Dissertations / Theses: 'Steel castings Mathematical models'

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Spinelli, Jose Eduardo. "Simulação do lingotamento continuo de tiras finas de aços." [s.n.], 2000. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264701.

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Orientador: Amauri Garcia
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Entende-se por modelagem de processo, o desenvolvimento de uma representação quantitativa ou qualitativa dos fenômenos físicos associados ao processo. Neste trabalho são realizadas simulações do processo twin roll de lingotamento contínuo de tiras de aços, utilizando como referência tecnológica o equipamento piloto instalado nas dependências do Instituto de Pesquisas Tecnológicas do Estado de São Paulo. São construídos dois simuladores para o processo: um simulador da solidificação unidirecional, com molde refrigerado de aço e paredes laterais de material refratário, utilizando-se o aço inoxidável 304 como material de simulação; e variando-se as temperaturas de vazamento; e outro simulador a frio, com componentes feitos de acrílico, água como fluido de simulação e permanganato de potássio como corante. Um modelo matemático previamente desenvolvido é utilizado para confrontar perfis térmicos teóricos com perfis experimentais, para a determinação do coeficiente de transferência de calor metal/molde. O levantamento de valores de espaçamento dendrítico secundário é realizado nas amostras, além da observação simultânea das estruturas de solidificação, o que comprovou a eficiência do simulador em caracterizar o processo de solidificação do equipamento piloto. O uso do modelo frio permitiu a caracterização do posicionamento de barreira a 15 cm ou a 20 cm da lateral esquerda do distribuidor como a melhor configuração
Abstract: It can be understood by process modeling the development of a quantitative or qualitative representation of the physical phenomena associated to the process. In this work, simulations concerning the twin roll continuous caster of steels process at IPT (Instituto de Pesquisas Tecnológicas do Estado de São Paulo) are performed. Two simulators were developed: (i) a simulator of unidirectional solidification with cooled steel mold and refractory lateral walls, by using a stainless steel as the reference metal (AISI 304), and varying superheat temperatures; (ii) a physical model, with components made of acrylic, water as the simulation fluid and potassium permanganate as a pigment. A previously developed mathematical model has been used to determine the metal/mold heat transfer coefficient by a method that compares experimenta1ltheoretical temperature curves. Measurement of secondary dendrite arm spacings is performed by microestructural examination of the samples, confirming the simulator efficiency in characterizing the solidification process in the pilot equipment. The use of the physical model has permitted to attain the best configuration for the tundish, by positioning the dam 15 cm or 20 cm from the left side of tundish
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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Moosbrugger, John C. "Numerical computation of metal/mold boundary heat flux in sand castings using a finite element enthalpy model." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/16365.

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Rees, C. S. "Mathematical models in an integrated steel making plant." Thesis, University of Hull, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383736.

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Sierra, Robinson. "Investigation of the mechanical behaviour of TRIP steels using FEM." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99793.

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The need to develop light-weight and high strength materials for car frames which improve fuel efficiency and provide increased passenger safety during dynamic events such as automobile crashes has been the focus of the steel and automobile industries for the past 30 years. In recent years, the development of high strength steels such as multi-phase TRIP (Transformation-Induced Plasticity)-aided steels have shown great promise due to their excellent combination of high strength and ductility. The savings in automobile weight is provided by the inherent strength of TRIP steels which allows for the use of thinner sections. The TRIP effect is characterized by the phenomenon known as strain-induced martensitic transformation (SIMT) which enhances the work hardenability of such steels as the austenite phase transforms to the much harder martensite phase during plastic straining. This results in a resistance to local necking which subsequently enhances the strength, ductility, and formability of such steels. However, various factors exist which affect the mechanical behaviour of TRIP steels. This study will aim, through the use of finite element models, to investigate the role and influence of each of these factors on the TRIP effect in type 304 austenitic and multi-phase TRIP steels. These factors include the rate at which the martensitic transformation proceeds, the state of stress to which the material is subjected to, the interaction between the surrounding matrix and embedded retained austenite islands in multi-phase TRIP steels, and the volume fraction and morphology of the retained austenite islands. Investigation of these factors will provide further insight on each of their contributions to the TRIP effect in order to exploit the potential benefits offered by these steels.

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Mahmoody, Sam. "Micromechancal modeling of dual-phase steel using a rate-dependent crystal plasticity model." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99778.

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Dual-phase (DP) steels consisting of a ferrite matrix with dispersed martensite particles have attracted a significant interest due to their combination of high work hardening and ductility. A great deal of experimental work has been done to obtain a better comprehension of the relation of their mechanical behaviour to their microstructural characteristics. In the present work, a micromechanical study of ferrite-martensite DP steels is conducted. The deformation of ferrite is described by a rate-dependent crystal plasticity theory, which relates the stress-strain field equations on the grain level to the macroscopic behaviour of the material. The crystal plasticity theory assumes that slip is the only deformation mechanism. Martensite, on the other hand, is considered an elastic-plastic isotropic solid. The interfaces of the grains are taken into account through an idealized form of grain boundaries. A FORTRAN program was coupled with the finite element method to solve the stress equations of the crystal plasticity. Including the grain boundaries made it possible to examine the effect of ferrite grain size on the strength of the material. It is shown that by decreasing the grain size, the yield stress increases according to Hall-Petch equation. Additionally, the effects of the volume fraction of martensite (Vm) on the onset strain, i.e. the strain at which martensite deforms plastically, and of the distribution of martensite on the stress are studied. The former showed that the onset strain of the DP steel declines linearly with increasing Vm up to 36%, beyond which the onset strain becomes independent of V m. The latter revealed that when martensite particles are formed as islands in the ferrite grains, the material exhibits higher strength and hardening rate; compared to when martensite is distributed as large blocks among the ferrite grains.

