clamping properties on the dynamic properties of clamped boring bars is also carried out in second part of the thesis. In relation to this, it is demonstrated that the number of clamping screws, the clamping screw diameter size, the screw tightening torque and the order the screws are tightened, have a significant influence on a clamped boring bar’s eigenfrequencies as well as on its mode shape orientation in the cutting speed - cutting depth plane. Also, an initial investigation of nonlinear dynamic properties of clamped boring bars was carried out. Furthermore, vibration in milling has also been studied in relation to millingtool holders with a long overhang. A basic investigation concerning the spatial dynamic properties of the tool holders of milling machines, both when not cutting and during cutting, has been carried out. Also, active control of milling tool holder vibration has been investigated and a first prototype of an active milling tool holder was implemented and tested. The challenge of transferring electrical power while maintaining good signal quality to and from a rotating object is addressed and a solution to this is proposed. Finally, vibration is also a problem for the hydroelectric power industry. In Sweden, hydroelectric power plants stand for approximately half of Sweden’s electrical power production and are also considered to be a so-called green source of energy. When renovating water turbines in small-scale hydroelectric power plants and modifying them to optimize efficiency, it is not uncommon that disturbing vibrations occur in the power plant. These vibrations have a negative influence on the production capacity and will wear various components quickly. Occasionally, these vibrations may cause severe damage to the power plant. To identify this vibration problem, experimental modal analysis and operating deflection shape analysis were utilized. To reduce the vibration problem, active control using inertial mass actuators was investigated. Preliminary results indicate a significant attenuation of the vibrations.

Fatigue has been observed to affect lower extremity mechanics during the cutting maneuver. However, there is a lack of research examining the effect of fatigue and limb dominance on lower extremity mechanics during unanticipated sidecutting. Objectives: This research sought to assess mechanical differences pre- and post-fatigue and with respect to limb dominance. Design: Repeated measures. Methods: Thirteen female collegiate soccer and field hockey players performed right and left unanticipated sidecutting following the Yo-Yo Intermittent Recovery test (Yo-Yo IR), a two minute treadmill run at a predicted VO2max, and maximum vertical jumps. Mechanical measures of ankle, knee, and hip motion were obtained during the stance phase of the cut. Repeated measures 2x2 ANOVAs were performed to look at fatigue and limb differences. Alpha level set a priori at 0.05. Results: At initial contact and peak stance, significant changes pre- to post-fatigue were observed. At initial contact there was a reduction in knee flexion angles along with increased ankle dorsiflexion angles postfatigue. At peak stance: increased knee adductor moments post-fatigue; greater ankle eversion moments on the dominant limb (DL) as well as increased eversion moments post-fatigue for both limbs. There was a differential effect of fatigue on peak hip abduction angles and hip internal rotation angles at initial contact which were altered in the DL only; decreased hip adductor moments occurred post-fatigue as well as decreased power absorption. Conclusions: Results from this study indicate that lower extremity mechanics are altered as an effect of fatigue such that injury risk may be elevated. / School of Physical Education, Sport, and Exercise Science