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1
Dean, David L. "Design of a robotic end-effector for automated bolting." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/100065.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaf 111.
by David L. Dean, Jr.
M.S.
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Rieger, Michael. "Research and development of a rescue robot end-effector." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/5479.
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Includes abstract.Includes bibliographical references.
This report details the research, design, development and testing of an end-effector system for use on an Urban Search and Rescue (USAR) robot which is in development in the Robotics and Agents Research Laboratory (RARL) at the University of Cape Town (UCT). This is the 5th generation Mobile Robot Platform (MRP) that UCT has developed ... codenamed ‘Ratel’. USAR robots used to be mainly of the observation type, but new robots (including UCT’s Ratel MRP) are being developed to deal with inherently dynamic, complex and unpredictable disaster response situations, particularly related to object manipulation and gripping. In order to actively interact with the environment, a flexible and robust gripping system is vital. [an] end-effector solution ... was developed for the Ratel manipulator arm to fulfil these functions.
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Cannon, Bennion R. "Design and analysis of end-effector systems for scribing on silicon /." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd259.pdf.
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Cannon, Bennion Rhead. "Design and Analysis of End-Effector Systems for Scribing on Silicon." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/95.
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This thesis investigates end-effector systems used in a chemomechanical scribing process. Chemomechanical scribing is a method of patterning silicon to selectively deposit a monolayer of material on the surface of the silicon. This thesis details the development of a unique end-effector for chemomechanical scribing using a compliant mechanism solution. The end-effector is developed to scribe lines that have uniform geometry and produce less chipping on the surface of the silicon. The resulting scribing mechanism is passively controlled, has high lateral stiffness, and low axial stiffness. The mechanism is analyzed using the pseudo-rigid-body model and linear-elastic beam method to determine the axial stiffness, finite element methods to determine the lateral stiffness, and fatigue analysis to determine mechanism cycle life. This thesis also investigates the significance of mechanical factors on the chemomechanical scribing process using the compliant end-effector. The factors examined are scribing force, scribing speed, tip geometry, wafer orientation, and wetting liquid. The factors are analyzed using a two-step approach: first, an analysis of the influence of the mechanical factors on line characteristics and second, an analysis of the influence of line characteristics on line performance.
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Söderström, Nils. "Product development of an end-effector for a collaborative robot." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-19636.
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With the ever-growing market of six-axis robots in the previous years, many different kinds of robots have been introduced into the market. A smaller group of so-called collaborative robots have during this time gotten increased popularity. One of the inconveniences with this type of smaller robot is the lack of internal pneumatic capabilities, which leads to external cables and tubing. This can cause problems with the cables attaching into unintended things and coming loose which could result in production stops, machine failure or other potential damage. Another part of this is that the external cabling hinders the robots sixth axis of rotation. The need for air pressure is to supply the common pneumatic grippers that the robots often use to gain pick-and-place capabilities. Cobotech Kalmar AB is a company based in Kalmar which specializes in robot integration with these collaborative robots. The purpose of this project is to together develop a product concept that can minimize the external cabling needed on the robot while still allow full rotation in the sixth axis. On top of this, the product should have plug-and-play capabilities to decrease the installation time of a robot unit. The method to develop the results is the participatory action research (PAR), with the five different steps that the method includes: problem approach, design/planning, acquiring data, analysis and reflection. The result of the thesis shows that it is possible to decrease the external air tubes and installation time of a collaborative robot. This can be achieved while not decreasing the robots range of motion. By developing an innovative end-effector for the robot the main problems caused by pneumatic grippers can be eliminated. The conclusion of this thesis is a concept product that has one air input and five outputs. This allows for the minimization of the external air tubes needed to only one. The product has a swivel function incorporated which allows full rotation of the robots sixth axis. This together with having the valves seated in the end-effector makes this conceptual product plug-and-play.Med en ständigt växande marknad för sexaxliga robotar de senaste åren har många olika robotar introducerats till marknaden. Av dessa har mindre kollaborativa robotar vuxit i popularitet. Ett problem med många av dessa mindre robotar är att de inte har tryckluft inbyggt i armen som många av sina större bröder vilket leder till att tryckluftslangar måste dras externt på roboten istället. Detta kan leda tillatt kabeln fastnar och rycks loss vilket i sin tur kan leda till produktionsstopp, att maskiner skadas eller annan potentiell skada på antingen maskiner eller människor.Ett annat problem med att externt dra kabel är att den hindrar robotens sjätte rotationsaxel. Anledningen till att ha tryckluft på roboten är för att ha möjlighet att installera pneumatiska gripdon. Cobotech Kalmar AB är ett företag bosatt i Kalmar som specialiserar sig på att integrera kollaborativa robotar i olika tillverkande industrier. Syftet med detta projekt är att tillsammans utveckla ett produktkoncept som minimerar de externa kablarna på roboten och ser till att roboten får full rörlighet i sin sjätte rotationsaxel. Utöver detta ska produkten arbeta mot att ha plug-and-play kapacitet för att minska installationstiden ute hos kunden. Metoden som används för att få fram resultaten var deltagande aktionsforskning,som innehåller de följande fem stegen: problemformulering, design/planering, in-samling av data och reflektion. Resultatet av denna rapport visar att det är möjligt att minska externa luftslangar samt minska installationstid på kollaborativa robotar. Detta kan göras utan att minska robotens funktion. Genom att utveckla en innovativ end-effector till Universal robots produktutbud kan man eliminera de främsta problemen med pneumatiska gripdon. Projektet har resulterat i en nära färdig konceptuell produkt som innovativt använder magnetiska miniatyrventiler tillsammans med en svivelfunktion för att enbart ha en tryckluftkabel som input till produkten. Produktens swivelfunktion frigör robotens sjätte rotations-axel. Detta tillsammans med ventilerna som sitter i produkten gör att den får plug-and-play funktion.
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Stiber, Stephanie A. "Development of an End-effector Sensory Suite for a Rehabilitation Robot." Scholar Commons, 2006. http://scholarcommons.usf.edu/etd/3796.
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This research presents an approach in assisting the control and operation of a rehabilitation robot manipulator to execute simple grasping tasks for persons with severe disabilities. It outlines the development of an end-effector sensory suite that includes the BarrettHand end-effector, laser range finder, and a low cost camera.
The approach taken in this research differs greatly from the currently available rehabilitation robot arms in that it requires minimal user instruction, it is easy to operate and more effective for persons severely disabled. A thorough study of the currently available systems; Manus, Raptor and Kares II arm, is also presented.
In order to test the end-effector sensory suite, experiments were performed to find the centroid of an object of interest to direct the robot end-effector towards it with minimal error. Analyses of centroid location data to ensure accurate results are also presented.
The long term goal of this research is to significantly enhance the ability of severely disabled persons to perform activities of daily living using wheelchair mounted robot arms. The sensory suite developed through this project is expected to be integrated into a seven-degree of freedom wheelchair mounted robot arm currently under development at the Rehabilitation Robots Laboratory at the University of South Florida.
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Robinson, Graham. "The mechanical design and evaluation of Amadeus #2 a dextrous continuum end-effector for marine intervention." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/451.
