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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 lubricants, in combination with the introduction of high and ultrahigh-strength sheet materials, continuously increases the demands on the forming tools. The major cause for tool failure during the forming process is transfer and accumulation of sheet material on the tool surfaces, generally referred to as galling. The adhered material creates unstable frictional conditions and scratching of the tool/sheet interface. To provide the means of forming new generations of sheet materials, development of new tool materialswith improved galling resistance is required, which may include tailored microstructures introducing specific carbides and nitrides, coatings and improved surface finish. In the present work, the galling wear mechanisms in real forming operations have been studied and emulated at a laboratory scale by developing a test equipment. The wear mechanisms, identified in the real forming process, were distinguished into a sequence of events. At the initial stage, local adhesive wear of the sheets led to transfer of sheet material to the tool surfaces. Successive forming operations resulted in growth of the transfer layer with initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated withgross macroscopic damage. The wear process was successfully repeated in the laboratory test equipment in sliding between several tool materials, ranging from cast iron and conventional ingot cast tool steels, to advanced powder metallurgy tool steel, sliding against medium and high-strength steel sheets. By use of the test equipment, selected tool materials were ranked regarding galling resistance. The controlling mechanism for galling in sheet metal forming is adhesion. The initial sheet material transfer was found to occur, preferably, to the metallic matrix of the tool steels. Hence, the carbides in the particular steels appeared less prone to adhesion as compared to the metallic matrix. Therefore, an improved galling resistance was observed for a tool steel comprising a high amount of small homogeneously distributed carbides offering a low-strength interface to the transferred sheet material.Further, atomic force microscopy showed that nanoscale adhesion was influenced by temperature, with increasing adhesion as temperature increases. A similar dependence was observed at the macroscale where increasing surface temperature led to initiation of severe adhesive wear. The results were in good agreement to the nano scale observations and temperature-induced high adhesion was suggested as a possible mechanism.

HUDOUSEK Jiří: Drawing of a tin-coated metal sheet. The project elaborated in frame of master studies is submitting design of the given part production - business card case from tin-coated metal sheet by deep drawing technology. From a variations of the design of the product has been chosen option, when the case is assembled from two identical drawn parts which form the bottom and the lid of the component, the connection of these two parts is arranged by a spacer in form of a plastic insert on which the metal parts are attached. Based on the literary survey and calculations drawing in die with blankholder was designed for metal parts production, according to the force needed and tool size a hydraulic press ZH 100 was selected. Part of the work is the process parameters determination, technical and economic evaluation and drawing documentation.

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<p>Abstract</p><p>Today sheet metal forming is used to make a variety of mass production because it has a high production rate. One of the biggest concerns in sheet metal forming is wear of the tool in form of galling. Galling in sheet metal forming is characterised by an increased tool surface roughness, unstable friction in the forming process and undesirable scratches on the final products.</p><p>Several ways of ranking materials resistance to galling exist today but only ASM G98 is standardised. Nevertheless, some different methods developed for ranking tool materials’ tendency to galling have also been developed.</p><p>The aim of this thesis is to develop and improve the Uddeholm Tooling Tribo Test rig located at Uddeholm Tooling AB. The rig, which is a variation of cylinder-on-cylinder test equipment, was improved with a new tool holder, a utilization of the real sheet material counter face and a new data acquisition system and software. The galling was detected using scratches on the sheet, metallographic analysis of the material adhered on the tool specimen, monitoring of coefficient of friction and the standard deviation of the coefficient of friction.</p><p>The obtained results show difficulties with ranking of tool materials in terms of galling resistance under non-lubricated conditions. The tool steels tested were SVERKER21 and UNIMAX. AISI304-10, DC04 and DOCOL1000DP sheets were used. Additionally a low friction coating of BalinitC on SVERKER21 was also included. All specimens of the tool steels showed signs of galling on every run, only the low friction coating showed a transition in behaviour of friction coefficient corresponding to galling initiation. The standard deviation of the coefficient of friction increased at low loads. A decrease of the test loads led to stability loss of the system detected by an increase in the standard deviation of the coefficient of friction. This might happen because the Kistler platform is originally designed for larger loads. Although, the test rig does not work properly in its present state, the concept looks promising.</p>

