In this research, the integration of the servomechanism control and process control for machining processes has been studied. As enabling strategies for next generation quality control, process monitoring and open architecture machine tools will be implemented on production floor. This trend brings a new method to implement control algorithm in machining processes. Instead of using separate modules for servomechanism control and process control individually, the integrated controller is proposed in this research to simultaneously achieve goals in servomechanism level and the process level. This research is motivated by the benefits brought by the integration of servomechanism control and process control. Firstly, the integration simplifies the control system design. Secondly, the integration promotes the adoption of process control on production floor. Thirdly, the integration facilitates portability between machine tools. Finally, the integration provides convenience for both the servomechanism and process simulation in virtual machine tool environment. The servomechanism control proposed in this research is based on error space approach. This approach is suitable for motion control for complex contour. When implement the integration of servomechanism control and process control, two kinds of processes may be encountered. One is the process whose model parameters can be aggregated with the servomechanism states and the tool path does not need real time offset. The other is the process which does not have direct relationship with the servomechanism states and tool path may need to be modified real time during machining. The integration strategies applied in error space are proposed for each case. Different integration strategies would propagate the process control goal into the motion control scheme such that the integrated control can simultaneously achieve goals of both the servomechanism and the process levels. Integrated force-contour-position control in turning is used as one example in which the process parameters can be aggregated with the servomechanism states. In this case, the process level aims to minimize cutting force variation while the servomechanism level is to achieve zero contour error. Both force variation and contour error can be represented by the servomechanism states. Then, the integrated control design is formulated as a linear quadratic regulator (LQR) problem in error space. Force variation and contour error are treated as part of performance index to be minimized in the LQR problem. On the other hand, the controller designed by LQR in error space can guarantee the asymptotic tracking stability of the servomechanism for complex contour. Therefore, the integrated controller can implement the process control and the servomechanism control simultaneously. Cutter deflection compensation for helical end milling processes is used as one example in which the process cannot be directly associated with the servomechanism states. Cutter deflection compensation requires real-time tool path offset to reduce the surface error due to cutter deflection. Therefore, real time interpolation is required to provide reference trajectory for the servomechanism controller. With the real time information about surface error, the servomechanism controller can not only implement motion control for contour requirement, but also compensation for the dimensional error caused by cutter deflection. In other words, the real time interpolator along with the servomechanism controller can achieve the goals of both the servomechanism and process level. In this study, the cutter deflection in helical end milling processes is analyzed first to illustrate the indirect relationship between cutter deflection and surface accuracy. Cutter deflection is examined for three kinds of surfaces including straight surface, circular surface, and curved surface. The simulation-based deflection analysis will be used to emulate measurement from sensors and update the real-time interpolator to offset tool path. The controller designed through pole placement in error space can guarantee the robust tracking performance of the updated reference trajectory combining both contour and tool path offset required for deflection compensation. A variety of cutting conditions are simulated to demonstrate the compensation results. In summary, the process control is integrated with the servomechanism control through either direct servomechanism controller design without tool path modification or servomechanism control with real time interpolation responding to process variation. Therefore, the process control can be implemented as a module within machine tools. Such integration will enhance the penetration of process control on production floor to increase machining productivity and product quality.

Micrometeoroids and orbital debris (MMOD) is a growing issue with international importance. Micrometeoroids are naturally occurring fragments of rock and dusk that exist throughout the solar system. Orbital debris is human made material like rocket bodies, paint flakes, and the effluent of spacecraft collisions. Even small MMOD particles on the order of 1 cm in diameter have the potential to destroy critical spacecraft systems. Because of this, MMOD is a threat to all spacecraft in orbit. Even governments that most sternly oppose US international policy have a stake when it comes to minimizing MMOD flux. Space-based assets are essential to support the growing demand for high-capacity communications networks around the world. These networks support services that civilian and military users have grown accustomed to using on a daily basis: Global Positioning System (GPS), Satellite Radio, Internet Backhaul, Unmanned Areal Vehicles (UAVs), and Reconnaissance Satellites [Figure \ref{figure:skynet}]. A sudden loss of these services could degrade the warfighter's capabilities and cripple commercial enterprises that rely on these technologies. Manned space efforts like the International Space Station (ISS) could also suffer as a result of increased MMOD flux.

