Thèses sur le sujet « Mechanical technique »
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1
Moharrami, Noushin. « Extracting reliable mechanical properties using the nanoindentation technique ». Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2738.
Texte intégralRésumé :
Extracting the mechanical properties of thin films and small volumes of bulk materials through the use of nanoindentation is a well established technique but getting good data from all types of test sample is not always easy. Factors such as surface roughness and oxidation, density/porosity of the material, adhesion/detachment of a thin film, pile-up/sink-in, the presence of the substrate, as well as grain size and its distribution have a significant effect on the observed mechanical properties (e.g. Young’s modulus and hardness). Considerable differences between predicted and observed performance can be seen depending on the material tested and how it has been prepared. This thesis concerns developing test protocols to get good nanoindentation data and reliable measurements of the properties for a range of material types (chiefly metals and ceramics). Firstly, this work highlights the effect of crystallographic anisotropy, grain size, shape and orientation on the mechanical response of metallic thin films such as copper used for semiconductor metallisation. Results obtained on highly polished semiconductor materials were compared with those from engineering surfaces with much higher roughness which show increased scatter in results across the complete range of contact scales. Further studies were carried out on hard coatings and bulk materials such as titanium carbide, zirconium nitride and tungsten. The scatter in data obtained at low tests loads is dominated by anisotropy and grain size effects but disappears at higher loads. For soft materials such as copper, the appearance of pile-up was shown to be significant when compared with harder materials which tend to sink-in. Secondly, to assess the effect of creep (time-dependent behaviour) and also grain boundary effects on the measured mechanical properties, soft materials with a range of grain sizes have been examined. Different indentation control cycles (load and displacement control, single indent and multicycling tests) have been investigated to determine what is most suitable with displacement control being essential in most cases. To study the effect of the density/porosity of the sample and its surface roughness on mechanical properties, the work was carried out on porous coatings of tin, copper and copper-tin alloy coatings with a low density. To further understand the behaviour of porous materials and their mechanical properties, finite element analysis was also used to compare the experimental results with a numerical model. The size, shape and location of porosity with respect to the indenter is critical in determining the mechanical properties of a porous material obtained from nanoindentation analysis. Finally, fully processed engineering surfaces were investigated at the component scale to compare with idealised flat plate samples. Titanium-based and cobalt-chrome alloys in the form of femoral heads and stems for replacement hips have been used to assess the effect of in service oxidation on mechanical properties. These have been studied to look at the effects of sample fixturing and support and surface contact in worn and virgin regions of the sample surface. The extent of oxidation and the mechanical properties of the oxide produced are critical in dictating performance.
2
Jung, Sunghwan. « Growing crack analyses using nodal release technique ». Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38075.
Texte intégral
3
Shilpiekandula, Vijay 1979. « A laser speckle based position sensing technique ». Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27131.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 129-131).
This thesis presents the design and development of a novel laser-speckle-based position sensing technique. In our prototype implementation, a He-Ne laser beam is directed at the surface of an air-bearing spindle. An imaging system is set up to capture speckle patterns scattered from the spindle surface. These patterns are highly correlated over small angular displacements of the spindle. We use correlation-based image-processing algorithms to measure offsets between the speckle patterns. These offsets are calibrated against the counts of a commercial incremental optical encoder. A custom-built bicell photointerrupter unit is used as a reference sensor for the incremental optical encoder. To test for the control performance of this speckle-based sensor, we have constructed a transmission drive to run the air-bearing spindle. Our speckle-based metrology system is able to run at update rates of 10 Hz with a measured closed loop -3 dB bandwidth of about 2 Hz. Using a real-time processor interfaced with a desktop PC, we have implemented a novel algorithm that interpolates position estimates with respect to two pre-stored global images. We predict that this technique can potentially achieve resolutions of 0.1 [mu]m for translational and 5 [mu]rad for rotational motion. The limitation of our current implementation is the low update rates resulting from the time-intensive nature of correlation-based methods. Possible methods to overcome this limitation are addressed and ideas for follow-on work are presented.
by Vijay Shilpiekandula.
S.M.
4
TANNERU, VENKAT SUNIL. « A STABILIZATION TECHNIQUE BASED ON MESHFREE METHOD ». University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1130385545.
Texte intégral
5
Smallwood, Gregory John. « A technique for two-colour particle image velocimetry ». Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7599.
Texte intégralRésumé :
To study the complex flowfields found in combustion, it is often necessary to acquire an instantaneous overall view of the flowfield. One method of achieving this is two-dimensional velocity mapping with particle image velocimetry (PIV). A two-colour PIV experimental apparatus has been developed expressly to meet the demands of combustion and related flowfields. This technique offers advantages over other PIV methods in that the absolute velocity vector direction is known and data processing requirements are reduced. A method for calculating the mean exposure from particles on colour film, based on Mie scattering theory, is developed. A technique optimized for analysis of two-colour PIV images is described. Two-colour PIV is demonstrated in the wake of a noncombusting n-heptane fuelled bluff-body burner, which presented a suitably complex flowfield including counter-rotating recirculation zones and centreline stagnation points. To complement these results, mean velocities obtained with LDA are also presented. This is the first report of spray velocity measurement by PIV.
6
Elmouelhi, Ahmed (Ahmed M. ). 1979. « Genome scanning : an AFM-based DNA sequencing technique ». Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/34149.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (p. 157-160).
Genome Scanning is a powerful new technique for DNA sequencing. The method presented in this thesis uses an atomic force microscope with a functionalized cantilever tip to sequence single stranded DNA immobilized to a mica surface. The functionalized cantilever tip hybridizes with only one base type (A, C, T, or G) and results in distinct peaks in the AFM-produced image. Genome Scanning has been successful at identifying 40 base strands of synthesized DNA and has been shown to detect a particular base type on 48 kilobase strands of lambda DNA. Currently, Genome Scanning is only accurate to 3-26 bases at a time, however, it can achieve a sequencing speed of 6000 bases/sec. In other words, Genome Scanning can be used to sequence the 3 billion bases of the human genome in 5.78 days.
by Ahmed Elmouelhi.
S.M.
7
Born, Melanie P. (Melanie Providencia) 1975. « Ice and abrasive particles : an alternative CMP polishing technique ». Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9570.
Texte intégral
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Barrett, Hannah (Hannah Jane). « Quantifying ballet technique through turn kinematics for injury assessment ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98953.
Texte intégralRésumé :
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (page 49).
The most common turns in ballet, pirouettes and fouettés require precise movement to match proper technique and prevent injury. Variation in knee angle of a dancer's supporting leg during pirouettes of 1-5 rotations was measured using a goniometer for 12 professional and pre-professional ballet dancers. Plié angle saw no significant difference for different numbers of rotations, but the effect of gender was significant: males pliéd at least 20.3 degrees deeper than females. Average knee angle while turning was less than zero for all pirouettes, highlighting dancers' tendency to bend their supporting knee to correct for instability, which may contribute to knee injuries. Knee angle trajectory closely matched a minimum jerk profile, indicating that dancers encode movements in angle coordinates. Knee angle was compared between pirouettes and fouettés using 2 goniometers and aerial video for 3 advanced amateurs. No difference was found in preparation plié or turn angle between turn types. Axis of rotation remained within 0.221 +/- 0.014 meters of starting position during fouettés. Maximum angular velocity of the head was nearly one and a half times that of the body during fouettés. This kinematic definition of ballet technique creates a framework for movement control of a dancer's lower extremities to prevent injury.
by Hannah Barrett.
S.B.
9
Janakiraman, Balasubramanian. « Mechanical property measurement by indentation techniques ». Texas A&M University, 2004. http://hdl.handle.net/1969.1/3111.
