• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 25
  • 24
  • 19
  • 6
  • 5
  • 3
  • 3
  • 3
  • 1
  • 1
  • Tagged with
  • 97
  • 19
  • 17
  • 14
  • 13
  • 12
  • 11
  • 10
  • 9
  • 9
  • 9
  • 9
  • 9
  • 8
  • 8
  • About
  • 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.
71

Optimalizace jádra formy na vstřikování plastů / Optimization of core molds for injection molding

Stavárek, Václav January 2019 (has links)
Diplomová práce vznikla ve spolupráci s průmyslovým partnerem, který vyrábí elektrické komponenty pro automobilový průmysl. Tato firma se potýká s problémy často se porušujících jader v některých jejich formách na vstřikování plastů, vyrábějících převážně housingy pro konektory. Firma disponuje licencemi na komerční software pro simulaci injekčního vstřikování Moldflow a Moldex3D a také pro simulaci metodou konečných prvků Ansys. Nejprve jsou shrnuty teoretické poznatky ohledně injekčního vstřikování a jeho simulace, řešení problémů interakce těles s tekutinou a únavy materiálu. Poté je popsán proces stanovení únavové životnosti jádra formy s využitím výše zmíněného softwaru. Proces je vysvětlen na příkladu konkrétní formy ve výrobě této firmy. Je zvolen takový přístup vyhodnocení únavy, který nejvíce odpovídá současné životnosti jader, a ten je pak použit pro analýzu vlivu změny geometrie jádra a parametrů vstřikování. Změny ostatních parametrů, které simulace neumožňuje zahrnout, jsou rovněž navrhnuty a pokud možno odůvodněny jinými způsoby. Jedno z doporučení je přidání zaoblení na obě jádra, což by mohlo prodloužit životnost toho problematičtějšího z nich z 30 dnů na více než 320 dnů. Toto by mohlo znamenat úspory až 10 600 EUR ročně. Další doporučení je změnit způsob obrábění jader a také přidat jejich tepelné zpracování.
72

Měření základních parametrů optických a optoelektronických komponent / Measurement of basic parameters of optical and optoelectronic components

Beneš, Pavel January 2021 (has links)
This diploma thesis deals with optical and optoelecronic components. The first part of the work describes the optical paths and methods of their measurement. The second part describes the coupler, circulator and isolator. Further described is a laser diode, a photodetector and a modulator. The third part describes the measurement procedure of the coupler, circulator, isolator, laser diode, photodetector and modulator. The measured values are compared with the catalog values.
73

Analýza tvorby třísky pomocí digitální vysokorychlostní kamery / Analysis of chip forming mechanism with a high-speed digital camera

Tichý, Vojtěch January 2015 (has links)
This thesis covers matters related to high-speed digital cameras and their usage in various spheres of human activities, mainly in research of chip forming. Thesis summarises important knowledge needed for creation of high-speed recordings and choice of suitable lenses. Focus is taken on creation of high-speed recordings of chip forming process in turning operation outside grooving by using of different types of chipformers. Main goal is to verify its functionality in specific value range of feed per revolution.
74

Textured insert for improved heat extraction in combination with high-pressure cooling in turning of superalloys

Tamil Alagan, Nageswaran January 2017 (has links)
Heat generated in a machining process is a common and critical obstacle faced in today's machining industries. The heat generated in the cutting zone has a direct negative influence on the tool life which, in turn contributes to increase the manufacturing costs. Especially, in machining of Heat Resistant Super Alloys, HRSA this is a very limiting factor. HRSA are capable of retaining their mechanical strength and hardness at elevated temperatures. This property is advantageous in the application in e.g. aero-engines but also a disadvantage, since it also lowers the machinability significantly. This work is an attempt to improve the heat transfer from the cutting zone, which would lead to an increase in the tool life. To achieve this goal, the cutting tool has been modified to create an improved interface between the coolant and tool in the high-temperature areas. Two generations of inserts have been designed and investigated. Firstly, an insert with surface texture features has been created with the purpose of increasing the available surface area for heat dissipation: First generation, Gen I. Secondly, a GenII was designed as a further improvement of Gen I. Here, several channel features on the rake face were added, reaching out from the contact zone to the near proximity of the cutting edge. This with the purpose of improving access of the coolant closer to the cutting edge. The experiments were conducted in facing operations of Alloy 718 with uncoated round carbide inserts. All experiments were carried out with high-pressure coolant assistance, with a pressure of 16 MPa on the rake face and 8 MPa on the flankface, respectively.The two generations of inserts, Gen I and Gen II, were experimentally evaluated by tool wear analysis in comparison with a regular insert. The results shows that the tool life increased significantly for the Gen I insert, compared to a catastrophic failure of the regular insert at the same conditions. Regarding the Gen II insert,an increase in tool life by approximately 30 to 40 percent compared to Gen I insert was observed.
75

Enabling high-fidelity measurements of turbulent boundary layer flow over wing sections in the MTL wind tunnel.

