Global ETD Search

41	Modeling Boundary Effect Problems of Heterogeneous Structures by Extending Mechanics of Structure Genome Bo Peng (5930135) 10 June 2019 (has links) First, the theory of MSG is extended to aperiodic heterogeneous solid structures. Integral constraints are introduced to decompose the displacements and strains of the heterogeneous material into a fluctuating part and a macroscopic part, of which the macroscopic part represents the responses of the homogenized material. One advantage of this theory is that boundary conditions are not required. Consequently, it is capable of handling micro-structures of arbitrary shapes. In addition, periodic constraints can be incorporated into this theory as needed to model periodic or partially periodic materials such as textile composites. In this study, the newly developed method is employed to investigate the finite thickness effect of textile composites.<div><br></div><div>Second, MSG is enabled to deal with Timoshenko beam-like structures with spanwise heterogeneity, which provide higher accuracy than the previous available Euler–Bernoulli beam model. Its reduced form, the MSG beam cross sectional analysis, is found to be able to analyze generalized free-edge problems with arbitrary layups and subjected to general loads. In this method, the only assumption applied is that the laminate is long enough so that the Saint-Venant principle can be adopted. There is no limitation on the cross section of the laminate since no ad hoc assumption is involved with the microstructure geometry. This method solve the free-edge problem from a multiscale simulation point of view.<br></div><div><br></div> Aerospace Materials Aerospace Structures Composite and Hybrid Materials Composites Woven Composites Mechanics of Structure Genome Free-edge stress analysis non-periodicity Micro-mechanics RVE analysis Initial failure Finite thickness effect Inter-ply shifting
42	Influence of hardwood, softwoodand fractionated pulp in a stratifiedthree-layered fine paper : Lövved, barrved och fraktionerad massa ochdess inverkan på ett treskiktat finpapper Mattison, Mariell January 2006 (has links) Four different trials of stratified three-layered fine paper, of sulphate pulp, were performed to investigate if stratified fine fraction or fibres from birch can improve the properties of a paper compared to a reference sheet. All trials had five different scenarios and each scenario was calendered with different linear load. All sheets had a grammage of 80 g/m2.In the first trial, the paper contained birch, pine and filler of calciumcarbonate (marble), and was manufactured with the pilot paper machine XPM and the stratified headbox Formator at RCF (Stora Enso Research Center in Falun). The furnish consisted of 75% birch and 25% pine.The second trial contained coated sheets with paper from trial one as the base paper. The coating slip contained calciumcarbonate and clay and the amount was approximately 10-12 g/m2.The third trial, also with birch and pine but without filler, was performed at STFI (Skogsindustrins Tekniska Forskningsinstitut in Stockholm) with the laboratory scaled paper machine StratEx and the stratified headbox AQ-vanes. The furnish consisted of 75% birch and 25% pine, except for one scenario which contained of 75% pine and 25% birch.The last trial contained fractionated pulp of birch and pine and was performed at STFI. 50% was fine fraction and 50% was coarse fraction.This test does not show any clear benefits of making stratified sheets of birch and pine when it comes to properties such as bending stiffness, tensile index and surface smoothness. The retention can be improved with birch in the surface plies. It is possible that the formation can be improved with birch in the surface plies and pine in the middle ply. It is also possible that fine fraction in the surface plies and coarse fraction in the middle ply can improve both surface smoothness and bending stiffness. The results in this test are shown with confidence intervals which points out the difficulties of analysing sheets manufactured with a pilot paper machine or a laboratory scaled paper machine. Multi-ply fine paper three-layer fine paper stratified forming simultaneous forming XPM Formator StratEx AQ-vane stratified headbox early wood late wood fractionation fine fraction coarse fraction hydrocyclone