This investigation, in consideration of the sudden separation increase involved in wing drop, was to determine if the incorporated 2-D airfoil exhibits abnormal shock sensitivity. A comparative airfoil study was used to determine if this particular transonic airfoil is prone to abrupt shock movement, resulting in increased regions of separation. / Master of Science

No / This paper presents analytical technique and simplified formulas for the calculations of cracking, yield and ultimate moments of different cases as well as deflections of ECC-concrete composite beams reinforced with steel bars. The technique is based on the simplified constitutive models of materials, strain compatibility, perforce bond of materials and equilibrium of internal forces and moment. Experimental testing of eleven ECC-concrete composite beams reinforced with steel bars is also presented. All beams tested had the same geometrical dimensions but different steel reinforcement strength and ECC thickness. The proposed formulas showed good agreement with the experimental results of various moment values and deflections. A parametric analysis shows that yield and ultimate moments increase with the increase of concrete strength in case of compression failure but, essentially, remain unchanged in case of tensile failure. With increasing the tensile resistance, for example by increasing ECC height replacement ratio, reinforcement ratio, strength of steel reinforcement and ECC, ultimate curvature and energy dissipation increase in case of tensile failure and decrease in case of compressive failure. On the other hand, ductility and energy dissipation ratio decrease with the increase of reinforcement ratio and strength, but, essentially, remain unchanged with increasing the height replacement ratio and strength of ECC. / National Natural Science Foundation of China (51678514, 51308490), the Natural Science Foundation of Jiangsu Province, China (BK20130450), Six Talent Peaks Project of Jiangsu Province (JZ-038, 2016), Graduate Practice Innovation Project of Jiangsu Province (SJCX17-0625) and the Jiangsu Government Scholarship for Overseas Studies.

Flexible high-deflection strain gauges have been demonstrated as cost-effective and accessible sensors for capturing human biomechanical deformations. However, the interpretation of these sensors is notably more complex compared to conventional strain gauges, partially owing to the viscoelastic nature of the strain gauges. On top of the non-linear viscoelastic behavior, dynamic resistance response is even more difficult to capture due to spikes in resistance during strain changes. This research examines the relationships between stress, strain, and resistance in nanocomposite sensors during dynamic strain situations. Under the assumption that both macroscopic stress and resistance are governed by microscopic stress concentrations at the junctions between nanoparticles and silicone matrix, the stress-resistance relationship is analyzed. Both stress and resistance are found to exhibit aspects of viscoelastic behavior, including creep decay and relaxation during constant strains. However, the resistance spikes are found to be more complex than a simple stress-resistance model can capture. This research then develops a model that captures the strain-resistance relationship of the sensors, including resistance spikes, during cyclical movements. The forward model, which converts strain to resistance, is comprised of four parts to accurately capture the different aspects of the sensor response: a quasi-static linear model, a spike magnitude model, a long-term creep decay model, and a short-term decay model. An inverse problem approach is used to create an inverse model, which predicts the strain vs time data that would result in the observed resistance data. The model is calibrated for a particular sensor from a small amount of cyclic data from a single test. The resulting sensor-specific model is able to accurately predict the resistance output with an R-squared value of 0.90. The inverse model is able to accurately predict key strain characteristics with a percent error of 0.5. The model can be used in a wide range of applications, including biomechanical modeling and analysis. It is found that the resistance spikes are directly correlated to the strain acceleration in terms of timing and in terms of magnitude. Poisson contraction rates and voids in the material are possible causes for resistance spikes during dynamic strain movements.

