O processo de conformação por jateamento com granalhas (peen forming) trata da conformação de chapas ou painéis através da ação de um jato de esferas de aço que, atingindo uma de suas superfícies, torna-a convexa na face de recepção do jato e gera tensões residuais superficiais de compressão. Tornar o processo de jateamento com granalhas reprodutível e controlável é um grande objetivo a ser alcançado para que o mesmo possa ser aplicado de forma segura na indústria aeronáutica. Buscando-se estudar a viabilidade e o desenvolvimento de conhecimento da técnica de jateamento de esferas, definiu-se uma metodologia para o projeto de experimentos focalizados nos dois tópicos principais: variáveis de processo e características do material jateado. As variáveis de processo observadas foram diâmetro de granalha, velocidade de impacto, porcentagem de cobertura e pré-tensão. No material jateado, variaram-se a liga de alumínio (7050-T7451 e 7475-T7351) e espessura. As chapas de alumínio foram caracterizadas em: raio de curvatura, microestrutura, dureza, profundidade e morfologia da camada deformada e perfis de tensões residuais. Avaliou-se o efeito do processo nas características do material. Analisando-se os dados, foi possível obter equações semi-empíricas de relação entre processo e raio de curvatura através de um novo parâmetro chamado densidade de energia cinética, que engloba os parâmetros diâmetro de granalha, velocidade de impacto e espessura da chapa. Encontrou-se ainda forte relação entre energia cinética e espessura da camada deformada e profundidade da máxima tensão residual. Os dados experimentais foram utilizados para o treinamento de uma rede neural artificial, que gerou boa previsibilidade do raio de curvatura. / The peen forming process is the forming of metal sheet or panels through the action of a jet of hard spheres, hitting one of the surfaces, making it convex and causing residual compressive stresses on surface. Making the peen forming process reproducible and controllable is a major goal to its safe application in the aircraft industry. Aiming the study of the feasibility of peen forming and the development of its technical knowledge, a methodology for the design of experiments was created focusing on two main topics: process variables and the properties of the formed material. The process variables observed were shot diameter, impact velocity, percentage of coverage and pre-tension. With respect to the formed material, two aluminum alloys (7050-T7451 and 7475-T7351) and four different thicknesses were used. The aluminum plates were characterized by: radius of curvature, microstructure, hardness, depth and morphology of the deformed layer and profiles of residual stresses. The effect of the process on material was evaluated. Analyzing the data, semi-empirical equations were obtained for the relationship between process and radius of curvature through a new parameter called the density of kinetic energy, which includes the parameters shot diameter, impact velocity and plate thickness. It was also found a strong relationship between kinetic energy and thickness of the deformed layer and depth of maximum residual stress. Experimental data were used to train an artificial neural network, which generated a good predictability of the radius of curvature.

Ribbed steel pipes made of Type 2 aluminized steel are commonly used for culvert pipes for highway drainage. Typically aluminized steel pipes have shown good durability and are expected to have long service life, e.g. 75 years; also, they are used in a wide variety of soil and water conditions. However, early corrosion of aluminized steel pipes has been recently observed in some inland locations. Initial observations showed severe corrosion in forms of pits, both along the ribs and at the nearby flat portions of the pipes. It is critical to determine the cause of early deterioration and establish methods of durability prediction. The possibility of unusual environmental conditions is being investigated elsewhere, but this research focuses on possible mechanical factors aggravating corrosion, since it is prevalent near pipe rib deformations. While forming the rib bends in the pipe, the outer bend surface is exposed to extreme tensile stresses which would cause small coating cracks (microfissures) exposing base metal. Those may lead to early corrosion as galvanic protection from the surrounding aluminum may not be sufficient under certain environments. Electrochemical impedance spectroscopy was used to measure corrosion rate of both formed and flat aluminized steel samples in simulated natural waters. Initial findings show that specimens formed by spherical indentation were susceptible to early corrosion development in moderately aggressive simulated natural water, but not in a more benign, precipitating simulated natural water solution.

