Fretting phenomenon occurs when two bodies in contact undergo small repetitive relative motion such that the localized surface and subsurface material properties are altered leading to damage or failures. Fretting conditions are obtained by controlling externally applied parameters such as load, frequency of displacement, displacement amplitude. Material properties which influence fretting behavior include hardness, ductility, hardening behavior. External parameters like surface roughness, temperature also play a role in deciding the extent of damage. Based on fretting conditions and specimen geometry, various fretting modes can be classified. Rotational fretting is one such damage mode, observed in industrial applications such as cable ropes under tension used for support in construction industry and variable stator vanes (VSVs) in compressors of turbines. In spite of industrial and engineering relevance, rotational fretting has received little attention. In the present work, rotational fretting of self-mated AISI 4340 material pair was studied, with the objective of characterizing subsurface damage induced by fretting. AISI 4340 (EN 24) is a low alloy martensitic steel with an excellent combination of strength, ductility and toughness. It is widely used in high strength cyclic loading applications like gears, bearings, automobile pistons and aircraft landing gears as well as in low corrosion, high strength offshore applications. It can be readily machined and surface hardened which makes it useful for wear related applications. A novel rotational fretting test set up, capable of operating under various test loads, frequencies, displacement amplitudes and temperatures was used to perform experiments. Specimens were subjected to a combination of normal load and rotational displacement and caused to mutually contact on non-conformal curved surfaces which simulate a bearing or bushing geometry. Fretting results were primarily determined by the frictional torque versus angular displacement plots. The running condition response was linked to the fretting material response regime. Surface and subsurface characterization studies of fretted regions were conducted using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). TEM studies revealed varying levels of fretting induced plastic deformation within the fretted contact zone. Good correlation with available literature relating to formation of dislocation cells and presence of high dislocation density in the fretting damaged regions was established. Although quantifying the dislocation density as a damage indicator is a challenge, it is proposed that a microstructural feature based approach has the potential to be developed into a useful tool for life assessment and life prediction studies.

In this thesis we used atomic force microscopy (AFM) to investigate systematically the behaviour of both electrostatically stabilised silica and sterically stabilised polystyrene (PS) colloidal systems on freshly cleaved mica substrates. For the silica colloidal nanoparticles we explored the effect of colloidal suspension concentration, particle size, and different application techniques on both the adsorption behaviour and subsequent structuring of the particles. For the PS colloidal nanoparticles we explored concentration effects and experimented with both dip-coating and droplet application techniques. We showed that silica nanoparticles adsorbed onto mica via irreversible adsorption that possessed lateral mobility due to the weak attraction between the nanoparticles and the substrate, facilitating subsequent capillary structuring of the nanoparticles during drying. We associated the effects of volume fraction with Debye screening, and kinetics effects with particle size and volume fraction. We also successfully imaged a partially dried film and showed the role of convective/capillary forces in the structuring of the nanoparticles. Studies with variations in particle size generated a number of different topography structures; with dewetting phenomena observed for 10 nm nanoparticles and the formation of crystalline structures for 100 nm nanoparticles. Spin coating techniques were used to produce even larger crystalline structures of nanoparticles. Size dependent ordering occurred for low concentration samples due to the polydispersity of the colloidal suspension. We showed that acceleration can affect interparticle spacing. We also studied the role of rotational speed on the crystallinity of the particle configurations and showed how fine tuning of rotational speed can generate large scale monolayer crystalline formations of nanoparticles.

The Equipment Controls and Electronics section (EN-STI-ECE) at CERN is developing a high precision piezo-actuated rotational stage for the UA9 crystal collimation project. This collaboration is investigating how tiny bent crystals can help to steer particle beams used in modern hadron colliders such as the Large Hadron Collider (LHC). Particles are deflected by following the crystal planar channels, "channeling" through the crystal. For high energy particles the angular acceptance for channeling is very low, demanding for a high angular precision mechanism, i.e. the rotational stage. Several control-related issues arising from the complexity and operational environment of the system make it difficult to design a controller that achieves the desired performance. This thesis investigates different control approaches that could be used to improve the tracking capability of the rotational stage. It shows that the IRC method could be used to efficiently control the rotational stage. Moreover it shows that a harmonic cancellation method could be used to increase the tracking accuracy by canceling known harmonic disturbances. The harmonic cancellation method (the RFDC) was implemented in this thesis and proposed as an add-on to the present control algorithm.

