Tesi sul tema "Marine steel"
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1
Gurusamy, K. "The marine durability of steel fibre reinforced concrete". Thesis, University of Aberdeen, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234802.
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2
Cheung, Chin Wa Sunny. "Biofilms of marine sulphate-reducing bacteria on mild steel". Thesis, University of Portsmouth, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241657.
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3
Barrett, S. J. "Marine fouling processes upon stainless steel and elastomeric surfaces". Thesis, University of Surrey, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233236.
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4
Paliwal, M. C. "Running-in and scuffing failure of marine gears". Thesis, Bucks New University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376640.
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5
Molloy, Brian T. "Steel fibre and rebar corrosion in concrete under marine curing". Thesis, University of Aberdeen, 1990. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU032222.
Testo completoAbstract (sommario):
Concern for durability of reinforced concrete structures has, in recent years, coincided with an increasing interest in the use of steel fibre reinforcement. In this investigation the corrosion behaviour of conventional and steel fibre reinforcement in concrete under long term marine curing have been studied. The corrosion behaviour of reinforcement has been assessed visually, and by using electrochemical techniques. Three types of steel fibre were investigated namely low carbon steel, stainless steel melt extract, and galvanised steel. Previous studies have shown that steel fibres exhibit good corrosion resistance in concrete exposed to marine curing. It has been suggested that this is due to the discrete nature of the individual steel fibres which prevents the development of electrochemical cells with large cathode/anode area ratios. In order to determine, therefore, whether a 'size-effect' phenomenon influences steel fibre corrosion rates, concrete specimens were cast with different lengths and diameters of steel wire and subsequently exposed to marine curing. Parallel concrete specimens containing samples of conventional reinforcing bar were also manufactured. Cement replacement materials such as pulverised fuel ash, ground granulated blast furnace slag and microsilica are widely used in order to enhance specific properties of fresh or hardened concrete. In this investigation durability characteristics of concrete containing cement replacement materials were studied. These characteristics, including alkalinity of pore fluid and diffusion rates of chloride ions are of importance in relation to the passivation or corrosion of steel reinforcement.
6
Sheikh, Abdi Mohamed, e Yosef Gebresilassie. "Consequences of Magnetic Properties in Stainless Steel for a High-efficiency Wave Power Generator". Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-229479.
Testo completoAbstract (sommario):
A new kind of wave power generator is being developed at KTH Royal Institute of Technology which potentially can reach an efficiency of 98 %. However, this generator’s small air gap sets strict requirements on the stiffness of the structure to withstand the large magnetic forces. The structure, therefore, need to be both stiff and non-magnetic. To tackle that problem austenitic stainless steel will be used. Then again, austenitic stainless steel tends to become slightly magnetic because of impurities and mechanical stress. The purpose of this report is to study the magnetic properties of the austenitic stainless steel and observe how mechanical stress can change their properties. Moreover, economic and environmental aspects considering the use and production of the steel are studied. Two experiments were applied to measure the magnetic properties, using an LCR-meter and an electrical circuit with a current amplifier. Both methods showed that mechanical stress will result in changing the magnetic property of austenitic stainless steel. Some steel types were less affected by the mechanical stress applied leading to the conclusion that they are more effective when placed near the generator’s air gap. Regarding sustainable development, it is uncertain to determine the impact the generator has on the environment, mainly because of the steel types manufacturing process is unknown. On the contrary, the maintenance costs of the generator are predicted to be low and if the prototype fulfills the efficiency expectations it will have a huge impact on the future of wave power technology.En ny typ av vågkraftsgenerator utvecklas på KTH som potentiellt kan uppnå en verkningsgrad på 98%. Denna generators lilla luftgap ställer dock strikta krav på strukturens styvhet för att stå emot de stora magnetiska krafterna. Strukturen måste därför vara både styv och icke-magnetisk. För att ta itu med det problemet kommer austenitiskt rostfritt stål att användas. Sedan tenderar austenitiskt rostfritt stål att bli något magnetiskt på grund av föroreningar och mekanisk stress. Syftet med denna rapport är att studera austenitiskt rostfritt ståls magnetiska egenskaper och observera hur mekanisk stress kan förändra deras egenskaper. Dessutom studeras ekonomiska och miljömässiga aspekter som beaktar stålets användning och produktion. Två experiment utfördes för att mäta de magnetiska egenskaperna, med användning av en LCR-mätare och en elektrisk krets med en strömförstärkare. Båda metoderna visade att mekanisk stress kommer att leda till förändring av den magnetiska egenskapen hos austenitiskt rostfritt stål. Vissa ståltyper påverkades mindre av den mekaniska påfrestningen som ledde till slutsatsen att de är mer effektiva när de placeras nära generatorns luftgap. När det gäller hållbar utveckling är det osäkert att bestämma vilken påverkan generatorn har på miljön, främst på grund av att detrostfria stålets tillverkningsprocess är okänd. Tvärtom förmodas att underhållskostnaderna för generatorn komme vara låga och om prototypen uppfyller effektivitetsförväntningarna kommer det att ha en stor inverkan på framtiden för vågkrafttekniken.
7
Sanchez, Andrea Nathalie. "Forecasting Corrosion of Steel in Concrete Introducing Chloride Threshold Dependence on Steel Potential". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5303.
Testo completoAbstract (sommario):
Corrosion initiates in reinforced concrete structures exposed to marine environments when the chloride ion concentration at the surface of an embedded steel reinforcing bar exceeds the chloride corrosion threshold (CT) value. The value of CT is generally assumed to have a conservative fixed value ranging from 0.2% to - 0.5 % of chloride ions by weight of cement. However, extensive experimental investigations confirmed that CT is not a fixed value and that the value of CT depends on many variables. Among those, the potential of passive steel embedded in concrete is a key influential factor on the value of CT and has received little attention in the literature. The phenomenon of a potential-dependent threshold (PDT) permits accounting for corrosion macrocell coupling between active and passive steel assembly components in corrosion forecast models, avoiding overly conservative long-term damage projections and leading to more efficient design. The objectives of this investigation was to 1) expand by a systematic experimental assessment the knowledge and data base on how dependent the chloride threshold is on the potential of the steel embedded in concrete and 2) introduce the chloride threshold dependence on steel potential as an integral part of corrosion-related service life prediction of reinforced concrete structures. Experimental assessments on PDT were found in the literature but for a limited set of conditions. Therefore, experiments were conducted with mortar and concrete specimens and exposed to conditions more representative of the field than those previously available. The experimental results confirmed the presence of the PDT effect and provided supporting information to use a value of -550 mV per decade of Cl- for the cathodic prevention slope βCT, a critical quantitative input for implementation in a practical model. A refinement of a previous corrosion initiation-propagation model that incorporated PDT in a partially submerged reinforced concrete column in sea water was developed. Corrosion was assumed to start when the chloride corrosion threshold was reached in an active steel zone of a given size, followed by recalculating the potential distribution and update threshold values over the entire system at each time step. Notably, results of this work indicated that when PDT is ignored, as is the case in present forecasting model practice, the corrosion damage prediction can be overly conservative which could lead to structural overdesign or misguided future damage management planning. Implementation of PDT in next-generation models is therefore highly desirable. However, developing a mathematical model that forecasts the corrosion damage of an entire marine structure with a fully implemented PDT module can result in excessive computational complexity. Hence, a provisional simplified approach for incorporating the effect of PDT was developed. The approach uses a correction function to be applied to projections that have been computed using the traditional procedures.
8
Boyd, Stephen William. "Strength and durability of steel to composite joints for marine application". Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/142615/.
Testo completoAbstract (sommario):
This thesis deals with the assessment of the strength and durability of steel to composite joints for composite superstructures on ships where reduced weight is a design driver. The purpose of the work is to understand the long-term performance characteristics of hybrid connections to allow for improvements to the design of hybrid structures. Two joints were investigated in the present research. The first was a full-scale connection suitable for application in superstructures of marine vehicles, specifically a helicopter hanger on a naval vessel. The second was a generic steel/composite connection for testing performance after hygrothermal ageing. The strength and durability of the full-scale connection were examined in compression, the loading scenario representative of in-service conditions. The results indicated that the static and fatigue performance were in excess of the realistic in-service loading conditions. Failure for both static and fatigue tests were comparable and therefore good confidence in the prediction of the joint’s failure was achieved. The generic hybrid connection was artificially aged through immersion in water. The results indicated that there was no significant reduction in the performance of the joint in either static tension or bending. The numerical modelling highlighted a number of issues. Due to the geometry of the joint high stress concentration factors were observed in some locations. It is in these areas that failure of the joint was predicted in the numerical modelling. Similar results were obtained experimentally and this gave confidence in the modelling of the joint. Numerical parametric and optimisation studies were conducted to assess the influence of the joint geometry on performance characteristics obtained from both the experimental and numerical studies. This highlighted that improvements to the performance of the joint could be obtained through geometric changes alone.
9
Watkins, Peter Gareth. "The corrosion of mild steel in the presence of two isolates of marine sulphate reducing bacteria". Thesis, University of Portsmouth, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340914.
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10
Kear, Gareth. "Electrochemical corrosion of marine alloys under flowing conditions". Thesis, University of Portsmouth, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369433.
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11
Williams, Kevin. "Feasibility of Application of Cathodic Prevention to Cracked Reinforced Concrete in Marine Service". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5333.
