喷射成形工艺参数及热挤压制度对8009耐热铝合金的组织及性能的影响

采用喷射成形方法制备了Al-8.5Fe-1.4V-1.7Si(8009)耐热铝合金，研究了喷射成形工艺参数及沉积坯件的热挤压工艺对材料的微观组织及性能的影响。结果表明：喷射成形工艺能够有效地抑制8009合金中粗大的富铁相的析出，获得均匀细小的组织；当射成形工艺参数选择适当时，沉积坯件具有良好的成形性与致密度，在随后的热挤压过程中，通过较低的挤压比即可使材料达到全致密。合金经过热挤压后，在室温及高温下均具有良好的力学性能。

Veränderungen der Farbe und thermischen Stabilität der Muskelproteine von Räucherforellen während der Kühllagerung

The aim of the investigation was to prove if different farming conditions like conventional and organical farming of rainbow trout may cause differences in quality which are detectable by physical methods such as colour measurement and differential scanning calorimetry. Colour measurement revealed remarkable differences in lightness. Smoked trouts originating from conventionally farmed fish were much lighter than those of organically farmed trouts. This difference in L* could already be found when colour measurements were taken on the raw material. However, during chilled storage differences were equalized. Redness and yellowness were not significantly influenced by farming and did not change remarkably during chill storage. Based on earlier investigations on changes in thermal stability caused by heating, DSC curves of smoked trout could be used to verify that the core temperature of smoked fish had reached at least 60 °C during hot smoking process. This temperature is demanded by the guidelines of the German Food Code. In the DSC curves only the actin peak was still visible. All other proteins were obviously denatured during the hot smoking. When DSC curves were taken from smoked trout after different durations of chilled storage it could be seen that the denaturation temperature of actin decreased almost linearly with progression of storage time.

Applications of plasticity theory to selected problems in soil mechanics

Two topics in plane strain perfect plasticity are studied using the method of characteristics. The first is the steady-state indentation of an infinite medium by either a rigid wedge having a triangular cross section or a smooth plate inclined to the direction of motion. Solutions are exact and results include deformation patterns and forces of resistance; the latter are also applicable for the case of incipient failure. Experiments on sharp wedges in clay, where forces and deformations are recorded, showed a good agreement with the mechanism of cutting assumed by the theory; on the other hand the indentation process for blunt wedges transforms into that of compression with a rigid part of clay moving with the wedge. Finite element solutions, for a bilinear material model, were obtained to establish a correspondence between the response of the plane strain wedge and its axi-symmetric counterpart, the cone. Results of the study afford a better understanding of the process of indentation of soils by penetrometers and piles as well as the mechanism of failure of deep foundations (piles and anchor plates).

The second topic concerns the plane strain steady-state free rolling of a rigid roller on clays. The problem is solved approximately for small loads by getting the exact solution of two problems that encompass the one of interest; the first is a steady-state with a geometry that approximates the one of the roller and the second is an instantaneous solution of the rolling process but is not a steady-state. Deformations and rolling resistance are derived. When compared with existing empirical formulae the latter was found to agree closely.

Simulación de la refrigeración en la estampación en caliente para una pieza de chapa.

[ES]El objetivo principal de este proyecto se centra en conseguir las características mecánicas requeridas por los componentes del chasis de los vehículos con una reducción de peso y mejora de productividad, para ellos es necesario simular el proceso de templado que se da durante la estampación en caliente de una pieza de chapa mediante utillajes con conductos de refrigeración. Para ello se ha utilizado el programa de elementos finitos ANSYS hasta obtener un proceso de embutición simulado que represente con una desviación dentro de los límites aceptables el comportamiento real de la chapa en la etapa de refrigeración. Como objetivo secundario se encuentra el afianzamiento de las bases teóricas de ciencia de materiales y la adquisición de más conocimientos relacionados con la transmisión de calor entre cuerpos sólidos, centrándose sobre todo en la distribución de temperaturas sobre la superficie de éstos. En una primera parte se tratarán los conceptos generales de la estampación en caliente y sus posibles variantes. También se explicará la necesidad del uso de nuevos materiales para la industria automovilística, así como la razón por la cual se utilizan conductos de refrigeración. A continuación, se definirá la geometría de la chapa a analizar, tanto las consecuentes geometrías de los utillajes, que tendrán diferentes distribuciones de conductos de refrigeración. Además se establecerán los criterios para realizar el análisis térmico transitorio del conjunto troquel – chapa – matriz. Una vez seleccionado el tipo de análisis se profundizará en su estudio, aplicándolo a los diferentes utillajes ya citados. Se analizarán los resultados obtenidos y los errores y se buscarán posibles alternativas. Finalmente, se procederá a sacar las conclusiones de la simulación realizada y se procederá a comparar los resultados obtenidos con las diferentes distribuciones de conductos de refrigeración en los utillajes.

