Doctor of Philosophy / Department of Grain Science and Industry / Hulya Dogan / The concept of thermal processing of foodstuffs has been used extensively since 1920 when the first scientific basis for calculating the minimum safe sterilization process was developed. There are several methods used in thermal processing of dry foods including infrared, microwave, hydrothermal treatments such as annealing and heat-moisture treatment, thermomechanical treatments (extrusion), and indirect (hot air) and indirect (steam) heating. Thermal processing has been the most widely used method for preserving and extending the shelf-life (via microbial reduction and enzyme inactivation, and for improving quality and functionality. In 2009 the Centers for Disease Control and Prevention released a report of an Escherichia coli outbreak resulting from consumers eating raw refrigerated cookie dough which brought attention to heat treatment of flours and powders. Chlorination of wheat flour in the European Union countries has been replaced in recent years by heat-treated flour which is used to produce high ratio cakes. By applying heat treatment, it is possible to modify the physical and rheological properties. The primary effect of heat treatment is denaturation of the proteins, partial reduction or inactivation of alpha-amylase, and partial gelatinization of the starch. Understanding of relationship between heat transfer, thermal properties of food, heating medium, thermodynamics and the functionality of the resulting heat-treated flour is of critical importance. Research reported in this dissertation has five chapters. Chapter 1 provides a general overview on the state-of-knowledge in the area. Chapter 2 focuses on developing a thermomechanical treatment (extrusion) for improving the functionality of low quality (ash > 1.3%) wheat flour. Chapter 3 deals with developing a direct, rapid and continuous thermal processing technique for treating whole wheat flour and whole wheat grain, and investigates physicochemical changes of heat-treated samples at various moisture-time-temperature combinations. Chapter 4 explores the mixing and development of composite flours in the presence of gluten fractions of at varying proportions, mixing speed and temperatures. Chapter 5 highlights general conclusions and identifies areas for future research.

Call number: LD2668 .T4 1956 C65 / Master of Science

Master of Science / Department of Grain Science and Industry / Subramanyam Bhadriraju / Heat treatment of food-processing facilities involves using elevated temperatures (46 to 60°C for 24 h) for management of stored-product insects. Heat treatment is a viable alternative to the fumigant methyl bromide, which is phased out in the United States as of 2005 because of its adverse effects on the stratospheric ozone. However, very little is known about responses of the cigarette beetle, Lasioderma serricorne (F.), a pest associated with food-processing facilities, to elevated temperatures. The main objective of my research was to evaluate stage-specific susceptibility of L. serricorne to elevated temperatures to identify the most heat tolerant stage. In the laboratory, I found L. serricorne was able to develop on ground, pelleted feed at 28°C and 65% RH; however, there is no data on the biology of this species on this diet. Therefore, several life history parameters of L. serricorne were studied on ground, pelleted feed at 28°C and 65% RH, to facilitate harvesting stages of specific ages in large numbers for assays with elevated temperatures. The mean duration for eggs was 8.1 d, and the mean egg survivorship was 92.0%. There were four discrete instars, and the mean durations of first, second, third, and fourth instars were 4.7, 4.5, 4.7, 11.8 d, respectively. The survivorship of first through third instars was about 99%, whereas that of fourth instars was 85%. The mean pupal duration was 4.6 d, and pupal survivorship was 98%. Newly eclosed unmated female adults lived 5 d longer than unmated males (29 d), whereas, mated males lived 6 d longer than mated females (17 d). Mated females started laying eggs on the third day after emergence and continued this activity for an additional six to eight days. Females, on average, laid 105 eggs with a mean daily output of 12 eggs. The data reported here provide new information on the biology of L. serricorne on ground, pelleted feed, which appears to be an optimal diet for mass rearing this species. Exposure of eggs, young larvae (3 to 4- July 2007 did not clearly show which of the life stages was heat- tolerant. However, exposure of all life stages to fixed times at 46, 50 and 54°C and 25% RH in the laboratory indicated eggs to be the most heat-tolerant stage. Time-mortality responses, at each of these three d old), old larvae (20 to 21-d old), and adults during heat treatment of a food-processing facility in 20-22 temperatures, showed that the time for 99% mortality (LT99) based on egg hatchability and egg-to-adult emergence was not significantly different at each temperature. The LT99 based on egg hatchability at 46°C was 605 min and it decreased to 190 min at 50°C and 39 min at 54°C. Therefore, during structural heat treatments eggs should be used in bioassays for gauging heat treatment effectiveness, because treatments aimed at controlling the egg stage should control all other life stages of L. serricorne.

