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  • 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.
1

Reduction in Wick Drain Effectiveness in Typical Utah Clays

Smith, Gabriel M. 09 December 2011 (has links) (PDF)
Consolidation theory states that decreasing the spacing of prefabricated vertical drains will decrease the time required to achieve primary consolidation. Previous field tests have shown that there exists a "critical" drain spacing, which is the point at which further spacing decrease does not decrease the time of primary consolidation. This "critical" spacing is thought to be due to disturbance effects from installation of the drains. Previous studies have found that the "critical" drain spacing may be dependent upon soil layering and drain and mandrel dimensions. Thin, interbedded clay layers have been found to be affected greatly due to the smear zone, while few tests have been conducted to determine the validity for thick bedded clays. Currently two design and analysis methods are in existence, neither of which is standardized. The two methods are the modeling of the smear zone, which requires knowledge of soil parameters within that zone, and the modeling using a back-calculated Ch/Cv ratio.In order to evaluate the validity of these design methods and to obtain more data that can be used in determining the relationship between anchor type, drain spacing, and soil profile, full-scale field tests were conducted at Mountain View Corridor in Lehi, Utah. These field tests were performed along a test section that was divided into sections containing 5.8, 5.0, 4.0 and 3.0 ft triangular spacings and rebar or plate anchors. By using the smear zone model, with a Ch/Cv ratio of 1.25 and ds of 3.07 times dm, the time rate of settlement was able to be predicted reasonably well, while using the back-calculated Ch/Cv ratio, with no smear zone, also predicted the time rate reasonably well. From the testing, it was found that the thick clay profile can facilitate closer spacings than a thin clay profile. Also, it was found that the rebar anchor type causes about twice the disturbance of the plate anchor. The results helped validate the existing models and show that the effectiveness of the drains is dependent upon drain spacing, soil profile, and anchor type
2

Estudo da fadiga termo-mecânica em um aço inoxidável martensítico da série X22

Alcântara, Árysson Penna de January 2008 (has links)
Submitted by Stéfany Moreira (stemellra@yahoo.com.br) on 2013-03-06T16:03:23Z No. of bitstreams: 1 DISSERTAÇÃO_EstudoFadigaTermo.pdf: 7242375 bytes, checksum: 060dcf26d497b5b6e84c7caa9beaf244 (MD5) / Approved for entry into archive by Neide Nativa (neide@sisbin.ufop.br) on 2013-03-13T22:09:01Z (GMT) No. of bitstreams: 1 DISSERTAÇÃO_EstudoFadigaTermo.pdf: 7242375 bytes, checksum: 060dcf26d497b5b6e84c7caa9beaf244 (MD5) / Made available in DSpace on 2013-03-13T22:09:01Z (GMT). No. of bitstreams: 1 DISSERTAÇÃO_EstudoFadigaTermo.pdf: 7242375 bytes, checksum: 060dcf26d497b5b6e84c7caa9beaf244 (MD5) Previous issue date: 2008 / O presente estudo constitui na análise de falha e na caracterização microestrutural e comportamental de um aço empregado em segmentos de mandril de bobinadeira de um laminador de tiras a quente. A análise de falhas envolveu os procedimentos convencionais para avaliação das causas de fratura do componente estrutural, notadamente análise macroscópica e microfratográfica da fratura, assim como a checagem das especificações para o aço. A caracterização microestrutural foi realizada por microscopia ótica e difratometria de raios-X. A avaliação comportamental envolveu ensaios de tenacidade à fratura (integral J e curva de resistência), ensaios de crescimento de trinca por fadiga, e uma tentativa de simulação de comportamento real do aço, através de ensaios com aplicação de ciclos térmicos. O processo de degradação do material foi caracterizado como sendo de fadiga térmica. O aço apresentou um comportamento mecânico relativamente frágil, indicando a possibilidade de substituição por outro material mais tenaz. A simulação de fadiga térmica foi insuficiente para iniciar o trincamento no material estudado. __________________________________________________________________________________________ / ABSTRACT: This study is based on analysis of failure and microstructural and behavioral characterization of a steel used in coiler mandrel segments of hot strip mill. The failures analysis involving the conventional procedures for assessing causes of fracture of the structural component, especially macroscopic and microscopic analysis of the fracture as well as checks in the steel specifications. The microstructural characterization was carried out by optical microscopy and X-ray diffraction. The evaluation involved behavioral tests of the fracture toughness (J integral and resistance curve), testing for crack growth caused by fatigue, and an attempt to simulate the actual behavior of steel, through testing with application of thermal cycles. The material degradation process was characterized as being of thermal fatigue. The steel mechanical behavior showed a relatively weak, indicating the possibility of change by other materials more tenacious. The thermal simulation fatigue was insufficient to start the crack in the material studied.
3

Novel Apparatus to Control Electrospinning Fiber Orientation for the Production of Tissue Engineering Scaffolds