Texte intégralRésumé :
The mechanical properties of materials are usually evaluated by performing a tensile or
hardness test on the sample. Tensile tests are often time consuming, destructive and need
specially prepared specimens. On the other hand, there is no direct theoretical correlation
between the hardness number and the mechanical properties of a material although
phenomenological relationships do exist. The advantages of indentation techniques are
that they are non-destructive, quick, and can be applied to small material samples and
localized in fashion. Mechanical properties are typically determined from spherical
indentation load-depth curves. This process is again a time consuming one and not
suitable for situations where a quick assessment is required such as in the sheet metal
rolling industry.
In the present study, a novel method of measuring mechanical properties of the material
by multiple spherical indentations is developed. A series of indentations are made on the
substrate with a spherical indenter with different loads. The diameter of the indentation is
related to the load applied to determine the mechanical properties of the material, namely
the yield strength and the work hardening parameters. To determine the diameter of the
indentation quickly, a fiber optic sensing technique is developed. An incident light beam
from a semiconductor laser is coupled back into an optical fiber upon reflection from the
metal surface. By measuring the diffused light power reflected from the metal surface,
the diameter of the indentation is measured.
The spherical indentation technique is difficult for real time mechanical property
measurement of sheet metal in a processing line. Problems arise as the strip is traveling at
2,000 to 4,000 ft/min (10,000 to 20,000 mm/sec) in the processing line. As a first step in
developing a process that could be implemented in a real time processing line, a
preliminary study has been conducted for the prediction of yield strength by laser shock
processing.
10
Kostic, Peter. « New methods for optimization of mechanical ventilation ». Doctoral thesis, Uppsala universitet, Anestesiologi och intensivvård, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-249172.
Texte intégralRésumé :
Mechanical ventilation saves lives, but it is an intervention fraught with the potential for serious complications. Prevention of these complications has become the focus of research and critical care in the last twenty years. This thesis presents the first use, or the application under new conditions, of three technologies that could contribute to optimization of mechanical ventilation. Optoelectronic plethysmography was used in Papers I and II for continuous assessment of changes in chest wall volume, configuration, and motion in the perioperative period. A forced oscillation technique (FOT) was used in Paper III to evaluate a novel positive end-expiratory pressure (PEEP) optimization strategy. Finally, in Paper IV, FOT in conjunction with an optical sensor based on a self-mixing laser interferometer (LIR) was used to study the oscillatory mechanics of the respiratory system and to measure the chest wall displacement. In Paper I, propofol anesthesia decreased end-expiratory chest wall volume (VeeCW) during induction, with a more pronounced effect on the abdominal compartment than on the rib cage. The main novel findings were an increased relative contribution of the rib cage to ventilation after induction of anesthesia, and the fact that the rib cage initiates post-apneic ventilation. In Paper II, a combination of recruitment maneuvers, PEEP, and reduced fraction of inspired oxygen, was found to preserve lung volume during and after anesthesia. Furthermore, the decrease in VeeCW during emergence from anesthesia, associated with activation of the expiratory muscles, suggested that active expiration may contribute to decreased functional residual capacity, during emergence from anesthesia. In the lavage model of lung injury studied in Paper III, a PEEP optimization strategy based on maximizing oscillatory reactance measured by FOT resulted in improved lung mechanics, increased oxygenation, and reduced histopathologic evidence of ventilator-induced lung injury. Paper IV showed that it is possible to apply both FOT and LIR simultaneously in various conditions ranging from awake quiet breathing to general anesthesia with controlled mechanical ventilation. In the case of LIR, an impedance map representing different regions of the chest wall showed reproducible changes during the different stages that suggested a high sensitivity of the LIR-based measurements.
11
Dixon, Theresa S. B. Massachusetts Institute of Technology. « Development of manufacturing technique for composite structures for robotic applications ». Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59906.
Texte intégralRésumé :
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 23-25).
An experimental study was performed with the aim of developing a technique for manufacturing composite parts for use in dynamic robotic applications in lieu of heavy and expensive metal parts used in conventional robotic systems. There is already a wide usage of sandwich board materials in load bearing applications, but these do not provide equal strength in all directions, particularly compressive strength. Additionally, these materials are only available in two-dimensional shapes. The process developed over the course of this project seeks to make a fully covered composite of any desired geometries. The specific robotics project addressed was the hyper dynamic quadruped robotic platform, which ultimately seeks to design and construct a robot capable of a high speed gallop. This thesis began exploring methods of fabricating parts for one of the legs of the platform, specifically a radius part. Manufactured components needed to be both light in weight to facilitate ease of movement for the robot and strong enough to withstand the forces from the shifting weight during running. Proposed design parameters called for a foam core with a hard plastic shell to meet these needs. This technique can lead to a cheaper manufacturing method with a potential impact on the future robotics industry. After an investigation into the properties of different liquid polyurethane foams and plastics, the manufacturing techniques explored began with machining molds for both the inner core and outer shell of composite parts into wax blocks. The project aims were to develop a prototyping process, but this can lead to mass-production. Two versions of a manufacturing process with these blocks were developed, one which uses an open mold and one which uses a closed mold. Either method is viable for fabrication, with a preference for the open mold in parts with simple geometry and small thickness, and for the closed mold in larger parts or ones with complicated or interrupted outer perimeters.
by Theresa Dixon.
S.B.
12
Agarwal, Shashank S. M. Massachusetts Institute of Technology. « Development of a reduced-order modeling technique for granular locomotion ». Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121854.
Texte intégralRésumé :
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 87-90).
The work is aimed towards the development and expansion of a reduced-order modeling technique called granular Resistive Force Theory(RFT) for modeling wheeled locomotion on granular beds. A combination of various modeling techniques, namely plasticity-based continuum modeling, discrete element method (DEM) modeling, along with RFT and collaborative experimentation are used for evaluation and expanding upon the capabilities of granular RFT. A dimensionless formulation corresponding to the onset of catastrophic rise in slipping of wheels during granular locomotion is proposed. This limit also corresponds to the limits of the existing form of RFT in modeling wheel-granular media interaction accurately. Along with granular locomotion, general problems of granular intrusion have also been studied extensively using continuum modeling to characterize the general force response of different granular media based on various system parameters.
by Shashank Agarwal.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
13
Rahman, M. Shafiqur. « A Hybrid Technique of Energy Harvesting from Mechanical Vibration and Ambient Illumination ». ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2220.
Texte intégralRésumé :
Hybrid energy harvesting is a concept applied for improving the performance of the conventional stand-alone energy harvesters. The thesis presents the analytical formulations and characterization of a hybrid energy harvester that incorporates photovoltaic, piezoelectric, electromagnetic, and electrostatic mechanisms. The initial voltage required for electrostatic mechanism is obtained by the photovoltaic technique. Other mechanisms are embedded into a bimorph piezoelectric cantilever beam having a tip magnet and two sets of comb electrodes on two sides of its substructure. All the segments are interconnected by an electric circuit to generate combined output when subjected to vibration and solar illumination. Results for power output have been obtained at resonance frequency using an optimum load resistance. As the power transduced by each of the mechanisms is combined, more power is generated than those obtained by stand-alone mechanisms. The synergistic feature of this research is further promoted by adding fatigue analysis using finite element method.
14
Cao, Arthur Y. (Arthur Yao). « Design and prototype : a manufacturing system for the soft lithography technique ». Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38562.
Texte intégralRésumé :
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, September 2006."August 2006."
Includes bibliographical references (leaves 155-158).
Ever since 1998 when the term "soft lithography" was first created, soft lithography techniques have drawn close attention of the academia and the industry. Micro contact printing is by far the most widely used soft lithography technique in the industry. The objective of this research project is to design and prototype a micro contact printing machine which could achieve high scalability, feature resolution and production rate. It should also fulfill quality requirements, in terms of minimizing the tool deformation and air trapping furing printing. A reel-to-reel design with wipers to create linear propagation during stamping was used in the final design. The final prototype was made of three stations, the printing station, the inking station and the rotary system, which switches the stamps between printing and inking station. The other important design novelty is that the PDMS stamp has been fixed and the Au coated PET was actually applied to the stamp to get printed. The design minimizes the deformation on the stamp and also eases the linear propagation of the printing interface. The reel-to-reel design can be easily scaled up for mass production with large volume. The prototype was tested and the printing samples were made.
by Arthur Y. Cao.
