Made available in DSpace on 2014-10-09T12:31:41Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:07Z (GMT). No. of bitstreams: 1 02594.pdf: 1955228 bytes, checksum: 34c0873d245b469a86c13624608fed2b (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares, IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:31:41Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:07Z (GMT). No. of bitstreams: 1 02594.pdf: 1955228 bytes, checksum: 34c0873d245b469a86c13624608fed2b (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares, IPEN-CNEN/SP

Este trabalho foi desenvolvido com o intuito principal de adquirir \"know how\" na fabricação de componentes fundidos e usinados de bombas centrífugas, para aplicações em plataformas \"offshore\". Os materiais utilizados para esse destino - aços inoxidáveis super duplex - constituem sistemas termodinamicamente meta estáveis, que buscam o estado de estabilidade termodinâmica quando excitados termicamente. Por outro lado, esses materiais apresentam uma grande instabilidade dimensional, devido às tensões residuais desenvolvidas no resfriamento do tratamento térmico e durante o processo de usinagem, principalmente quando se trabalha com tolerâncias extremamente pequenas (10 m a 15 μm). Nesse contexto, foram realizados tratamentos térmicos a partir de 520°C, variando-se de 20°C em 20°C até a temperatura limite de 1180°C, com o objetivo de verificar-se a influência dessas temperaturas na microestrutura, dureza e tenacidade ao impacto do material. O enfoque principal foi dado na dinâmica de precipitação da fase sigma, que é o intermetálico mais conhecido e estudado nessa categoria de aços. Sua precipitação é inevitável, durante o processo de solidificação, porém, pode ser minimizada controlando-se a composição química e a taxa de resfriamento. Partindo-se de uma estrutura solubilizada, foi possível determinar as temperaturas a partir das quais a fase sigma começa a precipitar e dissolve-se por completo, bem como a influência de sua presença na dureza e na energia absorvida no ensaio de impacto Charpy. Técnicas de microscopias óptica, eletrônica de varredura, eletrônica de transmissão e difração de raios-x foram utilizadas para caracterização microestrutural do material nas várias condições de tratamento térmico. Ensaios eletroquímicos utilizando-se água do mar sintética, aerada e saturada com C02, contendo 20000ppm, 40000ppm e 80000ppm de íons cloreto, a temperaturas de 5OC, 25OC e 60°C foram realizados somente para o material solubilizado a 1130°C, 1160°C e solubilizado a 1130°C, seguido por alívio de tensões a 520°C. Os resultados mostraram que o tratamento térmico de alivio de tensões a 520°C, não promoveu precipitação de fases intermetálicas na microestrutura e tampouco prejudicou a resistência a corrosão do material, indicando a possibilidade prática de seu uso. / The present work was developed to acquire know how in manufacturing of castings and machined components for centrifugal pumps for offshore platform applications. Normally, the materials used to do them are the super duplex stainless steels that are thermodynamically metastable systems which tend to equilibrium when thermally activated. On the other hand, these materials show a great dimensional instability due to the residual stresses developed during the cooling from heat treatment process and also after machining process. This is crucial when working with very small dimensional tolerances, typical for these components. It were made stress relief heat treatments from 520°C, increasing the temperatures in 20°C steps until 1180°C to check the influence of these temperatures on microstructures, hardness and absorbed energy in Charpy test of this materials. The main focus was given on sigma phase precipitation dynamic, because it is the most common and studied intermetalic in this kind of stainless steels. It is impossible to avoid its precipitation during the cooling from solidification process, but it can be minimized by controlling the chemical composition and the cooling rate from solidification. Starting with a solution annealed structure, it was possible to determine the temperature where the sigma phase begins to precipitate and also its dissolution temperature. The influence of sigma phase content on hardness and absorbed energy in impact test was evaluated. Microstructure characterization was made using optical, scanning and transmission electron microscopy, as well as X-ray diffraction analysis for each different temperature. The electrochemical corrosion tests using synthetic sea water with 20000ppm, 40000ppm and 80000ppm of chlorine ions, at 5oC, 25°C and 60°C were made. Samples solution annealed such at 1130°C and at 1160°C and solution annealed at 1130°C followed by aging at 520°C were tested electrochemically. The results showed that the stress relief heat treatment at 520°C did not promote the intermetalic phase precipitation on material\'s microstructure and also, did not diminish the material\'s corrosion resistance.