Automatización de un proceso de laminación en caliente.

[ES]En la situación actual, en que las empresas han tenido que automatizar los procesos a nivel mundial para hacer frente a los nuevos retos de la competitividad, pone de manifiesto la necesidad de nuevas tecnologías para innovar y redefinir sus procesos. Este proyecto se centra en la aplicación de las nuevas tecnologías en un proceso de laminación en caliente para así a aumentar la capacidad de producción y la calidad de la empresa. Para ello, en primer lugar, se analiza la planta y el proceso a automatizar, se señalan los problemas y se procede a estudiar la solución más adecuada. Después de seleccionar la solución, se colocan sensores y actuadores a lo largo del proceso en función de los pasos a seguir por la fabricación. Con todo ello se ha diseñado una secuencia de control para que el proceso sea autónomo. Además, se diseña un algoritmo para controlar el arranque de los motores, reduciendo así el consumo de energía. En conclusión, se desea mejorar un viejo proceso de producción a través de la automatización y las nuevas tecnologías. Breve descripción del trabajo (cinco líneas). Esta descripción debe destacar los puntos más relevantes del trabajo: su objetivo principal, los métodos a emplear para su desarrollo y los resultados que se pretenden conseguir, o que se han conseguido.

Structural and optical properties of 6H-SiC helium-implanted at 600 K

Single crystals of 6H-SiC were implanted at 600 K with 100 key He ions to three successively fluences and subsequently annealed at different temperatures ranging from 873 to 1473 K in vacuum. The recovery of lattice damage was investigated by different techniques including Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy and Fourier transform infrared spectroscopy. All three techniques showed that the damage induced by helium ion implantation in the lattice is closely related to the fluence. Rutherford backscattering spectrometry/channeling data on high temperature implantations suggest that for a fluence of 3 x 10(16) He+/cm(2), extended defects are created by thermal annealing to 1473 K. Apart from a well-known intensity decrease of scattering peaks in Raman spectroscopy it was found that the absorbance peak in Fourier transform infrared spectroscopy due to the stretching vibration of Si-C bond shifted to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with increasing annealing temperature. These phenomena are attributed to different lattice damage behavior induced by the hot implantation process, in which simultaneous recovery was prevailing. (C) 2010 Elsevier B.V. All rights reserved.

Undersökning av steady state och utvärdering av valskraft och friktion vid kallvalsning av aluminium

The purpose with this thesis was to examine the cold rolling mill located at Högskolan Dalarna and to stabilize the rolling process, to achieve steady state. Experiments with cold rolling of an aluminium strip have given results for rolling force, friction, reduction, strip tension and strain hardening. Results show that steady state has been found for the experiments with roll force and strain hardening, and not been found for the experiments with friction and reduction. Results show that increased strip tension gives lower roll forces. The roll force equation of Stone shows comparable results with reality for dry contact with reductions up to 30 %, but starts being incomparable with higher reductions. The roll force equation of Stone shows a bit higher roll forces than reality gave, but was comparable within reductions from 13 to 50 %. Experiments have shown that the aluminium strip has gone through strain hardening. Experiments show how the set roll gap did not yield the desired thickness reduction, there for the elastic spring constant for the rolling mill was examined and determined to be 417 N / mm for the specific alloy band. The influence of tension strip for roll force was examined and Results confirm the theory about how the roll force is decreased by increasing tension strip. The work rolls started to slip against the alumina strip as high tension strip; 70 N/mm2, gave low roll force; < 15kN.

Finite element analysis of warpage in laminated aluminium alloy plates for machining of primary aeronautic parts

The aim of this paper consists in presenting a method of simulating the warpage in 7xxx series aluminium alloy plates. To perform this simulation finite element software MSC.Patran and MSC.Marc were used. Another result of this analysis will be the influence on material residual stresses induced on the raw material during the rolling process upon the warpage of primary aeronautic parts, fabricated through machining (milling) at Embraer. The method used to determinate the aluminium plate residual stress was Layer Removal Test. The numerical algorithm Modified Flavenot Method was used to convert layer removal and beam deflection in stress level. With such information about the level and profile of residual stresses become possible, during the step that anticipate the manufacturing to incorporate these values in the finite-element approach for modelling warpage parts. Based on that warpage parameter surely the products are manufactured with low relative vulnerability propitiating competitiveness and price. © 2007 American Institute of Physics.