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Procházka, Jakub. "Automatizace obsluhy výrobního stroje a řešení robotického odjehlení na externích pneumatických nástrojích." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417746.
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The task of this master thesis is to design a robotic workcell for an automation of the production machine operation followed by robotic deburring of the parts within external pneumatic tools. There is chosen the most suitable concept of the workplace layout of its included sub-components based on the input parameters. The first part is dedicated to design or select sub-components of the workcell as input magazine, robots, end effectors, deburring station etc. Afterwards, there is created a simulation model of the workcell in Process Simulate software for the verification of demanded cycle times and workcell functionality. The final design has to meet safety standards and technical and economical evaluation is permormed at the end of the thesis.
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McCrate, Mark P. "Modern Mechanical Automata." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1291146053.
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Romatoski, Rebecca R. (Rebecca Rose). "Robust end effecter for the introduction to Robotics Laboratory robotic arms." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36707.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.In the MIT ci ss Introduction to Robotics, a two link robotic arm is used to learn about robots however, the arm is limited since its only function is movement. In order to create a more meaningful and useful experience for students in the class, an end effecter with position feedback is going to be design and created as a third link for the current arm. Once complete, it will add functionality to the robot, namely picking up objects, by providing students with hands-on experience accomplishing a fundamental human task with a robot. The end effecter is comprised of a gravity link with two finger grippers each having rotating compliant tips which will compress around the object selected for lifting. The gravity link will insure that the two fingers are always vertical and the rotation on the tips will allow the fingers to be in the correct orientation so they can grasp around an object and pick it up. This solution creates a more practical experience and provides increased learning tasks for students in Introduction to Robotics.
by Rebecca R. Romatoski.
S.B.
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Bollini, Mario Attilio. "The design of scaled robotic end effectors to mimic razor clam burrowing." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54526.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 75).
This thesis reviews the design of two scaled mechanical end effectors that mimic the digging of Ensis directus, the Atlantic Razor Clam. Modeled after a 0.5x Ensis scale device, the end effectors are 1.0x and 2.0x Ensis scale. The end effectors will be coupled to a pneumatic robotic actuator to explore the nondimensional relationships governing the digging dynamics of razor clams in littoral substrates. Such dynamics could be exploited to construct novel mimetic engineering devices which would provide an order-of-magnitude improvement over existing subsea burrowing and anchoring technologies.
by Mario Attilio Bollini.
S.B.
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Hughes, Jason Peter. "Fluid inertia and end effects in rheometer flows." Thesis, University of Plymouth, 1998. http://hdl.handle.net/10026.1/1889.
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This thesis is concerned with the characterisation of the flow behaviour of inelastic and viscoelastic fluids in steady shear and oscillatory shear flows on commercially available rheometers. The first part of this thesis is concerned with a linear viscoelastic theory to describe the oscillatory shear flow behaviour of fluids on a Weissenberg rheogoniometer. A fluid inertia perturbation analysis is used to produce analytical formulae for correcting complex viscosity data for first and second order fluid inertia effects. In order to validate the perturbation theory we perform a simulation of the oscillatory shear flow behaviour of Newtonian and single element Maxwell fluids on a Weissenberg rheogoniometer. A theoretical prediction of end effects and fluid inertia effects on steady shear viscosity measurements of Newtonian fluids in a recessed concentric cylinder geometry is developed for a GSR controlled stress rheometer and a Weissenberg rheogoniometer. The relevant equations are solved using a perturbation analysis which is valid for low Reynolds number flows. From this theory correction formulae are produced to compensate for end effects and second order fluid inertia effects in steady shear flows on these instruments. End effects and fluid inertia effects are also investigated for power law shear thinning fluids. The final part of the thesis is concerned with a theoretical prediction of the end effect of a recessed concentric cylinder geometry on complex viscosity measurements of a generalised linear viscoelastic fluid. The linear viscoelastic theory is carried out for oscillatory shear flows on a CSR controlled stress rheometer and a Weissenberg rheogoniometer. A fluid inertia perturbation analysis is used to produce analytical formulae to correct complex viscosity data for end effects and second order fluid inertia effects. Numerically simulated oscillatory shear data is used to establish the limitations of the second order fluid inertia correction formulae which include end effects.
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Wang, Lihui. "Quantum Mechanical Effects on MOSFET Scaling." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07072006-111805/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007.Philip First, Committee Member ; Ian F. Akyildiz, Committee Member ; Russell Dupuis, Committee Member ; James D. Meindl, Committee Chair ; Willianm R. Callen, Committee Member.
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Ni, Qi. "Droplet-based Mechanical Actuator Utilizing Electrowetting Effect." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6337.
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The goal of this work is to quantify the key design parameters such as the load capacity, actuation force, positioning repeatability, and reliability for droplet-based electrowetting actuators. Due to the fact that surface tension dominates gravity at both the mesoscale and microscale, droplet-based actuators can provide adequate force in manipulation tasks at those scales. Electrowetting, which uses an electric field to modulate the apparent surface tension of the liquid-ambient, provides a method to actuate droplets, which in turn transports the object carried by the droplet.
Most previous electrowetting actuation efforts have concentrated on manipulating droplets in a closed two-plate configuration. In these configurations, a voltage potential is applied between a series of electrodes. The droplets can merge, split, and mix with only a voltage input, and without any external machinery. While some mechanical actuation demonstrations have been done, limited studies have been performed to investigate the key actuation performance characteristics of droplet-based actuators carrying solid objects. Design criteria for using droplets to carry solid components are still not well defined.
The first part of this work provides fundamental understanding of the forces in electrowetting-based droplet actuation. The actuation force during electrowetting was experimentally validated according to the governing relation (Young–Lippmann equation) on a custom-designed testing apparatus. The results from the experiments show that the electrowetting actuation force is independent of surface tension below saturation, but the peak force is proportional to surface tension. Higher surface/interfacial tension would increase the actuation force in the horizontal direction, as well as the speed of the actuator.
The second part of the dissertation demonstrates two actuation configurations based on electrowetting. The first actuator uses a droplet to carry a solid object and can be actuated in discrete steps to function as a micro-stepping linear motor. By implementing a leaky dielectric coating, the droplet/substrate contact area acts as an electrical diode. By varying the duty cycle of a square waveform, a range of droplet/part equilibrium position combinations are established. The underlying actuation mechanism was investigated and the position versus duty cycle relation was shown to be symmetrical but non–linear around the center of the electrodes. In contrast to the conventional electrowetting control scheme, the proposed actuation method required no feedback control loop while achieving a repeatability of less than 0.8% of the droplet diameter. Positioning matched a theoretical model based on idealized electrical elements to within 2.5% of the droplet diameter.
The second type of electrowetting actuation uses metal-semiconductor diodes (Schottky diodes) in place of electrochemical diodes. This configuration uses only one pair of electrodes to actuate the droplet over a large distance (5X or more the droplet diameter). While the actuation concept had been previously demonstrated, the reliability of the diodes were shown to be insufficient. The new diodes actuated without degradation under repeated actuation (2000 cycles). Comparing this to electrochemical diodes, a 50% reduction in actuation voltage was also accomplished by Schottky diodes. The measured maximum speed also increased from 32 mm/s (electrochemical diodes) to 240 mm/s (Schottky), a 7.5 fold improvement.
