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The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 71 to 80 of 81 (0.019 seconds)| 71 |
Výroba tělesa pro klíčový zámek / Body manufacture of a key lockLeden, Pavel January 2011 (has links)
The diploma thesis is focused on the production of body for cylinder locks. This is production of very small and accurate parts. In the first part there is described the function of the lock, the sort of cylinder locks, their components and the basic types of safety elements. The second part is focused on the production of given type of body. The thesis deals with either existing production technology or proposals of possible innovation. This firstly consists in new organization of manufacturing operations. At the close we can find comparison of existing technology and new proposal.
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3D Printed Customized Tooling Development ApproachThawaba, Sami January 2021 (has links)
3D printing technologies have been gaining a lot of popularity in the last fifteen years, technologies like Fused Deposition Modeling (FDM) 3D printing have never been as accessible as they are today, and with the introduction of the desktop 3D printer, the technology is becoming a mainstream tool for developing prototypes and direct part production from a Computer-Aided Design (CAD) file. In an industrial context, the technology is utilized for different purposes, among which is the development and production of customized and task-specific tools. The proposed work in this thesis is an approach to simplify and streamline the development process of customized production tooling and workstation. The approach was used to identify problems and improvement opportunities at a production facility that delivered IT products. Furthermore, the Technical framework included in the proposed approach provided a guiding path to follow for the prototype development of tools to address identified problems. Developed tools and proposed solutions positively affected the production line work procedure and were accepted and adopted. While other solutions required further exploration and iterative cycles as some reluctance was experienced hence it implied changes in the workflow and daily routines.
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Capturing JUnit Behavior into Static Programs : Static Testing FrameworkSiddiqui, Asher January 2010 (has links)
<p>In this research paper, it evaluates the benefits achievable from static testing framework by analyzing and transforming the <em>JUnit3.8 </em>source code and static execution of transformed code. Static structure enables us to analyze the code statically during creation and execution of test cases. The concept of research is by now well established in static analysis and testing development. The research approach is also increasingly affecting the static testing process and such research oriented work has proved particularly valuable for those of us who want to understand the reflective behavior of <em>JUnit3.8 Framework</em>.</p><p><em> JUnit3.8 Framework</em> uses <em>Java Reflection API</em> to invoke core functionality (test cases creation and execution) dynamically. However, <em>Java Reflection API</em> allows developers to access and modify structure and behavior of a program. Reflection provides flexible solution for creating test cases and controlling the execution of test cases. Java reflection helps to encapsulate test cases in a single object representing the test suite. It also helps to associate each test method with a test object. Where reflection is a powerful tool to perform potential operations, on the other hand, it limits static analysis. Static analysis tools often cannot work effectively with reflection.</p><p>In order to avoid the reflection, <em>Static Testing Framework</em> provides a static platform to analyze the <em>JUnit3.8</em> source code and transform it into non-reflective version that emulates the dynamic behavior of <em>JUnit3.8</em>. The transformed source code has possible leverage to replace reflection with static code and does same things in an execution environment of <em>Static Testing Framework</em> that reflection does in <em>JUnit3.8</em>. More besides, the transformed code also enables execution environment of <em>Static Testing Framework</em> to run test methods statically. In order to measure the degree of efficiency, the implemented tool is evaluated. The evaluation of <em>Static Testing Framework</em> draws results for different Java projects and these statistical data is compared with <em>JUnit3.8</em> results to measure the effectiveness of <em>Static Testing Framework</em>. As a result of evaluation, <em>STF</em> can be used for static creation and execution of test cases up to <em>JUnit3.8</em> where test cases are not creating within a test class and where real definition of constructors is not required. These problems can be dealt as future work by introducing a middle layer to execute test fixtures for each test method and by generating test classes as per real definition of constructors.</p>
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Contribution à l'identification de nouveaux indicateurs de défaillance des modules de puissance à IGBT / Contribution to the identification of new failure indicators for power assemblyBelmehdi, Yassine 04 May 2011 (has links)
L’électronique de puissance a un rôle de plus en plus grandissant dans les systèmes de transports : voitures électriques et hybrides, trains et avions. Pour ces applications, la sécurité est un point critique et par conséquent la fiabilité du système de puissance doit être optimisée. La connaissance du temps de fonctionnement avant défaillance est une donnée recherchée par les concepteurs de ces systèmes. Dans cette optique, un indicateur de défaillance précoce permettrait de prédire la défaillance des systèmes avant que celle-ci soit effective. Dans cette thèse, nous nous sommes intéressés à la caractérisation électromécanique des puces de puissance IGBT et MOSFET. L’exploitation de cette caractérisation devrait permettre, à plus long terme, de mettre en évidence un indicateur de l’état mécanique des assemblages de puissance à des fins de fiabilité prédictive. / Power electronics has a role increasingly growing up in transport:electric and hybrid vehicles, trains and aircraft. For these applications, security is a critical point, thus the reliability of the power assembly must be optimized. The knowledge of time to failure is very important information for the designers of these systems. Inthis context, an early failure indicator would predict system failuresbefore it becomes effective. In this thesis, we focused on the electromechanical characterization of power transistors: MOSFET and IGBT. Based on these results this electromechanical characterization should help us in the longer term, to highlight an early failure indicator of the power assembly.