Boland, Eugene David 01 January 2004 (has links)
The conception of electrospinning can trace its roots back more than 400 years, when it was observed that rubbed amber can deform a droplet of water on a smooth surface, and is based upon simple concepts of charge separation and surface tension. Since that time, considerable effort has been directed at both the cause and utility of this phenomenon. The specific aim of this dissertation project was to develop an automated electrostatic processing apparatus that was capable of controlling the three-dimensional architecture of an electrospun scaffold to further improve its utility in tissue engineering. The efficacy of using this technique has been well documented and can be adapted to produce tissue engineering scaffolds for a variety of tissues and organs. This apparatus incorporates precise mandrel motion. The system is capable of 0 - 5000 revolution per minute rotation, 0 - 25 inch per second translation and ± 40° rotation about the electrospinning jet axis for repeatable scaffold production. Fiber alignment and scaffold density are precisely controlled by rotating a mandrel along one axis, translation along that same axis, and rotation around the second axis perpendicular to the electrospun fiber stream. The control is accomplished with a PC based "supervisory" control program written partially in the LabVIEW® programming language and partially in SI Programmer supplied by Applied Motion Products. Scaffold thickness and fiber diameters are determined by the syringe metering pump flow rate, material being electrospun and solution concentrations. Through extensive laboratory analysis (mechanical testing and both optical and electron microscopy), parameters such as fiber orientation, diameter and mechanics can be predictive from specific polymer setups. Our laboratory has demonstrated the ability to electrospin natural and synthetic polymers and this apparatus will be utilized to tailor scaffolds to meet specific tissue engineering needs by creating a truly biomimicking scaffold / extracellular matrix.
4

Utveckling av en resningsmaskin för tubformade förpackningar : Utveckling av resningsmaskin för SCA, Arcwise

Gårdestam, Julia January 2021 (has links)
I detta kandidatexamensarbete har syftet varit att undersöka metoder för att forma ett wellpappark, skapat av Arcwise (SCA), till en cylindrisk-, tubformad kartong. Arbete mynnade ut till ett koncept för en resningsmaskin som monterar ihop Arcwisetuben. Resningsmaskinen ska vara en instegsmodell från manuellt arbete till en automatisk produktion. För utveckling av maskinkonceptet tillämpades metoden produktutveckling inom industrin, kapitel 4, enligt boken ”Produktutveckling effektiva metoder för konstruktion och design”.  Ifrån produktutveckling inom industrin tillämpas endast fem av sju faser i detta projekt; förstudie, produktspecificering, konceptutveckling-konceptgenerering, konceptutvärdering och konceptval samt prototyp. Förstudien ledde fram till att sugkoppar och tryckluft var bra metoder för tillämpning vid lyft och förflyttning av arket mellan de olika stationerna. Ett wellpappark deformeras inte plastiskt vid formgivning som exempelvis metall och behöver därför formges från två håll. Maskinkoncepten som tas fram görs med hjälp av en kravspecifikation, mind map och en aktivitetsanalys. Konceptskisserna bedöms med hjälp av Pughs matris. Det vinnande konceptet var en länkarmslösning som slutligen visualiseras i CAD som en prototyp. Projektets syfte uppfylldes genom att Arcwise wellpappark går att forma till en cylindrisk kartong och ett koncept som är redo för tillverkningsanpassning har tagits fram. / The purpose of this project has been to investigate methods for shaping a corrugated sheet, created by Arcwise (SCA), into a cylindrical tube. The work led to a concept of a Corrugated cardboard machine that produces Arcwise tubes. The machine is an entry-level model from manual work to automatic production. The development of the machine concept used is the method of Product development of industry. In the method were five of seven phases used: Feasibility study, product specification, concept development and concept generation, concept evaluation and concept selection and prototype. The feasibility study led to the fact that a suction cup and compressed air were good methods for lifting and moving the sheet between different stations. A corrugated sheet does not deform plastically during forming and therefore needs to be shaped from two directions. The machine concept that is developed are made with help of a requirements specification, mind map and an activity analysis. Pughs matrix were used to evaluate and decide which concept to develop further. The winning concept was a link arm solution that is visualized in CAD as a prototype. The purpose of the project where fulfilled, the Arcwise corrugated board can be shaped into a cylindrical tube and a production concept ready for manufacturing adaptation has been developed.
5

Development of an affordable and flexible fixing system for a hobbing machine / Utveckling av ett flexibelt spännsystem för kuggbearbetning

van Loenen, Twan January 2023 (has links)
Last years, lead time, flexibility, cost, and quality have become significant factors for the manufacturing industry. This also applies to gears, which could be manufactured using hobbing and grinding. Fixing systems are used to precisely center and fully fix gears to reach high quality. These are expensive and not flexible which requires a new one for each gear dimension. This limits the production of prototypes and so new product for the market. Developing a 3D concept for affordable and flexible fixing is the purpose. Through literature research, analyzing the current process, discussions with the company, desk research, and benchmarking, requirements are made for the new concept. Then brainstorming sessions are done to come up with new concepts. The concepts are analyzed, discussed with the company, and combined into two better concepts. Even though the higher flexibility of the other concept, the robustness of the winning concept “CoNut”. The principle is that only a few parts have to be changed instead of the whole system. The concept is further developed in 3D, where design for cost and manufacturing are applied. Finally, test procedures are drafted to validate the concept against therequirements. While some require a prototype, others are already validated by using the 3D model. Ultimately, an affordable and more flexible fixing system is developed as a 3D concept, by using a structural design process, which is likely to meet all the requirements. Since the model is cheaper and easier to change within meeting the other requirements, the purpose is reached.
6

Metodika hodnocení stavu dřeva pomocí měření mechanického odporu při zatlačování trnu / Procedure of assessment of the wood state by the wood mechanical resistance measuring within pushing a pin

Daňková, Kateřina January 2012 (has links)
The main aim of the thesis is to gain an overview of diagnostic methods used in surveys of wooden structures, comparing the results of experimental evaluation of state timber using diagnostic methods that are based on measurements of the mechanical resistance of the wood. Detailed constructional - technical survey of the truss of the historic building in Šardice is also the part of this thesis.

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