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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

Crack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shell

Cowan, Amy Lorraine 28 August 1999 (has links)
A finite element model of a fracture test specimen is developed using the STAGS computer code (STructural Analysis of General Shells). The test specimen was an internally pressurized, aluminum cylindrical shell reinforced with two externally bonded aluminum tear straps around its circumference. The shell contained an initial, axial through-crack centered between the straps. The crack propagated slowly in the axial direction as the pressure increased above a certain value until a maximum pressure was attained, and then the crack propagated dynamically. The tear straps sufficiently toughened the shell such that the dynamic crack path bifurcated near the edges of the straps. The bifurcated crack branches ran circumferentially, parallel to the straps causing the shell wall to flap open. The STAGS analysis for the static equilibrium configurations of the fractured shell include geometric nonlinearity and elastic-plastic material behavior. The crack tip opening angle (CTOA) is used in the criterion for ductile crack growth, and the critical value of the CTOA is determined by correlating the STAGS predictions of the stable portion of the crack growth curve (internal pressure versus half crack length) to the test. With the employment of a new STAGS algorithm, the complete axial crack growth curve, including both the stable and unstable portions, through the tear strap is obtained. The complete axial crack growth curve indicates that crack growth through the strap is unlikely. STAGS models with long cracks which bifurcate at various half crack lengths are developed to assess the location of crack bifurcation. Three different stress based crack turning criteria are investigated from the axial crack growth results as a second method for assessing a location of bifurcation. The bifurcation analyses and stress based turning criteria corroborate the experimentally measured bifurcation point. A parametric study is then conducted to determine the influence of tear strap thickness and width on the location of crack bifurcation. / Master of Science
2

Effects of Surface Condition on the Fatigue Behavior of CFRP-to-Steel Joints

Carrera Loza, Bernardo Jose 23 January 2023 (has links)
The strengthening of steel bridges using CFRP laminates has become a commonly used technique because of its numerous advantages compared to conventional repairs which involve welding or bolting of new steel plates. These structures will experience some sort of irregular cyclic loading during their lifetime and to analyze these complex loading cases, small scale testing is used to evaluate the fatigue performance between the steel substrate, adhesive layer and the CFRP laminate. In this research, double-strap joints (DSJ) were fabricated consisting of two high-modulus CFRP laminates and ASTM A36 steel plates bonded using a two-part epoxy adhesive. Two types of steel surface conditions were considered to evaluate the fatigue behavior under constant force amplitudes. Roughness on the steel substrate was achieved by ½ in (13 mm) diameter pits approximately 1/8 in (3.18 mm) deep to simulate an irregular surface. The results show that the surface condition has marginal influence on the total life of the specimens. To assess the damage accumulation in the DSJ, phenomenological methods like the nonlinear strength wearout Model (NLSW) and stiffness degradation were used. It was found that residual strength and stiffness decreased in a non-linear fashion. A non-linear model was used that agrees well with the experimental results and can be used to predict the residual strength of the specimens under variable amplitude fatigue (VAF). / Master of Science / With an aging and deteriorating infrastructure potentially being subjected to heavier loads than initially designed for, bridge engineers are increasingly looking for innovative, yet cost-effective solutions for repairing and maintaining the existing bridge inventory with sufficient capacity to carry legal loads. One alternative is to enhance the flexural strength of deteriorated steel members using carbon fiber-reinforced polymers (CFRP). This research project will investigate whether the use of CFRP retrofits is feasible for fatigue strengthening. The research will serve as insight to help guide bridge engineers or researchers on when and where the use of CFRP retrofits is suitable for the strengthening of steel bridges.
3

The p53 response : a new mitochondrial role for cofactor strap

Maniam, Sandra January 2013 (has links)
Strap is a DNA damage responsive p53 cofactor, reflecting its control by the DNA damage signalling pathway. This study identified Strap at the mitochondria where it is damage regulated and can augment p53-dependent cytochrome c release leading to apoptosis. Moreover, p53 and Strap facilitate each other’s localisation from the mitochondria to the nucleus during the DNA damage response. Two ATM/ATR phosphorylation consensus sites in Strap were identified by mass spectrometry and phosphorylation of all the ATM/ATR consensus sites resulted in mitochondrial localisation of Strap during DNA damage. Targeting Strap to the mitochondria depletes cellular ATP when cells favour energy production through oxidative phosphorylation and sensitises cells to p53-dependent damage-induced apoptosis. These results thus imply that Strap co-ordinates different arms of the p53 response, and might be responsible for integrating its mitochondrial and nuclear functions.
4