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Warke, Virendra S. "Removal of Hydrogen and Solid Particles from Molten Aluminum Alloys in the Rotating Impeller Degasser: Mathematical Models and Computer Simulations." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0626103-111317.

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Thomas, Brian Gordon. "Investigation of panel crack formation in steel ingots using mathematical and physical models." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25980.

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An investigation of panel crack formation in steel ingots was undertaken to improve understanding of the mechanisms by which they develop and to evaluate possible solutions to the problem. The investigation revealed that two distinct types of panel cracks, both of which are partly caused by intermediate-temperature embrittlement of steel involving aluminum nitride precipitation, operate under different mechanisms. Isothermal, physical modelling experiments were conducted to determine the flow patterns, velocity profiles and flame geometry in a bottom-fired soaking pit and the resultant effects on heat transfer. An investigation involving comparison with analytical solutions determined the optimum numerical method to employ for the mathematical modelling of complex, two-dimensional, transient, heat-conduction problems. This method was formulated to calculate the temperature distribution in a steel ingot during the various processing stages from initial casting up to rolling and was verified with industrial measurements. A transient, elasto-visco-plastic, thermal-stress model employing the finite-element method was formulated, developed and verified using analytical solutions. Based on the temperatures calculated by the finite-element, heat-transfer model as input data, the transient, internal stress state of the ingot was calculated, taking into account the effects of phase-transformation volume changes and kinetics, creep, and temperature-dependent mechanical property behavior. The simulated stress histories were found to be directly linked to the progress of the phase-transformation front and were used to clarify the role of stress generation in panel crack formation. Finally, the results of a metallurgical investigation of steel ingot samples containing off-corner panel cracks were synthesized with the results of the physical and mathematical models to determine mechanisms and to suggest solutions for the formation of both mid-face and off-corner panel cracks. Mid-face panel cracks are apparently formed during air cooling when the mid-face surface is between the Ar₁ and 500 °C. Off-corner panel cracks appear to initiate internally during the early stages of reheating, but do not propagate to the surface until air cooling after removal from the soaking pit.
Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate

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Choi, Joonho. "Concurrent fire dynamic models and thermomechanical analysis of steel and concrete structures." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26679.

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Uslu, Cafer Harun. "3-d Finite Element Analysis Of Semi-rigid Steel Connections." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610835/index.pdf.

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Two types of connection are generally considered in the design of steel structures in practice. These are classified as completely rigid (moment) and simple (shear) connections. In theory, completely rigid connections can not undergo rotation and simple connections can not transfer moment. However, in reality rigid connections have a relative flexibility which makes them to rotate and simple connections have some reserve capacity to transfer moments. In many modern design specifications, this fact is realized and another type which is called partially restrained or semi-rigid connection is introduced. These types of connections have got the transfer of some beam moment to column together with shear. However, there is a lack of information on the amount of moment transferred and rotation of connection during the action of the moment transfer. The only way to quantify the moment and rotation of the partially restrained connections is to draw momentrotation curves. Nevertheless, drawing such curves requires great amount of expenses for experiments. Taking these into account, the use of finite elements with the help of increased computational power is one way to obtain moment-rotation curves of connections. Available test results guides the finite element analysis for justifications. So these analyses can be further implemented into design functions. This thesis is intended to conduct 3-D non-linear finite element analyses to compliment with tests results for different types of semi-rigid connections with angles and compare them with mathematical models developed by different researchers.

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Zhou, Li. "Machining chip-breaking prediction with grooved inserts in steel turning." Link to electronic thesis, 2002. http://www.wpi.edu/Pubs/ETD/Available/etd-0109102-140803.

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Patra, Anirban. "Modeling the mechanical behavior and deformed microstructure of irradiated BCC materials using continuum crystal plasticity." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50366.

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The mechanical behavior of structural materials used in nuclear applications is significantly degraded as a result of irradiation, typically characterized by an increase in yield stress, localization of inelastic deformation along narrow dislocation channels, and considerably reduced strains to failure. Further, creep rates are accelerated under irradiation. These changes in mechanical properties can be traced back to the irradiated microstructure which shows the formation of a large number of material defects, e.g., point defect clusters, dislocation loops, and complex dislocation networks. Interaction of dislocations with the irradiation-induced defects governs the mechanical behavior of irradiated metals. However, the mechanical properties are seldom systematically correlated to the underlying irradiated microstructure. Further, the current state of modeling of deformation behavior is mostly phenomenological and typically does not incorporate the effects of microstructure or defect densities. The present research develops a continuum constitutive crystal plasticity framework to model the mechanical behavior and deformed microstructure of bcc ferritic/martensitic steels exposed to irradiation. Physically-based constitutive models for various plasticity-induced dislocation migration processes such as climb and cross-slip are developed. We have also developed models for the interaction of dislocations with the irradiation-induced defects. A rate theory based approach is used to model the evolution of point defects generated due to irradiation, and coupled to the mechanical behavior. A void nucleation and growth based damage framework is also developed to model failure initiation in these irradiated materials. The framework is used to simulate the following major features of inelastic deformation in bcc ferritic/martensitic steels: irradiation hardening, flow localization due to dislocation channel formation, failure initiation at the interfaces of these dislocation channels and grain boundaries, irradiation creep deformation, and temperature-dependent non-Schmid yield behavior. Model results are compared to available experimental data. This framework represents the state-of-the-art in constitutive modeling of the deformation behavior of irradiated materials.