Testo completoAbstract (sommario):
Corrosion can take place as chloride ions accumulate above a critical concentration (CT) at the surface of a reinforcing bar inside concrete in marine service. The initiation of corrosion can be delayed by polarizing the steel cathodically, which is known to increase the value of CT. That effect is the basis of the cathodic prevention (CPrev) method to control corrosion of reinforcing steel in concrete. However, concrete cracks are a common occurrence and at cracks, the buildup of chloride ions is accelerated to the extent that CPrev may be less effective. The findings from an ongoing investigation to determine the effectiveness of cathodic prevention on cracked concrete exposed to a marine environment are presented. Experiments were conducted on reinforced concrete blocks with controlled-width cracks placed along the length of a central reinforcing steel bar. A ponding area on top of each specimen allowed for cyclic exposure to a 5% NaCl solution to imitate a marine environment. Crack widths ranging from 0.01 inch to 0.04 inch and polarization levels ranging from -330 mV to -540 mV were used. The onset of corrosion as a function of time of exposure was determined by measurements of the cathodic current demand needed to reach each target polarization level. The ranking of time to onset of corrosion was used as an indicator to determine how much cathodic prevention is necessary to effectively extend the life of cracked concrete. Results to date suggest that a minimum cathodic polarization level in the range of -540 mV would be needed.
12
Fabbri, Marco. "Effect of marine atmosphere on the fatigue behavior of CFRP strengthened steel plates". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Cerca il testo completoAbstract (sommario):
Fatigue still represents one of the most detrimental causes of steel structure failure. Carbon fiber-reinforced polymer (CFRP) composites offer a good opportunity in structural repair because of their high strength-to-weight ratio and the possibility to obtain the material in different forms, which can fit all desirable geometries. Commonly, steel structures experience either service load and environmental exposure simultaneously, and however, the effect of this combination is still not analyzed enough nowadays, especially in fatigue terms.
This paper highlights an experimental analysis of the fatigue performance of steel plates repaired with CFRP laminates subjected to the marine environment. Five degrees of initial damage to the steel plates were considered. The bond consisted of one layer of CFRP laminate adhesively bonded on both sides of the plate with two different patches, i.e., fully covered and partially covered. The specimens were exposed to a simulated marine atmosphere for up to one and six months. In order to reproduce service load stress, the plates were subjected to a static tensile load during exposure. After submergence, the fatigue life was tested at room temperature and the crack propagation was monitored throughout the beach marking technique. The effect of environmental exposure on the epoxy was also carefully investigated.
The improvements provided by CFRP bonded to steel were successfully maintained after exposure to harsh environmental conditions although decrements of fatigue life were accounted after six months of exposure. The decrements of the fatigue life due to the environmental effect ranged from 3% to 30% compared to the unexposed specimens. Marine atmosphere mostly affected the integrity of the interfaces, since adhesion failures occurred progressively from one to six months of exposure.
The work provides useful recommendations for practical purpose and it suggests topics which require further investigation.
13
Wang, Yikun. "Ultimate strength and mechano-electrochemical investigations of steel marine structures subject to corrosion". Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/378219/.
Testo completoAbstract (sommario):
It is well known that ageing steel marine structures are susceptible to corrosion in its all manifestations. The most critical areas are cargo and ballast tanks of merchant ships. However, due to the regulations such as the Performance Standard for Protective Coatings, which requires a 15-year target life of coating in ballast tanks, plus the cathodic protection systems, the internal structures within cargo holds have become more problematic but poorly studied. In the underdeck area and bottom plating, the structures are not normally fully protected. Also, the complex structural arrangement may place difficulties in inspection and repair. In extreme cases, it has been reported that the corrosion rate in these areas could be 5 to 7 times higher than a normal value, and has led to catastrophic structural failures. Currently, the classification societies apply both visual and gauging methods for corrosion inspection during ship surveys. However, it is time consuming especially for large vessels and is highly experience dependent. Therefore, to improve the survey efficiency, facilitate economical maintenance decisions, and even extend the structural life, it is essential to investigate the ultimate strength of such aged and corroded steel structures. Based on the identification of existing corrosion issues in cargo tanks of oil tankers and bulk carriers and the state-of-art of corroded marine structural strength assessments, a nonlinear finite element method was adopted to investigate the influences of pitting and grooving corrosion on the structural integrity. Two full-field experimental techniques were used for a complete validation of the numerical models. Based on the repair conditions provided by classification societies, the numerical results showed that 25% locally corroded area of a plate (800 mm × 800 mm × 15 mm) with 3.75 mm remaining thickness may reduce the ultimate strength by up to 20% compared to a uniformly corroded plate. The weld-induced grooving corrosion of a width of 59 mm and a remaining thickness of 3.75 mm would cause up to 26% strength capacity reduction for a stiffened plate (4750 mm × 950 mm × 15 mm). Moreover, it was shown that the corrosion depth had a greater influence on structural performance compared to corrosion area for the same volume/material loss. By combining mechano-electrochemical protocols with the stress and strain results obtained from the modelling, it enables predictions of the ‘hot spot’ locations of mechanically-induced corrosion acceleration. Results showed that the anodic current density inside grooving corrosion damage (24 mm in width and 3.75 mm in depth) was 7 times greater vis-a-vis the unstressed condition for the stiffened plate at its ultimate strength state. The results, which are closely related to the industrial corrosion inspection and repair requirement, will not only benefit the shipping industry, but are also applicable to a whole range of marine structures (offshore platforms and steel bridges).
14
Walsh, Michael Thomas. "Corrosion of Steel in Submerged Concrete Structures". Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/6048.
Testo completoAbstract (sommario):
This investigation determined that severe corrosion of steel can occur in the submerged portions of reinforced concrete structures in marine environments. Field studies of decommissioned pilings from actual bridges revealed multiple instances of strong corrosion localization, showing appreciable local loss of steel cross-section. Quantitative understanding of the phenomenon and its causes was developed and articulated in the form of a predictive model. The predictive model output was consistent with both the corrosion rate estimates and the extent of corrosion localization observed in the field observations. The most likely explanation for the observed phenomena that emerged from the understanding and modeling is that cathodic reaction rates under oxygen diffusional limitation that are negligible in cases of uniform corrosion can nevertheless support substantial corrosion rates if the corrosion becomes localized. A dynamic evolution form of the model was created based on the proposition that much of the steel in the submerged concrete zone remained in the passive condition given cathodic prevention that resulted from favorable macrocell coupling with regions of the steel that had experienced corrosion first. The model output also matched observations from the field, supporting the plausibility of the proposed scenario.
The modeling also projected that corrosion in the submerged zone could be virtually eliminated via the use of sacrificial anode cathodic protection; the rate of corrosion damage progression in the low elevation zone above water could also be significantly reduced. Continuation work should be conducted to define an alternative to the prevalent limit-state i.e., visible external cracks and spalls, for submerged reinforced concrete structures. Work should also be conducted to determine the possible structural consequences of this form of corrosion and to assess the technical feasibility and cost/benefit aspects of incorporating protective anodes in new pile construction.
15
Tapper, Rudi. "The use of biocides for the control of marine biofilms on stainless steel surfaces". Thesis, University of Portsmouth, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266797.
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El-Turki, Adel Abdulrazag. "Environmental degradation of construction materials". Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310656.
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Murray, Amanda. "Examination of SAW and FCAW high strength steel weld metals for offshore structural applications". Thesis, Cranfield University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389830.
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Yahya, Najeeb Ali. "Failure analysis of bonded steel/CFRP laminate connections". Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6659/.
Testo completoAbstract (sommario):
Adhesive-bonded applications are widely used in industry, because of significant advantages such as uniform stress distribution, design flexibility and suitability to bond similar and dissimilar structural materials. This study focuses the adhesive-bonded long overlap of steel/carbon fibre reinforced polymer (CFRP) composite double lap shear (DLS) joints. The purpose of the work is to predict and assess the structural failure and behaviour of the DLS joint, including delamination of the composite, and to determine the effects of the design parameters of adherend thickness, overlap length and fabric orientation on the joint’s failure. There are different ways for such a joint to fail, which makes predicting failure very difficult. Another important difference is the failure mode of composites, where the relatively low interlaminar shear or tensile strength of the resin system causes failure of the composite before failure of the adhesive bondline occurs. Both experimental and numerical methods were used for the analysis. The experimental programme includes fabrication, mechanical testing and failure examinations of various joints. The numerical methods are based on 2D models, using strength of materials and cohesive zone modelling (CZM) approaches. In order to model adhesive joints accurately and efficiently, fracture tests were implemented to determine the fracture criteria. Mode-I and mode-II fracture energies were obtained by double cantilever beam (DCB) and end notched flexure (ENF) tests. An inverse method was used to define the cohesive parameters of the bilinear relation, fitting the numerical and experimental load-displacement curves. The DLS model has been created in Abaqus software, and results for each approach have been presented. Critical locations of stress concentrations in the DLS joint were identified, and the CZM successfully predicted the delamination initiation and propagation region observed in the experiment. As a result, it was concluded that the data obtained from the analysis showed good agreement with the experimental results, and in addition to the fibre orientation angles of the CFRP laminate markedly affecting the failure load of joints, the failure mode and stress distributions appeared in adhesive and composite. Furthermore, the study shows that the cohesive elements enable the numerical results to be obtained in shorter simulation times than the strength of materials approach, which should encourage use of CZM to analyse large structural applications.
19
Alexander, Matthew S. "The influence of aggressive marine environments on the hydrogen embrittlement and hydrogen uptake of steel". Thesis, University of Manchester, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488077.
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Yang, Yuan Feng. "Calcium and magnesium containing anti-corrosion films on mild steel". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/calcium-and-magnesium-containing-anticorrosion-films-on-mild-steel(34a7b76f-8ba6-49a7-a1fa-d87f52dc230f).html.