No description available.

A study has been carried out to investigate the effects of heat treatment on microindentation hardness, abrasion and corrosion resistance of Electroless Nickel coatings. In particular, a proprietary coating system, NIKLAD 794 has been investigated. Samples of 4130 steel have been plated according to manufacturer's specifications. The plated samples have then been subjected to an array of heat treatment temperatures and times. Post heat treatment tests have been conducted including Taber Abrasion testing, salt fog chamber testing, and Knoop microindentation hardness testing. Results of the individual tests have been compared to determine the effects of heat treatment on, and the interactions between, the parameters examined.

Tourmaline is an aluminoborocyclosilicate mineral with a complex arrangement of atoms. With highly variable chemistry and multiple cation sites, tourmaline is one of the last complex minerals whose structure was unraveled, and its response to changes in Pressure-Temperature-Time (P-T-X) are not well understood. Due to its stability at high temperature and pressure, tourmaline has the potential to be an informative mineral in terms of petrogenetic indicators and could be used in assessing provenance, thermobarometry and geochronology. Three reactions were proposed to understand the cation exchange and disordering between the Y- and Z-sites in the tourmaline structure. These reactions include: 1. YFe2+ + ZAl + OH ; ZFe3+ + YAl + O + H ; in two samples with varying Fe2+ content. 2. YMg + ZAl ; ZMg + YAl. 3. YFe3+ + ZAl ; ZFe3+ + YAl. Using single crystal X-ray diffraction and stepwise heating, the extent and effect of the exchange between the Y- and Z-sites in response to changes in temperature was described. In response to increased temperature, equivalent amounts of Fe2+, Fe3+, Mg2+ of the Y-sites exchange with Al of the Z-sites. This leads to decreases in Y-site average bond length, increases in Z-site average bond length, shortening of a lattice parameters, lengthening of c lattice parameters and decreases in quadratic elongation. Additionally, the T-site experienced an increased in tetrahedral rotation and ditrigonality and changes to the crimping of the tetrahedral ring upon heating. The cation exchange and disordering in these samples relates to the stability of tourmaline at elevated temperatures in that tourmaline will undergo cation exchange and disordering to maintain the stability of the mineral. This has implications on the conditions in which tourmaline is formed as well as stability of tourmaline and other minerals and materials in different P-T-X conditions.

