This study aims to gain a fundamental understanding of the physics of triboelectri- cal charging of solid particles and the separation of the charged particles under an exter- nal DC electric field by computer simulations. A condenser model is used to implement charging mechanism and a soft sphere model is used to account for the Hertzian contact mechanics. The governing nondimensional parameters of the problem are identified and a parametric study is performed to investigate their effects on the charging efficiency and separation. The study finds relevance in a host of technologically important processes, such as recycling of plastic wastes, seed cleaning in agricultural industry and separation of coal from impurities in mining.

In recent years, the lifetime of an insulated railroad joint in the field has decreased due to increasing wheel loads. The goal of this research is to investigate possible changes in insulated rail joint design in order to improve the performance of the insulated joint. The finite element program ABAQUS is used to model the supported butt joint. In this model, the rail, joint bars, epoxy, and ties surrounding the joint are modeled using solid elements. The remaining ties are modeled as an elastic foundation. The rail is subjected to a tensile load, as well as a vertical wheel load that is applied to the rail using Hertz contact theory. Parametric studies are performed by varying the tie width, joint bar length, and joint bar dimensions. Two different wheel load locations are also investigated: centered about the end post, and halfway between the tie under the end post and the tie just to the left of the end post. The vertical displacement of the rail and insulated joint is one measure used to determine the effect of the parameters on the insulated joint. However, since the most common cause of failure in insulated rail joints is the debonding of the epoxy, this research also focuses on the stresses present in the epoxy when the joint is subjected to a static wheel load. The two out-of-plane shear stresses as well as the normal peel stress are used to compare the various designs of the joint. / Master of Science

During the project a test rig was constructed in which experiments were performed on radial bearings to evaluate the acoustic emission amplitude and RMS value of the signal. The acoustic emission amplitude depends on the Hertz contact time, i.e. the time it takes for the Hertz contact to roll over its own contact length. When the load remains constant on the bearing the Hertz contact time is directly reliant on the rotational speed of the inner ring of the bearing. Two experiments were performed, one on a spherical roller bearing and another identical experiment on a spherical ball bearing. Throughout both experiments the load on the bearing remained constant and the rotational speed of the inner ring was changed, the response of the speed change was measured using an acoustic emission sensor. The experiments found a quadratic dependency between the amplitude of the acoustic emission signal and the rotational speed of the inner ring. During the experiments the bearings were lubricated using grease and a total of 195 measurements were performed on each type of bearing at 13 different rotational speeds ranging between 1 and 3000 RPM.

According to the American Cancer Society, Cancer is the second most common cause of death in the United States, only exceeded by heart disease. Over the past decade, deciphering the complex structure of individual cells and understanding the symptoms of cancer disease has been a highly emphasized research area. The exact cause of Cancer and the genetic heterogeneity that determines the severity of the disease and its response to treatment has been a great challenge. Researchers from the engineering discipline have increasingly made use of recent technological innovations, namely the Atomic Force Microscope (AFM), to better understand cell physics and provide a means for cell biomechanical profiling. The presented work's research objective is to establish a fundamental framework for the development of novel biosensors for cell separation and disease diagnosis. By using AFM nanoindentation, several studies were conducted to identify key distinctions in the trends of cell viscoelasticity between healthy, nontumorigenic cells and their malignant, highly tumorigenic counterparts. The possibility of identifying useful 'biomarkers' was also investigated. Due to the lack of an available human ovarian cell line, experiments were done on a recently developed mouse ovarian surface epithelial (MOSE) cell line, which resembles to human cell characteristics and represents early, intermediate, and late stages of the ovarian cancer. Material properties were extracted via Hertz model contact theory. The experimental results illustrate that the elasticity of late stage MOSE cells were 50% less than that of the early stage. Cell viscosity also decreased by 65% from early to late stage, indicating that the increase in cell deformability directly correlates with increasing levels of malignancy. Various cancer treatment and component-specific drugs were used to identify the causes for the changes in cell biomechanical behavior, depicting that the decrease in the concentration levels of cell structural components, predominantly the actin filament framework, is directly associated with the changes in cell biomechanical property. The investigation of MOSE cells being subject to multiple mechanical loads illustrated that healthy cells react to shear forces by stiffening up to 25% of their original state. On the other hand, cancerous cells are void of such response and at times show signs of decreasing rigidity. Finally, deformation studies on MOSE cancer stem cells have shown that these cells carry a unique elasticity profile among other cell stage phenotypes that could allow for their detection. The results herein carry great potential into contributing to cell separation methods and analysis, furthering the understanding of cell mechanism dynamics. While prior literature emphasizes on the elastic modulus of cells, the study of cell viscosity and other key material properties holds a critical place in the realistic modeling of these complex microstructures. A comprehensive study of individual cells holds a great amount of promise in the development of effective clinical research in the fight against cancer. / Master of Science

The diploma thesis deals with The study of transition between fully flooded and starved regimes in EHL Contact. The work is focused on problems of starved contact and surface texturing of rubbing surfaces. Surface texturing of rubbing surfaces is one of the adjustments that cause in a sense improved lubricity and reduce friction and wear. The aim of this study is to compare numerical models with real experimental results measured on the Experimental apparatus.

Les travaux présentés à travers ce manuscrit s'inscrivent dans un contexte de recherches exploratoires sur l'optimisation des surfaces engrenantes. Après une étude approfondie de l'emploi des engrenages dans un environnement aéronautique, l'élaboration d'une nouvelle méthodologie de génération de profils de denture est proposée. Les travaux s'attachent à caractériser le comportement mécanique spécifique d'un montage d'engrenages dans les Boites de Transmission de Puissances (BTP) d'hélicoptère.Un outil informatique a été créé dans le module VBA (Visual Basic Application) d'Excel. Il permet de créer automatiquement des profils de denture conjugués et optimisés. Il a l'avantage de définir analytiquement plusieurs grandeurs physiques. L'outil a ainsi pour objectif de proposer des profils de denture optimisés selon plusieurs critères. Les « objectifs » retenus sont le rendement et la contrainte équivalente de Hertz au contact suivant le critère de Von Mises.Les travaux s'articulent autour de trois axes : - la reconstruction de profils conjugués de denture par une approche novatrice basée sur le « contact », - la construction de critères physiques (glissement, pression, contrainte, …), - la recherche de profils de denture optimaux en utilisant la simulation de Monte Carlo.Enfin, la perspective de rendre générique cette méthode afin qu'elle puisse générer n'importe quels types d'engrenage est envisagée en fin de manuscrit. / The work described in the present manuscript is part of exploratory researches dealing with gears meshing surfaces optimization. After a short study of gears used in an aeronautical environment, the development of an innovative tool for tooth profile design is defined. Then, the specific behavior of a gear mesh within a helicopter main gearbox (MGB) is evaluated.A VBA software has been coded under MS Excel to generate conjugated and optimized gear tooth profiles. It advantageously defines and uses several physical parameters with their analytical formulation. The software provides at the user optimized tooth profiles according to a couple of criteria. The two “objective” functions evaluated are the efficiency and the Hertz equivalent stress within the contact using the Von Mises criterion.The work has been focused on three aspects:- The design of conjugated tooth profiles by contact sharing,- The definition of the relevant physical parameters,- The optimization of tooth profiles using Monte Carlo SimulationEventually, a generic method to design gear profiles, taking into account any physical parameters related to a gear mesh, could be expected as a future of this thesis work.