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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.
21

Seam performance : analysis and modelling

Abdul Ghani, Suzaini January 2011 (has links)
Seam quality is affected by various fabric mechanical properties with a combination of their sewing parameters. Previously, a lot of research has been done on identifying the parameters that influencing seam quality by looking into correlation between fabric properties and sewing parameters. The purpose of this current study was to investigate the performance of seam quality in terms of seam appearance and strength constructed with different sewing parameters. Another aim was to identify parameters that influence the seam quality using the Structural Equation Modelling (SEM) by AMOS and leads to the development of multivariable predictive equations using SPSS. Finally, the validation between experimental and predicted results using newly developed equations was examined using a new set of fabrics. The investigation was done for five different fabric categories, namely light, light to medium, medium, medium to heavy and heavy weight. A total of 45 fabrics with different weave densities, fibre types and structures were used. Seams were produced using various sewing parameters such as threads with different fibre types and structures, needle sizes and stitch densities. All fabrics were tested for their mechanical properties using two established items of equipment known as Kawabata Evaluation System for Fabrics (KES-F) and Fabric Assurance by Simple Testing (FAST). Seam evaluations together with thread and fabric mechanical properties obtained from KES-F and FAST were used as input for modelling. From the experimental work, it was concluded that the usage of thicker threads did not always give better strength and the seam appearance was also poor. A combination of finer thread with moderate strength and a medium level of stitch density according to fabric weight category provided an effective result for both seam appearance and strength. From the modelling work, it was found that the extensibility, bending and shearing properties, together with thread properties including extensibility, tensile strength and size, were among the properties selected by SEM to be included in the predictive equations. The validation results showed that the standard deviation between fabric properties used to develop the equations and new fabric properties used for validation plays an important role. The principal conclusion was that the prediction equations developed using SEM and SPSS possible to be used and gave a strong validation between experimental and predicted results when the new fabric properties were within one standard deviation.
22

Tejpning av sömmar för vattentäta plagg : En studie där tejpade sömmar granskas och testas

Blomqvist, Lise January 2019 (has links)
Denna studie är en kandidatuppsats inom designteknik. Studien görs efter praktik på ett Svenskt företag som producerar arbetskläder. Företaget, som idag är min uppdragsgivare, har ett intresse i att starta egen produktion av produktgruppen 3-lagersjackor. För företaget ses det som en utmaning med produktgruppen, vilket skapade en nyfikenhet hos mig i att utforska ämnet. En 3-lagersjacka kräver tejpning för att bli ett vattentätt plagg, och detta är något som kräver mycket resurser, tid och kunskap. Vid uppstart av ny produktgrupp behöver arbetet starta från grunden med rätt materialval, för att sedan gå vidare till rätt konstruktion och sömnad. Studiens innehåll är vinklat för att undersöka tejpning av 3-lagersmaterial och konstruktion av dess sömmar. Syftet är att ta fram viktigt information- och identifiera vad som är svårt vid tejpning. Studiens resultat bygger till stor del på tester av de tejpade prototyper som skickats för test via ett externt testinstitut. Produktion av produkter bestående av 3-lagersmaterial är beroende av många olika faktorer under både sömnad och konstruktion och blir därför ett brett ämne, men studien har lyckats skrapa lite på ytan och kommit fram till slutsatser som kan vara hjälpsamma vid produktutveckling av 3-lagersprodukter. / This study is a bachelor thesis in design technology. The study is done after an internship at a Swedish company that produces work wear. The company, which today is my client, has an interest in starting its own production of the product group 3-layer jackets. For the company, it is seen as a challenge with the product group, which created a curiosity with me in exploring the subject. A 3-layer jacket requires taping to become a waterproof garment, and this is something that requires a lot of resources, time and knowledge. When starting a new product group, the work needs to start from scratch with the right choice of material, and then move on to the right design and sewing. The content of the study is angled to examine the taping of 3-layer material and the construction of its seams. The purpose is to produce important information and identify what is difficult when taping. The study's results are largely based on tests of the taped prototypes sent for testing via an external test institute. Production of products consisting of 3-layer material is dependent on many different factors during both sewing and construction and therefore becomes a broad subject, but the study has managed to scrape a little on the surface and come to conclusions that can be helpful in product development of 3-layer products.
23

R65 tipo bėgio termitinio suvirinimo mechaninių savybių tyrimas / The investigation of machanical properties of welding quality of R65 type