Mallor, Fermin January 2019 (has links)
A reinforced fiber-glass model of a NACA 4412 wing profile is designed and set-up in the Minimum Turbulence Level (MTL) wind tunnel facility at KTH. The model has 65 pressure taps orifices, and the set-up includes two mounting panels designed to allow for particle image velocimetry (PIV) and hot wire anemometry (HWA) measurements of the boundary layer (to be performed in a future campaign). In a first experimental campaign pressure scans are conducted at three angles of attack of interest (5,10 and 12 degrees), and at four different Reynolds numbers based on chord length and inflow velocity (200,000, 400,000, 1,000,000, and 1,640,000). The preliminary results show good agreement with DNS and LES data, however, the effective angle of attack of the wing is affected by the interference of the test section. In order to obtain proper flow conditions for future campaigns inside the test section, wall inserts are designed using 2D k-omega SST simulations. The side-walls are streamlined and the final geometry is corrected to account for the boundary-layer growth over them. The inserts are shown to avoid early separation near the trailing edge at higher angles of attack (10 and 12 degrees), but the 2D simulations fail to capture the aforementioned angle-of-attack issue affecting the pressure distributions. Future extensions of the present insert design should include both 3D simulations of the test-section and a robust optimization procedure to prescribe the resulting pressure distribution. / En NACA 4412 vingprofilsmodel av förstärkt glasfiber utformas och installeras enligt Minimum Turbulence Level (MTL) i vindtunnelanläggningen på KTH. Modellen har 65 tryckluftsöppningar, och uppsättningen innehåller två monteringspaneler som är utformade för att möjliggöra mätningar av particle image velocimetry (PIV) and hot wire anemometry (HWA) hos gränsskiktet (som ska utföras i en framtida kampanj). I en första experimentell kampanj utförs tryckskanningar vid tre anfallsvinklar av intresse (5, 10, och 12 grader) samt vid fyra olika Reynolds-nummer (200 000, 400 000, 1 000 000 och 1 640 000). De preliminära resultaten visar god överensstämmelse med DNS- och LES-data, men den effektiva anfallsvinkeln på vingen påverkas av störningar från testsektionen. För att tillhandahålla korrekta flödesförhållanden för framtida kampanjer i testdelen är vägginsatser konstruerade med 2D k-omega SST-simuleringar. Sidoväggarna är strömlinjeformade och den slutliga geometrin korrigeras för att ta hänsyn till gränsiktets tillväxt. Insatserna undviker den tidig separation som sker nära bakkanten vid högre anfallsvinklar (10 och 12 grader), men 2D-simuleringarna misslyckades med att fånga det ovan nämnda anfallsvinkelproblemet som påverkar tryckfördelningarna.
76

Automatiserad fotografering av verktygsförslitning med robot / Automated photography of tool wear using a robot

Mörk, Albin January 2023 (has links)
Vid skärande bearbetning av material för att framställa olika produkter med önskade egenskaper orsakas förslitningar av verktygen som är viktiga att fotografera och analysera för att uppskatta livslängden. Detta kräver erfaren personal med precision som är svår att upprepa där automation kan vara en lösning för att avlasta personal från ett monotont arbete.  Syftet med studien är att bidra med kunskap om hur man kan fotografera förslitningen av verktyg med hjälp av automation och ge förslag på en lösning. För att komma med ett lösningsförslag har en nulägesanalys genomförts med hjälp av observationer och intervjuerhos Sandvik Coromant, litteratursökning för att undersöka vad som gjorts inom området redan och simuleringar.  Resultatet blev ett konstruktionsförslag för en kamerafixtur och cykeltider för att fotografera samtliga förslitningsområden för de testade verktygen i ett simuleringsprogram. Om lösningsförslaget ska implementeras i verkligheten kommer den behöva testas för att med säkerhet kunna fotografera med tillräckligt bra fokus och ljussättning samt att kamerafixturen inte blir för skakig vid rörelse med roboten. / The use of cutting tools in cutting processing cause tool wear which need be analysed and photographed to predict tool life. To analyse the tool wear you need technicians with experience with precision that is hard to repeat in which automation could be a solution.  The purpose of this study is to contribute with knowledge on how you could photograph tool wear using automation and suggest a solution. This was done with a current situation analysis with the use of observation and interview of the technicians at Sandvik Coromant. A literature study was conducted to gather information about what has been done earlier in this field. Later a suggestion on the design of the camera fixture was made and simulated in a simulation program with the robotic cell to ensure it is possible to implement in real life.  The result from the study suggests that the camera fixture with the current robotic cell is capable of automatically photograph the tool wear of the tested tools. If the suggested camera fixture should be implemented in real life it needs to be tested with the camera to confirm it gets good enough focus and lightning inside the CNC-machine. It also needs to be tested so it does not wobble to much with the usage of the robot.
77