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Capturing JUnit Behavior into Static Programs : Static Testing FrameworkSiddiqui, Asher January 2010 (has links)
In this research paper, it evaluates the benefits achievable from static testing framework by analyzing and transforming the JUnit3.8 source code and static execution of transformed code. Static structure enables us to analyze the code statically during creation and execution of test cases. The concept of research is by now well established in static analysis and testing development. The research approach is also increasingly affecting the static testing process and such research oriented work has proved particularly valuable for those of us who want to understand the reflective behavior of JUnit3.8 Framework. JUnit3.8 Framework uses Java Reflection API to invoke core functionality (test cases creation and execution) dynamically. However, Java Reflection API allows developers to access and modify structure and behavior of a program. Reflection provides flexible solution for creating test cases and controlling the execution of test cases. Java reflection helps to encapsulate test cases in a single object representing the test suite. It also helps to associate each test method with a test object. Where reflection is a powerful tool to perform potential operations, on the other hand, it limits static analysis. Static analysis tools often cannot work effectively with reflection. In order to avoid the reflection, Static Testing Framework provides a static platform to analyze the JUnit3.8 source code and transform it into non-reflective version that emulates the dynamic behavior of JUnit3.8. The transformed source code has possible leverage to replace reflection with static code and does same things in an execution environment of Static Testing Framework that reflection does in JUnit3.8. More besides, the transformed code also enables execution environment of Static Testing Framework to run test methods statically. In order to measure the degree of efficiency, the implemented tool is evaluated. The evaluation of Static Testing Framework draws results for different Java projects and these statistical data is compared with JUnit3.8 results to measure the effectiveness of Static Testing Framework. As a result of evaluation, STF can be used for static creation and execution of test cases up to JUnit3.8 where test cases are not creating within a test class and where real definition of constructors is not required. These problems can be dealt as future work by introducing a middle layer to execute test fixtures for each test method and by generating test classes as per real definition of constructors.
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Konstrukce univerzálního zařízení na dělení pneumatik . / Design of Universal Equipment for Tire CuttingKohoutek, Petr January 2009 (has links)
The main content of of this thesis is a construction design and analysis of a machine for cutting tires. The resulting solution emerges from the design options and the option that meets the best selection criteria is chosen. Then the thesis stops for a while at the choice of cutting technology and tries to exemine its suitability for cutting tires. In its other part there is an attempt to clarify the relevant parts of the machine, where the benefits of three-dimensional views is used. Basic design and check calculations are done in the selected machine parts.
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Global-local Finite Element Fracture Analysis of Curvilinearly Stiffened Panels and Adhesive JointsIslam, Mohammad Majharul 25 July 2012 (has links)
Global-local finite element analyses were used to study the damage tolerance of curvilinearly stiffened panels; fabricated using the modern additive manufacturing process, the so-called unitized structures, and that of adhesive joints. A damage tolerance study of the unitized structures requires cracks to be defined in the vicinity of the critical stress zone. With the damage tolerance study of unitized structures as the focus, responses of curvilinearly stiffened panels to the combined shear and compression loadings were studied for different stiffeners' height. It was observed that the magnitude of the minimum principal stress in the panel was larger than the magnitudes of the maximum principal and von Mises stresses. It was also observed that the critical buckling load factor increased significantly with the increase of stiffeners' height.