Os Aços Avançados de Alta Resistência ou AHSS (do inglês Advanced High Strength Steels) apresentam muitas vantagens mecânicas em relação aos aços convencionais. Seu uso crescente na indústria automotiva deve-se principalmente à sua capacidade de possibilitar a redução de peso e, ao mesmo tempo, o aumento da segurança aos ocupantes do veículo em caso de colisões. No entanto, apresentam maiores dificuldades no que se refere à conformabilidade (maiores níveis de solicitação e desgaste das ferramentas, menor deformabilidade plástica, etc). Assim, alguns testes para avaliar a conformabilidade destes materiais ganham maior importância. É o caso do Teste de Expansão de Furos, cuja propriedade medida é a Razão de Expansão de Furos (REF). Neste trabalho investiga-se o processo de expansão de furos para o aço avançado de alta resistência (AHSS) martensítico DOCOL 190M, sob as seguintes condições de processo: duas formas de obtenção do furo (jato d’água e usinagem); duas geometrias distintas de punções (cônico de 60º e elíptico); diversos diâmetros do furo inicial; com e sem o uso de lubrificante; com acabamento diferenciado da borda do furo; e expansão com deslocamento do punção em etapas. Os experimentos demonstram que a expansão de furos possui uma estreita relação com a geometria do punção utilizado para a expansão, bem como com o diâmetro do furo inicial, acabamento da borda e condições de lubrificação. A partir dos resultados experimentais de expansão de furos foi possível realizar a calibração de um software de simulação computacional em relação ao dano crítico do material no momento da fatura na borda do furo. / Advanced High Strength Steels (AHSS) offer many mechanical advantages over conventional steels. Its increasing use in the automotive industry is mainly due to its ability to reduce weight and, at the same time, increase occupant safety in the event of collisions. However, they present greater difficulties with respect to the formability (higher levels of solicitation and wear of the tools, lower plastic formability, etc). Thus, some tests to evaluate the formability of these materials come to have greater importance. This is the case of the Hole Expansion Test, whose measured property is the Hole Expansion Ratio (REF). This work investigates the hole expansion process for a martensitic advanced high-strength steel (AHSS), DOCOL 190M, under the following process conditions: two ways of obtaining the hole (water jet and machining); two different geometries of punctures (conical of 60º and elliptical); various diameters of the initial hole; with and without the use of lubricant; with differentiated finishing of the hole edge; and expansion with punch displacement in steps. The experiments demonstrate that the hole expansion has a close relationship with the geometry of the punch used for the expansion, as well as the initial hole diameter, edge finish and lubrication conditions. From the experimental hole expansion results it was possible to carry out the calibration of a computational simulation software in relation to the critical damage of the material at the moment of hole edge rupture.

O presente trabalho tem por finalidade apresentar e discutir os resultados encontrados para o coeficiente de atrito de três tipos de diferentes chapas utilizadas em processos de estampagem na indústria automotiva. O método adotado para determinação do coeficiente de atrito foi o dobramento sob tensão, método este que tem por finalidade simular as condições de uma operação de embutimento. Os resultados apresentados demonstram que diferentes chapas em aço NBR 5915 EM e EMS ME 1508 EM, com ou sem proteção galvânica, apresentam diferentes condições tribológicas determinadas através do ensaio. Coeficientes de atrito que variam desde 0,103 até 0,151 foram determinados, considerando condições de lubrificação e de ferramenta constantes. A influência do coeficiente de atrito no processo é exemplificada através do cálculo da força máxima de estampagem, sendo que para as mesmas condições de propriedades mecânicas a variação do coeficiente de atrito provocou um aumento de 7,6% na força máxima. Através do cálculo determinou-se também a influência do coeficiente de atrito nas forças de atrito do processo. Para as condições apresentadas, a influência do coeficiente de atrito no prensa chapas na força máxima de estampagem é 20x menor em relação à influência do coeficiente de atrito no raio da matriz. / This research aims to show and discuss the friction coefficient of three different kinds of sheet metal used in sheet metal forming processes of automotive industry. The methodology for the determination of the coefficient of friction was the bending under tension, that purpose to simulate the deep drawing conditions. The results show different kinds of sheets metals, as NBR 5915 EM and EMS ME 1508 EM, with or not galvanized protection, show different tribological conditions by the tests. Friction coefficients from 0,103 to 0,151 were founded, considering invariable lubrication and tool conditions. The influence of friction coefficient in the stamping process is exemplified by the maximum stamping strength. For these tests conditions, the coefficient of friction caused an increase of 7.6% in the maximum stamping strength. The influence of the friction coefficient on the friction strengths of the process was determined. For these conditions, the influence of the friction coefficient in the friction strength of the blank holder is 20x smaller than in the friction strength of die's radius.