M.Eng.
15
Torres, James Ph D. Massachusetts Institute of Technology. « A leak detecting technique utilizing an abrupt and large pressure drop ». Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/65302.
Texte intégralRésumé :
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 29).
The distribution of clean, drinkable water is a problem that has been addressed in all civilizations. The most common form of transportation today, is the use of pressurized pipelines to carry the water long distances, but damage to the pipes, such as leaks, can cause considerable losses. The difficulty in detecting these leaks prompted this work, which attempts to find a reliable method of recognizing a leak and suggest possible designs that could be implemented on a pipe-navigating robot. This design would use thin flaps, or "leaves," that would be forced outward by the rapid pressure drop formed in proximity to the leak. In order to determine the characteristic behavior of the system, several simulations, with a circular hole as the leak, were ran that showed that the significant pressure gradient existed only within distance on the order of the diameter of the leak. To validate these results, a high precision pressure sensor was used to try and measure the pressure gradient, but the pressure sensor was too large sense a pressure difference. Therefore, rubber strips were used to emulate the use of "leaves" to perceive the leak. This confirmed the simulation results, as the rubber strips had to be incredibly close to the leak in order to be affected. Furthermore, once the strip was pulled up against the leak, the friction created between the wall and the strip became strong enough that it could be utilized. Both the simulation and experimental results suggest that the leak detecting module should start near the leak. Next, instead of detecting the leak via a motion towards the leak, the module should instead take advantage of the large frictional force that occurs when the leaf has made contact with the leak. Further experiments could include testing the magnitude of the frictional force and creating a prototype.
by James Torres.
S.B.
16
Sandford, Erika J. (Erika Jaye). « Experimental technique for optimizing aerosolized vaccine efficacy by Erika J. Sandford ». Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59930.
Texte intégralRésumé :
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 26).
Vaccination via aerosol has been proven to be as safe, as effective, and more appropriate for transportation when compared with vaccination via injection. These advantages make aerosolized vaccinations a realistic alternative to traditional injection vaccines for the developing world, where cold chain systems are impractical and the use of hypodermic needles can be unsafe. However, more research is needed to determine optimal parameters for vaccine aerosolization. This thesis presents an experimental setup to test Aerovax, a device designed to deliver aerosolized vaccinations in developing regions of the world. The experimental technique is the first effort to optimize vaccine aerosols across multiple variables, including input pressure, nebulizer geometry, and vaccine reconstitution. The setup provides a pressure input, sensors for ambient properties, and a device to measure particle size distribution.
S.B.
17
Huang, Ying. « Elaboration of customized maintenance document for complex mechanical products ». Strasbourg, 2011. http://www.theses.fr/2011STRA6006.
Texte intégralRésumé :
Traditionnellement les documents de maintenance sont sous la forme de support papier pour les différents utilisateurs, que ce soient les utilisateurs finaux, les techniciens expérimentés ou les fabricants industriels. Ces documents sont généralement élaborés pour une configuration standard du produit et pour les Conditions d’Utilisation (CU) générales. Dans un document de maintenance traditionnel, les besoins d’entretien sont souvent prédéfinis. Une fois qu’il est publié, il est difficile de le mettre à jour pour suivre les versions de changement de produit ou de l’adapter en fonction des différentes conditions d’utilisation. Par conséquent, les utilisateurs finaux ou les techniciens ont besoin de plus de temps pour décider les tâches de maintenance appropriées à accomplir sur le produit avec sa nouvelle configuration et dans ses Conditions d’utilisation spécifiques. Afin de résoudre les problèmes évoqués ci-dessus, un document de maintenance plus intelligent (dynamique, électronique, personnalisé) est proposé dans cette thèse qui porte le nom de Document de Maintenance Personnalisé (DMP). L’objectif de cette thèse est de décrire une méthodologie pour l’élaboration d’un Document de Maintenance Personnalisé (DMP) pour des produits mécaniques complexes destinés à être utilisés dans différentes conditions d’utilisation, et à l’usage des utilisateurs avec différents niveaux de compétence. Dans le DMP, les conditions d’utilisation sont prises en considération comprennent trois catégories de facteurs d’influence : les facteurs environnementaux, les profils d’utilisation du produit, et les comportements des utilisateursMaintenance documents are traditionally provided in the form of hardcopy supports for different users like end-users, maintenance technicians and manufacturers. These documents are generally elaborated for a standard product configuration and for general utilization conditions. In the traditional maintenance document, maintenance requirements are often predesigned. Once it is published, it is difficult to be updated to follow the product versions changing or to be adapted according to various Utilization Conditions (UCs). Therefore, the end users or technicians need more time to decide what appropriate maintenance tasks should be accomplished on the new configuration product with a new UC. In order to solve the problems discussed above, a more intelligent maintenance document (dynamic, electronic, customized) is proposed in this thesis which is named Customized Maintenance Document (CMD). The goal of this thesis is to outline a methodology for developing a CMD which shows how to customize the maintenance document for complex mechanical products to be used in different typical contextual conditions, for users with different skill levels and tasks. Three steps are focused in this thesis : knowledge integration process, decision making system design, and document model adoption. After collection and analysis of historical data (such as : utilization condition, structural data and operational data), knowledge is elicited in the form of case and embedded in the system to predict the failure rate of each unit. A multi-model decision making system is designed aiming to help users to find the most ideal maintenance tasks by analyzing the environment in which the complex mechanical product is operating. In order to present information in a better form and take the contextual knowledge into consideration, a semantic document modeling is designed which includes three layers : customized data modules layer, task-oriented document layer, and semantic network layer
18
Fowler, William Mark. « Experimental validation of the inverse structural filter force estimation technique ». Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17264.
Texte intégral
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Hernandez, Aguilar José Ramon. « An imaging technique for sizing bubbles in flotation systems / ». Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85555.
Texte intégralRésumé :
A sampling-followed-by-imaging technique for sizing bubbles in flotation systems has been developed and validated. The technique is based on directing a sample of bubbles into a viewing chamber where they are exposed and digitally imaged using incoherent backlighting. The images are automatically analyzed by means of a threshold criterion. The chamber is sloped to spread the bubbles over the surface of the viewing (glass) window. This configuration reduces bubble overlap and facilitates the definition of the focus plane.To validate the images, measurements were compared with standardized bubble sizes obtained with the displaced-volume method. It was observed that when thresholding at half the intensity level, sizes were systematically underestimated and the bias was correlated to bubble size, increasing from 0.3% at ca. 0.7 mm to 2% at ca. 4 mm. Experiments were designed to evaluate the bias due to system optics (i.e., the contribution of reflected/refracted rays and the defocus distance to image formation) and due to the sloped window. The results showed that reflected/refracted rays slightly biased towards underestimated sizes whereas the inclined window caused a small overestimation. The overestimation was due to the bubble flattening caused by the gravity force. These two effects were of similar magnitude and, therefore, tended to cancel. Consequently, the underestimation trend was attributed to the defocus distance which, in this unique system, is small and unambiguous (i.e., it is invariably negative since bubbles flow "behind" the focus plane, the underside of the window). A semi-empirical correction procedure is suggested which uses the fundamental method of Bongiovanni et al. (1997) to correct the bias due to system optics along with an empirical approach to compensate for bubble flattening.