To study the damage tolerance of curvilinearly stiffened panels, in the first step, buckling analysis of panels was performed to determine whether panels satisfied the buckling constraint. In the second step, stress distributions of the panel were analyzed to determine the location of the critical stress under the combined shear and compression loadings. Then, the fracture analysis of the curvilinearly stiffened panel with a crack of size 1.45 mm defined at the location of the critical stress, which was the common location with the maximum magnitude of the principal stresses and von Mises stress, was performed under combined shear and tensile loadings. This crack size was used because of the requirement of a sufficiently small crack, if the crack is in the vicinity of any stress raiser. A mesh sensitivity analysis was performed to validate the choice of the mesh density near the crack tip. All analyses were performed using global-local finite element method using MSC. Marc, and global finite element methods using MSC. Marc and ABAQUS. Negligible difference in results and 94% saving in the CPU time was achieved using the global-local finite element method over the global finite element method by using a mesh density of 8.4 element/mm ahead of the crack tip. To study the influence of different loads on basic modes of fracture, the shear and normal (tensile) loads were varied differently. It was observed that the case with the fixed shear load but variable normal loads and the case with the fixed normal load but variable shear loads were Mode-I. Under the maximum combined loading condition, the largest effective stress intensity factor was very smaller than the critical stress intensity factor. Therefore, considering the critical stress intensity factor of the panel with the crack of size 1.45 mm, the design of the stiffened panel was an optimum design satisfying damage tolerance constraints.
To acquire the trends in stress intensity factors for different crack lengths under different loadings, fracture analyses of curvilinearly stiffened panels with different crack lengths were performed by using a global-local finite element method under three different load cases: a) a shear load, b) a normal load, and c) a combined shear and normal loads. It was observed that 85% data storage space and the same amount in CPU time requirement could be saved using global-local finite element method compared to the standard global finite element analysis. It was also observed that the fracture mode in panels with different crack lengths was essentially Mode-I under the normal load case; Mode-II under the shear load case; and again Mode-I under the combined load case. Under the combined loading condition, the largest effective stress intensity factor of the panel with a crack of recommended size, if the crack is not in the vicinity of any stress raiser, was very smaller than the critical stress intensity factor.
This work also includes the performance evaluation of adhesive joints of two different materials. This research was motivated by our experience of an adhesive joint failure on a test-fixture that we used to experimentally validate the design of stiffened panels under a compression-shear load. In the test-fixture, steel tabs were adhesively bonded to an aluminum panel and this adhesive joint debonded before design loads on the test panel were fully applied. Therefore, the requirement of studying behavior of adhesive joints for assembling dissimilar materials was found to be necessary. To determine the failure load responsible for debonding of adhesive joints of two dissimilar materials, stress distributions in adhesive joints of the nonlinear finite element model of the test-fixture were studied under a gradually increasing compression-shear load. Since the design of the combined load test fixture was for transferring the in-plane shear and compression loads to the panel, in-plane loads might have been responsible for the debonding of the steel tabs, which was similar to the results obtained from the nonlinear finite element analysis of the combined load test fixture.
Then, fundamental studies were performed on the three-dimensional finite element models of adhesive lap joints and the Asymmetric Double Cantilever Beam (ADCB) joints for shear and peel deformations subjected to a loading similar to the in-plane loading conditions in the test-fixtures. The analysis was performed using ABAQUS, and the cohesive zone modeling was used to study the debonding growth. It was observed that the stronger adhesive joints could be obtained using the tougher adhesive and thicker adherends. The effect of end constraints on the fracture resistance of the ADCB specimen under compression was also investigated. The numerical observations showed that the delamination for the fixed end ADCB joints was more gradual than for the free end ADCB joints.