Rauduvė, Mindaugas 15 June 2010 (has links)
Baigiamajame magistro darbe nagrinėjama termitiniu būdu skirtingais parametrais suvirintų bėgių jungčių kokybė. Analizuojama termitinio suvirinimo mišinio kiekio bei pakaitinimo laiko įtaka suvirintų jungčių kokybei. Tam, kad būtų nustatytos suvirintų jungčių mechaninės savybės, buvo atlikti šie bandymai: viršutinės bėgio dalies kiečio bandymas, lėtojo lenkimo bandymas, termiškai suminkštintos zonos kiečio pasiskirstymo matavimas, ilgalaikiai bandymai. Tyrimais nustatyta kokią įtaką, turi suvirinus bėgių jungtis be pakaitinimo, esant skirtingiems pakaitinimo laikams ir skirtingam termito kiekiui. Remiantis gautais rezultatais pateiktos išvados. / In the final masters degree thesis examines the quality of using different parameters Aluminothermicaly welded rail joints. Influence of the quantity of Aluminothermic welding mixture for quality of welded joints, and heating time is analyzing. In order to determine the mechanical properties of welded joints following tests had been made: hardness test of upper part of the rail, long term bending test, hardness test of the distribution of heat-softened area, other long-term tests. Results of research have determined the influence of different heating time and different quanity of thermites content for welded joints without using heating. Based on this results the final conclusion was presented .
24

Prozessdatenanalyse zur Inline-Verminderung von Störeinflüssen beim Ultraschallsiegeln / Process data analysis at ultrasonic sealing for inline prevention of failure

Thürling, Karsten 06 December 2016 (has links) (PDF)
Beim Siegeln von Verpackungen können nicht-qualitätsgerechte Siegelnähte dadurch entstehen, dass sich Teile des Packguts zwischen den zu fügenden Packmittelbahnen befinden. Im Gegensatz zum konventionellen Wärmekontaktsiegeln besteht beim Ultraschallsiegeln die Möglichkeit, für jeden einzelnen Siegelvorgang Prozessdaten zu erfassen. Aus dem Bereich des Ultraschallschweißens ist bekannt, dass sich anhand dieser Daten der Prozess überwachen und dessen Güte bewerten lässt. Die vorliegende Arbeit untersucht den Informationsgehalt dieser Prozessdaten hinsichtlich störungsbehafteter Siegelnähte und leistet damit einen Beitrag zur Verbesserung der Verpackungsqualität und damit im besten Fall auch zu weniger Lebensmittelverlusten. Es wird dazu zunächst eine Systematisierung von möglichen Störprinzipen beim Siegeln hinsichtlich ihrer physikalischen Wirkprinzipe vorgenommen. Darauf aufbauend konnte ein Versuchsstand und eine Methodik zur Untersuchung der Thematik entwickelt werden. Abschließend wurden ausgewählte Störprinzipe untersucht, wobei sich ein sehr starker Packstoff- und Einfluss der Prozessführung herausstellte. Es konnte ein prinzipieller Zusammenhang zwischen Auswirkung einer Störung auf die Nahtqualität und die Prozessdaten gezeigt werden, welcher sich jedoch auf Basis der erarbeiteten Ergebnisse nicht verallgemeinern lässt.
25

Proposta para a estimativa da resistência à compressão uniaxial in situ de camadas de carvão com a utilização de geofísica / Methodology to estimate the in situ uniaxial compressive strength of coal seams based on geophysical data