To verify whether the computed size distributions were representative of the actual dispersion, bubble populations with significantly different size classes were mixed in a bubble column (0.1 m x 2.5 m). The column was equipped with two independently aerated spargers with nominal porosities of 0.5 mum (generating bubbles from 0.2 mm to 1 mm) and 100 mum (generating bubbles from 1 mm to 5 mm), respectively. Various proportions of airflow rates were injected through each sparger. The results showed bi-modal distributions in which the real and calculated proportions corresponded with a deviation of less than 15%, considered good given the severity of the test. However, the deviation was correlated to the superficial gas velocity (J g) and bias was consistently against smaller bubbles. The data were not sufficient to reveal the cause of the bias, but several possibilities were entertained.
The technique was demonstrated in an industrial-scale flotation machine, where it was compared with a capillary technique. It was also used to determine the bubble surface area flux (Sb) in a micro-flotation cell, setting up a test of the proposed relationship between the flotation rate constant k and Sb for the pulp zone.
20
Neill, William Stuart. « Local natural convection heat transfer measurements using a thin gold-film technique ». Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61928.
Texte intégral
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Parbatani, Karim. « Reliability analysis of lunar rover wheel designs - methodology and visual inspection technique ». Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107903.
Texte intégralRésumé :
This thesis presents a methodology for prediction of reliability for a lunar rover and a technique to evaluate reliability where data for operation in the lunar environment are not available in order to conduct traditional reliability analysis. This technique was applied to lunar rover wheel designs.The maximum distance travelled by the Lunar Roving Vehicle (LRV) during the Apollo 17 mission was approximately 35.9 km. Presently, McGill University, Neptec and the Canadian Space Agency are collaborating to develop a wheel set for an LRV, which is targeted to have a five-year operational service. This underlines the importance of the reliability of an LRV, which will be required to travel thousands of kilometres. The Neptec Design Group has developed a methodology to estimate the reliability of a lunar rover, i.e., the Lunar Rover Reliability Prediction (LRRP) where the project was divided into two phases. Phase 1 consisted of three milestones which included background research of the various reliability models currently available, the specific software tools that execute these models, and the ability to adapt these tools to account for lunar environmental factors (e.g., temperature, regolith, low gravity). Results demonstrated that Relex provided a strong package of fully integrated software tools to execute a group of reliability models (FMEA [Failure Modes and Effects Analysis], Fault Tree, Standards Prediction, ALT [Accelerated Life Testing]). Mission simulation software was identified to be a worthwhile addition and GoldSim was considered to be the best choice to provide mission simulation analysis. Phase 2 outlined the process for estimating the reliability of a lunar rover for a 5-year operational life on the moon based on the recommendations detailed in Phase 1. LRRP has been a success, but Neptec was only able to obtain earth bound data for use in the methodology. Hence, research on cryogenic wear was explored and the summary of relevant findings is as follows: the wear rate of steel and titanium at 293K and 77K are about the same below a sliding speed of 1m/s; the wear rate at 77K above 1m/s is higher for most materials and the coefficient of friction for steel on steel at 77K and 273 K is about the same. The information present in the literature is insufficient to evaluate LRV reliability under lunar environmental conditions. This underlines the necessity for an alternative methodology, for instance, the visual inspection technique, to evaluate reliability of systems (e.g., a lunar rover), where useful data are not available.The visual inspection technique is described and an analysis of five historical wheels and four new wheels designed by McGill University is given. The wheel designs were visually analysed according to specific criteria with respect to potential failure under lunar conditions (temperature, vacuum, regolith) considering wear resistance, thermal compatibility, excess loading, torque, etc. Potential wheel performance was quantified using a numerical scale with respect to potential failure due to events, such as temperature fluctuation, wheel-rock impact, excess payload and abrasive wear. The best designs were the Apollo 17 wire mesh wheel (historical) and the iRing wheel (McGill). A reliability checklist for lunar wheel designs is given to serve as a guideline to avoid unreliable design features. The visual inspection technique was successful and can be applied to other complex systems where experimental testing under actual conditions is not possible, although background knowledge and expert opinion are necessary to perform an evaluation.Cette thèse présente une méthodologie pour la prédiction de la fiabilité des roues lunaires, et une technique pour évaluer la fiabilité de la conception de ces roues, pour lesquelles les données d'opération dans l'environnement lunaire ne sont pas disponibles, afin que nous puissions effectuer une analyse de fiabilité traditionnelle. La distance maximale traversée par le Rover Lunaire durant la mission Apollo 17 était d'environ 35.9 km. Aujourd'hui, l'Université de McGill, le groupe Neptec Design et l'Agence Spatiale Canadienne travaillent ensemble afin de développer une roue de Rover Lunaire pouvant être opérationnelle pendant 5 ans. Cela souligne l'importance de la fiabilité des roues, qui auront à traverser des milliers de kilomètres. Le groupe Neptec Design a réussi à développer une méthodologie afin d'estimer la fiabilité d'un rover lunaire, comme nous le montre le document Prédiction de Fiabilité de Rover Lunaire (PFRL) qui a été publié par l'entreprise. Cette méthodologie comprend deux phases. Phase 1 contient trois étapes incluant les recherches approfondies concernant les différents modèles de fiabilité disponibles, les outils logiciels spécifiques qui permettent la mise en place de ces modèles, et l'habilité à adapter ces outils à l'environnement lunaire (par exemple, la température, la présence de régolite, les radiations, l'apesanteur). La Phase 2 décrit le processus d'estimation de la fiabilité du rover lunaire pour une durée de 5 ans sur la Lune, basé sur les recommandations détaillées dans la Phase 1. Le PFRL a été un succès mais Neptec est seulement capable d'utiliser des données earthbound pour la méthodologie, ce qui est insuffisant. Donc, le domaine de l'usure à la cryogénie à été exploré à travers la littérature et les bases de données, et le résumé des éléments qui ont été relevés intéressants est le suivant : le taux d'usure de l'acier et du titane à 293K et 77K sont à peu près les mêmes, en dessous de 1m/s ; le taux d'usure à 77K en dessous de 1m/s est plus haut pour la plupart des matériaux et le coefficient de frottements pour l'acier sur l'acier à 77K et 273K est à peu près le même. Cela souligne la nécessité d'une méthodologie alternative, par exemple, la technique d'inspection visuelle, pour évaluer la fiabilité d'un système quand des données utiles ne sont pas disponible. La technique d'inspection visuelle est décrite et une analyse de 9 conceptions de roues (cinq anciennes roues et quatre nouvelles roues conçues par l'Université de McGill) est démontrée. Les conceptions des roues sont analysées visuellement en fonction de critères spécifiques, sans négliger les risques d'échec potentiels si l'on transpose aux conditions lunaires (température, aspiration, et régolites), la fiabilité mécanique, sans oublier les obstacles à la performance, la résistance à l'usure, la compatibilité thermale, la vitesse de chargement, la torsion, etc. Une échelle numérique a été créée et la performance potentielle de la roue a été quantifiée en prenant compte des évènements pouvant causer un échec comme les fluctuations de températures, le soudage à froid, les impacts de rochers, un excès de charge et une usure abrasive. Les résultats ont indiqué que la meilleure conception historique était la roue à treillis métallique d'Apollo 17 et que la meilleure conception contemporaine est la roue iRing. L'exposé donne aussi une "liste de conception pour la fiabilité", qui peut potentiellement servir de guide afin d'éviter les traits de conceptions avec des failles. La technique d'inspection visuelle a été un succès et peut être appliquée à d'autres systèmes complexes où les tests expérimentaux dans les conditions actuelles ne sont pas possibles. Cependant, des connaissances préliminaires et une expertise sont nécessaires afin de mettre en place l'évaluation.
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Palmer, Timothy R. (Timothy Richard). « Investigation of electrophoretic deposition as a fabrication technique for high performance composites ». Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/68951.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, September 2011."September 2011." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 105-108).