Finally, both the crack propagation and the characteristics of adhesive joints were studied using a global-local finite element method. Three cases were studied using the proposed global-local finite element method: a) adhesively bonded Double Cantilever Beam (DCB), b) an adhesive lap joint, and c) a three-point bending test specimen. Using global-local methods, in a crack propagation problem of an adhesively bonded DCB, more than 80% data storage space and more than 65% CPU time requirement could be saved. In the adhesive lap joints, around 70% data storage space and 70% CPU time requirement could be saved using the global-local method. For the three-point bending test specimen case, more than 90% for both data storage space and CPU time requirement could be saved using the global-local method. / Ph. D.
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Bebouing (inaedificatio) in die Suid-Afrikaanse Reg – ’n regsvergelykende studieKnobel, Ina Magdalena 27 October 2016 (has links)
Hierdie proefskrif handel oor aspekte van inaedificatio (bebouing) in die Suid-Afrikaanse, Engelse
en Nederlandse reg. Die klem val op die maatstawwe wat aangewend word om te bepaal of
aanhegting van ‘n roerende saak aan ‘n onroerende saak plaasgevind het.
Die maatstawwe in die drie stelsels toon ooreenkomste en verskille. Een ooreenkoms is dat die
graad en wyse van aanhegting in die Suid-Afrikaanse reg oorweeg word, terwyl daar in die
Engelse reg slegs na die graad van aanhegting gekyk word. In die Nederlandse reg word ’n
duursame verbinding vereis om te bepaal of bestanddeelvorming plaasgevind het, en word gevra
of verwydering van die saak sonder beskadiging kan plaasvind. In die Suid-Afrikaanse reg word
die doel van die aangehegte saak oorweeg, hoewel Innes HR dit nie in MacDonald Ltd v Radin
NO & The Potchefstroom Dairies & Industries Co Ltd so formuleer nie. Die aard van die roerende
saak word in die Suid-Afrikaanse reg oorweeg, terwyl die aard en ontwerp van die roerende saak
in die Nederlandse reg oorweeg word. In die Engelse reg word die doel waarvoor die aanhegting
gemaak is oorweeg om die bedoeling met die aanhegting te bepaal. Die vraag is of die saak vir
die permanente en substansiële verbetering van die gebou (grond) aangeheg is, of vir ’n tydelike
doel of vir die beter benutting van die chattel. Die Nederlandse reg beklemtoon die bestemming
van die aanhegting. Die opvallendste verskil tussen die Suid-Afrikaanse reg en die ander twee
stelsels is die belang van die subjektiewe bedoeling van een of ander betrokkene.
Die regsposisie van huurders wat sake aanheg verskil van dié van ander aanhegters. In al drie
regstelsels kan huurders voor afloop van die huurtermyn sommige aangehegte sake verwyder,
mits die huurgrond in dieselfde toestand gelaat word as waarin dit was voor die aanhegting. Die
drie stelsels vertoon verskille soos dat onsekerheid bestaan oor wie die eienaar van die
aangehegte sake is voor verwydering. In die Engelse reg heg bedryfsaanhegtings en ornamentele
aanhegtings, nie aan nie. Ingevolge die Nederlandse reg is die verhuurder gedurende die
huurtermyn eienaar van die aanhegtings, aangesien aanhegting plaasvind sodra die roerende
sake aan die huurgrond heg. Die Suid-Afrikaanse reg hieroor is onduidelik. / This thesis deals with aspects of inaedificatio (building) in South African, English and Dutch law.
The emphasis falls on the criteria that are applied to determine whether attachment of a movable
to an immovable thing occurred.
The criteria in the three systems show similarities and differences. One similarity is that in South
African law the degree and manner of attachment are considered, while in English law only the
degree of attachment is considered. To determine whether one thing became a component part of
another thing (bestanddeelvorming) a durable connection is required In Dutch law. The question is
whether removal can take place without causing damage. The purpose of the attached thing is
considered in South African law, although Innes CJ did not formulate this criterion in this manner
in MacDonald Ltd v Radin NO & The Potchefstroom Dairies & Industries Co Ltd. The nature of the
movable thing is relevant, while the nature and design of the movable thing are considered in
Dutch law. In English law the purpose of the attachment is considered to determine the intention
with the attachment. The question is whether the thing was attached for the permanent and
substantial improvement of the building (land) or for a temporary purpose or for the better use of
the chattel. The destination (bestemming) of the attachment is considered in Dutch law. The most
significant difference between South African law and the other two systems is the importance of
the subjective intention of some person involved in the situation.
