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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

Prediction of dynamic bending stresses of ships at sea /

Rogers, Frederick, January 1999 (has links)
Thesis (M. Eng.), Memorial University of Newfoundland, 1999. / Bibliography: p. 52.
2

Secondary stresses in bowstring timber trusses

Bradford, John F. 01 January 1983 (has links)
This study was undertaken in order to determine analytically the magnitude of the secondary (i.e., joint deflection induced) moments in the continuous glued-laminated chords of bowstring timber trusses. Traditionally, these moments have been assumed to be small and therefore neglected. The American Institute of Timber Construction makes no mention of these moments in their recommended design procedure.
3

The Effects of Pruning on Wind Resistance of Shade Trees

Pavlis, Michael William 24 September 2007 (has links)
Three tree species, Freeman maple (Acer x. freemanii), swamp white oak (Quercus bicolor (Willd.)) and shingle oak (Quercus imbricaria (Michx.)) were tested before and after pruning to determine the effectiveness of pruning on reducing drag and bending moment. Pruning methods were thin, reduce and raise and meet the requirements set by the American National Standard Institute A300 standards for Tree Care Operations Trees, Shrub, and Other Woody Plant Maintenance - Standard Practices (Pruning). Trees were tested up to speeds of 22.4m*s-1 over 1.6km by driving them in the bed of a truck. Drag, based on a centroid of the crown, and a bending moment was calculated. Drag and bending moment were also normalized by tree mass and crown area. Reduction pruning worked more effectively for Freeman maple and raise pruning for swamp white oak at reducing drag. Simple to measure tree characteristics were analyzed to determine the best predictors of drag and bending moment in the field. Tree mass frequently was the best predictor of drag and bending moment. Information should be used with caution due to the fact that the trees tested were small stature and a limited number of trees were tested. / Master of Science
4

The transformation behaviour and hot strength of 3CR12 during the continuous casting process

Siyasiya, Charles Witness 20 June 2005 (has links)
Extensive research has been done over the years and has contributed quite a lot to the development of 3CR12 stainless steel. Nevertheless, there is still much to be understood about the behaviour of this steel during its production. One of the problems that are occasionally encountered is the side bulging effect i.e. the unconstrained narrow faces of the strand plastically bulge due to ferrostatic pressure from the liquid core of the strand at high temperatures. In general, this problem is prevalent in ferritic stainless steels as they exhibit a weaker hot strength than austenitic stainless steels. Coupled with side bulging, there is also strand width variation at high temperatures i.e. when the steel is in the ferrite-austenite dual phase region. Both of these dimensional changes to the slab profile create some processing problems in subsequent hot rolling operations when unacceptable width variations are encountered. This work was, therefore, motivated by the requirement to quantify the role that the metallurgical behaviour of this steel plays with regard to the above width variation problem. The research work involved studies of the <font face="symbol">d</font>-ferrite to austenite phase change during continuous cooling (simulating cooling during continuous casting) and the establishment of CCT diagrams, the influence of chemical composition on the austenite start temperature and the hot ductility and hot strength visà-vis the side bulging effect. The casting conditions in the mould are crucial to ensure that the solidification shell is thick enough to withstand the ferrostatic pressure exerted on the unconstrained narrow sides of the strand as it exits from the mould. Therefore, part of the solution lies in the study of the optimisation of the cooling rate, mould flux properties, casting speed, mould taper angle and the chemical composition of this steel, among other factors. Additions of austenite formers, within the specification range of 3CR12, should be favourable for a stronger solidification shell since austenite exhibits superior hot strength to <font face="symbol">d</font>-ferrite. The good hot ductility observed in 3CR12 may also provide a leeway for increasing the secondary cooling rate in order to form a thicker solidification shell soon after emerging from the mould. This may reduce the side bulging effect. This can be achieved without a risk of transverse cracking if the cooling is adjusted carefully. As long as the <font face="symbol">d</font>-ferrite to austenite phase ratio keeps fluctuating due to variations in (i) the chemical composition within the specification range and (ii) the cooling rate in the dual phase region from cast to cast, the strand width variation effect will persist. This is simply because of the effect these have on the ferrite to austenite phase ratios through the differences between the lattice structures of these two phases. Ferrite being less dense than austenite, occupies more volume than austenite, thereby affecting the slab width. The remedy to this problem is to control within stricter chemical composition limits in order to reduce or completely avert this width variation effect. / Dissertation (MSc (Metallurgy))--University of Pretoria, 2006. / Materials Science and Metallurgical Engineering / unrestricted
5

Development of a Computational Method for the Prediction of Wave Induced Longitudinal Bending in Ships

Rogers, Charles 01 May 2012 (has links)
This thesis documents the development of a computational method for wave induced longitudinal bending in ships. First, there will be a discussion about the importance of longitudinal bending in ship design. The paper will then outline the basic physics at work in the system. It will review the wave forcing computation as well as the response of the vessel. It will then document the progression of the program, which was constructed in Fortran 90, as it solves the linear differential equation for the vessel bending caused by an incoming wave. The entire program then appears at the end of the paper. While the current program is not complete the theory behind it is valid and the code can be augmented to include non-linear components in the future.
6

A novel method to measure finite strain fields in human skeletal muscles with cine phase contrast MRI in vivo, non-invasively and dynamically