Electrophoretic deposition (EPD) is a colloidal processing method for the deposition of materials from charged nanoparticles suspended in solution with the application of an external electric field. It is an increasingly popular manufacturing method for engineered materials because of its low cost, simple equipment, flexibility, and efficiency. Yet, little research has been done in the area of composite material fabrication using EPD to infiltrate porous substrates (known as electrophoretic infiltration, or EPI). In addition, what work has been done has focused on 2-D porous substrates such as fiber mats or porous membranes. This thesis endeavors to demonstrate the applicability of EPD for the infiltration and coating of porous materials to create advanced composites. The underlying theory of EPD is discussed to give foundation for experiment parameters. Two sample materials, boron carbide and silicon dioxide, are deposited within and on commercially available porous stainless steel filter discs using constant voltage DC EPD. Surfaces are characterized using a scanning electron microscope (SEM) and energetic dispersive x-ray (EDX)/Auger spectrometers to visualize coating quality and penetration of the material into the substrate. Limitations of EDX/Auger spectroscopy are briefly discussed with respect to the analysis of boron carbide. After the first set of experiments using DC EPD, the study is expanded to include pulsed DC EPD. Pulsed DC EPD is a valuable technique for mitigating bubble formation due to electrolysis in aqueous suspensions, thus reducing macropore generation from gas evolution. The ability of EPD to infiltrate into pores is confirmed by visual inspection of samples under a SEM and EDX. At low voltage, the deposited mass in constant voltage EPD increases linearly with time while at high voltage it asymptotically approaches a maximum yield of 1.988 grams. Pulsed EPD experiments demonstrate a reduction in deposition yield but also elimination of pore generation in the low voltage case. A nondimensional parameter, [delta]*, relating electrophoretic kinetics and diffusion is derived which improves process design for pulsed EPD cells.
by Timothy R. Palmer.
S.M.
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Chau, Alexandra H. (Alexandra Hung) 1980. « Elastography using optical coherence tomography : development and validation of a novel technique ». Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/91380.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 161-167).
Atherosclerosis is an inflammatory disease characterized by an accumulation of lipid and fibrous tissue in the arterial wall. Postmortem studies have characterized rupture-prone atherosclerotic plaques by the presence of a large lipid-rich core covered by a thin fibrous cap. Studies employing finite element analysis (FEA) based on ex vivo plaque geometry have found that most plaques rupture at sites of high circumferential stress, thus diagnosis of plaque vulnerability may be enhanced by probing the mechanical behavior of individual plaques. Elastography is a method of strain imaging in which an image sequence of the artery undergoing deformation is acquired, pixel motion is estimated between each frame, and the resulting velocity field is used to calculate strain. In this thesis, optical coherence tomography (OCT), a high-resolution optical imaging modality, is investigated as a basis for FEA and elastography of atherosclerotic plaques. FEA was performed using plaque geometries derived from both histology and OCT images of the same plaque. Patterns of mechanical stress and strain distributions computed from OCT-based models were compared with those from histology-based models, the current gold standard for FEA. The results indicate that the vascular structure and composition determined by OCT provides an adequate basis for investigating the biomechanical factors relevant to atherosclerosis. A new variational algorithm was developed for OCT elastography that improves upon the conventional algorithm by incorporating strain smoothness and incompressibility constraints into the estimation algorithm.
(cont.) In simulated OCT images, the variational algorithm offers significant improvement in velocity and strain accuracy over the conventional algorithm, particularly in the presence of image noise. Polyvinyl alcohol (PVA) phantoms of homogeneous and heterogeneous elastic modulus distribution were developed for further testing of the variational algorithm. Testing with the phantoms indicated that motion- and strain-induced decorrelation between images presents a practical challenge to the implementation of OCT elastography. Analysis of the experimental results led to the identification of potential improvements to the elastography algorithm that may increase accuracy. These improvements may include relaxation of the strain smoothness constraint to incorporate strain discontinuities at boundaries of elastic modulus in heterogeneous regions, and enforcement of geometry compatibility to prevent the estimation of non-physical velocity fields.
by Alexandra H. Chau.
S.M.
24
Karlin, Joseph H. (Joseph Howard). « 3D imaging methods for manufacturing, with emphasis on the laser speckle technique ». Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38074.
Texte intégral
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Rossiter, Ian Barclay. « Performance of mild steel perforated plates as a blast wave mitigation technique ». Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5477.
Texte intégralRésumé :
Includes abstract.Includes bibliographical references (leaves 148-152).
This thesis presents the results of an investigation into the effects of several geometric parameters on the performance of perforated plates as a blast wave mitigation technique. Results of experimental and numerical simulations are reported. The main objective of this investigation was to determine the effects of the perforated plate hole size on the blast wave mitigation capability of the plate. The blast wave was created by detonating plastic explosives. The blast wave travelled unhindered down the length of a cylindrical tube where it came into contact with the perforated plate.
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BONINI, Claudio. « Optimization Techniques Applied to Mechanical Design ». Doctoral thesis, Università degli studi di Bergamo, 2014. http://hdl.handle.net/10446/30756.
Texte intégralRésumé :
The present work deals with the application of optimization techniques to mechanical design. After an initial section devoted to a theoretical review of optimization algorithms in common use, the thesis consists of two parts.
The first part is about the use of the adjoint method in the framework of aerodynamic shape optimization. After a theoretical review, the discrete adjoint method has been implemented in a research code based on the Discontinuous Galerkin (DG) method. This activity represents a new direction of development within the research group operating at University of Bergamo on DG methods for Computational Fluid Dynamics (CFD). Starting from the simple quasi-1D Euler equations, the implementation of the discrete adjoint method has been validated by comparing the values of computed adjoint variables with results of analytical solutions available in the literature. The method has then been applied to a shape optimization problem, using a gradient based algorithm with an inexact line search approach.
The second part of the thesis deals with the application of optimization techniques to an industrial problem. This activity has been carried out at the R&D Centre of TenarisDalmine S.p.A., one of the largest seamless steel pipe producers in the world. This work focuses on the optimization of the thermal cycle of the mandrel of a longitudinal mandrel mill, with the objective of reducing the peak temperature of the mandrel during the rolling phase. The activity for this part of the thesis required the preliminary set up of a number of computational tools for the analysis of the physical aspects involved in the problem. Such tools have then been integrated in a comprehensive optimization approach driven by the optimization tools available in the Optimization Toolbox of the commercial software Matlab. The results of optimization are encouraging, showing the possibility of a considerable increase of the mandrel life cycle.
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Wen, Xin. « A hybrid intelligent technique for induction motor condition monitoring ». Thesis, University of Portsmouth, 2011. https://researchportal.port.ac.uk/portal/en/theses/a-hybrid-intelligent-technique-for-induction-motor-condition-monitoring(bafbf73a-0813-44f8-8f00-9212cc54c890).html.
Texte intégralRésumé :
The objective of this research is to advance the field of condition monitoring and fault diagnosis for induction motors. This involves processing the signals produced by induction motors, classifying the types and estimating the severity of induction motors faults. A typical process of condition monitoring and fault diagnosis for induction motors consists of four steps: data acquisition, signal analysis, fault detection and post-processing. A description of various kinds of faults that can occur in induction motors is presented. The features reflecting faults are usually embedded in transient motor signals. The signal analysis is a very important step in the motor fault diagnosis process, which is to extract features which are related to specific fault modes. The signal analysis methods available in feature extraction for motor signals are discussed. The wavelet packet decomposition results consist of the time-frequency representation of a signal in the same time, which is inherently suited to the transient events in the motor fault signals. The wavelet packet transform-based analysis method is proposed to extract the features of motor signals. Fault detection has to establish a relationship between the motor symptoms and the condition. Classifying motor condition and estimating the severity of faults from the motor signals have never been easy tasks and they are affected by many factors. AI techniques, such as expert system (ES), fuzzy logic system (FLS), artificial neural network (ANN) and support vector machine (SVM), have been applied in fault diagnosis of very complex system, where accurate mathematical models are difficult to be built. These techniques use association, reasoning and decision making processes as would the human brain in solving diagnostic problems. ANN is a computation and information processing method that mimics the process found in biological neurons. But when ANN-based methods are used for fault diagnosis, local minimums caused by the traditional training algorithms often result in large approximation error that may destroy their reliability. In this research, a novel method of condition monitoring and fault diagnosis for induction motor is proposed using hybrid intelligent techniques based on WPT. ANN is trained by improved genetic algorithm (IGA). WPT is used to decompose motor signals to extract the feature parameters. The extracted features with different frequency resolutions are used as the input of ANN for the fault diagnosis. Finally, the proposed method is tested in 1.5 kW and 3.7 kW induction motor rigs. The experimental results demonstrate that the proposed method improves the sensitivity and accuracy of the ANN-based methods of condition monitoring and fault diagnosis for induction motors.