The legal position of lessees who attach movales differs from that of other persons who make
such attachments. In all three legal systems lessees may remove certain attached movables
before the expiry of the term of lease as long as the leased land is left in the same condition that it
was in before the attachment. The three systems also differs for example it is not certain who the
owner of the attached things is before removal of the attachments. In English law trade and
ornamental fixtures do not attach. In Dutch law the lessor is the owner of the attachments during
the term of lease, because attachment takes place when the movable things are fixed to the
leased land. The position in South African law on this is unclear. / Private Law / LL. D.
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ON-MACHINE MEASUREMENT OF WORKPIECE FORM ERRORS IN ULTRAPRECISION MACHININGGomersall, Fiona January 2016 (has links)
Ultraprecision single point diamond turning is required to produce parts with sub-nanometer surface roughness and sub-micrometer surface profiles tolerances. These parts have applications in the optics industry, where tight form accuracy is required while achieving high surface finish quality. Generally, parts can be polished to achieve the desired finish, but then the form accuracy can easily be lost in the process rendering the part unusable.
Currently, most mid to low spatial frequency surface finish errors are inspected offline. This is done by physically removing the workpiece from the machining fixture and mounting the part in a laser interferometer. This action introduces errors in itself through minute differences in the support conditions of the over constrained part on a machine as compared to the mounting conditions used for part measurement. Once removed, the fixture induced stresses and the part’s internal residual stresses relax and change the shape of the generally thin parts machined in these applications. Thereby, the offline inspection provides an erroneous description of the performance of the machine.
This research explores the use of a single, high resolution, capacitance sensor to quickly and qualitatively measure the low to mid spatial frequencies on the workpiece surface, while it is mounted in a fixture on a standard ultraprecision single point diamond turning machine after a standard facing operation. Following initial testing, a strong qualitative correlation exists between the surface profiling on a standard offline system and this online measuring system. Despite environmental effects and the effects of the machine on the measurement system, the capacitive system with some modifications and awareness of its measurement method is a viable option for measuring mid to low spatial frequencies on a workpiece surface mounted on an ultraprecision machine with a resolution of 1nm with an error band of ±5nm with a 20kHz bandwidth. / Thesis / Master of Applied Science (MASc)
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BBT Acoustic Alternative Top Bracing CADD Data Set-NoRev-2022Jun28Hemphill, Bill 22 July 2022 (has links)
This electronic document file set consists of an overview presentation (PDF-formatted) file and companion video (MP4) and CADD files (DWG & DXF) for laser cutting the ETSU-developed alternate top bracing designs and marking templates for the STEM Guitar Project’s BBT (OM-sized) standard acoustic guitar kit. The three (3) alternative BBT top bracing designs in this release are (a) a one-piece base for the standard kit's (Martin-style) bracing, (b) 277 Ladder-style bracing, and (c) an X-braced fan-style bracing similar to traditional European or so-called 'classical' acoustic guitars.
The CADD data set for each of the three (3) top bracing designs includes (a) a nominal 24" x 18" x 3mm (0.118") Baltic birch plywood laser layout of (1) the one-piece base with slots, (2) pre-radiused and pre-scalloped vertical braces with tabs to ensure proper orientation and alignment, and (3) various gages and jigs and (b) a nominal 15" x 20" marking template.
The 'provided as is" CADD data is formatted for use on a Universal Laser Systems (ULS) laser cutter digital (CNC) device. Each CADD drawing is also provided in two (2) formats: Autodesk AutoCAD 2007 .DWG and .DXF R12. Users should modify and adapt the CADD data as required to fit their equipment. This CADD data set is released and distributed under a Creative Commons license; users are also encouraged to make changes o the data and share (with attribution) their designs with the worldwide acoustic guitar building community.
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