Rotational grazing is being promoted by some land managers, government agencies, and conservation groups as superior to season-long grazing for improving pasture and cattle production, and for grassland bird conservation; however, the assumed benefits have not been comprehensively studied. In 2011 and 2012, I examined the effects of twice-over rotational grazing on the nesting success of grassland songbirds in southwestern Manitoba, Canada. I monitored nesting attempts and collected structural vegetation data for five species of obligate grassland bird (n=110) and one shrub-nesting species (n=41). Nesting analyses were conducted using logistic exposure models. Twice-over grazing had a significantly negative effect on the nesting success of the ground nesting species, including Savannah sparrows (Passerculus sandwichensis). Grazing system did not have an effect on vegetation structure. The results are consistent with other rotational grazing studies, and suggest that twice-over rotational grazing does not benefit grassland songbirds in mixed-grass prairie habitats. / October 2016

The problem of the quadrupole interaction occurring in a vibrating-rotating C₃v symmetric top molecule has been studied in detail. The quadrupole interaction has been treated as another perturbation term to a general frequency expression accounting for the vibrating-rotating interaction of the molecule so that a complete frequency formula is obtained for both interactions, and from which hyperfine spectral components are predicted and measured. The hyperfine transitions in the ground, and v₈=1 and v₈=2 excited vibrational states of the ¹³C isotopes of methyl cyanide have been investigated in the frequency range 17-72 GHz, primarily in the low J transitions (0≤J≤3). The study of the ground state of isotope i3CH3i3CN, and the v₈=1, v₈=2 excited vibrational states for all the isotopes have been conducted here for the first time. A substantial perturbation has been discovered and discussed at the ΔJ=3→4 transitions within the Kl=1 sets in the v₈=1 mode for isotopes ¹³CH₃CN and CH₃¹³CN. A total of 716 hyperfine transitions have been assigned from measurements, only 7 of which have been measured previously. A total of 84 molecular constants have been reported; 70 of these constants are derived for the first time from microwave data.

The problem of a vibrating-rotating polyatomic molecule is treated, with emphasis given to the case of molecules with C_3v symmetry. It is shown that several of the gross features of the rotational spectra of polyatomic molecules in excited vibrational states can be predicted by group theoretical considerations. Expressions for the rotational transition frequencies of molecules of C_3v symmetry in the ground vibrational state, singly excited degenerate vibrational states, and doubly excited degenerate vibrational states are given. The derivation of these expressions by fourth order perturbation theory as given by Amat, Nielsen, and Tarrago is discussed. The ground and V_10=1 rotational spectra of propyne have been investigated in the 17 to 70 GHz, and 17 to 53 GHz regions, respectively, and compared with predictions based on higher frequency measurements. The V_9=1 and V_10=2 rotational spectra of propyne have been investigated and assigned for the first time. A perturbation of the V_9=1 rotational spectra for K=-l has been discovered and discussed.

The rotational spectrum of ScO (X-2 Sigma(+)) has been measured in the gas phase in the frequency range 30-493 GHz using a combination of Fourier transform microwave/millimeter-wave (FTM/mmW) and submillimeter direct absorption methods. This work is the first pure rotational study of this radical. Both the ground vibrational and v=1 states were observed. ScO was created from the reaction of metal vapor, produced either by a laser ablation source or a Broida-type oven, and N2O, in the former case heavily diluted in argon. Extensive hyperfine structure was observed in the FTM/mmW data, although the spin-rotation splitting was found to be small (similar to 3 MHz). In the mm-wave spectra, however, the fine and hyperfine structure was blended together, resulting in broad, single lines for a given transition N + 1 <- N. The data were analyzed in a combined fit using the very accurate hyperfine measurements of Childs and Steimle (1988), employing a Hund's case b Hamiltonian, and an improved set of rotational and centrifugal distortion constants were determined. These measurements improve the accuracy of predicted frequencies for astronomical searches by 14-18 MHz, or 16-20 km/s, in the 1 mm region - a difference of half to a full linewidth for certain interstellar sources. This work also demonstrates the capabilities of the FTM/mmW spectrometer at 61 GHz.

A source-modulation microwave spectrograph was utilized to measure line width parameters for several spectral lines in the pure rotational spectrum of formaldehyde (H₂CO). The spectrograph featured high-gain ac amplification and phase-sensitive detection, and was capable of measuring microwave lines having absorption coefficients as small as 10⁻⁷ cm⁻¹ with a frequency resolution on the order of 30 kHz. Center frequencies of the measured lines varied from 4,830 MHz to 72,838 MHz; hence, most of the observations were made on transitions between K-doublets in the rotational spectrum. Corrections were applied to the measured line width parameters to account for Doppler broadening and, where possible, for deviations due to magnetic hyperfine structure in some of the K-doubled lines. Low modulation voltages and low microwave power levels were used to minimize modulation and saturation broadenings; other extraneous broadenings were found to be insignificant. The primary broadening mechanism at low gas pressure is pressure broadening, and a review of this topic is included. Line width parameters for the several observed transitions were determined by graphing half-widths versus pressure for each spectral line, and performing a linear least-squares fit to the data points. Repeatability measurements indicated the accuracy of the line width parameters to be better than ±10 percent. The reasons for this repeatability spread are discussed, Broadening of each line was measured for self- and foreign-gas broadening by atomic helium and diatomic hydrogen. Effective collision diameters were calculated for each broadening interaction, based on the observed rates of broadening.