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Dean, Andrew W. « Feasibility of a New Technique to Determine Dynamic Tensile Behavior of Brittle Materials ». Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849768/.
Texte intégralRésumé :
Dynamic tensile characterization of geo-materials is critical to the modeling and design of protective structures that are often made of concrete. One of the most commonly used techniques currently associated with this type of testing is performed with a Kolsky bar and is known as the spall technique. The validity of the data from the spall technique is highly debated because the necessary boundary conditions for the experiment are not satisfied. By using a technique called pulse shaping, a new “controlled” spall technique was developed to satisfy all boundary conditions so that the analyzed data may be useful in modeling and design. The results from this project were promising and show the potential to revolutionize the way Kolsky bar testing is performed.
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de, Koninck David Andrew. « Thermal conductivity measurement using the 3-omega technique : applications to power harvesting microsystems ». Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22039.
Texte intégralRésumé :
The optimal design of power generating microsystems requires accurate knowledge of the thermal properties of their constituent materials at the appropriate length scale. The goal of this thesis was to build an apparatus for measuring the thermal conductivity of thermally-insulating dielectric materials using the so-called 3-omega technique. This technique utilizes a microfabricated metal line deposited on the specimen to act as a resistive heater. When an alternating current (AC) voltage signal is used to excite the heater at a frequency ω, the periodic heating generates oscillations in the electrical resistance of the metal line at a frequency of 2ω. In turn, this leads to a third harmonic (3ω) in the voltage signal, which is used to infer the magnitude of the temperature oscillations. The frequency dependence of these oscillations can be analyzed to obtain the thermal properties of the specimen. The device consisted of a voltage source, a custom-built analog circuit and sample mount, a lock-in amplifier. The sample was placed within a vacuum chamber and evacuated using a made-to-order vacuum system. Personalised LabVIEW and MATLAB programs were created for autonomous data acquisition and analysis. The 3ω technique is simple, quick and accurate; tests using a standard fused quartz specimen (k = 1.38+/-0.04 W/m•K) yielded a measured thermal conductivity of 1.47+/-0.16 W/m•K. Subsequently, the technique was used to measure the thermal conductivity of Lead Zirconate Titanate (PZT-5A4E), which is a piezoelectric ceramic of interest for integration with microfabricated vibration energy harvesters. This material was found to exhibit a low thermal conductivity of 1.38+/-0.10 W/m•K.Le design optimal de microsystèmes pour la génération d'énergie demande une connaissance précise des propriétés thermiques des matériaux utilisés, à la bonne échelle. Le but de ce projet fut de créer un instrument pour mesurer la conductivité thermique des matériaux fonctionnels pour ces microsystèmes en utilisant la méthode 3-oméga. Cette méthode se sert d'une ligne métallique déposée en surface qui agit comme élément chauffant. Quand le filament métallique est alimenté par un courant alternatif (CA) à une fréquence ω, la puissance dissipée par effet Joule génère une oscillation sinusoïdale dans la résistance électrique à une fréquence 2ω. Cette résistance électrique sinusoïdale à son tour crée une harmonique de rang 3 (3ω) dans la tension électrique de l'élément chauffant. Cette harmonique est utilisée pour déduire l'amplitude des oscillations de température dans le spécimen. La variation de ces oscillations thermiques en fonction de la fréquence d'excitation nous permet d'obtenir la conductivité thermique de l'échantillon. L'instrument consiste d'une source de tension, un « lock-in amplifier », un circuit analogique et une monture à échantillon personnalisés. L'échantillon fut placé dans une chambre à vide et évacué à l'aide d'un système à vide fait sur mesure. Des programmes LabVIEW et MATLAB fut écrits pour réaliser l'acquisition et l'analyse de donnés automatisées. La méthode 3ω est facile à réaliser et donne des résultats précis : des tests avec des échantillons de quartz amorphe (k = 1.38+/-0.04 W/m•K) ont donné une conductivité thermique de 1.47+/-0.16 W/m•K. Le quartz amorphe fut utilisé comme référence pour valider l'instrument. Par la suite, l'appareil fut utilisé pour caractériser une céramique PZT (Titano-Zirconate de Plomb), un matériau piézoélectrique souvent utilisé dans la fabrication de microgénérateurs pour la récupération d'énergie vibratoire. Un
30
Wong, Terence. « A new technique for measuring the wettability of fibrous preforms by liquid metal ». Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14596.
Texte intégral
31
Sergeev, Boris Anatolievich 1964. « Analysis of composite laminates with multiple fasteners by boundary collocation technique ». Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282412.
Texte intégralRésumé :
Mechanical fasteners remain the primary means of load transfer between structural components made of composite laminates. As, in pursuit of increasing efficiency of the structure, the operational load continues to grow, the load carried by each fastener increases accordingly. This accelerates initiation of fatigue-related cracks near the fasteners holes and increases probability of failure. Therefore, the assessment of the stresses around the fastener holes and the stress intensity factors associated with edge cracks becomes critical for damage-tolerant design. Because of the presence of unknown contact stresses and the contact region between the fastener and the laminate, the analysis of a pin-loaded hole becomes considerably more complex than that of a traction-free hole. The accurate prediction of the contact stress distribution along the hole boundary is critical for determining the stress intensity factors and is essential for reliable strength evaluation and failure prediction. This study concerns the development of an analytical methodology, based on the boundary collocation technique, to determine the contact stresses and stress intensity factors required for strength and life prediction of bolted joints with many fasteners. It provides an analytical capability for determining the non-linear contact stresses in mechanically fastened composite laminates while capturing the effects of finite geometry, presence of edge cracks, interaction among fasteners, material anisotropy, fastener flexibility, fastener-hole clearance, friction between the pin and the laminate, and by-pass loading. Also, the proposed approach permits the determination of the fastener load distribution, which significantly influences the failure load of a multi-fastener joint. The well known phenomenon of the fastener tightening torque (clamping force) influence on the load distribution among the different fastener in a multi-fastener joints is taken into account by means of bi-linear representation of the elastic fastener deflection. Finally, two different failure criteria, maximum strains averaged over the characteristic distances and Tsai-Wu criterion, were used to predict the failure load and failure mode in two composite-aluminum joints. The comparison of the present predictions with the published experimental results reveals their agreement.
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Jones, Ryan Edward 1974. « Thermally driven visco-elastic measurement technique via spectral variations in scanning probe microscopy cantilevers ». Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27098.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 166-167).
Understanding how fluids respond to various deformations is of great importance to a spectrum of disciplines ranging from bio-medical research on joint replacements to sealing technology in industrial machinery. Specifically, this work addresses the need for probing interfacial rheology to understand how lubricants fail as system scales are reduced from bulk dimensions to molecular length scales. In the pursuit of interfacial rheology, one needs a platform capable of the temporal and spatial range and resolution required to quantify the visco-elastic fluid properties in the interfacial regime. With the availability and versatility of AFMs and the mounting models and data related to the performance of SPM probes in a fluid environment, the AFM is an attractive platform to exploit. This thesis will discuss the use of thermal oscillations of an SPM probe to quantify the visco-elastic properties of fluids via spectral variations. There exist theoretical models for the Fluid-Structure Interactions (FSI) of vibrating bodies in incompressible viscous mediums that have been validated. This thesis will discuss how these models have been extended to develop a new visco-elastic FSI model. The analytical results of these models will be quantitatively compared to thermally driven SPM cantilevers to extract fluid properties. The new theory required for modeling the probe dynamics is outlined and the present limitations, for both the analytical and experimental techniques, are discussed.
by Ryan Edward Jones.