The last part of this dissertation used numerical simulations to investigate the load bearing capability and the stiffness variation of droplet-based actuators. The vertical force and stiffness - which are the primary figure of merit in designing droplet-based actuators are quantified. Three types of loading conditions were analyzed using simulation software and a simple analytical equation is shown to provide a useful approximation of the droplet force and stiffness. The results were further used in various case studies to demonstrate the optimal design strategy when using an electrowetting driven droplet as a fluidic bearing.
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Losey, Bradley. "Analysis of Magnetic Gear End-Effects to Increase Torque and Reduce Computation Time." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595514209192582.
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Martin, Holly Joy. "The chemical and mechanical effects of binding chitosan to implant quality titanium." Diss., Mississippi State : Mississippi State University, 2006. http://library.msstate.edu/etd/show.asp?etd=etd-09112006-150127.
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Luo, Ying. "SLURRY CHEMISTRY EFFECTS ON COPPER CHEMICAL MECHANICAL PLANARIZATION." Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4470.
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Chemical-mechanical Planarization (CMP) has emerged as one of the fastest-growing processes in the semiconductor manufacturing industry, and it is expected to show equally explosive growth in the future (Braun, 2001). The development of CMP has been fueled by the introduction of copper interconnects in microelectronic devices. Other novel applications of CMP include the fabrications of microelectromechanical systems (MEMS), advanced displays, three dimensional systems, and so on (Evans, 2002). CMP is expected to play a key role in the next-generation micro- and nanofabrication technologies (Singh, et al., 2002). Despite the rapid increase in CMP applications, the fundamental understanding of the CMP process has been lacking, particularly the understanding of the wafer-slurry-pad interactions that occur during the CMP process. Novel applications of CMP are expected to expand to materials that are complex chemically and fragile mechanically. Thus, fundamental understanding and improvement of slurry design for CMP is the key to the development of sophisticated next-generation CMP processes. Slurry performance for CMP can be determined by several output parameters including removal rate, global planarity, surface topography, and surface defectivity. To achieve global planarity, it is essential to form a very thin passivating surface layer (<2 nm) that is subsequently removed by the mechanical component of the slurry (Kaufman et al., 1991) or by combined chemo-mechanical effects (Tamboli, 2000). Chemical additives like hydrogen peroxide (H?O?), potassium ferricyanide, and ferric chloride are added to slurries as oxidizers in order to form a desirable surface layer. Other chemical additives such as inhibitors (e.g. benzotriazole) and complexing agents (e.g. ammonia) are added to the copper slurry in order to modify the oxide layer. That the removal rate of the thin surface layer is greater at the highest regions of the wafer surface than at the lowest regions leads to surface planarity. In this study, various complexing agents and inhibitors are combined to form slurry chemistry for copper CMP processing in H?O? based slurries at pH values ranging from 2 to 10. Two complexing agents (glycine and Ethylenediamine) and one inhibitor (3-amino-1, 2, 4-triazole) were selected as slurry constituents for detailed chemical synergistic effect study because they showed good materials removal and surface planarity performances. To understand the fundamental mechanisms involved in copper CMP process with the afore-mentioned slurry chemical formations, various techniques, such as electrochemical testing techniques (including potentiodynamic polarization and electrochemical impedance spectroscopy), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM), were applied. As a result, guidelines for optimized slurry chemical formulation were arrived at and the possible mechanisms of surface-chemical-abrasive interactions were determined. From applications point of view, this study serves as a guide for further investigations in pursuing highly effective slurry formulations for copper/low-k interconnect applications.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical, Materials and Aerospace Engineering;
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Moleejane, Cullen Mayuni. "An experimental investigation of the effect of microstructural features on mechanical properties of EN8 steel." Thesis, Cape Peninsula University of Technology, 2009. http://hdl.handle.net/20.500.11838/1254.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2009.Materials in almost all components are subjected to some kind of loading that must be correctly predicted to produce reliable designs. The understanding of a material's properties significantly impacts appropriate selection for a structure. This kind of material characterization is also important in the development of improved or new materials for high strength and novel applications. There are numerous metallurgical variables (composition and process parameters) that influence the physical and mechanical properties of materials. The aim of this work has been to study the influence of microstructure on mechanical properties of steel, specifically the effect of grain sizes within solid phase mixtures. Parameters for simple models of the variation of material properties with grain size can be determined. These models can then be incorporated in the material data sets of Finite Element Analysis programs which will then allow for structural analysis with zones in a material having different grain sizes. The deformation and damage behaviour of EN 8 steel have been stUdied with emphasis on the effects of grain size on the elastic-plastic response of the material. For that purpose, EN 8 specimens with a range of microstructures (grain size and phase) were prepared by heat treatment The microstructural features were carefully characterized using two different experimental surface microscopy techniques; Light Optical Microscope and Scanning Electron Microscope. The deformation and hardness characteristics have been studied with the help of tensile and hardness tests. The mechanical properties were determined as a function of microstructure (grain size and phase). The yield stress followed the classical Hall-Petch relation. The results indicated that tensile strength and hardness increases with decrease in grain size while elongation decreases. The main philosophy behind this research has been the study of the microstructure and information from the iron-carbon phase diagram together with numerical analysis of stress-strain data, in order, to understand the influence of grain size on mechanical behaviour of EN8 steel. This combination was then used to make general conclusions on mechanical behaviour of EN 8 based on heat treatment history.
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Baum, Elyse Jeannette Weinhold Paul S. "Characterizing the effects of prostaglandin E2 on tendon mechanical properties." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1199.
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Thesis (M.S.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Mar. 26, 2008). "... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Biomedical Engineering." Discipline: Biomedical Engineering; Department/School: Medicine. On title page, 2 appears as subscript.
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De, Jesús Aribet M. "Effects of mechanical stimulation on fibroblast-guided microstructural and compositional remodeling." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/3068.
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Many physiological and pathological processes, such as wound healing and tissue remodeling, are heavily influenced by continuous mechanical cell-cell and cell-ECM communication. Abnormalities that may compromise the biomechanical communication between the cells and the ECM can have significant repercussions on these physiological and pathological processes. The state of the mechanical environment and the reciprocal communication of mechanical signals between the ECM and the cell during wound healing and aged dermal tissue regeneration may be key in controlling the quality of the structure and physical properties of regenerated tissue.
This dissertation encompasses a series of studies developed for characterizing the effects of mechanical cues on altering and controlling tissue remodeling, and regeneration in the context of controlling scar formation during wound healing, and the maintenance and regeneration of the dermal extracellular matrix (ECM) during aging. In order to achieve this goal, in vitro models that contained some features of the provisional ECM, and the ECM of the dermis were developed and subjected to an array of quantifiable mechanical cues. Wound models were studied with different mechanical boundary conditions, and found to exhibit differences in initial short-term structural remodeling that lead to significant differences in the long-term synthesis of collagen after four weeks in culture. Dermal models seeded with fibroblasts from individuals of different ages were treated with a hyaluronic acid (HA)-based dermal filler. Changes in the mechanical environment of the dermal models caused by swelling of the hydrophilc HA, resulted in changes in the expression of mechanosensitive, and ECM remodeling genes, essential for the maintenance and regeneration of dermal tissue. Taken together, these data provide new insights on the role of mechanical signals in directing tissue remodeling.
