The focus of this study is on the development of a state-of-the-art single-wheel roller rig for studying contact mechanics and dynamics in railroad applications. The use of indoor-based simulation tools has become a mainstay in vehicle testing for the automotive and railroad industries. In contrast to field-testing, roller rigs offer a controlled laboratory environment that can provide a successful path for obtaining data on the mechanics and dynamics of railway systems for a variety of operating conditions. The idea to develop a laboratory test rig started from the observation that there is a need for better-developed testing fixtures capable of accurately explaining the complex physics of wheel-rail contact toward designing faster, safer, and more efficient railway systems. A review of current roller rigs indicated that many desired functional requirements for studying contact mechanics currently are not available. Thus, the Virginia Tech Railway Technologies Laboratory (RTL) has embarked on a mission to develop a state-of-the-art testing facility that will allow experimental testing of contact mechanics in a dynamic, controlled, and consistent manner. VT roller rig will allow for closely replicating the boundary conditions of railroad wheel-rail contact via actively controlling all the wheel-rail interface degrees of freedom: cant angle, angle of attack, and lateral displacement. Two sophisticated independent drivelines are configured to precisely control the rotational speed of the wheels, and therefore their relative slip or creepage. A novel force measurement system, suitable for steel on steel contact, is configured to precisely measure the contact forces and moments at the contact patch. The control architecture is developed based on the SynqNet data acquisition system offered by Kollmorgen, the motors supplier. SynqNet provides a unified communication protocol between actuators, drives, and data acquisition system, hence eliminating data conversion among them. Various design analysis indicates that the rig successfully meets the set requirements: additional accuracy in measurements, and better control on the design of experiments. The test results show that the rig is capable of conducting various contact mechanics studies aimed for advancing the existing art. Beyond developing the experimental testing fixture for studying contact mechanics, this study provides a comprehensive review of the contact models. It discusses the simplifying assumptions for developing the models, compares the models functionality, and highlights the open areas that require further experimental and theoretical research. In addition, a multi-body dynamic model of the entire rig, using software package SIMPACK, is developed for conducting modal analysis of the rig and evaluating the performance of the rig's components. A MATLAB routine is also developed that provides a benchmark for developing creep curves from measurements of the rig and comparing them with existing creep curves. / Ph. D.

Human beings have a touch and force estimation mechanism beneath their feet. They use this feeling of touch and force to maintain balance, walk, run and perform various agile motions. This paper presents a new sensor platform beneath the humanoid feet, enabled by a pragmatic model based compliant foot design and sensor configuration that mimics the human tactile sensory system for contact force measurement in humanoid robots. Unlike previous force sensor based approaches, the system is defined as a total and sufficient method of Ground Reaction Force (GRF) and Zero Moment Point (ZMP) measurement for balancing and walking using contact force feedback in mid to full sized humanoids. The conventional systems for the GRF and ZMP measurement are made of heavy metallic parts that tend to be bulky and vulnerable to inertial noises upon high acceleration. In addition to low cost and reliable operation, the proposed system can withstand shock and enable agile motion much like humans do with their footpad. The proposed foot is manufactured using state-of-the-art technique with elastomer padding which not only protects the sensors but also acts as a compliance beneath the foot giving integrity in structural design. This composite layer provides compliance and traction for foot collision while the contact surfaces are sampled for pressure distribution which can be mapped into three axis force and ZMP. A single step training process is required to relate the sensor readings to force measurement. The system’s capability of contact force measurement, subsequent ZMP estimation is experimentally verified with the application of appropriate software. Moreover, a simulation study has been conducted via Finite Element Analysis (FEA) of the footpad structure to analyze the proposed footpad structure. The experimental results demonstrate why this can be a major step toward a biomimetic, affordable yet robust contact force and ZMP measurement method for humanoid robots. This work was supported by the Office of Naval Research, Grant N00014-15-1-2128 as part of development of Project SAFFiR (Shipboard Autonomous Firefighting Robot). / Master of Science / How we interact with the surfaces in contact with us has a crucial role for balancing and walking with agility. The biological touch and force measurement systems in human is currently unmatched, not even mimicked in a significant way in the state-of-the-art humanoid robots’ systems. Human beings use this feeling of touch and force beneath the feet to maintain balance, walk, run and perform various agile motions. This research aims to find a holistic system in humanoid robot’s feet design that can mimic this human characteristics of force estimation beneath the feet and using that estimation for balancing and walking. A practical model based sensor configuration is derived from the rigorous study of human and humanoid robot’s feet contact with the ground. The sensors are tactile in nature, and unlike previous below feet based approaches, the system is defined as a total and sufficient system of Ground Reaction Force (GRF) and Center of Pressure (CoP) measurement. The conventional systems for this purpose are not only highly expensive but also having error in quantification during accelerated movement. The proposed foot is designed following the practical model derived and manufactured using the state-of-the-art mechanism for having a soft cushion between the sensors and the contact surfaces. In addition to low cost and reliable operation, the proposed system can withstand shock and enable agile motion much like humans do with their footpad. The quantification of the forces and pressure from the sensor readings and developed using appropriate software and algorithms. The system’s capability of contact force measurement, subsequent Center of Pressure measurement is experimentally verified with the application of appropriate software. Moreover, a simulation study has been conducted of the footpad structure to analyze the proposed footpad structure. The experimental results demonstrate why this can be a major step toward a biomimetic, affordable yet robust contact force and Center of Pressure measurement method for human-like robots.