Testo completoAbstract (sommario):
Under normal conditions, cathodically protected mild steel in seawater is protected by a precipitated film of calcium carbonate and magnesium hydroxide, the so-called calcareous film. This study has attempted to investigate the dynamics of calcareous deposit formation during cathodic protection and the composition of calcareous deposits formed under different applied current densities, and also the role played by the initial current density in forming a good quality calcareous deposit. In addition, an under protection situation can occur where current demand values are under estimated, or where structures are approaching the end of their design lives. In these conditions, a calcareous film might well occur but complete protection is probably not possible. These situations have also been studied. At low insufficient current densities where steel corrosion is still occurring, a clear correlation exists between the iron containing corrosion product and the overlaying magnesium hydroxide layer. Such effects have also been investigated using pH titration analysis, where the effect of co-precipitation of the iron and magnesium oxides/hydroxides has been shown. At higher current densities a layered precipitate has been shown to occur consisting of an inner magnesium containing layer and an outer calcium containing layer. At obvious overprotection current densities, the mechanical stresses involved in hydrogen evolution are assumed to give rise to film cracking. To augment and compliment the study on calcareous calcium/magnesium films formed during cathodic protection, a calcium-magnesium containing pigment has also been investigated in aqueous solutions at open circuit as a possible corrosion inhibitor. Another study looked at the same inhibitor in conjunction with a sacrificial zinc anode. Very effective inhibition has been shown with the film containing not only magnesium, calcium and phosphorous but also zinc. In all the investigations electrochemical methods have been used together with various surface analytical techniques.
21
Raymond, Ian K. Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Tools for the formation of optimised X-80 steel blast tolerant transverse bulkheads". Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2001. http://handle.unsw.edu.au/1959.4/20467.
Testo completoAbstract (sommario):
The Australian Maritime Engineering Cooperative Research Centre, and its partner organisation initiated this research effort. In particular, BHP and the Defence Science and Technology Organisation held the principal interest, as this research effort was a part of the investigation into the utilisation of X-80 steel in naval platforms. After some initial considerations, this research effort focussed on the development of X-80 steel blast tolerant transverse bulkheads. Unfortunately, due to the Australian Maritime Engineering Cooperative Research Centre not being re-funded after June 2000 and other project factors, the planned blast tests were not conducted, hence this research effort focussed on the tools needed for the formation of optimised blast tolerant transverse bulkheads rather than on the development of a single structural arrangement. Design criteria were formed from the worst case operational requirements for a transverse bulkhead, which would experience a 150 kg equivalent blast load at 8 m from the source. Since the development of any optimised blast tolerant structure had to be carried out using finite element analysis, material constants for X-80 steel under high strain rates were obtained. These material constants were implemented in the finite element analysis and the appropriate solid element size was evolved. The behaviour and effects of stress waves and high strain rates were considered and the literature reviewed, in particular consideration was given to joint structures and weld areas effects on the entire structural response to a blast load. Furthermore, to support the design criteria, rupture prediction and determination methodologies have been investigated and recommendations developed about their relevance. Since the response of transverse bulkheads is significantly affected by their joint and stiffener arrangements, separate investigations of these structures were undertaken. The outcomes of these investigations led to improvements in the blast tolerance behaviour of joints and stiffeners, which also improved the overall response of the transverse bulkhead to air blast loads. Finally, an optimisation procedure was developed that met all the design criteria and its relevant requirements. This optimisation procedure was implemented with the available data, to show the potential to develop optimised X-80 steel blast tolerant transverse bulkheads. Due to the constraints mentioned above the optimisation procedure was restricted, but did show progression towards more effective blast tolerant transverse bulkhead designs. Factors, such as double skin bulkheads, maximising plate separation, and the use of higher yield steel all showed to be beneficial in the development of optimal X-80 steel blast tolerant transverse bulkheads, when compared to the ANZACclass D-36 steel transverse bulkheads.
22
Genin, Clément. "Cathodic Protection of carbon steel in the tidal zone : involved mechanisms". Electronic Thesis or Diss., La Rochelle, 2023. http://www.theses.fr/2023LAROS028.
Testo completoAbstract (sommario):
Ces travaux s’intéressent aux mécanismes mis en jeu dans la protection cathodique (PC) en zone de marnage (ZdM, zone verticale balayée par les marées). En effet, une étude de 2015 menée par Ph. Refait et coll. a mis en exergue une persistance de la PC même pendant les périodes émergées, a priori impossible à cause du retrait de l’eau de mer. Comprendre les mécanismes intervenant dans cette protection étendue pourrait, à terme, permettre de réduire l’impact environnemental de la conception et la maintenance de structures telles que les éoliennes offshores. Une première étude, sur toute la hauteur de la ZdM du port de commerce de La Rochelle, a permis de mettre en évidence que la PC pourrait être considérée efficace jusqu’à 45% de taux d’immersion (soit 74% de la hauteur de la ZdM). En parallèle, une étude menée au LaSIE visait à s’interroger de façon plus fondamentale sur le comportement de l’acier à marée descendante. Pour cela, des échantillons disposés à l’horizontal, sous de fines couches d’électrolyte (1 mm ou 5 mm) ont été placés en condition de protection satisfaisante (-950 mV/Ag/AgCl3M) et en condition de sous-protection (-750 mV/Ag/AgCl3M). Il apparaît alors qu’une protection insuffisante conduit à la formation d’une épaisse couche d’aragonite recouvrant une fine couche de produits de corrosion résiduels. De plus, une fine couche d’eau de mer augmente le caractère protecteur du dépôt formé sous PC suffisante (-950 mV/Ag/AgCl3M). Enfin, à mi-chemin entre les deux études précédentes, le dernier axe de recherche évoqué ici a permis de suivre l’évolution des paramètres de PC au cours des marées pendant 16 mois. Aux temps courts (8 j), la PC était efficace jusqu’à 40% d’immersion alors que toute la colonne était protégée pour des temps plus longs (180 j). Finalement, la persistance de la PC en ZdM est multifactorielle. Elle dépend de l’amplitude des marées, du temps d’exposition ainsi que du taux d’immersion. Son efficacité a été démontrée valable jusqu’à 45% d’immersion, pour des ZdM étenduesThis PhD work focuses on understanding the mechanisms involved in cathodic protection (CP) in tidal zones (vertical zone between high tide and low tide levels). In 2015 a study by led by Ph. Refait et al. highlighted the unexpected persistence of CP even during emerged periods, which theoretically should not occur because of seawater withdrawal. Understanding the mechanisms involved in this spread-out CP could ultimately contribute to diminish the environmental impact of production and maintenance of structures such as offshore wind turbines. An initial study, covering the entire height of the La Rochelle commercial port tidal zone, showed that CP could be considered effective up to 45% of immersion rate (i.e. 74% of the tidal zone height). On the other hand, a study carried out at LaSIE laboratory aimed to investigate the behavior of steel during ebb tides in a more fundamental way. To this purpose, samples were set horizontally under thin layers of seawater (1 mm or 5 mm) and polarised under conditions of sufficient protection (-950 mV/Ag/AgCl3M) and insufficient protection (-750 mV/Ag/AgCl3M). Insufficient protection led to the formation of a thick layer of aragonite overlying a thin residual corrosion products layer. In addition, a thin layer of seawater enhances the protective character of the deposit formed under sufficient CP (-950 mV/Ag/AgCl3M). Furthermore, in the last research axis mentioned here, the evolution of CP parameters was monitored for 16 months of tidal cycles. For short periods (8 days), CP remained effective up to 40 % of immersion rate, while the entire column was protected for longer times (180 days). Finally, the persistence of CP in tidal zone is multifactorial. It depends on tidal amplitude, exposure time and immersion rate. Its effectiveness has been demonstrated to be valid up to 45% immersion, for extended tidal zones
23
ITOH, Yoshito, Atsushi GOTO, Naofumi HOSOMI, Shigenobu KAINUMA, 義人 伊藤, 淳. 後藤, 直史 細見 e 重信 貝沼. "海洋環境下における長尺鋼部材の腐食挙動の評価・予測に関する基礎的研究". 土木学会, 2009. http://hdl.handle.net/2237/18833.
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Kabir, MD H. "Environmental durability study of CFRP strengthened steel tubular structures under four-point bending". Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/91853/1/MD_Kabir_Thesis.pdf.
Testo completoAbstract (sommario):
This research has studied the environmental durability of CFRP strengthened steel circular hollow section (CHS) member under cold weather and a marine environment at different temperatures experimentally and numerically under bending. A significant reduction of tensile strength was found for adhesives material in both environments. The cold weather and a marine environment adversely affected the durability by reducing strength and stiffness of CFRP strengthened CHS members. An embedded GFRP layer together with CFRP layers enhanced durability in marine environment. A suitable durability design factor has been proposed under both environments.
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Weirich, Timothy Douglas. "Evaluating the Potential for Atmospheric Corrosion of 304 Stainless Steel Used for Dry Storage of Spent Nuclear Fuel". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557098372186951.
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Otieno, Mike Benjamin. "The development of empirical chloride-induced corrosion rate prediction models for cracked and uncracked steel reinforced concrete structures in the marine tidal zone". Doctoral thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9520.