43	Srovnávací studie únosnosti a tuhosti vybraných spojů kovové a kompozitní části konstrukce / A comparative study of ultimate load and stiffness of metal-to-composite joints Tchír, Michal January 2016 (has links) V současnosti jedna z metod spojování zejména tlustých a vysoce zatížených kompozitních komponent je šroubový spoj, který je možné rozebrat pro případ opravy na rozdíl od lepeného spoje. Kompozitní konstrukce se tradičně dimenzují tak, aby během provozu nedošlo k porušení první vrstvy laminátu, nicméně důležité je taky poznat chování laminátu po porušení první vrstvy. Pro strukturální analýzu nejenom spojů, ale také dalších komponent se používá metoda konečných prvků a protože moderní nelineání řešiče jsou schopné modelovat chování laminátu po porušení první vrstvy, tato schopnost jednoho z nich byla využita v této práci při zkoumaní chování sklolaminátu spojeného s hliníkovou částí šrouby. Konečno-prvkové modely dvou spojů kovové a kompozitní části konstrukce schopné popsat progresivní porušování laminátu byly postaveny s využitím tří různých poruchových kritérií – kritéria maximálního napětí, kritéria Hill a kritéria Tsai-Wu. Problém byl řešen s využitím řešiče Nastran. Křivky síla-posuv, tuhost-posuv a hodnoty zatížení při hraničním posuvu byly porov-nány s výsledky experimentů. Jelikož faktor zbytkové tuhosti ovlivňuje výsledky ana-lýzy progresivního porušování, byly provedeny citlivostní studie zkoumajíci vliv faktoru na přesnost a stabilitu výpočtu. Shoda výpočtu s experimentem v případe prvního šroubového spoje je méně uspokojivá, nicméně shoda v případě druhého spoje, který má zesilující tenkou ocelovou destičku na spodní straně, je podstatně lepší. Vý-borná shoda je zejména při použití interaktivních kritérií Hill a Tsai-Wu.
44	Scaling Effects on Damage Development, Strength, and Stress-Rupture Life on Laminated Composites in Tension Lavoie, J. André 04 April 1997 (has links) The damage development and strength of ply-level scaled carbon/epoxy composite laminates having stacking sequence of [+Tn/-Tn/902n]s where constraint ply angle, T, was 0, 15, 30, 45, 60, and 75 degrees, and size was scaled as n=1,2,3, and 4, is reported in Part I. X-radiography was used to monitor damage developments. First-ply failure stress, and tensile strength were recorded. First-ply failure of the midplane 90 deg. plies depended on the stiffness of constraint plies, and size. All 24 cases were predicted using Zhang's shear-lag model and data generated from cross-ply tests. Laminate strength was controlled by the initiation of a triangular-shaped local delamination of the surface angle plies. This delamination was predicted using O'Brien's strain energy release rate model for delamination of surface angle plies. For each ply angle, the smallest laminate was used to predict delamination (and strength) of the other sizes. The in-situ tensile strength of the 0 deg. plies within different cross-ply, and quasi-isotropic laminates of varying size and stacking sequence is reported in Part II. No size effect was observed in the strength of 0 deg. plies for those lay-ups having failure confined to the gauge section. Laminates exhibiting a size-strength relationship, had grip region failures for the larger sizes. A statistically significant set of 3-point bend tests of unidirectional beams were used to provide parameters for a Weibull model, to re-examine relationship between ultimate strength of 0 deg. plies and specimen volume. The maximum stress in the 0 deg. plies in bending, and the tensile strength of the 0 deg. plies (from valid tests only) was the same. Weibull theory predicted loss of strength which was not observed in the experiments. An effort to model the durability and life of quasi-isotropic E-glass/913 epoxy composite laminates under steady load and in an acidic environment is reported in Part III. Stress-rupture tests of unidirectional coupons immersed in a weak hydrochloric acid solution was conducted to determine their stress-life response. Creep tests were conducted on unidirectional coupons parallel and transverse to the fibers, and on ±45°. layups to characterize the lamina stress- and time-dependent compliances. These data were used in a composite stress-rupture life model, based on the critical element modeling philosophy of Reifsnider, to predict the life of two ply-level thickness-scaled quasi-isotropic laminates. / Ph. D. stress-corrosion cracking stress relaxation strength scaling size effects microcracking first-ply failure delamination composite material weibull statistics tension testing flexural testing carbon/epoxy glass/epoxy creep stress0cupture creep-rupture durabilty life LD5655.V856 1997.L386
45	Měření parametrů pneumatik / Tyre Parameters Measurement Pokorný, Pavel January 2012 (has links) It is the tyre that ensures the interaction between a wheel and road surface and it is the the tyre which also acts as a primary cushioning. Its construction, features and condition highly influence driving properties of a car and thus passenger safety as well. In motorsports the tyre is a key part of the vehicle and therefore it is necessary to make use of its complete potential for reaching the best results. The aim of this thesis is a device construction suitable for tyre parameter and their characteristics measurement. The next task is to design a measuring system for tyre pressure and temperature monitoring. With using of these devices a few real-tyre measurements and subsequent result evaluation will be done. The output of the thesis is an overview of construction details, overview of selected tyre parameters, design and drawing documentation of multipurpose measuring device and the results of my measurements.