Ph.D.
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Tham, Hoe Phong 1977. « Design of a novel centrifugal casting technique for the fabrication of metal matrix composites ». Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/89922.
Texte intégral
34
Massimini, Daniel Frank. « Technique and application for quantifying dynamic shoulder joint kinematics and glenohumeral joint contact patterns ». Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87979.
Texte intégralRésumé :
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
The shoulder (glenohumeral) joint has the greatest range of motion of all human joints; as a result, it is particularly vulnerable to dislocation and injury. The ability to accurately measure dynamic in-vivo joint kinematics in 6-Degrees-of-Freedom (6-DOF) (translations and rotations) and subsequently quantify articular cartilage contact patterns of that joint has been and remains a difficult biomechanics problem. As a result, little is known about normal in-vivo glenohumeral joint contact patterns or the consequences of surgery on: shoulder joint kinematics, the soft tissue anatomy around the shoulder, and glenohumeral joint contact patterns. Additionally, the effect of quantifying glenohumeral joint contact patterns by means of proximity mapping, both with and without cartilage data is unknown. Therefore, the objectives of this thesis are to (1) describe and validate a noninvasive Dual Fluoroscopic Imaging System (DFIS) to measure dynamic shoulder joint motion; (2) describe a technique to quantify in-vivo glenohumeral joint contact patterns from the measured shoulder motion; (3) quantify normal glenohumeral joint contact patterns in the young healthy adult; (4) compare glenohumeral joint contact patterns determined both with and without articular cartilage data; and (5) demonstrate that the DFIS technique can evaluate the dynamic suprascapular nerve (a soft tissue around the shoulder) anatomy in 6-DOF in a proof of concept cadaveric model. Our results show that for the shoulder motion tested, glenohumeral joint contact was located on the anterior-inferior glenoid surface, and that the inclusion of articular cartilage data when quantifying in-vivo glenohumeral joint contact patterns has significant effects on the contact centroid location, the contact centroid range of travel, and the total contact path length. As a result, our technique offers an advantage over glenohumeral joint contact pattern measurement techniques that neglect articular cartilage data. Likewise, this technique may be more sensitive than traditional 6-DOF joint kinematics for the assessment of overall glenohumeral joint health. Lastly, in the proof of concept cadaveric model, we demonstrated that the DFIS technique can evaluate the dynamic suprascapular nerve anatomy in 6-DOF and that the anatomical course of the nerve may be altered by a rotator cuff tendon tear and subsequent to surgical intervention.
by Daniel Frank Massimini.
Ph. D.
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Nex, Christopher Paul. « The effect of joining technique on the mechanical properties of stainless steel structures ». Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284383.
Texte intégral
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Bulthaup, Colin A. (Colin Aaron) 1976. « Liquid embossing : a technique for fabricating sub-micron electrical, mechanical and biological structures ». Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/81571.
Texte intégralRésumé :
Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaf 92).
by Colin A. Bulthaup.
M.Eng.and S.B.
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Akkaya, S. S., V. V. Vasyliev, K. Kazmanl, A. A. Luchaninov, E. N. Reshetnyak, N. Solak, V. E. Strel’nitskij et M. Ürgen. « Mechanical and Tribological Properties of TiN Coatings Produced by PIII&D Technique ». Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35187.
Texte intégralRésumé :
The structure, mechanical and tribological properties TiN coatings рroduced with PIII&D by using
rectilinear filtered vacuum arc plasma system are present. The results of scratch testing and wear
reciprocating testing clearly revealed the positive effect of pulse bias (0.5÷2.5 kV) application on
tribological behavior of the TiN coatings in comparison the coatings deposited with DC bias (150 V).
Application of pulsed bias potential leads to a significant reduction in the friction coefficient and increasing
of coatings wear resistance due to a change in their structure. The orientation of crystal planes parallel to
the surface changes from (111) to (220) with the application of pulse bias, which is accompanied by a
transition from fibrous grains structure to denser columnar grains.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35187
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Goldberg, Benjamin M. « Picosecond Electric Field CARS ; A Diagnostic Technique to Measure the Electric Field Development within Nanosecond Repetitively Pulsed Plasmas ». The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354303147.
Texte intégral
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Hua, Zilong. « Hybrid Photothermal Technique for Microscale Thermal Conductivity Measurement ». DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1491.
Texte intégralRésumé :
Most existing thermal conductivity measurement techniques of nuclear fuel only measure the overall effective thermal conductivity of the fuel, cladding, and gap, with low spatial-resolution. However, damage to nuclear fuel microstructure caused by neutron-irradiation can result in sharp, local changes of thermal conductivity. Additionally, extremely large temperature-gradients (~1600 K/cm) from the fuel centerline to the coolant result in similar gradients of thermal conductivity. Therefore, in pursuit of greater understanding of nuclear fuel performance, the objective of this study was to develop a non-contact thermal conductivity measurement technique to provide micron-sized spatial-resolution capability. Based on photothermal techniques and using both frequency and spatial-domain photothermal reflectance methods, an experimental measurement system was designed, built, and tested for measuring the thermal conductivity of a thin-film coated material with micron resolution. This hybrid method involves separate measurement of thermal diffusivity, D, and thermal effusivity, e, from which, thermal conductivity, k = (e2/D)1/2 is calculated. A detailed parametric analysis using analytical solutions and a numerical model has been performed to guide the experiment and optimize measurement conditions. The measurement system was validated using two calibration samples having thermal conductivities at both the upper and lower limit of the common range of nuclear fuels (~1 - 10 W/m/K). Sources of experimental errors are discussed qualitatively and the uncertainty of the measurement system for the thermal conductivity range of interest is quantified. The measured error is found to be about 10%, and up to close to 20% for the worst case (upper limit of k range). An extended application of the modulated laser excitation technique is explored to measure mechanical properties of solid materials. This technique involves obtaining the natural frequencies of different vibrational modes of a cantilever beam sample allowing for the extraction of the elasticity constants of the material. From Neumann's principle, the number of independent elasticity constants is dependent on the symmetry of the material structure. Specifically, symmetries of crystalline materials and composite materials are analyzed. Experimental results of two validation samples with cubic crystal system agreed well with the published values with experimental errors of ~10%.
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Johnson, Timothy Paul Mahal. « High strain rate mechanical characterization of trabecular bone utilizing the split-Hopkinson pressure bar technique ». Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/38294.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 185-188).
The split-Hopkinson pressure bar (SHPB) technique has been in use in one form or another for more than fifty years and has recently gained a great deal of attention for its ability to characterize materials such as metals, plastics, and even stiff foams at strain rates of up to 105 sec-1. Historically, however, numerous obstacles have stood in the way of applying this technique to softer biological tissues. This study is aimed at bridging this gap by employing various innovations in the field of split-Hopkinson pressure bar techniques (including hollow aluminum and solid polymeric pressure bars) to the characterization of trabecular bone. A preliminary study is conducted on a polyurea (PU) blend to assess the advantages and shortcomings of these approaches, as well as to validate the results obtained with each. Bovine trabecular bone with marrow in-situ, which was chosen for its ability to be tested with a wide spectrum of techniques, is then characterized with the selected techniques at rates of up to 1300 s-1 and strains of 0.07. The results are presented for each technique in the form of engineering stress vs. engineering strain curves.