Testo completoAbstract (sommario):
Includes bibliographical references.Empirical chloride-induced corrosion rate prediction models for cracked and uncracked reinforced concrete (RC) structures in the marine tidal exposure zone are proposed in this study. The data used to develop the models were obtained from parallel corrosion experiments carried out by exposing half of 210 beam specimens to accelerated laboratory corrosion (cyclic 3 days wetting with 5% NaCl solution followed by 4 days air-drying) while the other half were left to undergo natural corrosion in a marine tidal zone in Cape Town (Table Bay). The main experimental variables were pre-corrosion flexural cover cracking, cover depth and concrete quality (binder type and w/b ratio). Corrosion rate, half-cell potential and concrete resistivity were monitored bi-weekly throughout the experimental period. The experimental results show that even though each of the variables investigated affects corrosion rate in a certain manner, their combined influence is complex. In general, regardless of the exposure environment (laboratory or marine tidal zone), for a given concrete quality and cover depth, pre-corrosion cover cracking was found to result in higher corrosion rates than in uncracked concrete, but with the field corrosion rates being much lower than the corresponding laboratory ones. Even though corrosion rates in both the field and laboratory specimens increased with an increase in crack width, the influence of concrete quality and cover depth was still evident. However, the effect of cover cracking on corrosion rate diminished with increasing concrete quality. In the blended cement concretes, the effect of concrete quality is further diminished by the inherent high resistivities of these concretes. The increase in corrosion rate due to increase in crack width, regardless of w/b ratio and cover depth, was generally higher in the 100% CEM I 42.5N concrete specimens than in the blended ones. A framework is proposed that can be used to objectively compare predicted corrosion rates for specimens with similar concrete quality (influenced by binder type and w/b ratio) but different cover depths and crack widths. The framework, which incorporates the combined influence of cover depth, crack width and concrete quality (quantified using chloride diffusion coefficient) on corrosion rate, is the basis of the proposed corrosion rate prediction models for cracked concrete. Sensitivity analyses on the proposed models show that if any two of the three input parameters (cover depth, crack width and concrete quality) are simultaneously varied, their effect on corrosion rate is dependent on the value of the third (unchanged) parameter. Furthermore, (i) the initial cover depth was found to have no effect on the extent to which a change in cover depth affects corrosion rate; a similar trend was found in the case of sensitivity of corrosion rate to change in crack width , and (ii) the extent to which a change in either crack width or cover depth affects corrosion rate is dependent mainly on the concrete quality. In general, the sensitivity analyses showed that corrosion rate is more sensitive to change in concrete quality than crack width and cover depth. The proposed models can be used to (i) quantify the propagation phase with respect to a given performance limit using relevant corrosion-induced damage prediction models, and (ii) select suitable design combinations of cover depth, concrete quality and crack width to meet the desired durability performance of a given RC structure in the marine environment.
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Langumier, Mikaël. "Biodétérioration des structures portuaires en acier : synergie entre la physico-chimie du fer en milieu marin et les micro-organismes sulfurogènes". Phd thesis, Université de La Rochelle, 2011. http://tel.archives-ouvertes.fr/tel-00717856.
Testo completoAbstract (sommario):
Le but de ce travail était de mieux comprendre les mécanismes mis en jeu lors de la corrosion marine des structures en acier. Ces mécanismes impliquant l'influence de micro-organismes vivants, et notamment des bactéries sulfurogènes, l'étude a couplé des méthodes physico-chimiques à des techniques de microbiologie et de biologie moléculaire. Dans un premier temps, un système modèle de laboratoire a été élaboré afin d'étudier en détail les interactions entre les bactéries sulfato-réductrices (BSR) et le principal produit de la corrosion électrochimique des aciers en milieu marin, à savoir la rouille verte sulfatée RV(SO42-). Nous avons ainsi pu reproduire une partie des mécanismes mis en jeu, en montrant que les BSR pouvaient se développer en consommant les ions SO42- issus de la rouille verte et générer ainsi la mackinawite FeS observée sur sites. Dans un deuxième temps, l'évolution de la couche composite " rouille/biofilm " se formant sur acier en milieu marin a été suivie pour des temps courts d'immersion, allant de 1 semaine à deux mois. Le suivi simultané des données microbiologiques et physicochimiques a permis de montrer que l'influence des BSR ne se faisait pratiquement pas sentir à ce stade. Cependant, le développement préférentiel de bactéries associées au fer et au soufre au sein de la couche de rouille a pu être mis en évidence. Par ailleurs, très localement, le processus influencé par les BSR a été détecté. Enfin, une étude électrochimique en solutions désaérées simulant l'eau de mer a été confrontée aux résultats de l'analyse physico-chimique et microbiologique d'un coupon immergé 11 ans en milieu portuaire. L'ensemble des résultats montrent que RV(SO42-) se forme également lorsque des conditions anoxiques sont établies à la surface du métal. La formation de RV(SO42-) entre cependant en compétition avec celle de FeS et Fe3O4 suite aux modifications du milieu que peuvent engendrer les micro-organismes. A ces temps d'immersion long, l'influence des bactéries semblent néanmoins s'amoindrir, les micro-organismes tendant à s'éloigner des strates internes de la couche de rouille et donc du métal pour coloniser des zones externes plus riches en substances nutritives.
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Migliorini, Alessandra Vieira. "Estudo de fibras de aço em blocos de concreto para a possível utilização em carapaça de molhes". reponame:Repositório Institucional da FURG, 2011. http://repositorio.furg.br/handle/1/3448.
Testo completoAbstract (sommario):
Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia Oceânica, Escola de Engenharia, 2011.Submitted by Lilian M. Silva (lilianmadeirasilva@hotmail.com) on 2013-04-20T20:11:55Z No. of bitstreams: 1 Estudo de fibras de aço em blocos de concreto para a possível utilização em carapaça de molhes.pdf: 6421003 bytes, checksum: 60c7e55066658c2ba4d808a487cc9c33 (MD5)
Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2013-06-04T17:05:53Z (GMT) No. of bitstreams: 1 Estudo de fibras de aço em blocos de concreto para a possível utilização em carapaça de molhes.pdf: 6421003 bytes, checksum: 60c7e55066658c2ba4d808a487cc9c33 (MD5)
Made available in DSpace on 2013-06-04T17:05:53Z (GMT). No. of bitstreams: 1 Estudo de fibras de aço em blocos de concreto para a possível utilização em carapaça de molhes.pdf: 6421003 bytes, checksum: 60c7e55066658c2ba4d808a487cc9c33 (MD5) Previous issue date: 2011
Este trabalho tem como propósito de estudo o possível uso da utilização das fibras de aço em blocos de contenção às ondas marinhas, de modo a influenciar a resistência e durabilidade dos mesmos. Foram analisados em exame visual, os tetrápodes do molhe leste da Barra do Cassino (Rio Grande – RS), nos quais, pode-se verificar sua deterioração através de quebras e desgastes nos recentes 10 anos seguidos após sua instalação. De modo a diminuir custos com reposições, serviços com mão-de-obra e influenciar na durabilidade dos blocos, buscando um aumento da ductibilidade e uma melhora quanto a ações dinâmicas, a adição de fibras de aço no concreto pode ser uma alternativa vantajosa. Para isso, foram estudados três diferentes teores de fibras além do concreto base(referência) com o intuito de verificar as resistências obtidas. Paralelamente aos ensaios de resistência, foram desenvolvidos ao longo dos 24 meses de curso, ensaios de durabilidade com blocos de concreto expostos às intempéries do ambiente marítimo, como também ensaio de imersão e secagem a blocos em solução contendo íons cloreto. Foram realizados ensaios de compressão axial, resistência à tração por compressão diametral e ensaios de resistência à tração na flexão em corpos de prova cilíndricos e prismáticos de forma analisar o comportamento da resistência de influência das fibras a estes blocos. Com o intento de verificar a energia necessária para fissurar e gerar o colapso em corpos de prova cilíndricos (10 x 80 cm) – estes reforçados por diferentes teores de fibras, ou não – foi desenvolvido um equipamento que simulasse o impacto recebido no cilindro pela batida constante de uma esfera, simulando a batida de um tetrápode contra outro provocada pela ação das ondas. O teor que apresentou melhor desempenho das propriedades mecânicas foi o traço de 90 kg/m³, devido a este ser o mais próximo do volume crítico do concreto analisado, pois com esse teor os ganhos de resistência são significativos quando comparados aos traços com teores menores.
This paper aims to study the possible use of steel fibers in blocks of contention to sea waves, in order to influence at their strength and durability. It was analyzed by visual examination, the tetra pod of the east breakwater of Cassino beach (Rio Grande – RS), in which their deterioration through wear and breaks in the recent 10 consecutive years after its installation were verified. Conductive to reduce replacement costs, services with manpower and influence in the durability of the blocks, seeking an increase in ductility and an improvement in the dynamic action, the addition of fibers of steel in concrete can be an attractive alternative. Aiming that, it was studied three different fiber content besides the base of concrete (reference) targeting an economic viability related to the obtained resistances. Alongside the resistance tests, it has been developed over the 24 months of the course, with durability testing on concrete blocks exposed to the elements of the maritime environment, as well as testing of immersion and drying of blocks in a solution containing chloride ions. In contemplation of this, it was performed axial compression tests, tensile strength by diametrical compression tests and tensile strength in bending specimens used in prismatic and cylindrical specimens in order to analyze the behavior of the strength of influence of the fibers to these blocks. Aiming to verify the energy needed to crack and generate the collapse on the body of cylindrical specimens (10 x 80 cm)- reinforced by different levels of fiber, or not – it was developed a device which simulates the received impact on a cylinder by the steady beat of a sphere, simulating the tetra pods impacts against each other caused by the wave action. The content that has presented the best performance of the mechanical properties was the print of 90 kg/m³, due to the aspect that it is closer to the critical volume of concrete analysis, since with this level, the strength gains are significant when compared to traits with lower levels.
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Moser, Robert David. "High-strength stainless steels for corrosion mitigation in prestressed concrete: development and evaluation". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41083.