Development of an insert for a gripper and a fastening system : Exemplified for a human robot collaborative assembly process

Dimuro Duckwitz, Gonzalo January 2022 (has links)
Nowadays, the use of robots in industrial tasks is growing constantly. However, manual assembly is one area that is hard to make fully automated since manual assembly operations work with different shapes and products that require human finesse to do some operations. Humans, on the other hand, have a lot of limitations since this kind of task can be unergonomic and repetitive for operators, which can cause them stress, fatigue, repetitive stress injuries(RSI), and repetitive motion injuries. This project involved designing an insert for the gripper 2F-85 (version 3) that would allow the collaborative robot (UR5) to carry out more assembly tasks in order to relieve human workers of repetitive tasks. The insert has to handle cylindrical shapes in addition to bigger parts that the actual insert cannot handle due to its parallel stroke. For that, a detailed market analysis and insert research were conducted in the initial study. The new insert was then developed using a double-diamond design process. The needs were ranked using the Moscow prioritization method, and ideas were then generated using the brainstorming technique. The final concept was chosen using the weighted decision matrix method. After the final concept selection, computer-aided design (CAD) technology was employed to create the new insert's 3D model and its technical specifications. The mechanical behaviour of the new insert was analysed to reflect its range of workability, expressing the maximum force that it can withstand on each of its grip work surfaces without presenting plastic deformation. For this study, finite element analyses were conducted following the general method for linear structural analysis using Abaqus. Achieving an insert that can reach, transport, and assemble different shapes will help integrate collaborative robots into manual assembly processes, avoiding the cost of a new gripper.
78

Untersuchungen an Verbindungselementen für Holzkonstruktionen im Maschinen- und Anlagenbau

Eckardt, Ronny 22 February 2013 (has links) (PDF)
In dieser Arbeit werden Berechnungsvorschriften für Insertverbindungen in Holzfurnierlagenverbundwerkstoffen (WVC) mit dem Ziel erstellt, diese zur Auslegung und Nachweisführung in Anwendungen des Maschinenbaus zu verwenden. Nach Definition eines entsprechenden Anforderungsprofils erfolgt eine umfangreiche Darstellung des Standes der Technik. Dabei wird speziell auf die rechnerische Nachweisführung von Verbindungen im Bauwesen eingegangen, schwerpunktmäßig durch die im Eurocode 5 (DIN EN 1995) definierten Modelle für stiftförmige Verbindungsmittel. Im zweiten, praktischen Teil der Arbeit erfolgt die Durchführung und Auswertung umfangreicher Versuche. Dabei werden in einem ersten Schritt wesentliche Materialkennwerte der verwendeten Holzwerkstoffe bestimmt. Die zweite Gruppe der experimentellen Untersuchungen hat das Trag- und Verformungsverhalten vollständiger Insertverbindungen zum Inhalt. Dabei werden die unter statischen Aspekten wichtigen Einflussparameter auf die Tragfähigkeit bei Belastungen in Richtung sowie quer zur Stiftachse bestimmt und geometrische Vorzugsparameter ermittelt. Unter deren Zugrundelegung erfolgt eine Ausweitung der experimentellen Untersuchungen auf dynamische Lastfälle durch eine Ableitung von Wöhlerlinien bei Zugschwellbelastung. Auf Grundlage der durchgeführten Versuche werden Modelle zur Berechnung von Insertverbindungen nach den Methoden des Ingenieurholzbaus abgeleitet. Deren Anwendbarkeit wird an einem konkreten Beispiel in Form einer Transportrollenbahn für die Verwendung in der technischen Intralogistik demonstriert. / In this work, calculation fundamentals for insert fastenings in wood veneer composites (WVC) are developed with the aim to use them for the dimensioning and verification in mechanical engineering applications. After defining the functional requirements there is a comprehensive description of the best demonstrated available technology. The arithmetical verifications of connections used in civil engineering are thereby specifically addressed with the main focus on defined models for dowel type fasteners within Eurocode 5 (EN 1995). In the second part of the work comprehensive technical tests are implemented and evaluated. At first essential material properties of the used wood materials are determined. The following experiments contain the load bearing and deformation behavior of complete insert connections. The determination of important influencing parameters of the statical strength under axial and traverse loads is thereby involved, followed by an extension on dynamic load cases by a derivative of Woehler curves (stress - cycle diagram). Based on these experiments are models derived to provide calculation fundamentals to dimension insert connections. The practical applicability of the developed specifications is shown by dimensioning the connections of a roller conveyor made of WVC (technical logistics).
79