46	Verfahren zur Ermittlung des Einflusses von infrastrukturellen und betrieblichen Faktoren auf die spezifischen Kosten der Eisenbahninfrastruktur Alsalamat, Hassan 05 September 2012 (has links) (PDF) Die Arbeit ist ein Beitrag zur betrieblich-ökonomischen Optimierung der Eisenbahninfrastruktur auf der Grundlage ihres Kosten-Nutzen-Verhältnisses. Der wesentliche Inhalt der Arbeit ist die Erarbeitung einer Methodik, mit deren Hilfe die Kosten einer Eisenbahnstrecke je fahrbarer Zugtrasse, basierend auf Streckenstandards, der Deutsche Bahn AG, berechnet werden können. Kosten Erneuerungskosten Instandhaltungskosten Betriebserschwerniskosten Betriebsleistung Eisenbahninfrastruktur Oberbau Unterbau Leit- und Sicherungstechnik Oberleitung Bahnhofsabstand Blocklänge Geschwindigkeit Zugmischung Gleisanzahl spezifische Kosten Costs replacement costs maintenance costs operational hindrance costs operating performance railway infrastructure superstructure substructure Signaling Powers ply distance between stations block length speed specific cost ddc:380 ddc:620 rvk:QR 820
47	Systémy vytápění a chlazení v kancelářských provozech / Heating and cooling systems in office operations Dostál, Petr January 2020 (has links) The diploma thesis deals with the design of the heating and cooling system, inclu-ding hot water preparation for the administrative part of the production hall. The first part of the thesis briefly discusses the history of heating and cooling of office buildings, legislative requirements and current solutions. The second part contains the design of the entire heating and cooling system with heat pump as a source of heat and cold. The final part of the thesis describes the experimental measure-ment and evaluation of the efficiency of the ice rink source.
48	Sportovní hala / Sports hall Hindráková, Kateřina January 2013 (has links) The aim of this master‘s thesis is to design a sports hall including an accommodation facility in Hradec Králové. Sports hall is situated in a town district called Věkoše. It is tree-storey building equipped with combined pillar‘s and wall‘s support system. Building is founded on solid slab and propped piles. Pillars are made of steel, walls are made of ceramic bricks and curved roof is made of gluelam beams and roof trusses with aluminum cover system Kalzip. There are two single ply flat roofs. Also basement is a part of the building. For spectators two separated auditoriums with steel support system are designed. The accommodation for twenty people was split into ten rooms. It is designed as barrier free building for both sportsmen and audience.
49	Verfahren zur Ermittlung des Einflusses von infrastrukturellen und betrieblichen Faktoren auf die spezifischen Kosten der Eisenbahninfrastruktur Alsalamat, Hassan 25 June 2012 (has links) Die Arbeit ist ein Beitrag zur betrieblich-ökonomischen Optimierung der Eisenbahninfrastruktur auf der Grundlage ihres Kosten-Nutzen-Verhältnisses. Der wesentliche Inhalt der Arbeit ist die Erarbeitung einer Methodik, mit deren Hilfe die Kosten einer Eisenbahnstrecke je fahrbarer Zugtrasse, basierend auf Streckenstandards, der Deutsche Bahn AG, berechnet werden können. info:eu-repo/classification/ddc/380 ddc:380 info:eu-repo/classification/ddc/620 ddc:620

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