Zhou, Hehe. January 2006 (has links)
Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: John E . Novotny, Dept. of Mechanical Engineering. Includes bibliographical references.
7

Skillnaden i det dorsala böjmomentet vid MTP, utan rullsula och med två olika styvheter på rullsulan

Kassberg, Fanny, Antonsson, Johan January 2019 (has links)
Bakgrund: Rullsulor används för att kompensera för ledstelhet, förbättra avveckling av steget, minska höga tryck plantart och minska böjningen vid tålederna.  Det finns dock få studier som undersöker om rullsulan verkligen minskar ledrörlighet i framfoten. Det saknas även information för betydelsen av rullsulans styvhet för böjmomentet av framfoten, vid avvecklingen av steget.   Metod: Fem friska kvinnor (n=5) gick med tre olika par skor, två par var modifierade med en likadan rullsula med olika styvheter och ett par utan rullsula. Fem upprepade mätningar för de tre olika skorna samlades in för alla deltagare. Det dorsala böjmomentet analyserades med sensorsulan (VebitoSCIENCE) som ersatte skons innersula.   Resultat: Det dorsala böjmomentet minskade för samtliga deltagare med en rullsula. Signifikant minskning av det dorsala böjmomentet vid MTP 1, för alla deltagare, när den styva rullsulan jämfördes med utan rullsula (94,4 – 20,1 Nmm) och mellan styv och flexibel rullsula för deltagare 1,2, 4 &amp; 5 (68 – 22,2 Nmm).   Konklusion: Det dorsala böjmomentet minskade signifikant för MTP1 och MTP5 när en rullsula användes av friska kvinnor. Studien har också visat att en styv rullsula har en betydelse för att uppnå ett minskat dorsalt böjmoment vid MTP. / Background: Rocker soles are used to compensate for joint stiffness, reduce high plantar pressure and reduce the bending of the toe joints. Despite this, few studies have investigated if the rocker shoe really reduce the joint movement at the forefoot. There is also a lack of information regarding the importance of the rocker shoes stiffness for the bending moment of the forefoot, at the third rocker.   Method: Five healthy women (n=5) walked with three different pairs of shoes, two pairs were modified with the same rocker shape with different stiffness and one pair without a rocker. Five repeated measurements for the three different shoes were collected for all the participants. The dorsal bending moment was analyzed with a sensor sole (VebitoSCIENCE) that replaced the shoes insole.   Result: The dorsal bending moment was reduced for all participants with a rocker shoe. Significant reduction of the dorsal bending moment at MTP1, for all participants, when the stiff rocker was compared to the shoe without rocker (94,4 – 20,1 Nmm) and between the stiff and flexible rocker for participants 1,2,4 and 5 (68 -22,2 Nmm).   Conclusion: The dorsal bending moment was significantly reduced for MTP 1 and MTP 5 when a rocker shoe was used by healthy women, the study has also shown that the stiffness has an importance in order to achieve a reduction of the dorsal bending moment at MTP.
8

Capacity calculator of rotary draw tube bending

Köseoğlu, Seda, Parlak, Hasan January 2012 (has links)
Plastic  deformation of tubes can be achieved in numerous ways. One of the most useful type is CNC tube bending machines which is used in many industries such as aerospace, automotive, HVAC systems and so on. It is important that all components of system should mate properly after producing and because of this bend shaping requires sensitive operation on each components to ensure regularity of production processes with high quality end-product. Thus, the CNC tube bending industry to become widespread. However it brings some troubleshooting like wrinkling, springback, breakage and ovalisation. This failures depends on geometry of the material such as bending radius, tube thickness and also friction factor between dies and the tube. Effects of all parameters should be examined before generating the theory for a best solution. Therefore, prediction of the required moment for the proper bending process with low cost and shortened production time is needed. All of these requirements can be achieved through a C++ form application program.
9

Distribution Of Bending Moments In Laterally Loaded Passive Pile Groups A Model Study

Ozturk, Sevki 01 February 2009 (has links) (PDF)
In this study, bending moment distributions developed in laterally loaded passive pile and passive pile groups in cohesionless soil were investigated in laboratory conditions through model pile experiments. Different from the active pile loading, the lateral load was given directly to the piles using a movable large direct shear box. In these experiments strain gauges fastened to the piles and a computer based data reading system were used. The strain values were measured at five levels on the piles. The behavior of a single pile and a pile group having five piles were investigated through strain measurements in order to observe bending moment distribution on the piles. After evaluating the test results, the behavior of passive single pile was found to be similar to the results obtained in early studies. Negative bending moments were observed at the specified depths above the shear plane and positive bending moments were measured at the level of the shear plane and below the shear plane. Maximum bending moments were obtained at 0.7L (L: Length of Pile) for single piles and piles in the group. Above the shear plane, maximum bending moments within the pile group were found to be developed on the piles nearest to the loading. On the shear plane maximum bending moments were developed on the piles farthest from the loading just like active piles. Below the shear plane, maximum bending moments were developed mainly on the piles nearest to the loading.
10

Estimation of wave-induced ship hull bending moment from ship motion measurements /

Xu, Jinsong, January 2000 (has links)
Thesis (Ph.D.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 117-120.

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