Untersuchungen an Verbindungselementen für Holzkonstruktionen im Maschinen- und Anlagenbau

Eckardt, Ronny 19 December 2012 (has links)
In dieser Arbeit werden Berechnungsvorschriften für Insertverbindungen in Holzfurnierlagenverbundwerkstoffen (WVC) mit dem Ziel erstellt, diese zur Auslegung und Nachweisführung in Anwendungen des Maschinenbaus zu verwenden. Nach Definition eines entsprechenden Anforderungsprofils erfolgt eine umfangreiche Darstellung des Standes der Technik. Dabei wird speziell auf die rechnerische Nachweisführung von Verbindungen im Bauwesen eingegangen, schwerpunktmäßig durch die im Eurocode 5 (DIN EN 1995) definierten Modelle für stiftförmige Verbindungsmittel. Im zweiten, praktischen Teil der Arbeit erfolgt die Durchführung und Auswertung umfangreicher Versuche. Dabei werden in einem ersten Schritt wesentliche Materialkennwerte der verwendeten Holzwerkstoffe bestimmt. Die zweite Gruppe der experimentellen Untersuchungen hat das Trag- und Verformungsverhalten vollständiger Insertverbindungen zum Inhalt. Dabei werden die unter statischen Aspekten wichtigen Einflussparameter auf die Tragfähigkeit bei Belastungen in Richtung sowie quer zur Stiftachse bestimmt und geometrische Vorzugsparameter ermittelt. Unter deren Zugrundelegung erfolgt eine Ausweitung der experimentellen Untersuchungen auf dynamische Lastfälle durch eine Ableitung von Wöhlerlinien bei Zugschwellbelastung. Auf Grundlage der durchgeführten Versuche werden Modelle zur Berechnung von Insertverbindungen nach den Methoden des Ingenieurholzbaus abgeleitet. Deren Anwendbarkeit wird an einem konkreten Beispiel in Form einer Transportrollenbahn für die Verwendung in der technischen Intralogistik demonstriert. / In this work, calculation fundamentals for insert fastenings in wood veneer composites (WVC) are developed with the aim to use them for the dimensioning and verification in mechanical engineering applications. After defining the functional requirements there is a comprehensive description of the best demonstrated available technology. The arithmetical verifications of connections used in civil engineering are thereby specifically addressed with the main focus on defined models for dowel type fasteners within Eurocode 5 (EN 1995). In the second part of the work comprehensive technical tests are implemented and evaluated. At first essential material properties of the used wood materials are determined. The following experiments contain the load bearing and deformation behavior of complete insert connections. The determination of important influencing parameters of the statical strength under axial and traverse loads is thereby involved, followed by an extension on dynamic load cases by a derivative of Woehler curves (stress - cycle diagram). Based on these experiments are models derived to provide calculation fundamentals to dimension insert connections. The practical applicability of the developed specifications is shown by dimensioning the connections of a roller conveyor made of WVC (technical logistics).
80

Modeling defect structure evolution in spent nuclear fuel container materials

Delandar, Arash Hosseinzadeh January 2017 (has links)
Materials intended for disposal of spent nuclear fuel require a particular combination of physical and chemical properties. The driving forces and mechanisms underlying the material’s behavior must be scientifically understood in order to enable modeling at the relevant time- and length-scales. The processes that determine the mechanical behavior of copper canisters and iron inserts, as well as the evolution of their mechanical properties, are strongly dependent on the properties of various defects in the bulk copper and iron alloys. The first part of the present thesis deals with precipitation in the cast iron insert. A nodular cast iron insert will be used as the inner container of the spent nuclear fuel. Precipitation is investigated by computing effective interaction energies for point defect pairs (solute–solute and vacancy–solute) in bcc iron using first-principles calculations. The main considered impurities in the iron matrix include 3sp (Si, P, S) and 3d (Cr, Mn, Ni, Cu) solute elements. By computing interaction energies possibility of formation of different second phase particles such as late blooming phases (LBPs) in the cast iron insert is evaluated. The second part is devoted to the fundamentals of dislocations and their role in plastic deformation of metals. Deformation of single-crystal copper under high strain rates is simulated by employing dislocation dynamics (DD) method to examine the effect of strain rate on mechanical properties as well as dislocation microstructure development. Creep deformation of copper canister at low temperatures is studied. The copper canister will be used in the long-term storage of spent nuclear fuel as the outer shell of the waste package to provide corrosion protection. A glide rate is derived based on the assumption that at low temperatures it is controlled by the climb rate of jogs on the dislocations. Using DD simulation creep deformation of copper at low temperatures is modeled by taking glide but not climb into account. Moreover, effective stresses acting on dislocations are computed using the data extracted from DD simulations. / <p>QC 20170428</p>

Page generated in 0.046 seconds