Abstract not available

The WiggleZ Dark Energy survey is currently being carried out using the AAOmega instrument on the AAT. It is measuring redshifts for 240,000 emission line galaxies with high star-formation rates over 1,000 sq. degrees of sky. These galaxies are selected for spectroscopic observation from a combination of optical and ultraviolet imaging. The target selection criterion applied to these datasets is highly optimised to select high redshift emission line galaxies. The redshift distribution of these galaxies peaks at z

<p>The general trend in the car body manufacturing industry is towards low-series production and reduction of press lubricants and car weight. The limited use of press lubricants, in combination with the introduction of high and ultra-high strength sheet materials, continuously increases the demands of the forming tools. To provide the means of forming new generations of sheet material, development of new tool materials with improved galling resistance is required, which may include tailored microstructures, introducing of specific(MC, M(C,N))carbides and nitrides, coatings and improved surface finish. In the present work, the wear mechanisms in real forming operations have been studied and emulated on a laboratory scale by developing a test equipment. The wear mechanisms identified in the real forming process, were distinguished into a sequence of events consisting of initial local adhesive wear of the sheets resulting in transfer of sheet material to the tool surfaces. Successive forming operations led to growth of the transfer layer and initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated with gross macroscopic damage. The wear process was repeated in the laboratory test-equipment in sliding between several tool materials, ranging from cast iron to conventional ingot cast tool steels to advanced powder metallurgy tool steel, against dual-phase carbon steel sheets. By use of the test-equipment, selected tool materials were ranked regarding wear resistance in sliding against ferritic-martensitic steel sheets at different contact pressures.</p><p>Wear in sheet metal forming is mainly determined by adhesion; initially between the tool and sheet surface interaction and subsequently, after initiation of material transfer, between a sheet to sheet contact. Atomic force microscopy force curves showed that adhesion is sensitive to both chemical composition and temperature. By alloying of iron with 18wt.% Cr and 8wt.% Ni, alloying in itself, or changes in crystal structure, led to an increase of 3 times in adhesion at room temperature. Hence, alloying may be assumed a promising way for control of adhesive properties. Additionally, frictional heating should be controlled to avoid high adhesion as, generally, adhesion was found to increase with increasing temperature for all investigated materials.</p>

In the application of cycle-to-cycle control to manufacturing processes, the model of the process reduces to a gain matrix and a pure delay. For a general multiple input – multiple output process, this matrix shows the degree of influence each input has on each output. For a system of high order, determining this gain matrix requires excessive numbers of experiments to be performed, and thus a simplified, but non-ideal form for the gain matrix must be developed. In this paper, the model takes the form of a Gaussian distribution with experimentally determined standard deviation and scaling coefficients. Discrete die sheet metal forming, a multiple input-multiple output process with high dimensionality, is chosen as a test application. Results of the prediction capabilities of the Gaussian model, as well as those of two previously existing models, are presented. It is shown that the Gaussian distribution model does the best job of predicting the output for a given input. The model’s invariance over a set of different formed parts is also presented. However, as shown in the companion paper on cycle-to-cycle control, the errors inherent in this model will cause non-ideal performance of the resulting control system. However, this model appears to be the best form for this problem, given the limit of minimal experimentation. / Singapore-MIT Alliance (SMA)

The present study aims to determine the optimum blank shape design for the deep drawing of arbitrary shaped cups with a uniform trimming allowance at the flange i.e. cups without ears. This earing defect is caused by planar anisotropy in the sheet and the friction between the blank and punch/die. In this research, a new method for optimum blank shape design using finite element analysis has been proposed. Explicit non-linear finite element (FE) code LSDYNA is used to simulate the deep drawing process. FE models are constructed incorporating the exact physical conditions of the process such as tooling design like die profile radius, punch corner radius, etc., material used, coefficient of friction, punch speed and blank holder force. The material used for the analysis is mild steel. A quantitative error metric called shape error is defined to measure the amount of earing and to compare the deformed shape and target shape set for each stage of the analysis. This error metric is then used to decide whether the blank needs to be modified or not. The cycle is repeated until the converged results are achieved. This iterative design process leads to optimal blank shape. In order to verify the proposed method, examples of square cup and cylindrical cup have been investigated. In every case converged results are achieved after a few iterations. So through the investigation the proposed systematic method of optimal blank design is found to be very effective in the deep drawing process and can be further applied to other stamping applications.