Analýza a konstrukční návrh uložení hasícího přístroje v osobních vozidlech / Analysis and design of extinguisher fastening in passanger vehicles

Koutný, Martin January 2020 (has links)
This thesis looks into current requirements of having fire extinguisher in a car in both the Czech Republic and other countries. At first, there is an evaluation of current ways of mounting fire extinguishers in cars, as well as evaluation of various requirements concering safety and ergonomy of mounting fire extinguisher in a car and also what are the hazards of having unattached fire extihnguisher in the passenger compartment. The objective of this thesis is to desing and test a fire extinguisher holder which would fullfil these requirements and which will not require changes in the body of the vehicle. The final part of this thesis deals with evaluating of possibilities of mounting this holder into several types of vehicles.
5

Predictive Modelling of CFRP-Steel Double Strap Joints

Jiwani, Preet Deepak 19 January 2023 (has links)
Carbon fiber reinforced polymers (CFRP), which can be used to strengthen and repair damaged steel structures, have gained popularity in recent years. On the one hand, CFRP has demonstrated substantial advantages over conventional reinforcing techniques like welding and bolting, such as light weight, high strength, and corrosion resistance. Additionally, the CFRP application process is relatively easy, rapid, and labor-intensive. On the other hand, failure is more likely to happen at the bond interface due to the high strength characteristics of steel and CFRP. Thus, studying the bond behavior and failure mechanism of CFRP strengthened steel structures as well as the variables that are crucial to the bond quality. Prior to implementing these elements in an actual construction, it is necessary to thoroughly study the factors affecting this bond strength. Despite the fact that some theoretical predictive modeling for the strength between steel/CFRP joints under various loading situations has been published, in this work, by using finite element modelling, one may compute the failure loads and effective length of the steel/CFRP specimens quickly, simply and accurately. Additionally, factors affecting these parameters are also investigated in this study. / Master of Science / Structural Steel deteriorates over time. Due to this, engineers are constantly on the look-out for cheap and easy ways to repair and maintain these structures. One of the methods is the use of carbon fibred polymer or CFRP. In the literature, it has been frequently documented that CFRPs can make existing structures stronger. Additionally, CFRP has the advantages of not corroding and prevents the structure from becoming significantly heavier. Due to this high strength of CFRP, the failure occurs at the steel-CFRP interface and thus this bond and the factors affecting this bond needs to be studied. One way to do this is experimental testing and another way is finite element modelling which can give you data that is harder to get using experimental testing. Thus, this study focuses on finite element modelling of these joints and how it can be used for studying these joints.
6

En undersökning om möjligheterna att använda återanvändningsbara pallband till enhetslaster omlastade till träpallar. / An investigation of the possibility to use reusable pallet strapping for unit loads reloaded to wooden pallets.

Björk, Tomas January 2007 (has links)
<p>En undersökning om möjligheterna att använda återandvändningsbara pallband och de ekonomiska förutsättningarna för detta. En genomsökning av vad som finns på marknaden. Beräkning av de krafter som enhetslasten kan utsätta pallbanden för. Utveckling av egna förslag till återanvändningsbart pallband med snabbspänne och bandning på tre sidor. En översikt av de positiva och negativa effekter som blir vid ett byte från dagens bandning med PP-band till ett återanvändningsbart pallband</p> / <p>An investigation of the possibility to use reusable strapping and the economic conditions for this. Going trough what exist on the market. Calculation of the forces that the unit load can expose the strapping for. Developing of own suggestions for reusable strapping with quick buckle and strapping on three sides. A short look at the positive and negative effects that comes from a change from today’s strapping with PP-strap to a reusable strapping.</p>
7

En undersökning om möjligheterna att använda återanvändningsbara pallband till enhetslaster omlastade till träpallar. / An investigation of the possibility to use reusable pallet strapping for unit loads reloaded to wooden pallets.