Orientador: Amauri Hassui / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-21T02:15:20Z (GMT). No. of bitstreams: 1 Zanuto_RodolfodeSouza_M.pdf: 2395857 bytes, checksum: 8416f382a0b6fea6d86adb4d90e04b73 (MD5) Previous issue date: 2012 / Resumo: Com o rápido avanço tecnológico que o mundo vem passando desde a revolução industrial, novos materiais vão sendo desenvolvidos a todo momento, sendo o aço inoxidável aeronáutico 15-5 PH um destes exemplos contemporâneos, com grande potencial de aplicações, no entanto, ainda com poucas informações de como processá-lo. Com este cenário em mente, este trabalho tem por objetivo contribuir para a compreensão do fresamento de faceamento desse material. Para isso foram feitos ensaios de vida da ferramenta com três diferentes estratégias de entrada na peça (direta, reduzida e rolagem) para os cortes predominantemente concordante e discordante. Foram avaliadas também duas geometrias (positiva e neutra) e duas classes de ferramentas (M 40 e M 25), bem como duas velocidades de corte (170 m/min e 195 m/min) e dois avanços por dente (0,15 mm/dente e 0,25 mm/dente). Por fim, foram medidos os esforços de corte e realizada a caracterização microestrutural da ferramenta (MEV e EDS) para as três estratégias de entrada. A rugosidade também foi acompanhada ao longo de todos os ensaios. Os melhores resultados foram obtidos para a estratégia de entrada por rolagem no corte discordante, já no corte concordante não houve uma melhora quando utilizada esta estratégia. Avanços maiores também propiciaram melhores vidas, mesmo com velocidades de corte mais altas. A geometria da ferramenta neutra apresentou melhor resultado quando combinado a uma classe mais tenaz, porém se a classe da ferramenta for mais dura, uma geometria mais positiva, que propicia um corte menos severo, teve desempenho melhor / Abstract: The world has passing through a fast technological advance since the Industrial Revolution, so new materials have been developed every moment. The 15-5 PH stainless steel is an example of one of these new materials, with great potential of applications, nevertheless with fill information about the way of processing it. With this scenario in mind the present work has the goal of contribute to the comprehension of the face milling of this material. To achieve this several tool life tests were carried out with three different tool entry strategies in workpiece (direct, reduced and rolling) to the mainly up milling and mainly down milling. They were evaluated two cutting tool geometries (positive and neutral) and two grades (M 40 and M 25), as well as two cutting speeds (170 m/min and 195 m/min) and two feed per tooth (0.15 mm/tooth and 0.25 mm/tooth). Finally, we measured the cutting forces and did the tool microstructural characterization (SEM and EDS) for the three entry strategies. The surface roughness was also monitored throughout all experiments. The best results were obtained for the rolling entry strategy in the down milling, on the other hand, no cutting improvement when utilizing this strategy for up milling. Higher feed per tooth also resulted in longer tool lives, even with higher cutting speeds. The neutral cutting tool geometry presented better result when combined with a tougher grade, but if the tool grade is harder, then a positive geometry, that generate a less severe cut, presented better performance / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Although the phenomena of stress corrosion cracking is known to occur in 316L stainless steel in chloride environments, there is little knowledge regarding the incubation stage, i.e. when the cracks are very short and about a few grains in length scale. The project aimed to determine whether Grain Boundary Engineering GBE, through thermo-mechanical processing, could improve resistance to transgranular chloride stress corrosion crack nucleation in austenitic stainless steels. The material studied is type 316L austenitic stainless steel, with cracking developing in conditions of controlled humidity at 80°C under saturated MgCl2 salt deposits. Three batches were used; as received (AR), Heat treated at 950ºC designated as TM950ºC, treated at 1075ºC; designated as TM1075ºC and also treated at 1150ºC; designated as TM1150ºC for modifying the structure. The thermo mechanical treatment resulted in increase of ∑(3-29) and ∑3 in both fractions by almost 20% as the annealing temperature increased between 950ºC to TM1150ºC, on the other hand (AR) has sustained on 10% improvement over the TM950ºC in both fractions CSL% = ∑(3-29) and ∑3.In-situ observations show that the short cracks may grow to larger scale length in the (AR), TM950ºCand TM1150ºC than can grow in TM1075ºC.DIC analysis was not suitable for testing in this environment might be due to many factors, such as salt content residual effects, evaporation of the salt liquid, surface detritions and lateral movements due to tensile testing. The interaction between short stress corrosion cracks and microstructure was characterised by Electron backscatter diffraction (EBSD). The high angle grain boundaries (HAGB) are shown to act as barriers to cracking resulting in hindering or deviating the crack tip, which slows the overall crack growth rate. The type of microstructure that would have superior TGSCC resistance would be that, possess much higher fraction of both fractions CSL%= ∑(3-29) and ∑3.