Testo completoAbstract (sommario):
The use of stainless steel alloys in reinforced concrete structures has shown great success in mitigating corrosion in even the most severe of exposures. However, the use of high-strength stainless steels (HSSSs) for corrosion mitigation in prestressed concrete (PSC) structures has received limited attention. To address these deficiencies in knowledge, an experimental study was conducted to investigate the feasibility of using HSSSs for corrosion mitigation in PSC. The study examined mechanical behavior, corrosion resistance, and techniques for the production of HSSS prestressing strands. Stainless steel grades 304, 316, 2101, 2205, 2304, and 17-7 along with a 1080 prestressing steel control were included in the study. Tensile strengths of 1250 to 1550 MPa (181 to 225 ksi) were achieved in the cold-drawn HSSSs. 1000 hr stress relaxation of all candidate HSSSs was predicted to be between 6 and 8 % based on the results of 200 hr tests conducted at 70 % of the ultimate tensile strength. Residual stresses due to the cold drawing had a significant influence on stress vs. strain behavior and stress relaxation. Electrochemical corrosion testing found that in solutions simulating alkaline concrete, all HSSSs showed exceptional corrosion resistance at chloride (Cl-) concentrations from zero to 0.25 M. However, when exposed to solutions simulating carbonated concrete, corrosion resistance was reduced and the only HSSSs with acceptable corrosion resistance were duplex grades 2205 and 2304, with 2205 resistant to corrosion initiation at Cl- concentrations up to 1.0 M (twice that in seawater). Based on these results, duplex grades 2205 and 2304 were identified as optimal HSSSs and were included in additional studies which found that: (1) 2304 is susceptible to corrosion when tested in a stranded geometry, (2) 2205 and 2304 are not susceptible to stress corrosion cracking, and (3) 2205 and 2304 are susceptible to hydrogen embrittlement. Efforts focused on the production of 2205 and 2304 prestressing strands showed that they could be produced as strands using existing ASTM A416 prestressing strand production facilities. Due to the ferromagnetic properties of 2205 and 2304, a low-relaxation heat treatment was found to be a viable option to reduce stress relaxation and improve mechanical properties. The overall conclusion of the study was that HSSSs, especially duplex grades 2205 and 2304, show excellent promise to mitigate corrosion if utilized as prestressing reinforcement in PSC structures exposed to severe marine environments.
30
Muraleedharan, Atmaram. "Fatigue design and dynamic analysis of Steel catenary risers at Touch down zone with nonlinear soil structure interaction model under randomly generated waves". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Cerca il testo completoAbstract (sommario):
The offshore industry is moving deeper and deeper into the ocean depths and a subsequent technological advancement are inevitable factors. Steel Catenary Risers (SCRs) are the most popular type of deep water risers and are very important part of any deep-water developments. Although the simplicity in installation and the associated economic advantage makes it widely popular, these highly slender structures are very sensitive to dynamic loads and fatigue. Hang-off point where the riser is connected to the floater and Touch Down Zone (TDZ) where the riser interacts with the seabed are the two-important fatigue critical regions in an SCR.
Fatigue design at TDZ remains a challenging topic among riser engineers and the soil structure interaction here makes it extremely complex to design for fatigue. Linear soil structure models, which are popular among the design professionals due to its simplicity are extremely conservative and the industry is slowly moving towards the nonlinear soil models. This research investigates the effects of implementing the nonlinear soil model into the fatigue design of SCRs under randomly generated waves with detailed comparison with the linear soil model. The uncertainties related to estimation of fatigue damage at TDZ and the influence of duration of simulation are studied in detail and some significant observations and findings are presented in this research. A very extensive effort to understand the effect of different order of waves (of varying intensities) also formed a part of this study which yielded crucial results which opens new doors in this topic.
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Hutchison, Michael John. "Corrosion of Post-Tensioning Strands in Ungrouted Ducts - Unstressed Condition". Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4905.
Testo completoAbstract (sommario):
Recent failures and severe corrosion distress of post-tensioned (PT) bridges in Florida have revealed corrosion of the 7-wire strands in tendons. Post-tensioned duct assemblies are fitted with multiple 7-wire steel strands and ducts are subsequently filled with grout. During construction, the length of time from the moment in which the strands have been inserted into the ducts, until the ducts are grouted, is referred to as the `ungrouted' period. During this phase, the steel strands are vulnerable to corrosion and consequently the length of this period is restricted (typically to 7 days) by construction guidelines. This investigation focuses on determining the extent of corrosion that may take place during that period, but limited to strands that were in the unstressed condition. Visual inspections and tensile testing were used to identify trends in corrosion development. Corrosion induced cracking mechanisms were also investigated via wire bending and metallographic cross section evaluation. Corrosion damage on unstressed strands during ungrouted periods of durations in the order of those otherwise currently prescribed did not appear to seriously degrade mechanical performance as measured by standardized tests. However the presence of stress in the ungrouted period, as is normally the case, may activate other mechanisms (e.g., EAC) that require further investigation. As expected in the unstressed condition, no evidence of transverse cracking was observed.
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Aggoun, Kahina. "Renforcement de la résistance à la corrosion marine du revêtement CeO2 par dépôt calcomagnésien, calcaire et magnésien : Synthèse, caractérisations et tests de corrosion en eau de mer artificielle". Thesis, La Rochelle, 2020. http://www.theses.fr/2020LAROS014.
Testo completoAbstract (sommario):
Depuis la restriction de l’utilisation de composés à base de chrome (VI) par une directive européenne (Directive 2000/53/CE), en raison de sa toxicité élevée vis-à-vis de l’environnement, les composés à base de terre rare tel que l’oxyde de cérium ont été beaucoup privilégiés en tant qu’alternatifs compatibles avec les normes environnementales et présentant des propriétés comparables à celles des traitements conventionnels à base de Cr(VI) sur de nombreux alliages métalliques. Cependant, les dépôts CeO2 sont caractérisés par une morphologie fortement poreuse et craquelée, ce qui limite leur protection en milieux très agressif comme l’eau de mer. Ce projet de thèse a donc pour objectif d’améliorer la résistance à la corrosion de ces couches d’oxyde en faisant combler ses défauts ouverts, par la formation d’un dépôt calcomagnésien, calcaire ou magnésien par électrodéposition cathodique sur la couche de CeO2 déposée sur acier faiblement allié. Des analyses de surface ont permis d’identifier les propriétés morphologiques et structurales de ces couches mixtes ainsi que leur composition chimique. Tandis que des tests d’immersion en eau de mer artificielle ont permis de mettre en évidence le caractère protecteur des dépôts vis-à-vis la corrosion marine. Le dépôt mixte Mg(OH)2/CeO2 a montré un intérêt particulier contre la corrosion de l’acier dans l’eau de mer, par la dissolution partielle de la couche de brucite offrant l’avantage d’une protection à double effet (active et passive) grâce à la formation d’aragonite au sein de la couche de cérium et à la passivation de l’acierSince the restriction of the use of chromium (VI) based compounds by a European directive (Directive 2000/53/EC) due to its high toxicity towards the environment, the compounds based on rare earths such as cerium oxide were used a lot as alternatives to conventional Cr(VI) treatments on many metal alloys, due to their eco-friendly and comparable properties. However, CeO2 coatings are characterized by a highly porous and cracked morphology, which limits their protection in very aggressive media such as seawater. This thesis project aims to improve the corrosion resistance of these layers oxide by filling its open defects, by the formation of calcareous, calcium carbonate or magnesium hydroxide deposit obtained by cathodic electrodeposition on CeO2 layer deposited on a low alloyed steel. Surface analyses permitted to identify the morphological and structural properties of these mixed layers as well as their chemical composition. While the immersion tests in artificial seawater have determined the marine anticorrosion performances of the deposits. The mixed coating Mg(OH)2/CeO2 has shown a particular interest against the marine corrosion of steel, by the dissolution of the brucite layer which combine both passive and active protection true the formation of Aragonite inside and above the ceria layer and the steel passivation
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田村, 功., Isao Tamura, 英一 渡邊, Eiichi Watanabe, 義人 伊藤, Yoshito Itoh, 堅. 藤井 et al. "海洋環境において腐食した鋼管の形状計測と残存耐力に関する検討". 土木学会, 2005. http://hdl.handle.net/2237/8540.
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Beres, Miloslav. "Welding of thin sheet steels in marine applications". Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6050.
Testo completoAbstract (sommario):
Many metal structures are assembled from thin plate with welded supports for stiffness to resist local loadings. However, welded joints, which require large heat input, may incur significant distortion in the finished plate. Although the causes of distortion are known, and have been the focus of number of studies, there is still a lack of fundamental understanding of process and physical parameters in causing distortion. The overall aim of this work is to identify the interaction of process and physical parameters in causing distortion of welded ferritic thin steel plates. Experimental measurements and the finite element method are used to identify the relationship between distortion and the influence of pre-existing (residual) stresses in the plates. Effect of onset of transformation temperature on distortion is examined. An improved comprehension of the mechanisms causing distortion, and a readily useable model to explore alternatives has significant potential in wide range of industries and thus is a major driving force for continued research. The ability to predict with reasonable certainty the geometry of distortion will enable users to evaluate alternative design and production parameters. The work is divided into eight chapters: The first chapter gives an introduction and lists the objectives of the research. A theoretical exploration of the problem in addition to a survey of relevant work with regard to the welding of ferritic steels, weld microstructures, residual stresses, finite element modelling (FEM) and an overview of experimental techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), neutron diffraction (ND) is given in chapter 2. In chapter 3 experimental investigation results including both post-weld and in-situ microstructure observation and residual stress distribution are presented and discussed [1, 2]. To provide a qualitative insight into fundamental understanding of development of residual stress, a finite element model that considers both the thermal and the transformation strains caused by solid-state phase transformation was developed and is presented in the chapter 4 [3]. A validated finite element model for computation of residual stresses is presented in the chapter 5 [4]. Special emphasis was placed on the effect of transformation temperature on residual stress development in both the actual weld and the model. Most of the modelling results were validated against experimental measurements. Chapter 6 presents a sensitivity study on the effect of parameter changes on distortion. An attempt was made to elucidate both the effect of transformation start temperature and the initial distortion on the final distortion [5]. Chapter 7 details application of a model for variant selection [6], which is based on work published in [7, 8] to actual welds. This work was performed to elucidate the effect of texture on residual stress. Finally the last chapter draws together the major conclusions of the thesis, and suggests future avenues of investigation to progress the research discussed here.
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Cooker, Mark. "The interaction between steep water waves and coastal structures". Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292466.