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Zanker, Matthew John. "Real gas effects in heated gas inflators." Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/768.
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Currently, almost all new vehicles are equipped with airbags. A common type of airbag inflator is the Heated Gas Inflator (HGI). These inflators are cylindrical shaped canisters that are filled to very high pressures with a gaseous mixture of fuel and air. The mixture is ignited from one or both ends of the cylinder. The resulting high temperatures from combustion heats the excess air, which is then used to inflate the airbag. Once the mixture is ignited, large pressure waves form, traveling along the length of the tube. These waves, inherent to the design of the inflator, do not allow the use of a volume averaged assumption for the combustion chamber. Therefore, it is necessary to use a Computational Fluid Dynamics (CFD) code to model the dynamic nature of the inflator. Commercial CFD codes are readily available that could be used to model the HGI. These codes use the Ideal Gas Law to calculate the properties of the mixture. The high pressures in an HGI do allow for the use of an ideal gas assumption. Instead, a Real Gas equation of state must be used.
An existing Airbag Inflator Model that was capable of Real Gas equation of state calculations had been previously created to simulate solid propellant inflators. In order to properly model the wave dynamics in an HGI and include Real Gas calculations, a CFD model has been added to the Airbag Inflator Model. The CFD model must be capable of handling multiple species of gases and be able to properly model the sharp gradients associated with large pressure waves and changes in chemical species. Therefore, a high-resolution shock capturing technique is used to handle the homogeneous part of the governing equations. The non-homogeneous terms of the governing equations are solved using an ordinary differential equations solver. In order to combine the solutions, a time splitting technique is used to combine the solutions from the homogeneous and non-homogeneous parts of the governing equations.
The addition of the CFD model to an Airbag Inflator Model with Real Gas equation of state capabilities provides a very useful tool in the design of HGIs. The model can be used to ensure that a design does not produce unexpected large magnitude pressure waves that could possibly cause dangerous mechanical failures. Later models of HGIs have ignitors at each end of the cylinder. The secondary ignitor can be delayed to vary the production rate of the exhaust gasses, depending on the severity of the crash. This time delay is an additional parameter that can have an effect on the wave dynamics in the HGI. The addition of the CFD model to the Airbag Inflator Model provides a fast and economical way to predict the outcome of any change in the design parameters of an HGI.
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Wartella, Karin. "Effect of Mechanical Stimulation on Mesenchymal Stem Cell Seeded Cartilage Constructs." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2231.
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Cartilage tissue engineered constructs using mesenchymal stem cells were stimulated with 3 different stimulation algorithms to achieve characteristics mimicking the superficial tangential zone of articular cartilage. The stimulation algorithm of both compression and tension without an offset had the best properties out of all the evaluated groups.
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Brindle, Eric Robert. "The effect of treatments on the mechanical properites of Staphylococcus epidermidis biofilms under fluid shear and mechanical indentation." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/brindle/BrindleE1209.pdf.
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Biofilms exist on most every wetted surface both in the natural environment and in industrial and medical settings. The bacterial cells are surrounded by protective extracellular polymeric substances (EPS) which provide the mechanical stability for these biofilms. Little is known about the material properties of attached biofilms, making it difficult to predict how a biofilm will behave in response to an applied force. The work presented here measured the force-deflection characteristics of biofilm by two different techniques. The first method involved time lapse imaging of a biofilm grown in a capillary flow cell reactor under a constant fluid shear stress and the second method was based on micro-indentation using an atomic force microscope. For the flow cell experiments Staphylococcus epidermidis was grown in a capillary flow cell reactor. After a day of growth the biofilms received a pretreatment fluid shear while displacements were measured. The biofilms were then treated with different agents which alter the structure of the EPS matrix and thus change the mechanical properties/response of the biofilm. The four treatments examined in these experiments were FeCl 2, chlorhexidine, DispersinB®, and urea. The same fluid shear was applied after the fifteen minute treatment soak and the deflections were recorded. These measurements revealed that i) biofilms behave viscoelastically ii) FeCl 2 and chlorhexidine made the biofilm stiffer while urea and DispersinB® reduced the viscosity of the biofilm. For the micro-indentation experiments Staphylococcus epidermidis was grown in a drip-flow reactor. After four hours of growth the biofilms received a pretreatment indentation (5 microns depth) in which force-displacements were measured. The biofilms were then treated with FeCl 2, chlorhexidine, DispersinB®, and urea. The 5 microns indentation was applied after the fifteen minute treatment soak and force displacements were again measured. The measurements revealed that again i) biofilms behave viscoelastically ii) FeCl 2 and chlorhexidine made the biofilm stiffer while urea and DispersinB® reduced the viscosity of the biofilm. Quantification of biofilm material properties and demonstration that their properties can be altered by chemical or enzymatic treatments opens the door to development of new technologies for controlling detrimental biofilm based on targeting biofilm cohesion rather than killing microorganisms.
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Deshpande, Jayesh U. "The effect of mechanical mold vibration on the characteristics of aluminum alloys." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-092106-151830/.
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Deceuster, Andrew I. "THE EFFECTS OF LASER ETCHING ON BIOCOMPATABILITY AND MECHANICAL PROPERTIES OF POLYETHERETHERKETONE." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/3085.
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Polyetheretherketone (PEEK) is a Federal and Drug Administration (FDA) approved biomaterial that has been used as an orthopedic implant material due to its inherent properties. Laser etching has become a popular means to create identication markers on the individual implants as required by the FDA. The interaction of laser energy with polymeric materials could potentially cause changes in the material's biocompatibility and mechanical properties. The objective of this study was to determine the effect of laser energy on the biocompatibility and mechanical properties of implantable PEEK by measuring contact angle, micro-tensile testing, nite-element modeling (FEM), and biocompatibility testing according to International Organization for Standardization (ISO) 10993 for cytotoxicity. The results of the study showed that the etching characteristics were mostly in by the laser power and the laser pulse spacing. The mechanical properties were degraded by the laser and the tensile strength of the material was decreased by 50% is some cases. The laser, however, did not affect the biocompatibility. The biocompatibility testing of the material showed no cytotoxic effect using an agar overlay method. The contact angle measurements demonstrated that the laser etching produced a hydrophobic effect to the surface. The FEM model demonstrated a good correlation between the laser power and the vaporization of the PEEK material. The results of the study showed the effect of laser energy on biocompatibility and mechanical properties.
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Cooley, Dane A. "Effects of Reclaimed Asphalt Pavement on Mechanical Properties of Base Materials." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1094.pdf.
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Gales, ShaRolyn. "Effects of Pressurization on Aluminum 319 and A356.2 Alloy Castings." MSSTATE, 2001. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04062001-163331/.
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Castings made of aluminum 319 and A356.2 alloy were examined to determine the effectiveness of using pressure application during solidification to reduce porosity levels. Pyknometry was the method chosen to measure porosity. It was determined that the porosity of castings poured in both alloys was reduced in some instances. During the study, the surfaces of these castings were also examined and some were found to have defects present. After the porosity was evaluated, specimens of castings poured in both alloys were tested to determine whether or not the surface intrusions affected the castings. The defects were found to reduce the strength of the castings poured in aluminum 319. The castings poured in A356.2 did not have surface intrusions or any significant decreases in strength. Therefore it was concluded that of the two alloys tested, A356.2 alloy is most suited for using pressurization as a method of reducing porosity.