Björk, Tomas January 2007 (has links)
En undersökning om möjligheterna att använda återandvändningsbara pallband och de ekonomiska förutsättningarna för detta. En genomsökning av vad som finns på marknaden. Beräkning av de krafter som enhetslasten kan utsätta pallbanden för. Utveckling av egna förslag till återanvändningsbart pallband med snabbspänne och bandning på tre sidor. En översikt av de positiva och negativa effekter som blir vid ett byte från dagens bandning med PP-band till ett återanvändningsbart pallband / An investigation of the possibility to use reusable strapping and the economic conditions for this. Going trough what exist on the market. Calculation of the forces that the unit load can expose the strapping for. Developing of own suggestions for reusable strapping with quick buckle and strapping on three sides. A short look at the positive and negative effects that comes from a change from today’s strapping with PP-strap to a reusable strapping.
8

Low-Cost Semi-Active Laser Seekers for US Army Application

Hubbard, Keith, Katulka, Gary, Lyon, Dave, Petrick, Doug, Fresconi, Frank, Horwath, T. G. 10 1900 (has links)
ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / The U.S. Army Research Laboratory (ARL) is exploring technologies to provide low-cost precision fires, applicable across both direct and indirect fire weapon systems. One of these applications involves a forward observer (FO) designating the target with a laser spot and a seeker on-board the munition detecting the reflected energy to allow terminal guidance. This approach, referred to as semi-active laser (SAL) guidance, has been utilized on numerous air-delivered munitions to include bombs, missiles and projectiles. However, the cost of these systems, driven by high quality optics, high sensitivity detectors and specialized electronics, has hampered their migration into gun-fired munitions such as mortars, artillery and grenades. To explore, develop and demonstrate minimal cost solutions, ARL invested in an Army Technical Objective (ATO) called Smaller, Lighter, Cheaper Munition Components (SLCMC). Specifically, SAL seeker hardware, predicated upon commercial components (COTS) and mass production techniques, is being prototyped for use with gun launched projectiles and laser target designators. The seeker system is comprised of several printed circuit board boards, a microprocessor, a quad-photo detector and, a molded optical lens unit. This seeker is designed to rapidly update the projectile boresight angle, interface with other strap-down sensors, and feed data into an on-board guidance, navigation & control (G,N&C) system to allow for projectile maneuvers. The seeker design and basic characteristics are discussed and presented through-out the paper and presentation.
9