Testo completo
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Batt, C. "Optimising cathodic protection requirements for high strength steels in the marine environment". Thesis, Cranfield University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323886.
Testo completo
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Aribo, Sunday. "Corrosion and erosion-corrosion behaviour of lean duplex stainless steels in marine and oilfield environments". Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7170/.
Testo completoAbstract (sommario):
Lean duplex stainless steels are becoming attractive for applications in oilfield and marine environments due to their economic advantages, very good mechanical properties and relatively good corrosion resistance. One such application is in the production of the carcass of flexible pipes. However, materials selection for such oilfield applications becomes more complex as a result of the interactions between corrosion and erosion. Much effort has been directed towards the study of erosion-corrosion behaviour of carbon steels and other passive alloys. However, the subject of erosion-corrosion of lean duplex stainless steels is still rarely reported. Moreover, data available in the literature on the localized corrosion resistance of the lean duplex stainless steels are limited to alkaline environments. Efforts have been made in this thesis to add to the existing data and to the understanding of the subject of localized corrosion and erosion-corrosion resistance of lean duplex stainless steels UNS S32101, UNS S32304 and UNS S82441 in oilfield environments. The lean duplex alloy UNS S32101 has been studied in detail because of its combination of high strength and good corrosion resistance. This research also compared the corrosion and erosion-corrosion resistance of lean duplex stainless steels with standard austenitic stainless steels UNS S30403 and UNS S31603 as well as duplex stainless steel alloy UNS S32205. Aerated 3.5% NaCl and synthesized CO2-saturated oilfield brines were considered as the corrosion media. Extreme erosion-corrosion conditions were simulated to design for severe environments often encountered in sand-containing oilfield pipeline systems. Breakdown potentials, under static conditions, were found to be more positive in the aerated 3.5% NaCl than the CO2-saturated oilfield brine solution. Also, lean duplex stainless steels and standard austenitic stainless steels exhibited similar resistance in both environments. X-ray Photoelectron Spectroscopy (XPS) analysis of the passive film indicated higher chloride incorporation in the CO2-saturated oilfield brine. This, in addition to lower pH of the CO2-saturated oilfield brine appeared to be the reason why the breakdown potential was more negative in this environment. Erosion-corrosion results showed that lean duplex stainless steels, UNS S32101 and UNS S32304, have higher resistance to pure-erosion damage than UNS S30403 and UNS S32205; better erosion-corrosion resistance than UNS S30403 austenitic stainless steel; and equivalent erosion-corrosion resistance to UNS S32205 standard duplex stainless steel. There was also a correlation between the erosion-corrosion resistance of the alloys and the sub-surface crystallography, microstructure and phase transformation. This, together with repassivation kinetics of the passive film, may be used to explain the erosion-corrosion behaviour of UNS S32101 and UNS S30403 in the oilfield slurry.
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Toumpis, Athanasios I. "Characterisation of metallurgical and mechanical properties of friction stir welded low alloy steels for marine applications". Thesis, University of Strathclyde, 2015. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=26008.
Testo completo
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Dahlström, Alexander. "Wear mechanisms in austenitic stainless steel drilling : A comprehensive wear study". Thesis, KTH, Materialteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175771.
Testo completoAbstract (sommario):
This thesis is meant to serve as part of a competence platform for future product development projects at Sandvik Coromant AB, Solid Round Tools Department, Västberga, Sweden. The project objective is to gain generic knowledge of the wear mechanisms that restrict tool lifetime when drilling austenitic stainless steel. Thus, identifying if the weakest link of the tool is located within the coating, the coating adherence or in the strength of the substrate. A theoretical review of the work-piece and tool materials has been conducted as a background, along with definition of tool geometry and process parameters. Furthermore, the review includes chemical and process design effect on mechanical properties of the austenitic stainless steel, TiAlN coatings and cemented carbide substrates. Additionally, the basic principles of the wear mechanisms and wear types that are specific to drilling have been reviewed. During the experimental procedures both solid and exchangeable tip drills from cemented carbide with multilayered PVD TiAlN coatings were tested. Two series of tests were conducted, the first series aimed to identify wear type dependency on cutting speed, focusing on wear of the tool margin. The second test series was performed to map the wear progression depending on distance. Analyses including identification the main wear mechanism, quantification the amount of wear, identify wear location on the tool, crack investigation and WDS analysis of chemical wear. Adhesive coating wear was found on the tool margin at an early stage. The adhesive wear rapidly progressed into a stable intermediate stage. Leaving the substrate exposed and more susceptible to other wear types resulting in crack and oxide layer formation.
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Berhorst, Arnim [Verfasser]. "Die Struktur des aktiven Kontinentalhangs vor Nicaragua und Costa Rica : marin-seismische Steil- und Weitwinkelmessungen / Arnim Berhorst". Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019670428/34.
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Reilhac, Pierre. "Influence du traitement de nitruration ionique sur les propriétés fonctionnelles des aciers inoxydables martensitiques". Thesis, La Rochelle, 2019. http://www.theses.fr/2019LAROS005.
Testo completoAbstract (sommario):
La nitruration des aciers est un procédé thermochimique très largement utilisé aujourd’hui dans l’industrie. Il permet notamment d’améliorer sensiblement les propriétés mécaniques de surface des pièces traitées qui nécessitent des performances mécaniques élevées. Le but de cette étude est d’étudier l’influence de la nitruration ionique d’aciers inoxydables martensitiques à travers une description fine des microstructures obtenues et de leurs impacts sur les propriétés fonctionnelles des alliages considérés (tribologie, résistance à la corrosion marine). La nitruration est effectuée par un traitement ionique assisté par plasma (mode DCPN). L’objectif est de comprendre l’impact des paramètres de nitruration ainsi que de mettre en relief les principales relations procédés/microstructures et procédés/propriétés. La microstructure est analysée par différentes techniques complémentaires MET, MEB et DRX. Il est observé une augmentation de l’épaisseur de la couche nitrurée ainsi qu’une précipitation de CrN et de diverses phases nitrurées (ε, γ’ ou α’N) en lien avec la température de traitement, formant une structure complexe en strates. Les propriétés électrochimiques étudiées en eau de mer artificielle par voltammétrie et à partir du test Mott-Schottky montrent un impact, d’une part de la température de traitement sur le comportement à la corrosion, et d’autre part de la formation d’une couche de combinaison nitrurée à la surface des échantillons. Des liens ont ainsi pu être établis entre la structuration en strates de la couche nitrurée, sa nature et les propriétés de tenue à la corrosion. Des tests tribologiques ont également été menés permettant d’observer une amélioration sensible des propriétés de résistance à l’usure (dureté, tenue au frottement)The nitriding process of steels is a well known thermochemical surface treatment generally used for manufacturing components of type sprocket or gearings, requiring high superficial hardness. The aim of our present work is mainly focused on the optimizing of the nitriding treatment in order to understand the relationship between the metallurgical state and the marine corrosion resistance of nitrided martensitic stainless steels thanks to a multi-scale approach. Nitriding were performed by a low temperature plasma treatment (Direct Current mode). The objective is to understand the relationship between the metallurgical state of the nitrided layer and its corrosion resistance thanks to a multi scale analysis and characterization. The evolution of microstructure is studied by electron microscopy (TEM and SEM) and X-ray diffraction. An increase of the thickness of the nitrided layer with temperature is observed and a precipitation of CrN and others nitrided phases (ε, γ’ ou α’N) in relation with temperature treatment for each alloys occurred. The electrochemical properties of nitrided samples are assessed by voltametry test and Mott-Schottky test. The results highlight a thermal effect and an impact of the compound layers on resistance to pitting corrosion. Relations were established between different nitrided sublayers, their nature and the properties of corrosion resistance. Tribological tests have also been occurred, allow to observe a significant improvement in wear resistance properties (hardness, wear resistance)
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Grant, Joe W. III. "Raubeaux Scientician". VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/1458.
Testo completoAbstract (sommario):
The works contained in "Raubeaux Scientician" are about a triadic relationship between people, science, and art. The obsessions, of individuals and the apparent change brought about by their physical presence guide my artistic research. I am awestruck at the capabilities of the individual to overcome conventional thought and through creative action yield a new vision. Some of the people I am fascinated by put forth theories and inventions that continue to affect myriad aspects of our world today. Among those at the forefront are, Robert Oppenheimer, and Edward Teller. Their contributions to science and mathematics remain almost unmatched. These and many others on the Manhattan Project team were employing cutting edge physics in their atomic research. The decisions to go through with the testing and the resulting construction of atomic weapons quite simply changed the face of humanity forever. With the knowledge of how to obliterate mankind, however, came a closer understanding of nature and the universe. But was it all worth it? And what about the not so famous men and women on this project, those such as Stanislaw Ulam who felt the calculations for atomic testing were all wrong and traveled the scientific community to try and stop the making of the bomb. What if he had been successful in ending the use of these postulates?
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El, May Mohamed. "Étude de la tenue en fatigue d'un acier inoxydable pour l'aéronautique en milieu marin corrosif". Thesis, Paris, ENSAM, 2013. http://www.theses.fr/2013ENAM0012/document.