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Hastings, William Chad. "CRYOGENIC TEMPERATURE EFFECTS ON THE MECHANICAL PROPERTIES OF CARBON, ARAMID, AND PBO FIBERS." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04032008-203657/.
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This study examines the effects of cryogenic temperatures on the mechanical properties of carbon, aramid, and poly(p-phenylene-2, 6-benzobisoxazole) (PBO) fibers. Although the mechanical properties are documented for these fibers at ambient and elevated temperatures, there is an absence of data in the open literature for how these fibers behave at very low temperatures. To evaluate the mechanical properties, the ASTM standard method for testing at ambient temperature was used as a baseline. The low temperature tests were conducted inside a double walled cryogenic chamber to evaluate the fiber performance at 100K. Fiber properties at low temperatures displayed differences from room temperature properties in the form of increased ultimate tensile strength (UTS), decreased in elongation to failure, and increased Youngs Modulus. The change in properties due to the effect of temperature was more pronounced in fibers with a higher degree of crystallinity.
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Mathis, Rebecca Lynn Pounders. "Effects of Vasoactive Agents on the Mechanical Properties of Aortic Heart Valve Leaflets." MSSTATE, 2006. http://sun.library.msstate.edu/ETD-db/theses/available/etd-08032006-160530/.
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Heart valve disease is currently one of the leading forms of heart disease. Current literature has shown that endothelin I, angiotension II and 5-HT are vasoactive agents which cause concentration dependent contractions in aortic valve leaflet tissue. This study tested the mechanical properties of leaflets cut in the radial direction after they were exposed to the agents at varied concentrations or for 0.5, 6 or 24 hours. The elastic modulus, ultimate tensile strength and the yield strength were calculated. In the time trials the elastic modulus and the ultimate tensile strength both showed a significant increase at 24-hours. However, there were no significant differences found between the concentrations. Indicating the amount of vasoactive agent is not as significant as the length of exposure.
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Decker, Gifford Zach. "Modeling the Mechanical Effects of Liquid Mediated Adhesion Between the Human Vocal Folds." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/501.
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The vocal folds are a complex self-oscillating biological system. In the current research, an equation was developed to model viscous adhesion forces that occur when the collision of the vocal folds results in the formation of a liquid bridge. The adhesion equation was validated using experimental data, and simplified to a one-dimensional approximation with an included correction factor that adjusted the predicted pressure in situations where the one-dimensional approximation was invalid. A non-oscillating vocal fold model with a modeled liquid bridge was used to study stress resulting from viscous adhesion. The vertical normal stress magnitude ranged from about 80 to 1700 Pa. This was shown to be of the same order of magnitude as the stress due to collision of the vocal folds. Also the stress resulted in large normal strains that occurred at small distances below the surface of the vocal folds consistent with lesion development. Therefore, it was determined that the viscous adhesion may be a contributor to damage of the vocal folds that leads to the development of benign lesions, such as vocal nodules. This conclusion was further validated by adding the adhesion equation in a self-oscillating vocal fold model. The influence of adhesion on the dynamics of the model was significant. The frequency of vibration was reduced by nearly 2.5% for the case of adhesion with a mucus viscosity of 0.01 Pa-s. Also adhesion induced positive tensile stress that resulted in normal strain distributions similar to those seen in the non-oscillating cases. These results also indicated that liquid mediated viscous adhesion may be a contributor to the development of benign lesions (nodules). However, further research is needed to validate these conclusions.
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Li, Xuan. "Hydrogen Effects on X80 Steel Mechanical Properties Measured by Tensile and Impact Testing." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6110.
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The effect of hydrogen charging current density and tensile strain rate on the mechanical properties of X80 pipeline steel were investigated by slow strain rate test (SSRT), Charpy impact test, and scanning electron microscopy (SEM) in this thesis. The results show that both the ultimate tensile strength and elongation to failure of X80 steel were deteriorated significantly after charging with hydrogen. With a strain rate of 5 x 10-5 s-1, the relative tensile strength and plasticity loss of X80 steel had no significant change within the range of assumed hydrogen partial pressures at room temperature. At room temperature, X80 steel had no apparent variation in ultimate tensile strength and elongation, except at the strain rate of 10-6 s-1. Specimens obtained the greatest relative tensile strength loss and plasticity loss when strained at 10-6 s-1 with a current density of 4.6 mA/cm2. The fracture morphology of two test groups of X80 steel exhibited significant brittle rupture when tested with dynamic hydrogen charging. The impact energy of X80 was not affected by hydrogen charging. Different current density also had no influence on the results of the impact test.
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Xia, Zichao. "Effect of neutron radiation on the mechanical properties of B4C." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5087.
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B4C is an important engineering ceramic used in a number of different applications. One of the promising applications of B4C is in the nuclear industry. B4C has a high neutron absorption cross-section (600 barns) and that is why it can absorb neutrons without forming long lived radio nuclides. As a result, B4C is extensively used as control rods, shielding material and as neutron detectors in nuclear reactors.
During the reactor’s operation, the B4C undergoes severe neutron radiation and defects, such as vacancies and helium bubbles, are generated in the structure. These defects are responsible for the degradation of mechanical performance of B4C and can make this material unsuitable for further exploitation. Therefore, both crystal structure and mechanical properties of B4C were studied before and after radiation, as well as for the case when irradiated by neutrons B4C samples has been annealed in order to heal the defects introduced by the radiation. Fully dense B4C ceramics were produced by hot pressing at 2100ºC, 30MPa, and 45 minutes dwell time. 120 small bars of 2×2.5×25mm were machined according to the MOR bar standard. 40 bars after machining were tested as they were, 80 bars were irradiated with neutrons in neutron source for 3.5 months. 40 out of the 80 irradiated bars were annealed at 400ºC for 1 hour with an attempt to heal the defects possibly introduced by the irradiation.
4-point bending strength, SEVNB fracture toughness, and Vickers hardness have been measured on as received B4C, B4C after radiation, and B4C after radiation and annealing. The Weibull parameters were determined for each set of the conditions. The fracture surfaces of the B4C samples before and after radiation as well as after radiation and annealing have also been analyzed using SEM. X-ray diffractometer was used to collect diffraction pattern of the B4C, and Raman spectrometer was used to evaluate the vibrational response of B4C. Thus the effect of neutron radiation and annealing on the mechanical performance and structure of B4C has been analyzed.ID: 029809317; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.)--University of Central Florida, 2011.; Includes bibliographical references (p. 94-107).
M.S.
Masters
Mechanical, Materials, and Aerospace Engineering
Engineering and Computer Science
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Udas, Amit. "Road variability and its effect on vehicle dynamics simulation." Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/1097.