The desire to achieve higher heat transfer augmentation for turbine blades is fueled by the increased power output and efficiency that is achievable with high turbine inlet temperatures. The use of internal cooling channels fitted with pin fin arrays serves as one method of accomplishing this goal. Consequently, the addition of pin fin arrays comes at the expense of increased pressure drop. Therefore the pin fin geometry must be judiciously chosen to achieve the required heat transfer rate while minimizing the associated pressure drop. This project culminates in the measurement of both pin fin force and array pressure drop as they related to changes in the array geometry. Specifically, the effects of Reynolds number, spanwise pin spacing, streamwise pin spacing, pin aspect ratio, and flow incidence angle. Direct two-component force measurement is achieved with a cantilever beam force sensor that uses highly sensitive piezoresistive strain gauges, relating the strain at the base of the beam to the applied force. With proper characterization, forces as small as one-tenth the weight of a paper clip are successfully measured. Additionally, array pressure drop measurements are achieved using static pressure taps. Experiments were conducted over a range of Reynolds numbers between 7,500 and 35,000. Changes in the spanwise pin spacing were shown to substantially alter the pin fin drag and array pressure drop, while changes in the streamwise pin spacing were less influential. The experimental results also showed a dramatic reduction in the pin fin drag and array pressure drop for an inline flow incidence angle. Finally, changes in the pin aspect ratio were shown to have little effect on the array pressure drop. / Master of Science

The desire for smaller, faster, and more efficient products places a strain on thermal management in components ranging from gas turbine blades to computers. Heat exchangers that utilize internal cooling flows have shown promise in both of these industries. Although pin fins are often placed in the cooling channels to augment heat transfer, their addition comes at the expense of increased pressure drop. Consequently, the pin fin geometry must be judiciously chosen to achieve the desired heat transfer rate while minimizing the pressure drop and accompanying pumping requirements. This project culminates in the construction of a new test facility and the development of a unique force measurement methodology. Direct force measurement is achieved with a cantilever beam force sensor that uses sensitive piezoresistive strain gauges to simultaneously measure aerodynamic lift and drag forces on a pin fin. After eliminating the detrimental environmental influences, forces as small as one-tenth the weight of a paper clip are successfully measured. Although the drag of an infinitely long cylinder in uniform cross flow is well documented, the literature does not discuss the aerodynamic forces on a cylinder with an aspect ratio of unity in channel flow. Measured results indicate that the drag coefficient of a cylindrical pin in a single row array is greater than the drag coefficient of an infinite cylinder in cross flow. This phenomenon is believed to be caused by an augmentation of viscous drag on the pin fin induced by the increased viscous effects inherent in channel flow. / Master of Science