Testo completoAbstract (sommario):
Ces travaux ont pour objectif l'identification et la compréhension de l'effet de la corrosion aqueuse sur la durée de vie en fatigue à grand nombre de cycles (HCF) d'un acier inoxydable martensitique utilisé dans des applications aéronautiques. Tout d'abord, l'effet géométrique des défauts de corrosion sur la limite de fatigue à 10^7 cycles à l'air a été étudié avec quatre tailles différentes de piqûres de corrosion. A partir de ces résultats, une nouvelle approche volumique non locale de modélisation numérique a été proposée pour prendre en compte une géométrie réelle d'un défaut de corrosion issu des analyses en microtomographie X. Ensuite, les phénomènes de couplage chargement cyclique/corrosion ont été identifiés par des essais de fatigue à grande durée de vie (entre 10^5 et 10^7 cycles) dans une solution aqueuse à 0,1 M NaCl (à pH = 6) pour deux rapports de charge (R = -1 et 0,1). Le comportement électrochimique du film passif a été étudié in situ au cours des essais de fatigue-corrosion par le suivi du potentiel libre de corrosion et des mesures d'impédance électrochimique. Les observations des mécanismes d'amorçage de fissures et des mesures électrochimiques in-situ ont permis d'identifier un scénario d'amorçage de fissures de fatigue. Ce scénario implique des processus de rupture locale du film passif (induite par le chargement cyclique) et de corrosion assistée par le chargement cyclique. Finalement un modèle analytiquede prévision de la durée de vie en fatigue dans un milieu aqueux corrosif a été proposé à partir des résultats expérimentauxThis study addresses the effects of corrosion on the high cycle fatigue (HCF)strength of a martensitic stainless steel used in aeronautic applications. First, the geometry of corrosion pits on the fatigue strength in air at 10^7 cycles were studied with four different pit sizes. A new non-local fatigue criterion was proposed to simulate real shapes of pits as identified by X-ray microtomography. Corrosion fatigue synergy phenomena was studied by HCF tests (between 10^5 and 10^7 cycles) in a 0.1 M NaCl aqueous solution (pH = 6) with two load ratios (R = -1 and 0.1). Next, the electrochemical behavior of the passive film was investigated during in situ corrosion fatigue tests by free potential measurements and electrochemical impedance spectroscopy (EIS). Based on fractography analysis and electrochemical test results, corrosion fatigue crack initiation mechanisms were investigated. A scenario of fatigue crack initiation was proposed based on physical evidence. This scenario implied combined processes of local passive film rupture (induced by the cyclic loading), stress-assisted corrosion and enhanced pitting development. Local passive film ruptures were the main cause of the corrosion fatigue crack initiation. Finally, a analytical model for corrosion fatigue crack initiation was proposed based
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Zhang, Jie. "Intéractions vagues-fond marin et mécanismes de formation des vagues scélérates en zone côtière Wave-bottom interaction and extreme wave statistics due to shoaling and de-shoaling of irregular long-crested wave trains over steep seabed changes". Thesis, Ecole centrale de Marseille, 2020. http://www.theses.fr/2020ECDM0003.
Testo completoAbstract (sommario):
Dans la communauté maritime, le terme de "vague scélérate" est utilisé pour les vagues dont la hauteur dépasse le double de la hauteur significative de l'état de mer ambiant, et qui apparaissent plus fréquemment que prédit par la distribution de Rayleigh pour les hauteurs de vagues, fondée sur une hypothèse d’état de mer gaussien. En domaine océanique, des vagues scélérates ayant causé des pertes de vies humaines et de graves dommages ont été massivement signalées au cours des dernières décennies. Dans les zones côtières, une bathymétrie irrégulière peut également provoquer des vagues extrêmes du fait des interactions entre le fond marin et les vagues. Dans cette thèse, nous nous concentrons sur trois mécanismes ou scénarios d'interactions vagues-fond pouvant entraîner la formation de vagues extrêmes. Le premier scénario est un phénomène de résonance, connu sous le nom de résonance de Fabry-Perot, qui peut se développer lorsque des vagues monochromatiques se propagent sur une bathymétrie comportant deux zones d'ondulations sinusoïdales sur un fond par ailleurs plat. Dans la zone du résonateur située entre les deux zones de rides, une augmentation significative de la hauteur de l'onde incidente peut être obtenue si la condition de résonance est satisfaite. En comparant des simulations numériques avec une condition limite de fond exacte ou approchée et une solution analytique linéaire asymptotique, nous observons un décalage de fréquence de résonance pour la condition de résonance dans les cas où le rapport entre l'amplitude des ondulations et la profondeur de l'eau est grand : la résonance se produit pour un nombre d'onde plus petit que celui prévu par la théorie analytique approchée. Cet effet de décalage de fréquence de résonance joue un rôle secondaire pour la résonance de Bragg, mais il s'avère très important pour la résonance de Fabry-Perot. Le second scénario correspond aux instabilités des trains de houle modulés en amplitude, appelés communément « breathers », qui se propagent sur des fonds irréguliers. Trois types de profils bathymétriques sont étudiés expérimentalement et numériquement avec un modèle entièrement non-linéaire et avec l'équation non-linéaire (cubique) de Schrödinger. Cette étude a permis de montrer que pour de faibles profondeurs et pour certaines conditions, l’amplitude de la modulation peut atteindre deux fois l’amplitude du train initial. Cette amplification en faible profondeur résulte de mécanismes qui n’existent pas en profondeur constante. Les influences des paramètres pouvant affecter la dynamique des breathers, y compris le paramètre du breather d’Akhmediev, la profondeur d'eau, la cambrure de l’onde porteuse, la période de la vague et les pentes du fond sont analysées. Le troisième scénario correspond à des trains de vagues irrégulières unidirectionnelles se propageant sur des profils de fond côtier variables. Lorsqu'un état de mer incident en condition d’équilibre passe sur une barre ou une marche submergée, une dynamique de non-équilibre apparaît et force l'état de mer à un nouvel équilibre compatible avec la profondeur finie, caractérisé par des statistiques fortement non-gaussiennes et une probabilité accrue d'occurrence de vagues extrêmes. La combinaison d'expériences à grande échelle et de simulations complètement non-linéaires permet de mieux comprendre la réponse dynamique du train de vagues. Les données obtenues ont été analysées en profondeur en utilisant une combinaison d'approches spectrales, bispectrales et statistiquesIn the maritime community, the term "rogue wave" or “freak wave” is used for waves whose wave height exceeds twice the significant wave height of the ambient sea state, and which appear more frequently than predicted by the Rayleigh distribution for wave height based on a Gaussian sea state hypothesis. In the oceanic domain, rogue waves that have caused loss of lives and severe damage have been widely reported in recent decades. In coastal areas, irregular bathymetry can also trigger such high extreme waves due to seabed-wave interactions. In this thesis, we focus on three mechanisms or scenarios of wave-bottom interactions that can lead to the formation of high waves.The first scenario is a resonance phenomenon, known as Fabry-Perot resonance, which can develop when monochromatic waves propagate over a bathymetry with two areas of sinusoidal undulations on an otherwise flat bottom. In the resonator zone located between the two areas of ripples, a significant increase in the height of the incident wave can be obtained if the resonance condition is met. By comparing numerical simulations with either exact or approximated bottom boundary condition and an asymptotic linear analytical solution, we observe a shift of the resonance frequency at the resonance condition for cases where the ratio between the amplitude of the ripples and the water depth is large: resonance occurs for a smaller wave number than predicted by the approximate analytical theory. This downshift effect of resonance frequency plays a secondary role for Bragg resonance, but it is very important and sensitive for Fabry-Perot resonance.The second scenario corresponds to the instabilities of amplitude modulated wave trains, commonly called "breathers", which propagate over irregular bottoms. Three types of bathymetric profiles are studied experimentally and numerically with a fully nonlinear model and with nonlinear (cubic) Schrödinger equation. This study has shown that for shallow depths and for certain conditions, the amplitude of the modulation can reach twice the amplitude of the initial train. This shallow depth amplification results from mechanisms that do not exist at constant depth. The influences of parameters that can affect the dynamics of breathers, including the Akhmediev breather parameter, water depth, steepness of the carrier wave, wave period and bottom slopes are analysed.The third scenario corresponds to unidirectional irregular wave trains propagating on variable coastal bottom profiles. When an incident sea state in equilibrium condition passes over a submerged bar or step, non-equilibrium dynamics appear and force the sea state to a new equilibrium compatible with the finite depth, characterized by highly non-Gaussian statistics and an increased probability of extreme wave occurrence. The combination of large-scale experiments and fully nonlinear simulations allows a better understanding of the dynamic response of the wave train. The resulting data were analysed in depth using a combination of spectral, bispectral and statistical approaches
45
Soulet, Quentin. "Typologie, architecture et évolution des systèmes silicoclastiques des marges abruptes. Analyse comparée de la marge Ligure au Plio-Quaternaire et de la marge San-Pedro au Crétacé supérieur". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066694/document.