Gonzatti, Clovis 08 February 2008 (has links)
A arte de dimensionar pilares em minas subterrâneas de carvão tem sido objeto de pesquisa há mais de 100 anos no mundo inteiro. A maioria dos métodos de dimensionamento de pilares para a lavra segundo o método \"câmara e pilares\" se vale de parâmetros de resistência e geométricos das camadas de carvão. A resistência in situ da camada de carvão (S1) é um desses parâmetros. No Brasil, na Bacia Carbonífera Sul-Catarinense, uma nova camada de carvão, a Bonito, passou a ser minerada em volume considerável a partir da década de 1990. A sua resistência in situ ainda hoje é uma incógnita. Tendo como campo experimental a camada de carvão Bonito presente na mina Fontanella, no município de Treviso - SC, foram desenvolvidos diferentes estudos de laboratório e em subsolo, visando à caracterização mecânica, estrutural e geofísica dessa camada. Adicionalmente, foram realizadas investigações sobre uma segunda camada de carvão, a Irapuá, já relativamente conhecida, presente em outras duas minas na mesma bacia carbonífera. Os estudos realizados serviram de base para a proposição de uma nova metodologia para a estimativa da resistência à compressão uniaxial in situ de camadas de carvão (S1), levando em consideração a resistência de laboratório e informações geofísicas de laboratório e in situ. Com o uso da nova metodologia, são propostos valores de resistência à compressão uniaxial in situ da camada de carvão Bonito, para diferentes condições geológico-estruturais observadas na mina Fontanella, e para a camada Irapuá, nas minas Morozini Norte e Santa Augusta Norte. / Researchers in all over the world have spent a lot of time in developing techniques for pillar design in coal underground mines that use room and pillar method. Almost all the available methods are based on strength and geometric parameters of the coal seam. One of the most important is the coal seam in situ strength (S1). In Brazil, at Sul-Catarinense Carboniferous basin, a new coal seam (Bonito seam) is being mined since the last decade. Many instability problems have occured during mining. The coal seam strength is not very well known so far. Using the Bonito seam present at Fontanella mine in Treviso - SC, different studies were performed in laboratory and in situ. In adition, another coal seam, Irapuá, was also studied. The compilation of data at different sites was used to propose a new approach to estimates of the in situ uniaxial compressive strength of coal seams (S1) using three parameters. The uniaxial compressive strength and compressional wave ultra sonic velocity are determined in laboratory using small samples, while seismic velocity is measured in large scale conditions directly at the coal seam in situ. Using the new approach, values for in situ strength at Fontanella mine are proposed and also for two mines at Irapuá coal seam, Morozini Norte and Santa Augusta Norte.
26

Metodologia de detecção de trajetória de soldagem baseada em visão computacional

Bauernfeind, Omar Alejandro January 2017 (has links)
Em geral, um problema importante em um sistema de soldagem robotizado, ou com manipuladores automáticos, é a necessidade de uma trajetória ser reprogramada quando a forma ou a posição das peças mudam. Como solução a esse problema é proposto um método que utiliza técnicas de visão computacional, para assim detectar a trajetória de soldagem em juntas de topo. O método deve ser dinâmico permitindo a identificação de juntas de topo com cantos não próximos, linhas não retas e tamanhos diferentes entre as peças, assim como apresentar robustez contra variáveis desfavoráveis do ambiente industrial como riscos nas peças ou no fundo e mudanças de luminosidade. A trajetória é detectada baseando-se na linha de bordas da imagem global e adicionalmente trabalha-se sobre duas características da linha de solda: distância quase constante entre linhas paralelas e pixels de linha de solda com menor intensidade de luminosidade que as bordas. Uma etapa é proposta para robustez do método sobre linha de bordas descontinuas e possíveis erros em ponto inicial e final de solda. O trabalho proposto é validado com distintas configurações de junta de topo, como com cantos de peças não coincidentes, linha de solda não reta e diferentes orientações de peças. Os pontos da trajetória de solda obtidos são comparados com uma linha de solda considerada ideal, resultando em uma média e desvio padrão geral inferiores à um valor de 0,5 mm. Uma validação experimental é realizada com uma solda executada por um robô industrial seguindo os pontos de solda detectados, com os resultados demostrando que o método efetivamente pode definir uma trajetória de solda para aplicações industriais robotizadas. / In general, one of the most important problems in a robotic welding system, or in automatic manipulations, is the requirement of a path trajectory to be reprogramed when the shape or the position of the welding pieces are changed. In order to detect the welding seam in butt joints, a method that makes use of computational vision techniques is proposed. The method needs to be dynamic against variation in the configuration of the pieces, so as curved or not straight seam lines, not coincident corners; beside of that, it must to present robustness against unfavorable variables of the industrial environment, so as scratches in the pieces or illumination changes. Two features of the welding line are taken into account to develop the method: almost constant distance between parallel seam lines and darker pixels in the center of the seam than in the borders. Moreover a robustness step is proposed over two weaknesses of the method: discontinuities in the edges of the welding line and possible errors in the location of the start and end welding points. The validation step of the method involves different configuration of butt joints, as pieces without corner being coincident, not straight welding line and different orientations. The points of the welding seam detected by the method, are compared against a set of welding points considered as an ideal set of points, getting as results a mean and standard deviation lower than ± 0.5 mm. An experimental test is carried out by an industrial robot that welds two pieces following the welding line points, with the results showing that the method can effectively define a welding trajectory for industrial robotics applications.
27