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In the modern age, computer aided engineering software is used in nearly every engineering design application. In this thesis, a multibody dynamics vehicle model in LMS Virtual.Lab simulation platform was updated. The updates included measured hardpoint data of the vehicle studied, addition of two differential gear models to the vehicle drivetrain, and implementation of a multibody dynamics model of a trailer that is attached to the vehicle. To extend the length of the experimentally acquired road profile, a distribution function based methodology was developed to create road profile from the limited road data. The road parameter generated from the distribution function was used to recreate a road profile statistically representative of acquired road profile data. The updated vehicle dynamics model was validated by comparing the simulation results to the vehicle dynamics test results conducted at the Nevada Automotive Test Center. To validate the methodology for creating the road profile, vehicle dynamics simulation results with the distribution function generated road profile were compared to the results from the acquired road profile. The effects of road variability on the vehicle dynamics simulation were also examined. By using a Gamma distribution to define the road roughness, a sensitivity analysis was conducted to study how the variation in road roughness affects the vertical, longitudinal and lateral accelerations at the driver's location. The results show that the RMS values of the acceleration increase linearly with increasing mean roughness for variance up to ±30% and a quadratic response for variance up to ±100%.
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Downie, Brian. "Effect of moisture and temperature on the mechanical properties of concrete." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4240.
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Thesis (Ph. D.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains viii, 112 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 93-95).
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Pinn, Jarred Michael. "Effect of End-Plate Tabs on Drag Reduction of a 3D Bluff Body with a Blunt Base." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/698.
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This thesis involves the experimental testing of a bluff body with a blunt base to evaluate the effectiveness of end-plate tabs in reducing drag. The bluff body is fitted with interchangeable end plates; one plate is flush with the rest of the exterior and the other plate has small tabs protruding perpendicularly into the flow. The body is tested in the Cal Poly 3ft x 4ft low speed wind tunnel. Testing is conducted in three phases.
The first phase was the hot-wire measurement of streamwise velocity of the near wake behind the bluff body. An IFA300 thermal anemometry system with a hot-wire probe placed behind the model measures the wake velocity fluctuations. The power spectral density on the model without tabs shows large spikes at Strouhal numbers of 0.266, 0.300, and 0.287 at corresponding Re = 41,400, 82,800, 124,200 where vortex shedding occurs. The model with tabs shows no such peaks in power and therefore has attenuated vortex generation in the wake flow at that location.
The second phase of testing was pressure testing the model through the use of pressure ports on the exterior of the bluff body. A Scanivalve pressure transducer measured multiple ports almost simultaneously through tubing that was connected to the model internally and routed through the model’s strut mount and outside of the wind tunnel. This pressure testing shows that the model with tabs is able to achieve up to 36% increase in Cp at Reh = 41,400 on the base region of the bluff body and no negative pressure spikes that occur as a result of vortex shedding.
The last phase of testing is the measurement of total drag on the model through a sting balance mount. This testing shows that the drag on the model is reduced by 14% at Re = 41,400. However it also shows that as velocity increased, the drag reduction is reduced and ultimately negated at Re = 124,200 with no drag loss at all.
The addition of tabs as a passive flow control device did eliminate vortex shedding and alter the base pressure of the bluff body. This particular model however showed no reduction in total drag on the model at high Reynolds numbers higher than 124,000. Further study is necessary to isolate the exact geometry and flow velocities that should be able to produce more favorable drag results for a bluff body with this type of passive flow control device.
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Datye, Amit Vijaykumar. "Elasto-plastic analysis of stents : texture and grainsize effects on radial strength." FIU Digital Commons, 2003. http://digitalcommons.fiu.edu/etd/2739.
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A nonlinear finite element analysis of a stent was performed using ABAQUS® to analyze the elasto-plastic behavior during crimping and deploying of the stent and the effects of material properties on various characteristics like radial strength, recoil and foreshortening. Geomteric and material non-linearities are considered since the crimping and deployment of the stent involves large deformations. The stent is meshed using solid elements brick, wedge and tetrahedral elements to model the stent. An elastic-plastic material model described by von Mises-Hill constitutive model is considered due to the plastic deformations involved.
An entirely new stent was designed and analyzed. Characteristics of the stent like stress concentrations, the elastic recoil and the longitudinal foreshortening after crimping and expansion were computed. The width of the strut of the stent is very small and therefore the grainsize of the material also plays an important part in the radial strength of the stent. Single crystal elastic constants were used to model the grainsize effect on the radial strength of the stent. The effects of changes in grain orientation on the radial strength of the stent were analyzed. The effects of the deployment diameter and the strut thickness on the radial strength of the stent were also analyzed. The data obtained from the finite element analysis was also used to calculate the theoretical fatigue life of the stent.
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Jordon, James Brian. "DAMAGE AND STRESS STATE INFLUENCE ON BAUSCHINGER EFFECT IN ALUMINUM ALLOYS." MSSTATE, 2006. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04172006-133053/.
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In this work, the Bauschinger effect is shown to be intimately tied not only to plasticity but to damage as well. The plasticity-damage effect on the Bauschinger effect is demonstrated by employing different definitions (Bauschinger Stress Parameter, Bauschinger Effect Parameter, the Ratio of Forward-to-Reverse Yield, and the Ratio of Kinematic-to-Isotropic Hardening) for two differently processed aluminum alloys (rolled and cast) in which specimens were tested to different prestrain levels under tension and compression. Damage progression from second phase particles and inclusions that were generally equiaxed for the cast A356-T6 aluminum alloy and elongated for the rolled 7075 aluminum alloy was quantified from interrupted experiments. Observations showed that the Bauschinger effect had larger values for compression prestrains when compared to tension. The Bauschinger effect was also found to be a function of damage to particles/inclusions, dislocation/particle interaction, the work hardening rate, and the Bauschinger effect definition.
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Wang, Yanli. "Effect of reduction treatment on microstructure and mechanical properties of fluorite oxides." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0017364.
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Abiade, Jeremiah Terrell. "Characterization of the chemical effects of ceria slurries for dielectric chemical mechanical polishing." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008394.
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Guo, Guannan. "Aluminum microstructure evolution and effects on mechanical properties in quenching and aging process." Digital WPI, 2017. https://digitalcommons.wpi.edu/etd-dissertations/334.
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"High strength aluminum alloys are recently widely used in aircraft, automobile and construction industry fields. Typical T6 heat treatment process can be applied to improve the heat treatable aluminum alloy in order to facilitate the formation of prime strengthening precipitate phases. Critical steps in T6 heat treatment process include solution treatment, quenching and aging. Due to high thermal gradients in quenching process and aging process, large thermal stress will remain in the matrix and may bring unexpected deformation or distortion in further machining. Therefore, in order to predict the thermal stress effects, constitutive model and precipitate hardening model are needed to simulate the mechanical properties of alloy. In this dissertation, an optimized constitutive model, which is used to describe the mechanical behavior during quenching and intermediate period of quenching and aging process, was given based on constitutive models with Zenor-Holloman parameter. Modification for constitutive model is based on the microstructure model, which is developed for the quenching and aging processes. Quench factor analysis method was applied to describe the microstructure evolution and volume fraction of primary precipitate phases during quenching process. Some experimental phenomena are discussed and explained by precipitate distributions. Classical precipitate hardening models were reviewed and two models were selected for Al-Cu-Mn alloy aging treatment. Thermal growth model and Euler algorithm were used to improve the accuracy and the selected precipitate hardening models were validated by yield stress and microstructure observations of Al-Cu-Mn aging response experiments."