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Nassiri, Esmail. "Modelling nonlinear behaviour of two-dimensional steel structures subjected to cyclic loading." Thesis, Queensland University of Technology, 1998.

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Kahle, Matthew Gilbert. "Partially restrained composite connections : design and analysis of a prototype structure." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20830.

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Garcia, Victor Hugo Guzzo. "Modelagem computacional da corrosão por pites em aço inoxidável: efeito do potencial e de inclusões de MnS." Universidade do Estado do Rio de Janeiro, 2009. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=1243.

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Nesta dissertação, é apresentada uma rotina computacional para modelar a corrosão por pites em aço inoxidável baseada em modelos matemáticos existentes que levam em consideração efeitos determinísticos e estocásticos. Como contribuição, modificações baseadas em resultados experimentais foram inseridas no modelo, com o objetivo de avaliar a influência de inclusões de MnS na matriz metálica, locais típicos de maior nucleação de pites. Foi modelado também o efeito do potencial de aplicado verificando-se assim a sua influência na formação de pites e a determinação da faixa possível para o potencial de pite. A modelagem consiste da avaliação espaço-temporal da nucleação, com a possibilidade de visualização da evolução de pites metaestáveis e estáveis, além do transiente de corrente anódica gerado pelo processo. Os resultados são apresentados em termos da avaliação das variáveis de maior influência na suscetibilidade de formação de pites, tais como concentração de espécies agressivas, dano à camada passiva e queda no potencial ôhmico, o que possibilita estudos futuros para se obter formas mais eficientes de combate à corrosão por pites.
In this work is presented a computational routine to model pitting corrosion of stainless steel based on pre-existing mathematical models that take into account deterministics and stochastic effects. As contribution, modifications based on experimental results were inserted, evaluating the influence of MnS inclusions on metal surface, a typical site of major pitting nucleation. Applied potential effect was modeled, thus, it was possible to verify its influence on pitting formation and the possible range of pitting. The model consists on spatio-temporal evaluating of nucleation process, with visualization of metastable and stable pitting evolution and the anodic current transient. The results are presented in terms of variables with greatest influence on the susceptibility of pitting formation, such as concentration of aggressive species, passivity layer damage and ohmic potential drop, allowing future studies to obtains more efficient ways to combat pitting corrosion

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Oliveira, Willian Rafael de. "INFLUÊNCIA DOS PARÂMETROS DE IMPLANTAÇÃO IÔNICA POR IMERSÃO EM PLASMA NA EFICIÊNCIA DA NITRETAÇÃO DO AÇO INOXIDÁVEL SUPER DUPLEX." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2016. http://tede2.uepg.br/jspui/handle/prefix/858.