OPTIMIZACIÓN HEURISTICA MULTIOBJETIVO DE CIMENTACIONES DE SOPORTES EN MEDIANERIA

Cano Pérez, Carlos 05 April 2016 (has links)
[EN] The main goal of this Thesis is the application of a suitable heuristic optimization algorithm that allows finding optimal solutions to the structural problem of faced brackets foundation, when one of them is located in a sharecropping, and therefore, the disposition of its foundation is prevented in one direction. Since there are various structural models to solve the problem, it is the most commonly used in current practice. Isolated footings, constant width combined footing, asymmetrical combined footing, and beam brace eccentric shoe are the structural models finally selected. Also, it has been confirmed the existence of various analytical models to solve the problem. Included in this Thesis is the simplest analysis model, commonly used inprofessional practice, and a more complex model that we call elastic simplified method. The first is the named "Rigid foundation", which is based on the premise of a rigid behavior foundation. This implies the assumption of a linear distribution of the pressure transmitted to the ground. On the other hand, it will also analyze a model of analysis that does not limit the performance of the foundation only to the case of rigid foundation,modeling the terrain with springs through the so-called 'subgrade reaction'. As a further aim of the Thesis, is to determine the structural model and the most suitable analysis model for solving the problem and determine the differences with other commonly used models. Another objective of the thesis will be to evaluate the different objective functions, so that they may assess the optimal solution in terms of economic, environmental and ease of construction. From the literature review, it has noted the existence of numerous optimization studies conducted in search of economic optimum (cost of the solution, solution weight) and from the environmental point of view (CO2 emissions, energy consumption, solution weight). From the standpoint of ease of construction of the solution, studies are lower, including parameters 'Armed uniformity, number of reinforcing bars or number of different bar types'. In this Thesis all these objective functions will be evaluated, incorporating environmental features such as the study of water consumption of the constituent materials and from the point of view of ease of construction, the perimeter / area ratio and the parameter average diameter of the solution, which will be defined later. Another of the objectives set for the thesis has been to be able to compare the results obtained by applying the "Simulated Annealing" algorithm, with the results that have been obtained in routine practice, following the usual process of structural calculation.A sample calculation in joint shoe is included in the book "Cálculo de estructuras de cimentacion" 4th edition from Calavera, comparing the values of objective functions of the solution provided in the book, with those achieved after application of optimization SA algorithm and those collected after using a structural calculation software widely used in practice, as is "Cypecad ver 2014". Finally, the ultimate goal of the thesis has been conducting a parametric study that allows providing the optimal solutions for a wide range of the problem under study configurations / [ES] El objetivo fundamental de la presente Tesis es la aplicación de un algoritmo de optimización heurístico adecuado, que permita localizar soluciones óptimas al problema estructural consistente en la cimentación de dos soportes enfrentados, cuando uno de ellos se sitúa en una medianería, y por tanto, tiene impedida en una dirección la disposición de su cimiento. Dado que existen diversos modelos estructurales que permiten solucionar el problema, se ha seleccionado entre ellos, los más habitualmente utilizados en la práctica actual.. Los modelos estructurales finalmente seleccionados han sido los constituidos por zapatas aisladas, zapata combinada de ancho constante, zapata combinada asimétrica y zapata excéntrica con viga riostra. También se ha podido confirmar la existencia de diversos modelos de análisis para la solución del problema, incuyéndose en la tesis tanto el modelo más sencillo de análisis, utilizado habitualmente en la práctica profesional, como un modelo más complejo que denominaremos, modelo elástico simplificado. El primero de ellos será el denominado 'Cimiento Rígido', donde se partirá de la premisa de un comportamiento rígido del cimiento, lo que implicará la suposición de que presión transmitida al terreno sigue una distribución lineal. Por otro lado, se analizará también un modelo de análisis que no limitará el comportamiento del cimiento únicamente al caso de cimiento rígido, modelizando el terreno mediante muelles a través del denominado 'Módulo de Balasto'. Como objetivo adicional de la tesis se establecerá el poder determinar el modelo estructural y el modelo de análisis más adecuado para la resolución del problema y determinar las diferencias con el resto de modelos usualmente utilizados. Otro de los objetivos de la tesis será el de poder evaluar distintas funciones objetivo, de forma que se pueda evaluar el óptimo de una solución desde el punto de vista económico, medioambiental y de facilidad constructiva. De la revisión bibliográfica realizada, se ha podido constatar la existencia de numerosos estudios de optimización realizados en busca de óptimos económicos (coste de la solución, peso de la solución) y desde el punto de vista medioambiental (emisiones de CO2, consumo de energía, peso de la solución). Desde el punto de vista de la facilidad constructiva de la solución, los estudios realizados son menores, incluyéndose parámetros de 'Uniformidad de Armado, Número de barras de armado o número de tipo de barras distintos'. En la