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Faria, Maria Cândida Magalhães de. "Avaliação do efeito higrotérmico nas propriedades mecânicas de compósitos de PPS/fibras contínuas /." Guaratinguetá : [s.n.], 2008. http://hdl.handle.net/11449/99284.
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Resumo: O contínuo crescimento na utilização de compósitos termoplásticos em componentes estruturais na indústria aeroespacial deve-se, primordialmente, à flexibilidade de projeto, excelência de suas propriedades mecânicas e baixa massa específica, aliadas aos elevados valores de resistência mecânica e rigidez e baixa incidência de corrosão, atendendo aos severos requisitos de desempenho dessas estruturas quando em serviço. No entanto, componentes que requerem exigências estruturais, quando expostos a ambientes agressivos como elevada temperatura e umidade, podem ter suas propriedades mecânicas sensibilizadas por esses fatores ambientais, e devem ser cuidadosamente avaliados antes de serem colocados em serviço. Sendo assim, o objetivo deste trabalho é avaliar a influência do condicionamento higrotérmico (câmara climática e imersão em banho termostatizado) nas propriedades mecânicas (resistências à tração, fadiga e cisalhamento) e viscoelásticas de laminados PPS/Carbono e PPS/Vidro. Os laminados utilizados neste trabalho foram fornecidos pela empresa holandesa TenCate. Os resultados mostram que os laminados condicionados em câmara climática apresentaram absorção de umidade segundo as leis de Fick, entretanto, os laminados de PPS/Vidro submetidos ao condicionamento por imersão em banho termostatizado apresentaram um comportamento anômalo. Associado a estes resultados foi também observado que os laminados condicionados tiveram um decréscimo no valor de suas resistências ao cisalhamento, entretanto, apresentaram um aumento nos valores de temperatura de transição vítrea e resistência à tração. Os resultados obtidos a partir dos ensaios de fadiga praticamente não sofreram alteração com o condicionamento ambiental. A partir dos resultados obtidos neste trabalho, pode ser concluído que a utilização de laminados de PPS/Carbono e PPS/Vidro em aplicações... (Resumo completo, clicar acesso eletrônico abaixo)Abstract: The continuous use of thermoplastic composites in structural components of aerospace industry is due to essentially to the project flexibility, good mechanical properties and low specific mass, allied with elevated values of mechanical strength and rigidity and low corrosion incidence, attempted to severe requirements of these structures in service. However, components that require structural demand, when exposed in aggressive atmosphere such as high temperature and moisture, can have mechanical properties sensibility for these factors, and should be carefully studied before to be available in service. This way, the purpose of this work is to evaluate the hygrothermal conditioning influence (by using hygrothermal chamber and thermostatic bath immersion) on the mechanical properties (tensile strength fatigue and interlaminar shear) and on the viscoelastic behavior of PPS/carbon and PPS/glass laminates. The laminates used in this work were supplied by TenCate Dutch Company. The results obtained shows that conditioning laminates in hygrothermal chamber presented moisture absorption according to the Fick‟s law, however, the PPS/glass laminates submitted to thermostatic bath immersion presented a anomalous behavior. Associated to these results, it was also observed that the conditioned laminates had a decrease of shear strength values, however, presented an increase of glass transition temperature and tensile strength values. Results obtained according to fatigue tests practically do not change with the atmosphere conditioning. According to the results obtained in this work can be concluded that the use of thermoplastic laminates in aerospace applications is viable, because these laminates are less susceptible to atmosphere effect problems.
Orientador: Edson Cochieri Botelho
Coorientador: Maria Odila Hilário Cioffi
Banca: Herman Jacobus C. Voorwald
Banca: Mirabel Cerqueira Rezende
Mestre
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Zheng, Jie. "Effects of capillarity on the mechanical stability of small-scale interfaces." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-11212004-180952/unrestricted/zheng%5Fjie%5F200412%5Fphd.pdf.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2005.J. Carson Meredith, Committee Member ; J. Carlos Santamarina, Committee Member ; G. Paul Neitzel, Committee Member ; Richard F. Salant, Committee Member ; Jeffrey L. Streator, Committee Chair. Includes bibliographical references.
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Engineer, Hoshang K. "Mathematical modeling of platelet deposition in arterial stenosis with major emphasis on fluid flow effects." FIU Digital Commons, 1999. http://digitalcommons.fiu.edu/etd/3144.
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The intention of this study is to develop a numerical model that depicts flow and platelet behavior in a coronary stenosis, which contribute towards thrombosis, leading to possible embolism and sudden death. The model is intended to be the first step in applying a realistic approach to predict platelet behavior due to existing flow conditions. Using a 2-D axisymmetric geometry a two-phase turbulent flow is solved using statistically assigned variable boundary conditions at the wall. Platelets are released into the flow (Re = 300) and their convective transport is governed through turbulent modeling (to account for randomness) while their aggregation at the wall is dependent on the level of shear stress present throughout the boundary surface, Flow effects such as separation, reattachment, recirculation are emphasized in the model. Monte Carlo-type simulations indicate axial dependence of platelet-to-wall deposition by plotting normalized platelet densities (NPD) along with convergence criteria of the model results. A probability of particle occurance (Poccur) at a given wall section is statistically incorporated to assign B.C's. It was concluded from the model results that the particle insertion points and particle density offset the NPD distribution from the expected profile which was seen in some of the previous studies. Wall shear stresses as high as 123 dyne/cm2 and as low as 0.65 dyne/cm2 are documented by the model. The point of highest shear (at the neck) was not the point of lowest NPD due to particle insertion points in the recirculation zone distal to the neck.
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DeZego, Shawn Edward. "Experimental investigation of convective effects during solidification of a binary system in the continuous cast." FIU Digital Commons, 1996. http://digitalcommons.fiu.edu/etd/2789.
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A laboratory scale continuous casting facility is constructed to experimentally study the solidification of a binary system. Both initial and boundary conditions are varied in a parametric analysis to determine effects that these conditions have on convective transport in the critical liquid region of the continuous cast. A transparent Ammonium-Chloride and Water (NH4Cl-H20) solution is used to simulate cubic alloy solidification due to its dendritic microstructure. A hybrid Schlieren system is constructed to perform flow visualizations of heat and species transport for both eutectic and noneutectic solidification. Thermal and solutal profiles are measured via thermocouple grids and a multisensor fiber optic machine. Morphology images are also captured to serve as a photographic record of the two-phase region width along with tracking of the solidus and liquidus interfaces with respect to the mold walls. This data is used to substantiate origins and causes of defects known as macrosegregation in final casts.
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Yilmaz, Halil. "Mechanical properties of body-centred cubic nanopillars." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/mechanical-properties-of-bodycentred-cubic-nanopillars(ccb1efd0-30f2-4988-9af3-c8646257d826).html.