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This work aimed at study the correlation of variables in a plasma immersion ion implantation (PIII) system, as well as their synergistic combination for the nitriding of the UNS S32750 super duplex stainless steel ( SD 2507). The research comprised two phases, as follows. (i) Study of the system. The interconnection of variables, namely voltage (V), pulse width (L), frequency (f) and current (I), were systematically analyzed with respect to the cathode heating. A mathematical formulation was proposed for the ion average energy and the substrate temperature, which took into consideration the energy conservation in the system, and the basic theories for plasma and sheaths and the ion interaction with matter. Hereafter, such model is thought to be experimentally demonstrated, allowing inferring the actual PIII fraction of energy that is converted to heat. (ii) N-PIII of the SD. Mirror-like samples were nitrided under different V, f and L combinations, leading to the temperatures 295, 325, 355 and 400 oC. The surface characterization methods were the optical, field emission electron, and atomic force microscopies, X-ray diffraction, energy dispersive X-ray spectroscopy, backscattered electron diffraction, and instrumented indentation. The austenite and ferrite fraction in the as received material amounted to 43,7 % and 56,3 %, respectively. After nitriding, the modified layers were 0,5-1,5 m thick. Up to 355 ºC, the expanded phase N was produced in originally austenite grains, whereas Fe2-3N e Fe4N precipitates were formed in ferrite grains. The hardness profiles were similar among different temperatures and between the two phases in the same sample. However, in ferritic regions, the mechanism for plastic deformation changed from ductile to brittle. In the 400 ºC treatments, only N was formed. Finally, a correlation for the production of the expanded phase in PIII and the mean pulse energy Ei was attained, given by and . Where IN and I are the integrated intensities of diffraction peaks for austenite and expanded austenite, respectively.
O objetivo deste trabalho foi estudar o comportamento de um sistema de implantação iônica por imersão em plasma (PIII: “plasma immersion ion implantation”), em função de suas variáveis, bem como a influência destas na nitretação de superfícies do aço super duplex UNS S32750 (ou SD 2507). O trabalho foi dividido em dois momentos, como segue. (i) Estudo do sistema. O comportamento das variáveis associadas à implantação iônica, especificamente tensão (V), largura de pulsos (L), frequência (f) e corrente (I), foi sistematicamente analisado com relação ao aquecimento do cátodo. Com base na conservação de energia, física de plasmas e bainhas catódicas e interação de íons com a matéria, propôs-se uma formulação matemática relacionado a energia média dos íons à temperatura do substrato, a qual poderá, futuramente, ser posta à prova experimental, mensurando-se a fração de energia que é, de fato, transformada em calor. (ii) Nitretação por PIII do SD. Amostras com superfície especular foram nitretadas sob diferentes combinações de V, f e L, em temperaturas de 295, 325, 355 e 400 oC. As superfícies foram caracterizadas por métodos de microscopia (ótica, eletrônica com efeito de campo, de força atômica), difração de raios X, espectroscopia de raios X por energia dispersiva, difração de elétrons retroespalhados, e indentação instrumentada. O SD apresenta estrutura cristalina de austenita e ferrita na proporção de 43,7/56,3. A nitretação produziu camadas modificadas com espessura de 0,5 a 1,5 m. Observou-se, nos tratamentos até 355 ºC, a formação da fase expandida N nos grãos que originalmente eram austenita, e de precipitados de nitretos -Fe2-3N e -Fe4N em grãos de ferrita. Embora não houve diferenças significativas nos perfis de dureza, tanto entre as temperaturas quanto entre as fases em uma mesma amostra, o mecanismo de deformação plástica nas regiões ferríticas transitou de dúctil para frágil. Nas nitretações em 400 ºC, houve apenas a formação de N. Finalmente, determinou-se que a obtenção da fase expandida por PIII no SD se relaciona com a energia média por pulso Ei por e . Onde I e I são as intensidades integradas dos picos de difração da austenita expandida e da austenita, respectivamente.

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Fan, Chih-Ming, and 范志銘. "Application of Mathematical Model and Physical Model in Ladle Refining and Continuous Casting Processes of Steel." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/96636553685563930792.

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博士
國立成功大學
材料科學及工程學系碩博士班
91
The purpose of this study is to develop two mathematical models, which are based on a computational fluid dynamics technique, named SOLA, and the k-ε two-equation turbulence model, to analyze the fluid flow phenomena of molten steel in the ladle during the secondary refining process and the tundish operation in the continuous casting process of steel. The first mathematical model is used to analyze the fluid flow phenomena and the corresponding diffusion of the injected Ca-Si under various design and operating conditions to find the optimal Ca-Si injection position. The second mathematical model is used to analyze fluid flow phenomena and design the optimal flow control device during initial casting operation, steady state operation and ladle-interchange operation. Several physical models are also constructed in this study. Water model experiments are conducted to verify the accuracy and reliability of the mathematical models. Good agreements are observed between the simulations and measurements. As the mathematical model is verified to be a trustworthy tool, it is then applied to the actual operation to simulate the fluid flow; heat transfer and mass transfer phenomena of the secondary refining and continuous casting processes. 　　The flow pattern of two-phase flow in the stirred ladle for the secondary refining is simulated. The results show that the injection position of D, which has the coordinate of , has the shortest mixing time. The simulated results for the actual ladle operation show the similar trend to the water model. For the injection positions on the tuyere/circle center plane, the additives prematurely float to the top as the injection positions are near the plume zone. It helps the additives to transport to the bottom as the injection positions are away from the plume zone. The simulated results for the actual ladle operation show that the optimal positions for injection are located on the tuyere/circle-center plane, opposite side of the tuyere, and 0.5-0.8 r away from the circle center. For these injection positions, the mixing time is shorter and the flow pattern favors the transport of the additive to the bottom of the ladle. 　　The fluid flow and heat transfer phenomena of the molten steel in the tundish during its filling stage and subsequent initial casting operation are studied. The results show that the temperature field in LP-ND operation is not uniform Inclusion distribution and the extents of inclusion contamination among the outlets of the various strands in the tundish are also analyzed. The left half of tundish, inclusion contamination in the #2 strand is significantly more severe then that in the #1 strand. This is confirmed by the actual experience on the shop floor of that particular billet caster that the #2 strand experiences more difficulty in clogging problem during the initial casting operation than the #1 strand does. The LP-SD has no eddy near outlet strand and has more uniform temperature field. It shows that LP-SD lowers nozzle clogging and makes distribution of steel more uniform. 　　The fluid flow and mass transfer phenomena of the molten steel in the three different tundish caster during steady state are studied. Three tundish caster include A-shaped four strands billet tundish, twin strand billet tundish, and single strands slab tundish. In A-shaped four strands billet tundish, HP-SB reduces the difference of residence times between two strands, and makes distribution of steel more uniform. In twin strands billet tundish, the billet tundish with the HLPP design has the longest min-RT and it can inhibit turbulence as well as guide flow upward along slag/metal interface in the tundish. It is thus considered that HLPP arrangement is the optimal SEFCD design for twin strands billet tundish. In the single strand slab tundish, the result shows that the plain tundish has short circuit and the lowest inclusion removal ratio. The tundish with PP can reduce short circuit and has the highest inclusion removal ratio, even for inclusions, which is smaller than 50 μm. PP is the optimal SEFCD design for the single strand slab tundish. 　　The fluid flow and mass transfer phenomena of the molten steel in the tundish caster during ladle-change period are also studied. The results show that the weir and slanting dam reduce the velocity of steel and lower the chance for slag particles to flow into the outlet. WSLD40-F120 has the smallest number of slag particles to flow into the outlet and is considered the optimal flow control design in the T-shaped single strand slab tundish caster.