A flex-fan has flexible blades which undergo large deformation under centrifugal forces to give the desired air-flow and power-consumption characteristics with speed. The finite element technique has been used to obtain the deflected shape of the blade of such a fan used for automobile radiator cooling. The natural frequencies of vibration are also evaluated at different speeds, up to 5,000 rpm. A partially conforming deflection function has been used in the analysis. The blade has been treated as a thin shell, idealized as an assembly of thin flat triangular elements. / Thesis / Master of Engineering (ME)

This is a `sandwich thesis' comprising three distinct research streams I have pursued during the course of my master's degree. The first two streams have concluded, each resulting in a manuscript that is presented as a separate chapter of this thesis. The third research stream is ongoing, but preliminary results are presented in another chapter of this thesis. The first research stream presented in this thesis concerns the development of a technique to produce droplets with diameters as small as 5 microns with an extremely narrow size distribution in comparison to other methods. Other advantages of this technique, known as he snap-offf method, include its simplicity and ease of tuning droplet size. The results of this research are presented in chapter 3 in the form of a manuscript that is currently in press. The second research stream of this thesis explores the physics that drive droplet snap-off. A model was developed to predict the size of droplets, dependent on fluid properties, system geometry, and fluid flow rate. Experiments examined each of these parameters in turn, providing a cohesive understanding of the mechanism behind droplet snap-off. Multiple unanticipated predictions of the model were also verified experimentally. This research is presented in chapter 4 as a manuscript that will be submitted shortly. The final research stream of this thesis investigates forces in emulsions as they relate to a transition from glassy to crystalline dynamics. Specifically, 2D aggregates of droplets were compressed with micropipettes, providing both imaging of cluster evolution, as well as the force applied during compression. This research stream has demonstrated qualitative differences between droplet clusters that differ in composition so as to behave like crystals, glasses, or intermediate states. More quantitative analysis is required before this research stream is ready to be published. Preliminary results are presented in chapter 5. / Thesis / Master of Science (MSc)

No description available.

Emulsions and colloidal suspensions have various industrial applications but are also used in laboratories as model systems for studying the different phases of matter. They are versatile as their nature, size and inter-particle interactions are easily tuneable. These systems are perfect for studying questions such as the phase transition. In this thesis, we investigate the transition from an ordered crystal to a disordered glass. Perfectly ordered crystals are modeled by clusters of highly monodisperse droplets. We study the transition toward a glassy system by mixing two monodisperse populations of droplets in different proportions. The clusters are compressed between two thin glass rods, one of which is a force transducer. The forces within the clusters are directly measured and used as an indicator of the composition of the cluster. Upon introduction of disorder, the number of peaks in the force measurement increases drastically. We find that the way the energy is dissipated in the cluster is valuable information to characterize the crystal-to-glass transition. In addition to the experimental study of the crystal-to-glass transition, we have developed an analytical model that is in full agreement with the experimental observations. A crystal is modeled as an assembly of Hookean springs that will store elastic energy until it reaches a fracture point. We are able to predict the number of peaks in the force measurements when defects are introduced using simple geometric arguments. From this prediction, the way the work is dissipated in a given transition can be predicted. / Thesis / Master of Science (MSc)

yes / Tests results of three flanged and two rectangular cross-section concrete beams reinforced with carbon fibre reinforced polymer (CFRP) bars are reported. In addition, a companion concrete flanged beam reinforced with steel bars is tested for comparison purposes. The amount of CFRP reinforcement used and flange thickness were the main parameters investigated in the test specimens. One CFRP reinforced concrete rectangular beam exhibited concrete crushing failure mode, whereas the other four CFRP reinforced concrete beams failed due to tensile rupture of CFRP bars. The ACI 440 design guide for FRP reinforced concrete members underestimated the moment capacity of beams failed due to CFRP tensile rupture and reasonably predicted deflections of the beams tested. A simplified theoretical analysis for estimating the moment capacity of concrete flanged beams reinforced with FRP bars was developed. The experimental moment capacity of the CFRP reinforced concrete beams tested compared favourably with that predicted by the theoretical analysis developed.