Aktionskräfte stellen wesentliche Risikofaktoren für die Entstehung von Erkrankungen im Finger-, Hand- und Armbereich dar. Daher ist die Erfassung und Analyse von Aktionskräften ein wichtiger Bestandteil der ergonomischen Bewertung von Arbeitsplätzen. Zur Erfassung von Aktionskräften, insbesondere in der Automobilproduktion, existiert bisher jedoch weder eine einheitliche noch eine systematische Vorgehensweise. Es mangelt an konkreten Forschungserkenntnissen über den Messaufbau, die Messdurchführung und die Messauswertung von Kraftfällen. In der vorliegenden Arbeit wird deshalb ein erster Schritt unternommen, um die Erfassung von Aktionskräften auf Basis wissenschaftlich gestützter Erkenntnisse zu standardisieren. Hierzu werden insgesamt vier empirische Untersuchungen (zwei Vorstudien und zwei empirische Laborstudien) durchgeführt. In der ersten Studie (Kapitel 4) erfolgt eine Identifizierung der vorhandenen Arten von Kraftaufwendungen in verschiedenen Fertigungsbereichen der Automobilproduktion im Rahmen einer Dokumentenanalyse. In der zweiten Studie (Kapitel 5) wird der bedeutendste Fertigungsbereich ausgewählt, um darin eine Auszählung der Kraftaufwendungen anhand einer standardisierten Beobachtung definierter Arbeitsprozesse durchzuführen. Die dritte Untersuchung (Kapitel 6) ist als empirische Laborstudie konzipiert. Darin wird die technische Erfassung von Aktionskräften unter idealisierten Bedingungen ohne menschlichen Einfluss erprobt. In der vierten Untersuchung (Kapitel 7), ebenfalls als empirische Laborstudie konzipiert, werden spezifische Kraftaufwendungen im Labor systematisch durch Probanden nachgestellt und gemessen. Dabei wird das Vorgehen zur Durchführung und Auswertung von praxisnahen Kraftmessungen unter menschlichem Einfluss evaluiert. Die Erkenntnisse der Arbeit helfen dabei, bestehende Forschungsdefizite aufzuarbeiten und zu beheben. Sie stellen ferner eine Handlungshilfe für betriebliche Kraftanalysen sowie eine Orientierung für zukünftige Forschungsarbeiten dar. / Action forces have been identified as risk factors. Therefore, the collection and analysis of action forces is an essential part of the ergonomic evaluation. Up to now, there was a lack of a standardized and systematic approach to evaluate action forces, especially in the automotive production. Thus, in the present thesis a methodical approach is described to evaluate action forces systematically. The thesis is divided into four studies. The first study contains the identification of the variety of action forces in the different manufacturing areas of automotive production. The second study describes the detailed analysis of action forces in the assembly shop, which is the manufacturing area with the highest count of action forces in the automotive production. The third study describes the direct measurement of action forces in laboratory conditions. The action forces are applied by a testing machine. The fourth study consists of the direct measurement of action forces, which are applied by subjects. Thereby, the methodical approach to perform direct measurements has been evaluated. The findings of the thesis can be used as a guideline, to evaluate action forces in the automotive production. Also the findings highlight the potential for further research projects.