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Yeh, Jiunn-Lin, and 葉俊麟. "The Development of A Mathematical Model and Its Application in the Design/Operation of Tundishes for the Continuous Casting of Steel Slab." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/19515081379711814706.

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DePiero, Anthony H. "High cycle fatigue modeling and analysis for deck floor truss connection details." Thesis, 1997. http://hdl.handle.net/1957/33707.

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The Oregon Department of Transportation is responsible for many steel deck truss bridges containing connection details that are fatigue prone. A typical bridge, the Winchester Bridge in Roseburg, Oregon, was analyzed to assess the loading conditions, stress levels, and fatigue life of the connection details. The analysis included linear-elastic beam analysis, 2D and 3D finite element modeling, and fatigue modeling. A field identification methodology was developed to expand the analysis to other steel deck truss bridges. Five retrofit strategies were investigated to determine their effectiveness in reducing the stress ranges developed in the connection details.
Graduation date: 1998

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Jheng, Yi-Jhen, and 鄭亦真. "The development and performance analysis of the mathematical programming models for the steel production." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/85535804964061505506.

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碩士
國立聯合大學
管理研究所
96
This paper proposes the integrated programming model and the two-stage programming model for solving the production scheduling problem for steel process with the objective to minimize the total inventory, in which the demands of all product specification should be satisfied. The integrated model simultaneously solve the combination of some product specifications with corresponding available cutting length of steel slab and solve the producing quantity of each combination of product specifications. However, the two-stage programming model solves these two categorical variables by two related models iteratively and including predefined rules from experiences to reduce the complexity. A performance comparison basing on actual customer orders for these models is also provided.

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Liang, Bin. "Estimation of Time-dependent Reliability of Suspension Bridge Cables." Thesis, 2016. https://doi.org/10.7916/D8V69JTN.

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The reliability of the main cable of a suspension bridge is crucial to the reliability of the entire bridge. Throughout the life of a suspension bridge, its main cables are subject to corrosion due to various factors, and the deterioration of strength is a slowly evolving and dynamic process. The goal of this research is to find the pattern of how the strength of steel wires inside a suspension bridge cable changes with time. Two methodologies are proposed based on the analysis of five data sets which were collected by testing pristine wires, artificially corroded wires, and wires taken from three suspension bridges: Severn Bridge, Forth Road Bridge and Williamsburg Bridge. The first methodology is to model wire strength as a random process in space whose marginal probability distribution and power spectral density evolve with time. Both the marginal distribution and the power spectral density are parameterized with time-dependent parameters. This enables the use of Monte Carlo methods to estimate the failure probability of wires at any given time. An often encountered problem -- the incompatibility between the non-Gaussian marginal probability distribution and prescribed power spectral density -- which arises when simulating non-Gaussian random processes using translational field theory, is also studied. It is shown by copula theory that the selected marginal distribution imposes restrictions on the selection of power spectral density function. The second methodology is to model the deterioration rate of wire strength as a stochastic process in time, under Ito's stochastic calculus framework. The deterioration rate process is identified as a mean-reversion stochastic process taking non-negative values. It is proposed that the actual deterioration of wire strength depends on the deterioration rate, and may also depend on the state of the wire strength itself. The probability distribution of wire strength at any given time can be obtained by integrating the deterioration rate process. The model parameters are calibrated from the available data sets by matching moments or minimizing differences between probability distributions.

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Sabapathy, Prakash Niranjan. "Predicting weld cooling rates and the onset of failure during in-service welding / Prakash N. Sabapathy." 2002. http://hdl.handle.net/2440/22043.

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"1st February 2002"
Includes bibliographical references (leaves 265-273)
xi, 273 leaves : ill. (some col.), plates (col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Concerns the specialized requirements of welding procedures used on operational gas pipelines.
Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 2004?

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Sabapathy, Prakash Niranjan. "Predicting weld cooling rates and the onset of failure during in-service welding / Prakash N. Sabapathy." Thesis, 2002. http://hdl.handle.net/2440/22043.

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"1st February 2002"
Includes bibliographical references (leaves 265-273)
xi, 273 leaves : ill. (some col.), plates (col.) ; 30 cm.
Concerns the specialized requirements of welding procedures used on operational gas pipelines.
Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 2004?

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Mursi, Mohanad Civil &amp Environmental Engineering Faculty of Engineering UNSW. "The behaviour and design of thin walled concrete filled steel box columns." 2007. http://handle.unsw.edu.au/1959.4/40494.