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Understanding the mechanical properties and deformation characteristics of nanoscale metallic nanopillars and wires is a significant concern for designing reliable small devices that must resist loads in service. This thesis aims to extend understanding of the size dependent behaviour of nanopillars and wires in compression and tension by investigating their mechanical properties and deformation characteristics. Single crystal bcc pillars were fabricated by focussed ion beam (FIB) machining from Fe, Nb, V, Ta, Mo, W and Cr, as well as the ferrite (bcc) and austenite (fcc) components of a duplex stainless steel (DSS). These were tested in compression over a range of test temperatures from 193 K to 393 K using various types of nanomechanical devices. The effect of sample size (pillar diameter) on the strength was investigated and found to increase with decreasing pillar size. In bcc metals, the yield or flow stress, 􀀂􀀖, is inversely proportional with some power of the pillar diameter, d. In bcc metals tested, the power-law exponent, n, were found in the range of between -0.23 to -0.63, showing a less pronounced size effect than found for fcc pillars. The power-law exponent for bcc pillar deformation is also temperature dependent and was found to scale with the ratio of test temperature, Ttest to the critical temperature for screw dislocation mobility, Tc, of the bcc metal (T*= Ttest / Tc). It is notable that the size effect exponent weakens (approaches 0) as T* decreases. However, when the experiments are carried out at temperatures close to or just above Tc, the power-law exponents approaches the value reported in the literature for a range of fcc metals (-1 < n < -0.6). The variation in the power-law exponent observed for bcc metals can be explained by the change in mobility of thermally activated screw dislocations. Their mobility can be modelled by a threshold or lattice friction stress. If this friction stress is introduced into the empirical equation that relates the strength of fcc metal pillars to their diameter, a strong correlation between size effect exponent, the normalised test temperature (T*) and friction stress is obtained. It was found that the friction stress values (Fe, Nb and V) increase as Ttest decreases from 296 to 193 K. When the pillar diameter decreases, the friction stress would be more easily overcome due to the increase in surface-to-volume ratio. The contribution of lattice friction stress on the strength is higher at larger pillars than those for nanopillars. Thus, the divergence between best fit lines has become more apparent at micron-sized pillars, resulting in weaker size effects. Furthermore, the transition in deformation morphology from localized to wavy deformation was only found in Fe pillars, as the Ttest decreased from 296 to 193 K, further revealing that temperature has also strong influence on deformation behaviours of bcc pillars.
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Erazo, Fabio Ivan. "Effect of different drill bit geometries on the stability of the drilling process." FIU Digital Commons, 2004. http://digitalcommons.fiu.edu/etd/3241.
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The purpose of this study was to determine the effects of different drill bit geometries on the stability of the drilling process, based on a torsional-axial coupling model. Parameters such as number of cutting edges, helix angle and length were varied for this purpose.
The analysis was performed using a mathematical model, where the coefficients of the model were obtained experimentally by calculating the cutting forces and using modal analysis. This provided stability lobes for the four types of drill bits used, where free chatter zones were identified. These results, in conjunction with simulations performed in Matlab®, were used to run drilling experiments and validate the model. The results of this study showed that increasing the number of cutting edges or the helix angle, allowed increments in the removal rate of material. On the other hand, increasing the drill bit length has the opposite effect and reduces the removal rate of material. The model was successful predicting axial vibrations close to the blimit.
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Li, Zehao. "Quantum Mechanics on the Möbius Ring." Digital WPI, 2013. https://digitalcommons.wpi.edu/etd-theses/186.
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Recent advances in the chemical vapor deposition method of growing graphene sheets suggest that graphene rings can grow. We may anticipate that chemical methods can be developed to construct twisted nano-ribbons to form Möbius structures in the very near future. I investigated the quantum mechanics of an electron constrained to motion on a nanoscale Möbius ring by solving the Schrdinger equation on the curved surface. The close analogy between ordinary cylindrical rings and Möbius rings is displayed by the closeness of their energy spectra. The expectation values for the angular momentum component L_z are shown to be close, but not exactly equal, to integral or half-integral multiples of hbar. The half-integer angular momentum states are present only for the nontrivial topology of Möbius rings. The effect of the curvature of the Möbius rings manifests itself in the level splitting. This can be understood in terms of representations of the discrete rotational groups C_nv. The nonzero variance of L_z will allow weak transitions between integral and half-integral angular momentum states, while preserving the unit angular momentum for photons. Again, since the topology of the system is critical for the Aharonov-Bohm effect, I investigated the AB effect on Möbius rings and found a remarkable pattern in transmission through finite-width 2D ring structures with finite-width input and output contacts attached at the periphery. The periodicity in the magnetic flux, in units of h/e, is weakly broken on 2D rings of finite width. The unusual states with half-integer values of observed on Möbius rings, investigated earlier, display a different characteristic in transmission. In view of the fascinating properties displayed by the non-trivial topology in terms of its novel two-dimensional physics, we expect that the properties of carriers on the Möbius ring that we have presented here will be relevant for practical applications.
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Decker, Gifford Z. "Modeling the mechanical effects of liquid mediated adhesion between the human vocal folds /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1472.pdf.
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Rahman, Muhammad Ziaur. "Mechanical Performance of Natural / Natural Fiber Reinforced Hybrid Composite Materials Using Finite Element Method Based Micromechanics and Experiments." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6482.
Full textAbstract:
A micromechanical analysis of the representative volume element (RVE) of a unidirectional flax/jute fiber reinforced epoxy composite is performed using finite element analysis (FEA). To do so, first effective mechanical properties of flax fiber and jute fiber are evaluated numerically and then used in evaluating the effective properties of ax/jute/epoxy hybrid composite. Mechanics of Structure Genome (MSG), a new homogenization tool developed in Purdue University, is used to calculate the homogenized effective properties. Numerical results are compared with analytical solution based on rule of mixture, Halpin-Tsai as well as Tsai-Hahn equations. The effect of the volume fraction of the two different fibers is studied. Mechanical performance of hybrid composite is compared with the mechanical performance of single fiber composites. Synergistic effect due to hybridization is studied using analytical method given in literature, finite element method based MSG and Classical Lamination Theory (CLT). It is found that, when Poisson ratio is taken into consideration, elastic modulus shows synergy due to hybridization. Finally, impact properties of ax/jute/epoxy hybrid composite material are studied using Charpy impact testing.
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Exime, Ana S. "Effect of Ultrasonic Treatment on the microstructure and mechanical properties of Al6061 and composite." FIU Digital Commons, 2017. https://digitalcommons.fiu.edu/etd/3534.
Full textAbstract:
In this study, the effect of ultrasonic treatment (UST) parameters such as amplitude, sonication time, and melt temperature on microstructure and microhardness of Al 6061 alloy is evaluated. The effect of UST on the dispersion of tungsten disulfide (WS2) and carbon nanotubes (CNT) as reinforcement particles in Al 6061 during casting is also studied. The cast Al 6061 with UST demonstrated 32% grain size reduction and 8% increase in the microhardness for optimum processing conditions. The cavitation process induced by UST is responsible for the refinement in microstructure and increase of hardness by enhancing the degassing and nucleation process. UST treated 6061 Al alloy demonstrated Hall-Petch relationship for all processing conditions. The UST process also aids in excellent dispersion of WS2 and CNT as reinforcement particles. UST treated WS2 and CNT reinforced Al 6061 composites displayed improved wear resistance as compared to samples without cavitation.