Machine diagnostics is usually done via conditioned monitoring (CM). This approach analyses certain thresholds or patterns for diagnostic purposes. This approach can be costly and time consuming for industries. A larger downside is the difficulty in generalizing CM to a wider set of machines.There is a new trend of using a Machine learning (ML) approach to diagnose machines states. An ML approach would implement an autonomous system for diagnosing machines. It is highly desirable within industry to replace the manual labor performed when setting up CBM systems. Often the ML algorithms chosen are novelty/anomaly based. It is a popular hypothesis that detecting anomalous measurements from a system is a natural byproduct of a machine in a faulty state.The purpose of this thesis is to help CombiQ with an implementation strategy for a fault detection system. The idea of the fault detection system is to make prediction outcomes for machines within the system. More specifically, the prediction will inform whether a machine is in a faulty state or a normal state. An ML approach will be implemented to predict anomalous measurements that corresponds to a faulty state. The system will have no previous data on the machines. However, data for a machine will be acquired once sensors (designed by CombiQ) have been set up for the machine.The results of the thesis proposes an unsupervised and semi-supervised approach for creating the ML models used for the fault detection system. The unsupervised approach will rely on assumptions when selecting the hyperparameters for the ML. The semi-supervised approach will try to learn the hyperparameters through cross validation and grid search. An experiment was set up check whether three ML algorithms can learn optimal hyperparameter values for predicting rotational unbalance. The algorithm known as OneClassVM showed the best precision results and hence proved more useful for CombiQ’s criterium.

Le rotomoulage est une technique de transformation des polymères thermoplastiques qui souffre encore aujourd'hui d'un certain empirisme. Depuis de nombreuses années, la simulation du procédé de rotomoulage est considérée comme une nécessité à l'introduction de nouveaux matériaux et à l'élargissement de ses domaines applications. Ces travaux s'inscrivent à la suite de nombreuses études visant à développer un logiciel de simulation permettant de prédire le comportement de la matière en condition de mise en œuvre.L'objectif de cette thèse est de s'intéresser plus particulièrement à la simulation de la phase de refroidissement. Pour cela, il est nécessaire de mettre au point un modèle décrivant la cinétique de cristallisation et pouvant tenir compte des contraintes liées aux conditions thermiques extrêmes dans lequel se déroule le procédé (température, présence d'oxygène, temps de cycle long), lesquelles peuvent avoir une influence sur la thermostabilité du polymère. Dans le cadre de cette étude, le choix s'est porté sur le Polylactide (PLA). Le PLA présente une faible stabilité thermique et une cinétique de cristallisation lente, ce qui facilite l'observation de ces deux phénomènes. Dans un premier temps, la thermodégradation du PLA a été étudiée et un modèle visant à décrire son évolution dans des conditions proches de celles du procédé, a été mis en place. Puis, une étude de cristallisation considérant l'influence de la masse moléculaire et du polymorphisme du PLA, a été réalisée afin de modéliser sa cinétique. Enfin, un couplage des deux modèles a été envisagé dans l'optique de les intégrer à une simulation globale des transferts thermiques impliqués dans le procédé de rotomoulage. / Rotational molding is a thermoplastic polymer processing technology which has been, for many years, suffering from a kind of empiricism.The simulation of rotational molding is believed to be the key to introduce new materials and more diversity in its applications. This work follows several studies aimed to develop a simulation software which would predict the material behavior in processing conditions.Consequently, this thesis will focus specifically on the simulation of the cooling phase. This type of simulation requires kinetic crystallization modeling, acknowledging the influence that the extreme thermal conditions of the rotomolding process can have on the thermal stability of the material. In this study we chose to work with Polylactic acid (PLA), a material suffering poor thermal stability and presenting with slow kinetic crystallization, making it suitable to observe these phenomenona. First, the thermal degradation of PLA has been studied and a model describing its behavior, under similar conditions to processing, has been proposed. Then, a crystallization study including the influence of the molecular weight, as well as the polymorphism of PLA, has been completed and the kinetic crystallization modeling has been performed. Finally, the integration of both models in a global simulation of the thermal transfers describing the rotomolding process has been investigated.