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This thesis investigates the behaviour of hollow and concrete filled steel columns fabricated from thin steel plates. The columns are investigated under axial, uniaxial and biaxial loading. The currently available international standards for composite structures are limited to the design of concrete filled steel columns with compact sections and yield stress of steel up to 460 N/mm2. This thesis consists of both experimental and analytical studies and design recommendations for future use. Three comprehensive series of experimental tests are conducted on hollow and concrete filled steel columns. The principal parameters that have been considered in the test programmes are the slenderness of the component plates, the yield stress of the steel and the loading conditions. In the first test series, three slender hollow steel columns and three slender composite columns are tested under uniaxial loading. The steel utilised is mild steel. High strength steel is utilised in the second test programme. In this test series four stub columns, eight short columns and eight slender columns are tested, each set consists of four hollow and four composite columns. Short columns are tested under axial loading to investigate the confinement effect provided by the steel casing. Slender columns are tested under uniaxial loading to investigate the coupled instability of local and global buckling. The third test programme is quite novel and considers the behaviour of hollow and concrete filled steel columns fabricated with high strength structural steel plate and subjected to biaxial bending. In this test eight short columns and ten slender columns each of them consisting of hollow and composite columns are investigated under biaxial loading. Analytical models are developed herein to elucidate the behaviour of the hollow and composite columns considering cross section slenderness, yield stress and loading conditions. An iterative model considering the coupled global and local buckling in the elastic and plastic range incorporating material nonlinearities is developed to investigate the behaviour of slender columns fabricated from mild steel. An improved deformation control model is developed to investigate the behaviour of slender high strength steel columns considering the confinement effect and local and post-local buckling in the elastic and plastic range. Then a numerical model for biaxial bending is developed to study the behaviour of short and slender concrete filled high strength steel columns under biaxial loading incorporating interaction buckling considering material and geometric nonlinearities. The scope of the thesis presents a wide range of experimental and theoretical studies of an extremely novel nature. It demonstrates the benefit of confinement and the consideration of local and post-local buckling in the elastic and plastic range. It is hoped that this research will contribute to the area of composite steel-concrete structural applications.

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Karanci, Efe. "Modeling Corrosion in Suspension Bridge Main Cables." Thesis, 2017. https://doi.org/10.7916/D8RB7H05.

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Accurately determining the current state of a suspension bridge’s main cables is a critical component to reliably assessing the safety of the bridge. The primary cause for the deterioration of cable strength with time is universally recognized to be the corrosion of high strength steel wires, which together comprise the main cable. Hidden from view by the cable wrapping, this corrosion often goes undetected for years and is typically only discovered during costly and intrusive inspections. Furthermore, current inspection methods provide an incomplete picture of the variation in wire condition across the cable cross section. As a result, cable strength estimation techniques that rely solely on inspection data introduce a considerable degree of uncertainty. Finally, a method has not been developed for estimating the continuing decline in cable strength due to ongoing corrosion. A recent direction in research attempts to address the shortcomings of current inspection methodologies and the intent of this thesis is to further build upon these findings. In these recent studies, environmental conditions inside main cables are monitored to obtain information regarding the corrosive nature of the cable’s internal environment. The first goal of this thesis is to further this research direction by introducing a corrosion rate model for bridge wires that relates the monitored environmental parameters within a cable to the corrosion rate of bridge wires. Initially, temperature, relative humidity, pH, and Cl- concentration have been identified as the most relevant variables for predicting the corrosion rate of a bridge wire. By applying machine learning methods to a corrosion dataset in conjunction with these monitored environmental inputs, a long term corrosion rate model for bridge wires has been developed that is capable of capturing variability associated with these environmental parameters. This long term corrosion rate model is then applied to establish a methodology that will allow bridge owners and engineers to estimate the remaining strength of a main cable at any point in time. This is accomplished through the use of continually monitored environmental parameters which are input into the corrosion rate model. Incorporating the long term corrosion rate model developed in this thesis with current strength estimation techniques, the methodology presented in this thesis for the estimation of the remaining strength of suspension bridge cables may be readily adapted to other bridges and can be used to complement the current best practices for bridge inspection.

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Chen, Quan 1977. "Effects of thermal loads on Texas steel bridges." 2008. http://hdl.handle.net/2152/17802.