The general trend in the car body manufacturing industry is towards low-series production and reduction of press lubricants and car weight. The limited use of press lubricants, in combination with the introduction of high and ultra-high strength sheet materials, continuously increases the demands of the forming tools. To provide the means of forming new generations of sheet material, development of new tool materials with improved galling resistance is required, which may include tailored microstructures, introducing of specific(MC, M(C,N))carbides and nitrides, coatings and improved surface finish. In the present work, the wear mechanisms in real forming operations have been studied and emulated on a laboratory scale by developing a test equipment. The wear mechanisms identified in the real forming process, were distinguished into a sequence of events consisting of initial local adhesive wear of the sheets resulting in transfer of sheet material to the tool surfaces. Successive forming operations led to growth of the transfer layer and initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated with gross macroscopic damage. The wear process was repeated in the laboratory test-equipment in sliding between several tool materials, ranging from cast iron to conventional ingot cast tool steels to advanced powder metallurgy tool steel, against dual-phase carbon steel sheets. By use of the test-equipment, selected tool materials were ranked regarding wear resistance in sliding against ferritic-martensitic steel sheets at different contact pressures. Wear in sheet metal forming is mainly determined by adhesion; initially between the tool and sheet surface interaction and subsequently, after initiation of material transfer, between a sheet to sheet contact. Atomic force microscopy force curves showed that adhesion is sensitive to both chemical composition and temperature. By alloying of iron with 18wt.% Cr and 8wt.% Ni, alloying in itself, or changes in crystal structure, led to an increase of 3 times in adhesion at room temperature. Hence, alloying may be assumed a promising way for control of adhesive properties. Additionally, frictional heating should be controlled to avoid high adhesion as, generally, adhesion was found to increase with increasing temperature for all investigated materials.

Paper making involves three fabrics: forming, pressing, and drying. The forming fabric is responsible for sheet forming, the initial dewatering of a low concentration pulp suspension into a wet sheet of paper. In the process of forming, topographical and hydrodynamic marks can be transferred from the drainage media (the forming fabric) to the sheet produced. An experimental investigation of a model forming fabric was performed to identify the geometric parameters having the largest influence on hydrodynamic wire mark. The data were also compared with the numerical simulations of Huang. To simplify the problem, justifiable engineering simplifications were made. The second phase (the fibres) was removed and the machine-direction filaments were neglected. This reduced the problem to investigation of flow through a bank of dissimilar cylinders. It was desired to find the most important geometrical parameter to reduce flow non-uniformity in the paper side flow field. Particle image velocimetry, pressure drop and flow visualization tests were conducted to investigate the flow through the array of cylinders. It was found that with a cylinder surface separation of 0.75$\times$ the paper side cylinder diameter the pressure drop tended toward the sum of the rows, and the paper side flow field was nearly identical to the paper side row only flow field, regardless of the backing side cylinder dimensions and configuration. It was seen that when the pressure drop through the bank of cylinders was equal to the sum of the rows' pressure drops the paper side flow field was the same as the paper side row only flow field. As such, pressure drop can act as an indication of when the machine side row will not affect the paper side flow field.

Paper making involves three fabrics: forming, pressing, and drying. The forming fabric is responsible for sheet forming, the initial dewatering of a low concentration pulp suspension into a wet sheet of paper. In the process of forming, topographical and hydrodynamic marks can be transferred from the drainage media (the forming fabric) to the sheet produced. An experimental investigation of a model forming fabric was performed to identify the geometric parameters having the largest influence on hydrodynamic wire mark. The data were also compared with the numerical simulations of Huang. To simplify the problem, justifiable engineering simplifications were made. The second phase (the fibres) was removed and the machine-direction filaments were neglected. This reduced the problem to investigation of flow through a bank of dissimilar cylinders. It was desired to find the most important geometrical parameter to reduce flow non-uniformity in the paper side flow field. Particle image velocimetry, pressure drop and flow visualization tests were conducted to investigate the flow through the array of cylinders. It was found that with a cylinder surface separation of 0.75$\times$ the paper side cylinder diameter the pressure drop tended toward the sum of the rows, and the paper side flow field was nearly identical to the paper side row only flow field, regardless of the backing side cylinder dimensions and configuration. It was seen that when the pressure drop through the bank of cylinders was equal to the sum of the rows' pressure drops the paper side flow field was the same as the paper side row only flow field. As such, pressure drop can act as an indication of when the machine side row will not affect the paper side flow field.