Quantifying the Lateral Bracing Provided by Standing Steam Roof Systems

Sorensen, Taylor J. 01 May 2016 (has links)
One of the major challenges of engineering is finding the proper balance between economical and safe. Currently engineers at Nucor Corporation have ignored the additional lateral bracing provided by standing seam roofing systems to joists because of the lack of methods available to quantify the amount of bracing provided. Based on the results of testing performed herein, this bracing is significant, potentially resulting in excessively conservative designs and unnecessary costs. This project performed 26 tests with Vulcraft joists in a pressure box to investigate the effects of how many variables influence the lateral bracing provided to joists from standing seam roofing systems, including the variables joist length, panel gauge, clip height, thermal block presence, insulation thickness, and top chord size. Two methods were developed to account for this additional bracing: finite element computer modeling and an application of the Rayleigh-Ritz method called the Column-on-Elastic-Foundation Method. Variables influencing the pressure at failure, namely chord size and deck gauge, were those with the greatest effect on additional lateral bracing provided from standing seam roof systems. It was determined that higher roof stiffness values and higher failure pressures yield shorter effective lengths.
28

Bereitstellung von Materialkennwerten für die Simulation von Bekleidungsprodukten

Seif, Manal Abdel-Aziz Mohamed 17 August 2007 (has links) (PDF)
Die exakte Kenntnis vom Materialverhalten und speziell von lokalen Flächenmasseschwankungen der textilen Flächen ist Voraussetzung für eine Verbesserung der Produktentwicklung und für eine hohe Qualitätsverarbeitung in der Konfektionsindustrie. Dieser Fakt ist ebenfalls für die zunehmende Anwendung im Bereich der Simulationsberechnungen von erheblicher Bedeutung. Der Wandel von 2D-CAD- zu 3D-CAD-Systemen führt in der Bekleidungsindustrie zur zwingenden Berücksichtigung der Materialeigenschaften. Aufgrund des Montageprozesses zeigen die konfektionierten textilen Flächen im Vergleich zu unkonfektionierten textilen Flächen ein anderes Erscheinungsbild. Mehrlagige Gewebe (infolge einer Naht, einer Einlage oder eines Futterstoffes) beeinflussen das Biegeverhalten und das Fallverhalten der textilen Flächen erheblich. Zur Bestimmung der Biegesteifigkeit ist seit Jahrzehnten das manuell zu bedienende Prüfgerät nach dem Cantilever-Verfahren das Bekannteste. Die eigenen Untersuchungen bestätigen, dass das Prüfgerät viele Mängel hat, welche die Genauigkeit und die Reproduzierbarkeit der Messergebnisse wesentlich beeinflussen. Im Rahmen dieser Arbeit wird ein neues Biegesteifigkeitsprüfgerät (ACPM 200) entwickelt, um eine optimale Genauigkeit und hohe Reproduzierbarkeit der Messergebnisse zu erfassen. Eine neue Methode zur Ermittlung des Einflusses der Naht auf die Biegesteifigkeit einer größeren textilen Fläche ist in der Arbeit vorhanden, um die exakte Beschreibung des realen Verhaltens von textilen Bekleidungsprodukten zu ermitteln. Die Simulation des Biegeverhaltens textiler Flächen ohne und mit vertikaler Naht wird mit Hilfe der FEM durchgeführt. Abschließend wird eine neue Prüfnorm vorgestellt, welche die Biegesteifigkeit von textilen Flächen mit lokalen Flächenmasseschwankungen mittels des neuen Biegesteifigkeitsprüfgerätes ACPM 200 beinhaltet. / Bending stiffness and Drapeability are essential material parameters for simulating textile and clothing products. Due to assembling processes garments are showing different appearances through modelling than textile fabrics. This is based on stiffening, which is caused by assembling process and local variations within material’s mass throughout the fabric. Since decades the manual bending stiffness testing device, which is based on Cantilever method, has been known. This device is insufficient because of irregular feed speed of bending sample, the visual determination of reaching and reading the bending length, the little reading precision of the measurable slide (half Millimetre) and the form of the front edge of the sample does not stay linear. Obtaining an exact evaluation of this sample edge is not possible with this device. Extensive experiments have confirmed that these deficits influence the accuracy and the reproduction of the results in a high degree. To remedy these deficits and to obtain an exact description of the material’s behaviour in order to achieve an optimal modelling of the clothing products is the new bending stiffness testing device (ACPM 200) at the ITB of TU Dresden developed. Within the investigations a new method for determining the influence of the seam on the bending stiffness of the adjacent textile fabric will be introduced. The Influence of seams on the drapability of textile fabric is investigated. A static model of Fabric with and without vertical seams is analysed with using the finite element method (FEM).
29