Testo completoAbstract (sommario):
Les systèmes sédimentaires turbiditiques présentent un double intérêt académique et industriel puisqu’ils constituent à la fois des archives des conditions environnementales et des réservoirs pétroliers potentiels. Parmi les nombreux paramètres contrôlant l’organisation sédimentaire de ces systèmes l’inclinaison de la pente continentale apparait être un paramètre majeur. L’analyse de l’influence de l’inclinaison de la pente et de ces variations sur l’hydrodynamique des écoulements sédimentaires et ainsi sur l’architecture des systèmes turbiditiques revêt un caractère crucial tant du point de vue académique que pétrolier. Ce travail s’appuie sur l’analyse haute résolution de données acoustiques (bathymétrie, imagerie multifaisceaux, sismique THR, sonar latéral) acquises sur la marge abrupte du Golfe de Gênes (Malisar, Fables, Prisme, Gelo) et de l’analyse d’un bloc de sismique 3D sur la marge abrupte Ivoirienne. Les accumulations turbiditiques des deux sites témoignent de processus de ségrégation des particules avec le piégeage des particules les plus grossières dans des structures en plunge pools, cyclic steps ou slope break deposits. L’étude fine de ces corps liés au ressaut hydraulique apporte ici un éclairage inédit sur la continuité des corps sableux à la transition canyon/lobe et permet ainsi de proposer un nouveau scénario de modèle réservoir. De plus l’analyse de ces deux zones d’études met en évidence l’impact direct de l’activité tectonique sur l’architecture des accumulations turbiditiques par la mise en place et le maintien d’une zone de rupture de pente où le phénomène de ressaut hydraulique peut perdurer au cours du tempsTurbidite systems present both academic and industrial interests since they are archives of environmental conditions and potential oil reservoirs. Among many parameters controlling the sedimentary organization, the continental slope inclination appears to be a major parameter. The analysis of slope inclination’s and these variations on the hydrodynamic of sedimentary flows and thus on turbidite systems architecture is a crucial character for both academic and industrial interests. The Pliocene-Quaternary turbidite systems of the Gulf of Genoa and upper margin of the Ivorian Cretaceous develop on margins with steep slope profiles controlled by tectonic processes and are suitable and complementary items for the Study of turbidite sedimentation in context of abrupt margin. This work is based on the high-resolution analysis of acoustic data (bathymetry, multibeam imaging, seismic THR, sidescan sonar) acquired on the steep margin of the Gulf of Genova (Malisar, Fables, Prism, Gelo) and the analysis of a 3D seismic block on the Ivorian steep margin. Turbidite accumulations of two sites demonstrate particle segregation processes with trapping coarser particles into specific structures such as plunge pools and cyclic steps. The detailed study of these bodies related to hydraulic jump sheds a new light on the continuity of sand bodies in the transition canyon / lobe and allows the designing of a new reservoir model scenario. Further analysis of these two areas of study shows the direct impact of tectonic activity on the architecture of turbidite accumulations by establishing and maintaining a nick area where the phenomenon of hydraulic jump can be maintained over time
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Alves, Nelson Miguel Jacinto. "Competitive advantages as source of excess stock returns". Master's thesis, Instituto Superior de Economia e Gestão, 2011. http://hdl.handle.net/10400.5/3750.
Testo completoAbstract (sommario):
Mestrado em FinançasThe perspectives assessment of any given company is a vital step to the efficiency of the valuation process. A correct assessment will result in the definition of assumptions that will lead to better valuation results. Wrong conclusions are frequently taken because a bad assessment was made and this is the result of the lack of a proper framework that guides the analysis of company perspectives. To solve this problem we decided to use strategic management theory and test the relation between stock returns and competitive advantages relevant for a given industry. We applied this method to the Steel Industry and tested it statistically. The results showed us that, generally, improvements in the operational efficiency, measured by the first differences in gross margin, provide excess returns. This results show us that the use of Competitive Advantages to select portfolios, in the Steel Industry, yields better than average returns.
A avaliação das perspectivas para uma determinada empresa é um passo critico no processo de valorização de uma acção. Uma correcta avaliação resulta na definição de um conjunto de pressupostos que levarão a uma avaliação mais precisa. Analises erradas levam a conclusões erradas e são resultado da falta de um quadro orientador que direccione o estudo das perspectivas das empresas em causa. Para resolver este problema decidimos recorrer à teoria da gestão estratégica e testar a relação entre rendibilidades de acções e Vantagens Competitivas relevantes em determinada indústria. Aplicámos este método à Industria Siderúrgica e realizamos testes estatísticos. Os resultados mostram-nos que, na generalidade, melhorias na eficiência operacional, medida através das primeiras diferenças da margem bruta, oferece retornos acima da taxa de retorno sem risco. Estes resultados mostram-nos que a selecção de portfolios, utilizando Vantagens Competitivas, permitem-nos obter retornos acima da média.
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Marques, Rodrigo Pereira. "Efeito da corrosão atmosférica marinha sobre os aços ASTM Grau 80, Grau 100 e Grau 120, utilizados na montagem de lingas de corrente. /". Guaratinguetá, 2019. http://hdl.handle.net/11449/181415.
Testo completoAbstract (sommario):
Orientador: Eduardo Norberto CodaroResumo: O presente trabalho tem por objetivo avaliar o efeito da corrosão atmosférica marinha sobre os aços ASTM Grau 80, Grau 100 e Grau 120, que são utilizados na montagem de lingas de corrente destinadas à movimentação de cargas. Os problemas atribuídos à deterioração desses materiais são comuns e frequentes, pois basicamente em todos os ramos da atividade econômica há materiais que necessitam ser transportados. E para analisar o comportamento destes aços frente à corrosão, foram realizados ensaios eletroquímicos e ensaios de imersão por perda de massa utilizando uma solução contendo NaCl a 3,56% (em massa) que simula a atmosfera marinha em ambientes laboratoriais. Os resultados dos ensaios de OCP (Potencial em Circuito Aberto) e de Polarização de Tafel revelaram que o processo de corrosão é controlado pela difusão de O2 dissolvido neste meio. Pode-se concluir que os valores de OCP e de Ecorr (potencial de corrosão) obtidos foram muito similares entre si para todas as regiões do elo analisadas (solda, corpo e deformação). A região do corpo demonstrou maior resistência à corrosão, obtendo os maiores valores médios de resistência de polarização (Grau 80: 10,14 kΩ; Grau 100: 12,61 kΩ; e Grau 120: 11,74 kΩ). As densidades de corrente de corrosão (Icorr) observadas são baixas e da mesma ordem de magnitude (abaixo de 7µA/cm2). Nos ensaios de imersão, observou-se que a perda de massa relativa das amostras, após os 10 dias de permanência na solução, foi mínima (entre 0,05 e 0,08 %/cm2), i... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre
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Soulet, Quentin. "Typologie, architecture et évolution des systèmes silicoclastiques des marges abruptes. Analyse comparée de la marge Ligure au Plio-Quaternaire et de la marge San-Pedro au Crétacé supérieur". Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066694.
Testo completoAbstract (sommario):
Les systèmes sédimentaires turbiditiques présentent un double intérêt académique et industriel puisqu’ils constituent à la fois des archives des conditions environnementales et des réservoirs pétroliers potentiels. Parmi les nombreux paramètres contrôlant l’organisation sédimentaire de ces systèmes l’inclinaison de la pente continentale apparait être un paramètre majeur. L’analyse de l’influence de l’inclinaison de la pente et de ces variations sur l’hydrodynamique des écoulements sédimentaires et ainsi sur l’architecture des systèmes turbiditiques revêt un caractère crucial tant du point de vue académique que pétrolier. Ce travail s’appuie sur l’analyse haute résolution de données acoustiques (bathymétrie, imagerie multifaisceaux, sismique THR, sonar latéral) acquises sur la marge abrupte du Golfe de Gênes (Malisar, Fables, Prisme, Gelo) et de l’analyse d’un bloc de sismique 3D sur la marge abrupte Ivoirienne. Les accumulations turbiditiques des deux sites témoignent de processus de ségrégation des particules avec le piégeage des particules les plus grossières dans des structures en plunge pools, cyclic steps ou slope break deposits. L’étude fine de ces corps liés au ressaut hydraulique apporte ici un éclairage inédit sur la continuité des corps sableux à la transition canyon/lobe et permet ainsi de proposer un nouveau scénario de modèle réservoir. De plus l’analyse de ces deux zones d’études met en évidence l’impact direct de l’activité tectonique sur l’architecture des accumulations turbiditiques par la mise en place et le maintien d’une zone de rupture de pente où le phénomène de ressaut hydraulique peut perdurer au cours du tempsTurbidite systems present both academic and industrial interests since they are archives of environmental conditions and potential oil reservoirs. Among many parameters controlling the sedimentary organization, the continental slope inclination appears to be a major parameter. The analysis of slope inclination’s and these variations on the hydrodynamic of sedimentary flows and thus on turbidite systems architecture is a crucial character for both academic and industrial interests. The Pliocene-Quaternary turbidite systems of the Gulf of Genoa and upper margin of the Ivorian Cretaceous develop on margins with steep slope profiles controlled by tectonic processes and are suitable and complementary items for the Study of turbidite sedimentation in context of abrupt margin. This work is based on the high-resolution analysis of acoustic data (bathymetry, multibeam imaging, seismic THR, sidescan sonar) acquired on the steep margin of the Gulf of Genova (Malisar, Fables, Prism, Gelo) and the analysis of a 3D seismic block on the Ivorian steep margin. Turbidite accumulations of two sites demonstrate particle segregation processes with trapping coarser particles into specific structures such as plunge pools and cyclic steps. The detailed study of these bodies related to hydraulic jump sheds a new light on the continuity of sand bodies in the transition canyon / lobe and allows the designing of a new reservoir model scenario. Further analysis of these two areas of study shows the direct impact of tectonic activity on the architecture of turbidite accumulations by establishing and maintaining a nick area where the phenomenon of hydraulic jump can be maintained over time
49
Malečková, Kateřina. "Architektonická studie sakrálního objektu Brno - Líšeň". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-414268.
Testo completoAbstract (sommario):
The topic of this diploma thesis is design processing of a new sacral building in Brno-Líšeň district. It is a plot in the middle of a panel building between the health centre building and the building of the Salesian Youth Center, so-called Salesko. The Salesian community, which will use the building the most, has been waiting for the realization of this building for many years. The key theme is the creation of spaces enabling people to meet for worship, celebrations and social events. The design is processed by two interconnected operations - the building of the Church of the Descent of the Holy Spirit and the building of clergy house. The basic composition consists of three cubic masses - the entrance, the main liturgical space and the clergy house. The bell tower is the height dominant feature which indicates the sacral function of the building. The project consists a set of buildings with two above-ground floors and a basement in the entrance part of the church. This project also mentions the solution of open spaces around the plot and their conversion into quality public areas, marginally. The sacral space is to become a place that welcomes and takes in its visitors and gives them the feeling of safety. Inside this building, people will find peace, support and undestarstanding, so they may leave with the feeling of being a better person.
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Tunková, Martina. "Městské lázně". Master's thesis, Vysoké učení technické v Brně. Fakulta architektury, 2010. http://www.nusl.cz/ntk/nusl-215713.
Testo completo