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The effects of thermal loads on steel bridges are not well understood. Although thermal effects are discussed in the AASHTO specifications, the appropriateness of the recommended thermal gradients is questionable. Thermal effects on the bridges can impact the design of the steel superstructure, the support bearings, and even the bridge piers. Previous field monitoring of steel trapezoidal box girder bridges has shown that thermal stresses on the order of ±5 ksi were not uncommon under regular daily thermal cycles. Stresses induced during annual thermal cycles may be potentially larger than those during daily thermal cycles. Recent data has shown that the bearings that are to allow the girders to expand and contract freely due to thermal movements are not frictionless. Because of the bearing friction, the supporting piers must flex to accommodate the bridge movements. In curved girder applications, questions have been raised by designers and contractors regarding the proper orientation of guided bearings. This research study includes field measurements, laboratory tests and finite element parametric analyses. The bearings of nine bridges in the Houston area have been instrumented and monitored for more than a year to measure bearing movements due to changes in temperature. Instrumentation of the steel girders on one of the Houston bridges was made utilizing thermocouples and vibrating wire strain gages to measure temperature distribution and thermal stresses. In addition, strain gages and thermal couples were applied to the steel girders and concrete bridge deck on a simple twin box girder bridge located at the Ferguson Structural Engineering Laboratory in Austin, Texas. The data from the field monitoring and laboratory tests were used to validate a finite element model. Based on this model, a detailed parametric study was conducted to investigate the effects of bridge configuration. It is found that under the given weather conditions, the most critical thermal loads are achieved under the following bridge configurations: N-S bridge orientation, shorter lengths of the concrete deck overhang, deeper steel girder webs, thinner concrete decks, and larger spacing between two box girders. To evaluate the effect of environmental conditions and obtain extreme thermal loads for design purposes, the most critical configuration of bridge sections was modeled for thermal analysis with Texas weather data from 1961 to 2005 as the input environmental conditions. Four cities were considered to bound Texas weather conditions. Based on the thermal analyses, a 45-year sample data of thermal parameters were used to describe the temperature field over a section. Extreme value analyses of the sample data were performed to obtain the relationship between thermal loads and return periods. The thermal loads with 100-year return period were compared to the ones suggested by AASHTO. The thermal loads with 100-year return period were used to investigate structural response. The effect of bearing orientation and the point of fixity were studied. A rigid body model was proposed to estimate thermal movements at the ends, which matched those obtained from field monitoring and finite element analysis. The maximum possible thermal stresses were also evaluated. Design suggestions are put forward based on the analysis.
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Sokur, M., V. S. Biletskyi, M. Fyk, O. Fyk, and I. Zaselskiy. "The study of the lining layer abrasing wear in the semiautogenous grinding mill." Thesis, 2020. http://repository.kpi.kharkov.ua/handle/KhPI-Press/46212.

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In this work complex investigations of the abrasing wear of lining of self-grinding mills (semiautogenous grinding mills) are carried out with the obtaining of mathematical models of wear-abrasing of elevators in terms of height, weight, volume and worn-out area. In particular, according to the location and nature of the abrasing wear processes, the liner-lifters mill self-grinding are identified in three typical groups. During 1 year, in the conditions of Ingulets GOK, the monitoring of the abrasing wear of selected groups of lifters of self-grinding mills was performed. On the basis of the experimental data calculationed in the Microsoft Office Excel program, a set of mathematical models of lifter abrasing wear was obtained in terms of height, weight, volume and worn-out area. The obtained dependencies are recommended for prediction of abrasing wear of lining and necessary frequency of replacement of inserts-lifters. In addition, the research of wear of lining made of cast iron RF–4, showed a significant reduction in their abrasing wear compared with steel 110G13L. Thus, it has been shown that the selection of liner-lifters materials can reduce the inter–repair period by 3 times or more (replacement of worn-out lifters). A comparison of the actual picture of the abrasing wear of elevators and Simulation Statics simulated result (using SolidWorks) stresses shows the convergence of the arrangement of the zones of maximum stresses and the maximum abrasing wear of the lining. Investigation of the influence of the stressed state of lining plates on the intensity of their abrasing wear – a promising direction for further research.

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Seracino, R. (Rudolf). "Partial-interaction behaviour of composite steel-concrete bridge beams subjected to fatigue loading / by Rudolf Seracino." 1999. http://hdl.handle.net/2440/19519.

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Bibliography: leaves 140-144.
xix, 156 leaves : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Determines the effect of partial-interaction and interfacial friction on the fatigue behaviour of composite bridge beams and develops a set of design rules for the assessment of the residual strength and performance of composite bridge beams.
Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1999

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Seracino, R. (Rudolf). "Partial-interaction behaviour of composite steel-concrete bridge beams subjected to fatigue loading / by Rudolf Seracino." Thesis, 1999. http://hdl.handle.net/2440/19519.

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Bibliography: leaves 140-144.
xix, 156 leaves : ill. ; 30 cm.
Determines the effect of partial-interaction and interfacial friction on the fatigue behaviour of composite bridge beams and develops a set of design rules for the assessment of the residual strength and performance of composite bridge beams.
Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1999

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Ahmed, Mizan. "Experimental and Numerical Studies of Concrete-Filled Double Steel Tubular Columns." Thesis, 2020. https://vuir.vu.edu.au/40437/.