presente tesis se evaluarán todas estas funciones objetivo, incorporándose como funciones de tipo medioambiental, el estudio de consumo de agua de los materiales constituyentes de la solución y desde el punto de vista de la facilidad constructiva, la relación Perímetro/ Área y el parámetro Diámetro Medio de la solución, que se definirán más tarde. Otro de los objetivos establecidos para la tesis ha sido el de poder comparar los resultados obtenidos mediante la aplicación del algoritmo de Simulated Annealing, con los resultados que se hubieran obtenido en la práctica profesional habitual, siguiendo los procesos habituales de cálculo estructural. Para ello, se desarrolla un ejemplo de cálculo de zapata en medianería incluido en el libro "Cálculo de estructuras de cimentación" Edición 4, de Calavera, comparando los valores de las funciones objetivo de la solución aportada en el libro, con las alcanzadas tras la aplicación del algoritmo de optimización de SA y las conseguidas tras el uso de un software de cálculo estructural ampliamente utilizado en la práctica, como es 'Cypecad ver 2014'. Por último, el objetivo final de la tesis ha sido la realización de un estudio paramétrico, que permita aportar las soluciones óptimas de un amplio abanicos de configuraciones del problema en estudio. / [CAT] L'objectiu fonamental de la present Tesi és l'aplicació d'un algoritme d'optimització heurístic adequat, que permeta localitzar solucions òptimes al problema estructural consistent en la fonamentació de dos suports enfrontats, quan un d'ells se sitúa en una paret mitgera, i per tant, té impedida en una direcció la disposició del seu fonament.Atés que hi ha diversos models estructurals que permeten solucionar el problema, s'ha seleccionat entre ells, els més habitualment utilitzats en la pràctica. Els models estructurals finalment seleccionats han sigut els constituïts per zapatas aïllades, zapata combinada d'ample constant, zapata combinada asimètrica i zapata excèntrica amb biga riostra. També s'ha pogut confirmar l'existència de diversos models d'anàlisi per a la solució del problema, incuyéndose en la tesi tant el model més senzill d'analisis, utilitzat habitualment en la pràctica professional, com un model més complex que denominarem, model elàstic simplificat. El primer d'ells serà el denominat 'Cimiento Rígido', on es partirà de la premissa d'un comportament rígid del fonament, la qual cosa implicarà la suposició que pressió transmesa al terreny seguix una distribució lineal. D'altra banda, s'analitzarà també un model d'anàlisi que no limitarà el comportament del fonament unicamente al cas de fonament rígid, odelizando el terreny per mitjà de molls a través del denominat 'Módulo de Balasto'. Com a objectiu addicional de la tesi s'establirà el poder determinar el model estructural i el model d'anàlisi més adequat per a la resolució del problema i determinar les diferències amb la resta de models usualment utilitzats. Un altre dels objectius de la tesi sera el de poder avaluar distintes funcions objectiu, de manera que es puga avaluar l'òptim d'una solució des del punt de vista econòmic, mediambiental i de facilitat constructiva. De la revisió bibliogràfica realitzada, s'ha pogut constatar l'existència de nombrosos estudis d'optimització realitzats a la cerca d'òptims econòmics (cost de la solució, pes de la solució) i des del punt de vista mediambiental (emissions de CO2, consum d'energia, pes de la solució). Des del punt de vista de la facilitat constructiva de la solució, els estudis realitzats són menors, incloent-se paràmetres de 'Uniformidad d'Armat, nombre de barres d'armat o nombre de tipus de barres distintos'. En la present tesi s'avaluaren totes estàs funciones objectiu, incorporant-se com funciones de tipus mediambiental, l'estudi de consum d'aigua dels materials constituents de la solució i des del punt de vista de la facilitat constructiva, la relació Perímetro/ Àrea i el paràmetre Diàmetre Mitjà de la solució, que es definirà més tard. Un altre dels objectius establits per a la tesi ha sigut el de poder comparar els resultats obtinguts per mitjà de l'aplicació de l'algoritme de Simulated Annealing, amb els resultats que s'hagueren obtingut en la pràctica professional habitual, seguint els processos habituals de càlcul estructural. Per a això, es desenrotlla un exemple de càlcul de zapata en paret mitgera inclòs en el llibre "Cálculo d'estructures de cimentacion" Edició 4, de Calavera, comparant els valors de les funcions objectiu de la solució aportada en el llibre, amb les aconseguides després de l'aplicació de l'algoritme d'optimització de SA i les aconseguides després de l'ús d'un programari de càlcul estructural ampliament utilitzat en la pràctica, com és 'Cypecad ver 2014' Finalment, l'objectiu final de la tesi ha sigut la realització d'un estudi paramètric, que permeta aportar la solucions òptimes d'un ampli espectre de configuracions del problema en estudi / Cano Pérez, C. (2016). OPTIMIZACIÓN HEURISTICA MULTIOBJETIVO DE CIMENTACIONES DE SOPORTES EN MEDIANERIA [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62208 / TESIS
10

Výroba montážního pásku / Manufacturing of strap assembly

Furch, Michal January 2013 (has links)
The strap assembly serves to fix the ventilation duct. The used material is a ferritic stainless steel 1.4510 (DIN 17041) of unusual thickness 1.27 mm. As a production method from possible variations with regard to the production run 120000 pcs a year was selected the technology of shearing and bending. On the basis of structural calculations the tools were designed and the equipment chosen. The work includes drawings of selected parts of tools and complete sets. The cutting takes place in a fully automated line, the bending is controlled by employee. Costs were counted by economic calculations CZK 8.12 per part.

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