L'étude du couplage hybride entre les vibrations d'un résonateur mécanique et un degré de liberté quantique requiert une très grande sensibilité en force. Ceci a motivé le développement récent de nano-oscillateurs ultra-légers, qui constituent des sondes de force ultra-sensibles opérant désormais au niveau de l'attoNewton.Le premier volet de ce travail traite de l'habillage mécanique d'un nanofil suspendu de carbure de silicium, oscillant dans deux directions transverses. Son évolution Brownienne ou excitée dans un champ de force externe perturbe ses propriétés : fréquences et directions propres de vibration. Une technique de mesure optique des vibrations du nanofil en deux dimensions a été développée. Elle a permis, dans un premier temps, de cartographier un champ de force électrostatique, révélant une phénoménologie de l'habillage spécifique aux dimensions supérieures à un. En particulier, les composantes cisaillantes du champ induisent une rotation des directions propres de vibration. Dans un deuxième temps, la technique de mesure a été testée dans un champ de force optique, produit par un laser focalisé sur le nanofil, et qui contient une composante rotationnelle, non conservative. On rapporte l'observation d'une brisure de l'orthogonalité des modes propres, d'une distorsion et d'une amplification des spectres de mouvement Brownien, toutes en accord avec le modèle décrivant l'habillage mécanique du nanofil par ce champ de force externe non potentiel. A partir d'un protocole adapté à la multi-dimensionnalité du système, une déviation à la relation fluctuation-dissipation a également été mesurée : il s'agit d'une conséquence de la sortie de l'équilibre induite par la force optique non-conservative. L'étude des propriétés thermodynamiques du système suggère des corrections à la relation fluctuation-dissipation et prédit enfin un phénomène de compression du bruit thermique de l'oscillateur en champ de force rotationnel.Le deuxième volet de la thèse concerne le système hybride constitué d'un nanofil et d'un qubit de spin, un centre coloré NV du diamant attaché à son extrémité. Les propriétés optiques de cette source de photons uniques oscillante sont caractérisées à partir de la mesure de corrélations spatio-temporelles de la fluorescence du centre NV sur lesquelles les vibrations de l'oscillateur se retrouvent encodées. Nous avons ainsi développé un système de mesure du mouvement compatible avec de très faibles flux de photons, inférieurs en particulier au taux de décohérence mécanique. La dernière partie de ce manuscrit présente une étude préliminaire du couplage du spin-mécanique. Après l'observation d'un triplet de Mollow phononique, les développements expérimentaux de la première partie de la thèse ont été intégrés à une expérience hybride de seconde génération stabilisée amenant la mesure de force ultra-sensible à la portée du système hybride. / The study of the hybrid coupling between the vibrations of a mechanical resonator and a quantum degree of freedom requires extremely high force sensitivities. This was one of the motivations for the recent development of ultra-light nano-oscillators which are ultra-sensitive force probes now routinely operating at the attoNewton level.The first part of this work deals with the mechanical dressing of a silicon carbide suspended nanowire oscillating in two transverse directions. Its Brownian or driven evolution in an external force field modifies its mechanical properties: eigen-frequencies and eigen-directions of oscillation. An optical technique to measure the nanowire vibrations in two dimensions was developed. First, this technique enabled to map out an electrostatic force field, which revealed a dressing phenomenology specific to dimensions greater than one. In particular, shearing components of the force field are responsible for a rotation of the eigen-directions of vibration. Second, the measurement technique was tested in an optical force field applied by a laser focused on the nanowire. This field contains a rotational, non-conservative component. The reported experimental observations: eigenmodes orthogonality breaking, distorsion and amplification of Brownian motion spectra, are all in good agreement with the model of the mechanical dressing. Using a protocol adapted to the multidimensionality of the system, a deviation to the fluctuation-dissipation relation has also been measured, as a consequence of the non-conservative force bringing the system out of equilibrium. The study of this system's thermodynamic properties suggests corrections to the fluctuation-dissipation relation and predicts a squeezing of the oscillator's thermal noise in rotational force fields.The second part of the thesis concerns the hybrid system composed of a nanowire and a spin qubit: a colored NV center in diamond bound to its extremity. The optical properties of this oscillating single photon source are characterized through the measurement of space-time fluorescence correlations on which the oscillator's vibrations are encoded. We then developed a motion measurement technique compatible with very low photon fluxes, in particular inferior to the mechanical decoherence rate. The last part of the manuscript presents a preliminary study of the spin-mechanical coupling. After the observation of a phononic Mollow triplet, the experimental developments of the first part of the thesis were integrated in a second-generation stabilized hybrid experiment bringing the ultrasensitive force measurement within the reach of the hybrid system.

Reducing energy consumption in pulp and paper refining requires a deep understanding of all the processes involved. This dissertation investigates fundamental mechanics of the low consistency mechanical refining process. Three studies investigate forces applied to wood fibers with the focus on how force profiles during bar passing events change with process variables such as fiber length and refiner load. In the first study a high resolution rotary encoder and a piezo ceramic force sensor are implemented in a 16-inch laboratory-scale low consistency refiner to explore the effect of plate gaps on bar-force profiles. The rotary encoder data is used to locate the rotor bars relative to the stator bar in which the sensor is located. Force profiles for bar passing events are registered to the position of rotor bars relative to the stator bar in which the sensor is located and mean force profiles are produced. These mean force profiles have potential to shed light on the fundamental mechanisms of mechanical refining. For large gaps, there is a late peak in the force profiles that occurs toward the end of the bar passing event. For gaps that are less than the critical gap, below which fiber cutting occurs, there is an early peak in the force profiles that occurs at the start of the bar passing event. It is hypothesized that the early peak represents the corner force and, therefore, that corner force is causal in the onset of fiber cutting. In the second study a set of piezo ceramic force sensors is implemented in a 52-inch mill-scale low consistency refiner to explore the effect of varying operating conditions on bar force profiles. Force profiles for individual bar passing events are identified based on key features in the time domain force data based on the knowledge acquired from the previous study in the pilot-scale refiner. The individual bar force profiles are classified as single peak events which feature one peak corresponding to the fiber compression force and as dual peak events corresponding to fiber compression force and the corner force. It is shown that dual peak events which are considered to represent the corner force, are present throughout the whole range of refining and increase with increased refining energy. After applying the dual peak analysis to the data from the previous study this behaviour was also found in the pilot-scale refiner data. Furthermore, it is found that different radial positions on the stator plate are subjected to different force profiles. This is thought to be due to the difference in tangential speed and a change in the fiber and floc material properties at different radial positions. In the third study the effect of refiner plate wear on bar force sensor measurements is explored by applying the dual peak analysis to long term data acquired from the mill-scale refiner. Bar passing events are analysed based on the dual peak ratio and the timing of the early peak in the dual peak events. Force measurements are evaluated over the full run time of a set of refiner plates. When comparing force profiles with refiner plate wear measurements and discharge fiber analysis, it is found that the decrease in the prevalence of the corner force correlates with the wear of the leading edge of the refiner bars, or bar rounding, for the run time of the refiner plate. This is accompanied by a decrease in plate performance which is represented by a decrease in fiber length and freeness reduction for the same refiner load. / Graduate

No description available.