Characterization of asbestos exposure among automotive mechanics servicing and handling asbestos-containing materials

Dotson, Gary Scott 01 June 2006 (has links)
The historic use of asbestos-containing materials during the manufacturing of automobiles has resulted in a perception of an increased risk of asbestos-related pulmonary diseases within mechanics. This study was conducted to assess the potential asbestos exposures mechanics encounter while servicing vehicles assembled with parts containing asbestos, in addition to compare the cumulative lifetime asbestos exposures for different maintenance activities against theorical threshold exposures for asbestosis, lung cancer and mesothelioma. Exposure data were assembled from four independent exposure assessments performed to elucidate the airborne asbestos levels generated during the removal and replacement of brakes, gaskets, clutches and seam sealants containing asbestos. The phase contrast microscopy (PCM) and phase contrast microscopy equivalent (PCME) fiber concentrations for personal samples and air sampled identified to contain asbestos fibers through Transmission Electron Microscopy (TEM) analysis were applied to calculate the cumulative lifetime asbestos exposures. This index of exposure was compared to no-effect exposure thresholds identified through an extensive literature review for the selected pulmonary diseases. The results of this study indicate that mechanics encounter PCM fiber concentrations approximately 10 to 100 times lower than the current Occupational Safety Health Administration (OSHA) Permissible Limit Exposure (PEL) of 0.1 fibers per cubic centimeter (f/cc). Additionally, the cumulative lifetime asbestos exposures ranged from <1 fiber-year/cubic centimeter of air (f-yr/cc) to 2.0 f-yr/cc, and did not exceed the no-effect exposure thresholds for asbestosis, lung cancer and mesothelioma. The findings of this study provide additional support to previously published epidemiologic investigations and exposure assessments against an increased risk of asbestos-related disease within mechanics historically employed to service vehicles containing asbestos fibers.
30

Investigation of decommissioned reactor pressure vessels of the nuclear power plant Greifswald

Viehrig, Hans-Werner, Altstadt, Eberhard, Houska, Mario, Mueller, Gudrun, Ulbricht, Andreas, Konheiser, Joerg, Valo, Matti 05 June 2018 (has links) (PDF)
The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald nuclear power plant representing the first generation of Russian-type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs of 4 units represent different material conditions as follows: • Irradiated (Unit 4), • irradiated and recovery annealed (Units 2 and 3), and • irradiated, recovery annealed and re-irradiated (Unit1). The recovery annealing of the RPV was performed at a temperature of 475° for about 152 hours and included a region covering ±0.70 m above and below the core beltline welding seam. Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The research program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall. This report presents test results measured on the trepans from the beltline welding seam No. SN0.1.4. and forged base metal ring No. 0.3.1. of the Units 1 2 and 4 RPVs. The key part of the testing is focussed on the determination of the reference temperature T0 of the Master Curve (MC) approach following the ASTM standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation and is recovered by thermal annealing. Other than that the mentioned test results include Charpy-V and tensile test results. Following results have been determined: • The mitigation of the neutron embrittlement of the weld and base metal by recovery annealing could be confirmed. • KJc values of the weld metals generally followed the course of the MC though with a large scatter. • There was a large variation in the T0 values evaluated across the thickness of the multilayered welding seams. • The T0 measured on T-S oriented SE(B) specimens from different thickness locations of the welding seams strongly depended on the intrinsic structure along the crack front. • The reference temperature RT0 determined according to the “Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs - VERLIFE” and the fracture toughness lower bound curve based thereon are applicable on the investigated weld metals. • A strong scatter of the fracture toughness KJc values of the recovery annealed and re-irradiated and the irradiated base metal of Unit 1 and 4, respectively is observed with clearly more than 2% of the values below the MC for 2% fracture probability. The application of the multimodal MC-based approach was more suitable and described the temperature dependence of the KJc values in a satisfactory manner. • It was demonstrated that T0 evaluated according to the SINTAP MC extension represented the brittle fraction of the data sets and is therefore suitable for the nonhomogeneous base metal. • The efficiency of the large-scale thermal annealing of the Greifswald WWER 440/V230 Unit 1 and 2 RPVs could be confirmed.

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