Qualidade microbiológica e vida útil de filés defumados de tilápia-do-nilo sob refrigeração ou congelamento

The objective of this work was to evaluate the microbiological quality and shelf life of Nile tilapia fillets subjected to different smoking methods and storing conditions. Two smoking processes (cold or hot) were used in fillets with or without pigmentation. Products were stored under refrigeration or freezing, and monitored continually for 28 days for evaluation of their shelf life. Frozen fillets were monitored for 146 days for analysis of thiobarbituric acid (TBA) only. Hot- and cold-smoking reduced the coliform quantity, respectively, by 99.78% and 97.80%. Product storage under refrigeration allowed a 99.73% coliform reduction, and storage under freezing reduced them by 99.83%. Fecal coliform values were within the allowed limits. TBA values in fillets reached their maximum on the 14th storage day. TBA values were higher in treatments under refrigeration storage than in those under freezing, as well as in cold-smoked fillets in comparison to the hot-smoked ones. Hot-smoked process, followed by refrigeration storage, is the most adequate technique to ensure quality and a larger shelf life for Nile tilapia fillets, regardless of pigmentation process.

Lean six sigma como estratégia para o aumento de eficiência em laminação de alumínio

This study aims to assess the implementation of Lean Six Sigma in the preparation of plates and hot lamination process for a company of aluminum rolled products, to improve the quality, productivity and process efficiency. As a basis for achieving these goals, the DMAIC methodology and various quality tools such as Cause Effect Diagram, Process Flow, SIPOC, Pareto, FMEA and Control Chart were used, trying to propose improvements to processes and increase their efficiency. The results were significant and were the basis for the continuation of a continuous improvement project throughout the factory

Processo de fabricação de tarugos pelo método HotTop de ligas de alumínio da série 6XXX e as não conformidades desse processamento

The goal of this work is to report some problems that occur in the in the production of aluminum billets (series 6XXX) produced by the hot top process in the Alcoa aluminum Inc. The aluminum fabrication process is described from its first stage, since the mining until the reduction, smelting and treatment of the metal. One of the plant’s final product, are billets for clients that produce profiles by extrusion. The product’s final quality highly depends on the whole production process. Therefore it’s necessary to use good practices in the treatment of the metal, follow up its fabrication and control its thermal treatment, in order to meet the required standards to satisfy the clients. The billet’s production method and its variables will be detailed through temperature and casting speed, cone of water flow, cooling rate, duration of thermal treatment, degassing and metal “in line “filtering, in other words when it’s still found in its liquid state. The non-conformities of the process were studied by metallographic analysis, both macrostutural and microstructural that will be described and discussed in this work

Projeto de trocador de calor para uma máquina de aquecimento de vidro para laminação

The object of this study is a glass heating machine for rolling process, designed in 2006 and which is manufactured regularly. By customer request it is intended to increase the production capacity of this machine. However, initial tests have shown that the existing heat exchanger cannot supply the necessary thermal energy demand. A study of the thermal characteristics of the equipment was performed in order to obtain the required information to study alternatives for expanding its capacity taking into account space limitations and the need to rationalize costs, avoiding unnecessary oversizing

Análise do perfil de dureza e microestrutura de um aço forjado AISI A2 submetido a tratamento térmico com resfriamento em água

Due to the large use of steel in several processes around the world, there is the increasingly concern to find new materials and/or optimization and improvement of the processes, as the need to reduce the cost and a productivity increase in the primary industry, such as the siderurgy. The rolling is the most used mechanical process in the world and therefore is required the development of new tools in high volume and with optimum characteristics to support the market demand. Forged rolls used are for rolling. These rolls have heat treatment that has the purpose to achieve the appropriated mechanical properties to support the variables of the rolling process. The objective of this work is to analyze the hardness profile and the microstructure a tool steel similar to AISI A2, forged in an opened die process and submitted to heat treatment with water-cooling. The results allowed plotting a hardness profile and performing a microstructure analysis, and whereby to confirm that the heat treatment is not a quenching, but it is a material beneficiation by the hardening of superficial layer, since there is no martensitic microstructure. Therefore, this paper provides the support to future studies about the possibility to perform enhancements in this thermal heat made in the rolls produced at Gerdau Plant in Pindamonhangaba

Projeto de trocador de calor para uma máquina de aquecimento de vidro para laminação

The object of this study is a glass heating machine for rolling process, designed in 2006 and which is manufactured regularly. By customer request it is intended to increase the production capacity of this machine. However, initial tests have shown that the existing heat exchanger cannot supply the necessary thermal energy demand. A study of the thermal characteristics of the equipment was performed in order to obtain the required information to study alternatives for expanding its capacity taking into account space limitations and the need to rationalize costs, avoiding unnecessary oversizing