Master of Science / Food Science Institute / Jayendra K. Amamcharla / Fouling and biofilm formation on stainless-steel (SS) surfaces can be sources for cross-contamination and pose a great threat to the public health and food quality. The dairy industry needs an intervention strategy focusing on technologies discouraging the biofilm attachment and developing a sustainable eco-friendly approach for biofilm removal from the dairy processing surfaces. Since fouling encourages the attachment of bacteria to the SS surfaces, it becomes important to study the ways of reducing the fouling. The bacterial attachment to the fouled SS surfaces can be prevented by modifying the SS surface properties by chemical (using coatings) or mechanical methods. On the other hand, the degree of fouling can also be reduced by using good quality raw materials. The objective-1 of the study was focused on understanding the relationship between effect of milk protein concentrate (MPC80) solubility characteristics and fouling on SS surfaces during thermal processing. The powders were stored at different temperatures (25 ºC and 40 ºC) for 2 weeks to generate powders with different dissolution characteristics. Fouling characteristics of reconstituted MPC80 powder were studied using a custom-built benchtop plate heat exchanger. Exposing the MPC80 powder to a higher temperature during storage (40 ºC) significantly decreased the solubility and increased the amount of foulant on SS coupons (P < 0.05). Microscopic investigations (scanning electron microscopy and laser scanning confocal microscopy) of resulting fouled layers revealed heterogeneous fouling layers of varying tomographies, consisting of lipids, proteins, and calcium. In the second study, the efficacy of Micro- and Nano-bubble aqueous ozone (MNAO) as a disinfectant was studied in removal of Bacillus cereus and Bacillus licheniformis biofilm from the SS surface. For the Bacillus cereus biofilm removal, a log reduction of only 0.68 cfu/cm2 was observed after the de-ionized water wash. Whereas both MNAO and cleaning-in-place (CIP) treatments significantly reduced the bacterial counts by 2.43 and 2.88 log10 cfu/cm2, respectively. On the other hand, for the Bacillus licheniformis biofilm removal from SS surfaces, a significant log reduction observed was 1.45, 3.03, 2.92 log10 cfu/cm2, respectively after de-ionzed water, MNAO, and CIP treatments. Thus, it was observed that MNAO has great potential for removal of Bacillus cereus and Bacillus licheniformis biofilms from the SS surface, and can be used in the dairy industry as an effective sanitizer/disinfectant

University of Macau / Faculty of Science and Technology / Department of Electromechanical Engineering