When an aircraft is aerodynamically or structurally damaged in battle, it may not able to complete the mission and the damage may cause its loss. The subject of aircraft battle survivability is one of critical concern to many disciplines, whether military or civil. This thesis considered and focused on Computational Fluid Dynamics [CFD] predictions and experimental investigations into the effects of simulated battle damage on the low-speed aerodynamics of a fmite aspect ratio wing. Results showed that in two-dimensional [2d] and three-dimensional [3D] CFD simulations, Fluent's® models work reasonably well in predicting jets flow structures, pressure distributions, and pressure-coefficient Cp's contours but not for aerodynamic coefficients. The consequences were therefore that CFD prediction was poor on aerodynamic-coefficients increments. The prediction of Cp's achieved good agreement upstream and near the damage hole, but showed poor agreement at downstream of the hole. For the flow structure visualisation, at both weak and strong jet incidences, the solver always predicted pressure-distribution-coefficient lower at upstream and higher at downstream. The results showed relatively good agreement for the case of transitional and strong jet incidences but slightly poor for weak jet incidences. From the experimental results of Finite Wing, the increments for Aspect-ratio, AR6, AR8 and ARIO showed that as damage moves out towards the tip, aerodynamic-coefficients increments i.e. lift-loss and drag-rise decreased, and pitching-moment-coefficient increment indicated a more positive value at all incidence ranges and at all aspect ratios. Increasing the incidence resulted in greater magnitudes of lift-loss and drag-rise for all damage locations and aspect ratios. At the weak jet incidence 4° for AR8 and in all of the three damage locations, the main characteristics of the weak-jet were illustrated clearly. The increments were relatively small. Whilst at 8°, the flow structure was characterised as transitional to stronger-jet. In Finite Wing tests and for all damage locations, there was always a flow structure asymmetry. This was believed to be due to gravity, surface imperfection, and or genuine feature. An 'early strong jet' that indicated in Finite Wing-AR8 at 'transitional' incidence of 8°, also indicated in twodimensional results but at the weak-jet incidence of 4°. For the application of 2d data to AR6, AR8, and ARIO, an assessment of 2d force results led to the analysis that the tests in the AAE's Low Turbulence Tunnel for 2d were under-predicting the damage effects at low incidence, and over-predicting at high incidences. This suggested therefore that Irwin's 2d results could not be used immediately to predict three-dimensional.

Mechanical manipulation and characterization of biological cells have wide applications in genetics, reproductive biology, and cell mechanics. This research focuses on (1) the development of enabling microrobotic systems and techniques for automated cell microinjection and in situ mechanical characterization; and (2) the demonstration of molecule efficacy testing and cell quality assessment with the new technologies. Targeting high-speed cell injection for molecule screening, a first-of-its-kind automated microrobotic cell injection system is developed for injecting foreign materials (e.g., DNA, morpholinos, and proteins) into zebrafish embryos (~1.2 millimeter) and mouse oocytes/embryos (~100 micrometers), which overcomes the problems inherent in manual operation, such as long learning curves, human fatigue, and large variations in success rates due to poor reproducibility. Novel cell holding devices are developed for immobilizing a large number of embryos into a regular pattern, greatly facilitating sample preparation and increasing the sample preparation speed. Leveraging motion control and computer vision techniques, the microrobotic system is capable of performing robust cell injection at a high speed with high survival, success, and phenotypic rates. The mouse embryo injection system is applied to molecule testing of recombinant mitochondrial proteins. The efficacy of an anti-apoptotic Bcl-xL (Delta_TM) protein is, for the first time, quantitatively evaluated for enhancing the development competence of mouse embryos. For cell quality assessment, this research develops a vision-based technique for real-time cellular force measurement and in situ mechanical characterization of individual cells during microinjection. A microfabricated elastic device and a sub-pixel computer vision tracking algorithm together resolve cellular forces at the nanonewton level. Experimental results on young and old mouse oocytes demonstrate that the in situ obtained force-deformation data can be used for mechanically distinguishing healthy mouse oocytes from those with cellular dysfunctions. This work represents the first study that quantified the mechanical difference between young and old mouse oocytes, promising a practical way for oocyte quality assessment during microinjection.