(cont.) Average trend curves are also provided. Unfortunately, many of the samples were too damaged to allow for accurate measurement of apparent density. Consequently, a study into the effect of density on high strain rate responses is left as future work. Recommendations are made for increasing the strain imposed on the samples and suggestions for future studies on both trabecular bone and softer biological tissues are put forward.
by Timothy Paul Mahal Johnson.
S.M.
41
Garman, Mohamed Ammar. « Local Particle Velocity Measurements In Slurry Flow In Pipes And Centrifugal Pumps Using Ultrasound Technique ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1417518176.
Texte intégral
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Bright, Dominic. « Accurate characterisation of surface fatigue cracks (in steels) using the AC potential drop NDT technique ». Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5562.
Texte intégralRésumé :
Includes bibliographical references.In order to maintain the desired level of safety in an industrial environment, it is important that the structural integrity of all the components and equipment being utilised by the facilty is assured. To determine the structural integrity of an engineering system precisely, not only must the depth of the flaw be established, but the crack profile and orientation must also be obtained in order to assess the extent of the crack. The present work described in this thesis discusses the development of an AC potential drop (ACPD) system as a non-destructive testing (NDT) technique for flaw detection and sizing of variously shaped and oriented surface breaking fatigue cracks. The ACPD method was reviewed to establish its viability as an NDT technique, and to understand the response of the output to fatigue cracking. The proposed system using a mains power source with a frequency of 50Hz was investigated as a means of providing a sensitive and reliable measurement device that could be employed to analyse fatigue cracks in industrial components in situ.
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Schofield, Douglas M. (Douglas MacLean). « Diesel engine instantaneous oil consumption measurements using the sulfur dioxide tracer technique ». Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/28157.
Texte intégralRésumé :
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1995, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995.Includes bibliographical references (p. 49-50).
by Douglas M. Scholfield.
M.S.
44
Ragula, Vivian Vineeth Raj. « Streamline based Analysis and Design Technique for Turbomachines ». University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1304022216.
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Gonzalez, Beatriz Andrea. « Determining the effects of alloy composition, forging technique, and flux on the strength of forge welds ». Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119956.
Texte intégralRésumé :
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (page 41).
Welding is an essential manufacturing process in industries that require the joining of metal components such as the automotive and aerospace industries. While specialized techniques have developed for many of these industries, the process of welding remains fundamentality the same, and the effectiveness of these processes to securely join metal is always characterized by the material properties of the metal after welding. The tensile test performance of forge welds when made with different iron alloys, forge welding techniques, and fluxes was measured. The alloys used were 1018 steel, A36 steel and wrought iron. The forge welding techniques were the hydraulic press, the power hammer, and hand hammer. The fluxes were borax, fine silica sand, anti-borax, and no flux. Control tensile samples (un-welded) of each alloy, as received, were tested along with annealed samples. All testing was performed with an Instron 5984 Universal Testing Machine with 150kN capacity. The results of the welded alloy tests showed that welded 1018 and A36 steel both had considerably lower strength than their control annealed counterparts, whereas welded wrought iron remained just as strong. The results of the forge welding techniques test showed consistent welded A36 steel strengths across techniques used which may suggest that the effectiveness of particular techniques may be more dependent on experience and practice. The flux results show that silica sand and anti-borax work just as well as, if not better than, borax. Using no flux resulted in failed welding, revealing that achieving successful welds without flux requires more welding experience or a different method than the one performed by the welder of the samples for the present experiment. The results of the control alloys showed that 1018 and A36 steel both had considerably lower strength than their annealed counterparts, whereas wrought iron remained just as strong.
by Beatriz Andrea Gonzalez.
S.B.
46
Khan, Zein A. « Medical imaging using the acousto-electromagnetic technique ». Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:017c096e-c2fc-462a-9266-2b8731ff31b3.
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Kurppa, Kimmo. « A material and manufacturing technique comparison regarding the flooring of a bus ». Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-38785.
Texte intégralRésumé :
Purpose of this Master’s thesis is to compare the use of two alternative materials in the building the flooring of a bus. Currently the floors of Carrus Delta buses are built using plywood. Carrus Delta Oy wants to investigate the use of ready-made glass fibre elements instead of plywood elements which are custom cut at their factory in Lieto, Finland. Glass fibre is also presented as potential material of light-weight vehicles by Fenton and Hodkinson (2001).
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South, G. « A technique for measuring the electrical impedance of mechanical joints in electrically conductive structures ». Thesis, University of Central Lancashire, 1992. http://clok.uclan.ac.uk/20064/.
Texte intégralRésumé :
The impedance of a circular coil placed above a conducting surface is calculated using three mathematical models. The first considers the interaction of the test coil with a uniform, homogeneous and electrically thick conducting sheet. The model quantifies the interaction of the coil and the surface by calculating the field around the coil in the frequency domain. The sheet is included by using reflection coefficients, calculated from defined physical properties, to modify the field components surrounding the coil. Cylindrical symmetry is used to reduce the problem to two dimensions. The second model is a finite difference solution in the frequency domain of the differential equation describing the magnetic vector potential. Cylindrical symmetry is used to reduce the problem to two dimensions. An approximation allowing a mechanical joint of finite physical dimensions to be included is described. The third model is a finite difference, time domain solution of the differential form of the field equations. This is a complete three dimensional analysis of the problem, including the effect of fasteners and sealants. An algorithm allowing the inclusion of materials with anisotropic electrical conductivity is described. Fourier analysis is used to transform the time domain results into the frequency domain. The results calculated from the three models are compared with practical measurements. Two instruments are constructed and practically evaluated. The first is suitable for frequencies up to 50kHz. It is based upon two test coils in a bridge arrangement and the effect of the joint is measured in terms of the out-of-balance bridge voltage. The second instrument is based upon the effect of the joint of interest upon the resonant frequency of a test coil, measured using a modified Q meter circuit. Frequencies up to 70MHz have been considered.
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Yao, Hang. « Mechanical testing of bone and bone-like materials using image correlation strain measurement technique ». Ann Arbor, Mich. : ProQuest, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1445124.
Texte intégralRésumé :
Thesis (M.S. in Mechanical Engineering)--S.M.U., 2007.Title from PDF title page (viewed Mar. 18, 2008). Source: Masters Abstracts International, Volume: 46-01, page: . Adviser: Wei Tong. Includes bibliographical references.
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Izquierdo-Roman, Alondra. « Localized Mechanical Compression as a Technique for the Modification of Biological Tissue Optical Properties ». Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76856.
Texte intégralRésumé :
Tissue optical clearing aims to increase the penetration depth of near-collimated light in biological tissue to enhance optical diagnostic, therapeutic, and cosmetic procedures. Previous studies have shown the effects of chemical optical clearing on tissue optical properties. Drawbacks associated with chemical clearing include the introduction of potentially toxic exogenous chemicals into the tissue, poor site targeting, as well as slow transport of the chemicals through tissue. Thus, alternative clearing methods have been investigated. Mechanical compression is one such alternative tissue optical clearing technique. The mechanisms of action of mechanical compression may be similar to those of chemical clearing, though they have yet to be investigated systematically. This research describes the design and execution of a number of procedures useful for the quantification of the tissue optical clearing effects of localized mechanical compression. The first experimental chapter presents the effects of compression on image resolution and contrast of a target imaged through ex vivo biological tissue. It was found that mechanical optical clearing allowed recovery of smaller targets at higher contrast sensitivity when compared to chemical clearing. Also, thickness-independent tissue clearing effects were observed. In the second experimental chapter, dynamic changes in tissue optical properties, namely scattering and absorption coefficients (?s' and ?a, respectively) were monitored during a controlled compression protocol using different indentation geometries. A reduction in ?s' and ?a was evident for all indentation geometries, with greater changes occurring with smaller surface area. Results indicate that localized mechanical compression may be harnessed as a minimally-invasive tissue optical clearing technique.Master of Science