M.Ing. / In the design and analysis of components and structures, detailed information on the material behaviour and its properties is required. When a material is loaded dynamically, such as in metal punching, the material properties may not be the same as when loaded statically. This is known as the strain rate sensitivity of a material, which implies that properties such as the yield strength, tensile strength and ductility may vary with the rate at which the material is loaded. South Africa is one of the large stainless steel producing countries. Seventy percent of the known chromium ore reserves are found in the Bushveld Igneous Complex in the Northern Province and Mpumalanga. To compete on the global stainless steel market it is essential that the South African producers have all the relevant product information directly available. Considerable research has been performed on mild steel at different strain rates and temperatures[1]. Work has also been done on some austenitic stainless steels. Very little, or no work has been done in this regard on ferritic and martensitic stainless steels and on the proprietary alloy 3CR12[2]. The aim of this thesis is to investigate the strain rate sensitivity of Types 304, 430 and 316 stainless steel, 3CR12 corrosion resistant steel and mild steel at different temperatures. To achieve this, tensile tests are performed. at strain rates between 10's -1 to approximately 100s -1 and at temperatures ranging from -40°C to 140°C. Shear tests are also performed at various strain rates, to investigate the effect that material behaviour has on a typical metal working process. The results obtained show that all the materials tested are strain rate sensitive. The strain rate sensitivity varies as a function of the material tested and the testing temperature. Constitutive models which take into account the strain rate sensitivity at room temperature for all the materials are also presented. These models describe the behaviour of the material fairly accurately. Three dimensional plots are also presented which depict how the yield strength, tensile strength and elongation vary as a function of both strain rate and temperature. These plots clearly show material trends for the strain rates and temperatures tested.

In this work, the load-bearing structure of a wood kiln is analyzed with the finite element method (FEM). The analysis is done with the program Inventor Nastran and consist of a linear stress and buckling analysis. The dimensions of the kiln can vary, therefore reference values are used where it is 32 m long, 12 m high and 10.5 m wide. The kiln consists of different zones that are identical to each other, these zones are separated with load-bearing structures. This structure is made up of stainless steel sheet metal with a thickness of 2-3 mm. To stabilize the kiln against wind forces, a support structure is attached on the side of the load-bearing structure.  The requirements for the strength calculations have increased in the industry. The goal is to provide a FEM model that can perform and get a realistic result. This would also lead to get a better picture of whether there are any critical areas or parts and how important the support structure is for the stability of the kiln.  A large model requires simplifications to reduce the size of the model and enable it to carry out the analysis. This means the elimination of non-structure components, symmetry by a plane, define contact surfaces, and mesh convergence. The loads acting on the kiln consisting of wind and snow are according to the Eurocode.  It is proved possible to develop a model that could perform a realistic analysis using these simplifications. A large model consisting of many parts can create uncertainty in the analysis. Therefore, some parts need to be examined more carefully and some improvements in the FEM model is required.  The weakest components in the model could be located where some reinforcement may be needed to secure the structural strength. The importance of the support structure function to strengthen the load-bearing structure of the kiln could be proven.

Martensitic transformation is very important in austenitic stainless steels where the transformation induced plasticity phenomenon provides a combination of good mechanical properties, such as formability and strength. However, the difficulty of predicting the material behaviour is one of the major drawbacks of these steels. In order to model this behaviour it is of great importance to be able to characterize the morphology, crystallography and the amount of different types of martensite. The morphology and crystallography of thermal and deformation induced lath martensite in stainless steels were re-examined by means of optical microscopy and electron backscatter diffraction (EBSD) technique. The experiments were performed on AISI301, 304 and 204Cu austenitic stainless steels. Plastic deformation was carried out by means of uniaxial tensile tests at the strain rate of  to produce strain induced α’-martensite at a temperature ranging from 0 to 60ºC. An in-situ measurement of the martensite content was performed during the tensile testing using a Ferritescope to provide the necessary experimental values for modelling. Optical microscopy revealed the morphology of the strain induced α’-martensite as sets of thin parallel needles that go through the parent austenite grain and stop at the grain or annealing twin boundaries. Large amount of α’-martensite could be seen at the intersection of shear bands. However, considerable amount of α’-martensite was also observed when only one set of bands is activated. EBSD was successfully used to analyze the morphology and crystallography of martensite. The α’-martensite maintained the Kurdjumov-Sachs (K-S) orientation relationship with the austenite phase. Although all six possible variants did not appear within a single packet, one or two variants were often favoured out of six related to the specific {111} plane. The misorientations between the neighbouring variants were mainly &lt;111&gt; 60º or &lt;110&gt; 49.5º.