Os aços-ferramenta têm importante participação no mercado mundial de aços. São usados na indústria metal-mecânica como ferramentas de corte, moldes, punções, matrizes, etc. Devido ao uso de grande responsabilidade, é importante discutir a relação entre microestrutura e propriedades mecânicas, porque é uma prática comum na indústria especificar os tratamentos térmicos com base principalmente na dureza final do material, sem considerar que para um mesmo valor de dureza um aço-ferramenta pode apresentar diferenças nas propriedades mecânicas, dependendo do ciclo de tratamento térmico aplicado. Logo, esta seleção de tratamento térmico é um aspecto tecnológico relevante no desempenho de aços-ferramentas.Os materiais selecionados foram os aços VND, Calmax, VF-800 e Vanadis 10, sendo os três primeiros produzidos por fundição – rota convencional e o último produzido por processo de pressão isostática a quente (HIP) – rota sinterizada.O objetivo deste trabalho foi avaliar o tratamento térmico, a microestrutura e as propriedades mecânicas destes quatro açosferramenta para trabalho a frio, para determinar o tratamento térmico capaz de promover a melhor relação dureza-tenacidade. Os resultados mostraram para o aço VND a possibilidade de se trabalhar com nível de dureza um pouco superior ao recomendado pelo fabricante, com sensível melhora nos parâmetros de resistência sem, no entanto, a ocorrência de um decréscimo importante em termos de tenacidade. Para o aço Calmax os resultados mostraram a possibilidade de trabalhar com dureza um pouco inferior à recomendada pelo fabricante, com significativa melhora nos parâmetros de tenacidade, sem a ocorrência de um decréscimo na resistência. Para os aços VF-800 e Vanadis 10, os resultados obtidos utilizando-se temperatura de revenimento inferior à recomendada pelo fabricante mostraram um ótimo desempenho em todos os ensaios, com particular atenção aos resultados de energia absorvida. / Tool steels have important participation in the worldwide market of steels. They are used by metal-mechanical industry as cutting tools, molds, punches, dies etc.Due to the use of great responsibility, it is important to discuss the relationship between microstructure and mechanical properties because it is a common practice in industry to specify heat treatments based mainly in the final hardness of the material without considerations about that for the same value of hardness a tool-steel can present differences in mechanical properties, depending on the heat treatment cycle applied. Thus, the selection of the heat treatment is a relevant technological aspect in the performance of tool steels. The materials selected were VND, Calmax, VF800 and Vanadis 10, being the three first produced by hot ingot casting followed by hot working - conventional route, and the last one by hot isostatic pressing (HIP) process – sintering route. The aim of this work was to evaluate the heat treatment, microstructure and mechanical properties of these four tool steels for cold work application in order to determine the heat treatment able to promote the best relationship hardness-toughness. The results have shown for VND steel the possibility of working with hardness slightly higher than that recommended by the manufacturer, with sensible improvement of strength without, however, the occurrence of an important decrease in toughness. For the Calmax steel the results have shown the possibility of working with hardness values slightly lower than that recommended by the manufacturer, with significant improvement in toughness, without the occurrence of a strength decreasing. For the steels VF-800 and Vanadis 10, the results of lower temperature of tempering than the recommended by the manufacturer have indicated good performance in all mechanical tests, with attention to the absorbed energy results.

Additive manufacturing technologies place materials at the direct point of need of the warfighter, enabling the development of optimal, situation-specific means to produce and repair parts of Army and DoD weapons systems. In the case of solid-state AM, a full understanding of the metallic powder is critical with producing ideal consolidated material properties reliably and repeatably. By way of iteratively coupling computational models with supportive experimental testing, one can rapidly archetype differences in processing methods, alloy compositions, and heat treatments for metallic powders that serve as feedstock for these AM technologies. Through the combination of thermodynamic models, advanced characterization, and dynamic nano-indentation, representative correlations are established between microstructural features and mechanical properties, enabling the development of enhanced feedstock materials that can achieve the specific needs of the warfighter efficiently without forfeiting quality. This represents both a holistic and a materials-by-design approach to AM through the deliberate use of computation to drive down the discovery process and allow feedstock powders to be engineered with specific properties dictated by Army requirements for performance. In a case study of Al 6061, unique observations were made through the combination of modeling and experimentation. It was discovered that the precipitation kinetics were greatly accelerated in powders and therefore, typical heat treatment processes used for cast-aluminum alloys were not valid. Due to this shift in precipitation sequences, high-temperature treatment was limited to discourage precipitate and grain coarsening. Additionally, when compared to typical cast Al 6061, the main precipitation hardening phase shifts from Mg2Si to Al4Cu2Mg8Si7, changing how aging mechanisms were accounted for. These conclusions were supported by both the computational models and experimental results. Through the generation of numerous data, the models were calibrated, enabling more efficient and precise development of tailored material characteristics from specific microstructural features to serve as an input in a holistic through-process model for a solid-state AM process and guide future experimentation.