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Concrete-filled double steel tubular (CFDST) columns are high-performance composite columns, which have increasingly been used in high-rise composite buildings and bridges as well as in strengthening conventional concrete-filled steel tubular (CFST) columns. The additional confinement provided by the inner circular tube in CFDST columns considerably improves their strength and ductility compared to CFST columns. However, research studies on the behavior of CFDST columns have been very limited and no design rules are given in current design codes. This thesis presents experimental and numerical studies on the fundamental behavior of circular and rectangular CFDST short and slender columns subjected to axial compression, combined axial load and bending, and preloads. Experiments on the behavior of square CFDST short columns with circular inner tube, circular CFDST short columns with circular inner tube and rectangular CFDST short columns composed of inner rectangular tube loaded concentrically and eccentrically are undertaken. Fiber-based mathematical models are developed for predicting the structural responses of CFDST short and slender columns under various loading conditions. The formulations of the mathematical models consider the influences of concrete confinement, geometric and material nonlinearities, and local buckling. New confining pressure models are proposed based on test results for ascertaining the compressive and residual strengths of confined concrete in CFDST columns, and incorporated in the mathematical models. The highly dynamic nonlinear equilibrium equations of CFDST columns under eccentric loading are solved by the efficient computer solution algorithms, which are developed based on the inverse quadratic method. The validations of the numerical models are made by comparisons with experimental results. The influences of various geometric and material parameters on the behavior of CFDST columns are examined. The results obtained from experimental and numerical studies are used to propose design equations. This research makes significant contributions to the knowledge by adding new test results on CFDST short columns to the database. The numerical models developed provide researchers and structural designers with accurate and efficient computer simulation and design tools, which lead to safer and more economical designs of composite structures. The design equations proposed can be utilized to design CFDST short and slender columns under various loading conditions.

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Kwon, Gun Up 1977. "Strengthening existing steel bridge girders by the use of post-installed shear connectors." 2008. http://hdl.handle.net/2152/18079.

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A number of older bridges built before the 1970’s were constructed with floor systems consisting of a non-composite concrete slab over steel girders. Many of these bridges do not satisfy current load requirements and may require replacement or strengthening. A potentially economical means of strengthening these floor systems is to connect the existing concrete slab and steel girders to permit the development of composite action. This dissertation describes a research program investigating methods to develop composite action in existing non-composite floor systems by the use of postinstalled shear connectors. Three types of post-installed shear connection methods were investigated. These methods are referred to as the double-nut bolt, the high tension friction grip bolt, and the adhesive anchor. These post-installed shear connectors were tested under static and fatigue loading, and design equations for ultimate strength and fatigue strength were developed. These post-installed shear connectors showed significantly higher fatigue strength than conventional welded shear studs widely used for new construction. The superior fatigue strength of these post-installed shear connectors enables strengthening of existing bridge girders using partial composite design, thereby requiring significantly fewer shear connectors than possible with conventional welded shear studs. Five full-scale non-composite beams were constructed and four of these were retrofitted with post-installed shear connectors and tested under static load. The retrofitted composite beams were designed as partially composite with a 30-percent shear connection ratio. A non-composite beam was also tested as a baseline specimen. Test results of the full-scale composite beams showed that the strength and stiffness of existing non-composite bridge girders can be increased significantly. Further, excellent ductility of the strengthened partially composite girders was achieved by placing the postinstalled shear connectors near zero moment regions to reduce slip at the steel-concrete interface. Parametric studies using the finite element program ABAQUS were also conducted to investigate the effects of beam depth, span length, and shear connection ratio on the system behavior of strengthened partially composite beams. The studies showed that current simplified design approaches commonly used for partially composite beams in buildings provide good predictions of the strength and stiffness of partially composite bridge girders constructed using post-installed shear connectors.
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Law, J. R. "Time varying probability of failure of steel floor beams subjected to real fire." Thesis, 1997. https://vuir.vu.edu.au/18185/.

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A model for estimating the time-dependent reliability of steel beams under real fire conditions has been developed. It gives a more rational basis than time of failure modelling does for design. From risk modelling, some small resistance time from the probabilistic distribution times of failure can be deduced, which gives an acceptably small risk of failure. Time of failure modelling by itself can only give the mean time failure which could lead to excessive risk if the variability of time of failure is large. The model comprises submodels for fire severity, heat transfer, mechanical properties, loads, structural analysis and reliability. Simple submodels have been adopted commensurate with the level of accuracy of other models in fire safety engineering. The submodel for real fire severity is Lie's. Heat transfer submodels have been adopted for three and four sided exposure and have been taken from work by the European Regional Organisation for Steel Construction and the French Technical Centre for Steel Construction. Three sided arises when the beam supports a concrete slab. The mechanical properties submodel was derived from an empirical fit to available test data. It gave better results than the current model in AS4100. It is appropriate for the model but is too complex for replacing the model in AS4100. The structural model four sided exposure was developed from simple plastic theory. For three sided exposure, discrete element analysis was adopted. The load submodels were lognormal for dead load and Weibull arbitrary point in time values for live load. The Monte Carlo method was adopted for the reliability submodel. The overall model was used to obtain the following sensitivities. An increase of lOkg.m-2 in fire load density can increase the risk of failure by 40%. In relation to the sensitivity of risk to ventilation, a reduction of the opening factor from 0.12 to 0.04 m0.5 increases the risk of failure approximately 200 times. Doubling the insulation thickness reduces the risk of failure by a factor ten. Increasing the live load has less effect on the risk of failure than increasing the dead load. If the load present predominantly live load, there is much less risk of failure than if the load is predominantly live load. Four sided exposure has ten times the risk of failure compared with three sided exposure. Accepting larger proof strains reduces the risk of failure; for example, increasing proof strain from 0.2% to 1% reduces the risk of failure by 50%.

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Dissertations / Theses on the topic 'Steel castings Mathematical models'

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