<div>Self-pierce riveting as a relative new technology has been used by automotive industry for decades. Because of the several benefits of the SPR technique, it has been widely used for joining the similar or dissimilar materials to satisfy the light-weighting requirements of automobile. There were many researchers and automotive manufacturers that had been investigated the SPR by experiments and applied this technique to their products. The SPR was designed for joining the materials with sufficient ductility because the joining process was going to introduce the large plastic deformation on the joint button area. Die casting aluminum alloy products became more and more popular to be used for structural components. However, the casting aluminum components have relative low ductility than the wrought alloy product. The cracking problems were easy to occur during the riveting process.</div><div><br></div><div>In terms of the cracking issues on die casting aluminum products, an analysis was conducted in this study to investigate the influence of composition on cracking problem. And the cracking mechanism was also analyzed and summarized. Corresponding to the influence of silicon content difference and silicon morphology, heat treatment was used to modify the eutectic silicon morphology of the casting aluminum alloys to improve the rivetability. Once the silicon network was broken by the heat treatment, the rivetability of die casting aluminum was drastically increased and the cracks on joint button were also suppressed. Under the effect of heat treatment, the joint performance was tightly related to the variation of the eutectic silicon phase and the cracks on the joint button. The joint strength was obtained by shear test to investigate the influence of heat treatment and die depth. A novel cracking statistics has been generated and used to calculate the cracks on the joint button. Eventually, a comprehensive joint performance was obtained by taking into consideration of joint strength, heat treatment and die depth.</div><div><br></div><div>Finally, the simulation of the SPR process was conducted and analyzed by FORGE. The die depth as the variable was used to investigate the strain and fracture distribution in</div><div>cross-section view of the joint. In terms of the initial results of the simulation, the die cavity with various sidewall incline angles was simulated to find the optimal die cavity geometry in order to improve the rivetability of the bottom material sheet.</div>

Os aços-ferramenta têm importante participação no mercado mundial de aços. São usados na indústria metal-mecânica como ferramentas de corte, moldes, punções, matrizes, etc. Devido ao uso de grande responsabilidade, é importante discutir a relação entre microestrutura e propriedades mecânicas, porque é uma prática comum na indústria especificar os tratamentos térmicos com base principalmente na dureza final do material, sem considerar que para um mesmo valor de dureza um aço-ferramenta pode apresentar diferenças nas propriedades mecânicas, dependendo do ciclo de tratamento térmico aplicado. Logo, esta seleção de tratamento térmico é um aspecto tecnológico relevante no desempenho de aços-ferramentas.Os materiais selecionados foram os aços VND, Calmax, VF-800 e Vanadis 10, sendo os três primeiros produzidos por fundição – rota convencional e o último produzido por processo de pressão isostática a quente (HIP) – rota sinterizada.O objetivo deste trabalho foi avaliar o tratamento térmico, a microestrutura e as propriedades mecânicas destes quatro açosferramenta para trabalho a frio, para determinar o tratamento térmico capaz de promover a melhor relação dureza-tenacidade. Os resultados mostraram para o aço VND a possibilidade de se trabalhar com nível de dureza um pouco superior ao recomendado pelo fabricante, com sensível melhora nos parâmetros de resistência sem, no entanto, a ocorrência de um decréscimo importante em termos de tenacidade. Para o aço Calmax os resultados mostraram a possibilidade de trabalhar com dureza um pouco inferior à recomendada pelo fabricante, com significativa melhora nos parâmetros de tenacidade, sem a ocorrência de um decréscimo na resistência. Para os aços VF-800 e Vanadis 10, os resultados obtidos utilizando-se temperatura de revenimento inferior à recomendada pelo fabricante mostraram um ótimo desempenho em todos os ensaios, com particular atenção aos resultados de energia absorvida. / Tool steels have important participation in the worldwide market of steels. They are used by metal-mechanical industry as cutting tools, molds, punches, dies etc.Due to the use of great responsibility, it is important to discuss the relationship between microstructure and mechanical properties because it is a common practice in industry to specify heat treatments based mainly in the final hardness of the material without considerations about that for the same value of hardness a tool-steel can present differences in mechanical properties, depending on the heat treatment cycle applied. Thus, the selection of the heat treatment is a relevant technological aspect in the performance of tool steels. The materials selected were VND, Calmax, VF800 and Vanadis 10, being the three first produced by hot ingot casting followed by hot working - conventional route, and the last one by hot isostatic pressing (HIP) process – sintering route. The aim of this work was to evaluate the heat treatment, microstructure and mechanical properties of these four tool steels for cold work application in order to determine the heat treatment able to promote the best relationship hardness-toughness. The results have shown for VND steel the possibility of working with hardness slightly higher than that recommended by the manufacturer, with sensible improvement of strength without, however, the occurrence of an important decrease in toughness. For the Calmax steel the results have shown the possibility of working with hardness values slightly lower than that recommended by the manufacturer, with significant improvement in toughness, without the occurrence of a strength decreasing. For the steels VF-800 and Vanadis 10, the results of lower temperature of tempering than the recommended by the manufacturer have indicated good performance in all mechanical tests, with attention to the absorbed energy results.