Este trabalho apresenta um estudo sobre o processo de Estampagem Incremental de Chapas, em Latão C-268 de diferentes espessuras (s0: 0.50, 0.70 e 1.00 mm), motivado pela inobservância de pesquisas desta matéria prima neste processo de conformação de chapas. Atualmente, este material tem grande aplicação na confecção de utensílios domésticos (baixelas, travessas, etc) e ferragens para construção civil (espelhos, cubas, etc), instrumentos musicais de sopro e núcleos de radiadores automotivos, tendo assim, um amplo campo de aplicação industrial, e potencial para as aplicações do processo de Estampagem Incremental de Chapas. A pesquisa está pautada na caracterização das matérias primas, para a obtenção de dados como as Curvas de Escoamento, Índices de Anisotropia (r), Curvas Limite de Conformação (CLC) e em experimentos de Estampagem Incremental de Chapas, realizados em uma máquina dedicada a este processo de conformação. Para a realização dos experimentos, foram utilizados Incrementos Verticais com diferentes valores (∆Z: 0.10, 0.50 e 1.00 mm), assim como duas ferramentas de estampagem (DT: Ø10 e Ø15 mm). Foram aplicadas duas formas geométricas diferentes: Tronco de Cone e Tronco de Pirâmide, ambos com perfil radial das paredes verticais. Ao todo, foram realizados 15 experimentos diferentes na modalidade SPIF. Os experimentos foram realizados em uma máquina dedicada ao processo, capaz da aquisição dos valores de Força (FX, FY e FZ) durante a realização dos testes. Com a realização dos experimentos SPIF, foi possível a elaboração da Linha Limite de Fratura – LFC da chapa latão C-268 nas três espessuras investigadas, onde os resultados apontam para valores maiores de deformação verdadeira (1 vs 2), quando comparados aos valores da CLC. Adicionalmente, a LFC das três espessuras de chapas analisadas, apontam os valores das maiores deformações verdadeiras (1) muito próximos, evidenciando neste caso que a diminuição do Incremento Vertical (∆Z) é mais relevante para a estampagem do que o aumento da espessura da chapa. As geometrias Tronco de Cone e Tronco de Pirâmide apresentaram discrepâncias geométricas toleráveis em relação ao perfil projetado, mas diferentes entre si, influenciados pelo retorno elástico diferente de cada geometria. Entretanto, suas fraturas apresentaram o mesmo comportamento, propagação no sentido meridional. Os experimentos SPIF realizados com a ferramenta de estampagem com Ø10mm proporcionaram as maiores profundidades. A medição da espessura final (s1) próximas as regiões fraturadas, comprovou os valores medidos não ultrapassaram os respectivos valores resultantes da expressão matemática Lei do Seno, e ainda, que quanto menor a espessura inicial (s0) da chapa, menor a variação dos valores medidos e calculados. A análise das Forças (FX, FY e FZ) resultantes do processo SPIF mostram que quanto maior o Incremento Vertical (∆Z), maior a espessura inicial (s0) da chapa, e maior do diâmetro (DT) da ferramenta de estampagem, maiores serão as Forças necessárias no SPIF. Adicionalmente, foi possível determinar os valores de Atrito (µ), obtidos em função das Forças (FX, FY e FZ) do processo SPIF. / This paper presents a study of the Incremental Sheet Forming process, in Brass C-268 of different thicknesses (s0: 0.50, 0.70 and 1.00 mm), motivated by non-observance of research of this raw material in this sheet forming process. Currently, this material has great application in the manufacture of household items (plates, platters, etc.) and hardware for building (locks, vats, etc.), wind musical instruments and automotive radiator cores, having thus, a large industrial application field, and potential for the applications of the Incremental Sheet Forming process. The research is based on the characterization of raw materials, to obtain data such as Flow Curves, Anisotropy Indices (r), Forming Limit Curve and in Incremental Sheet Forming experiments, performed on a machine dedicated to this forming process. For the realization of the experiments, Vertical Increments with different values were used (∆Z: 0.10, 0.50 e 1.00 mm), As well as two forming tools (DT: Ø10 e Ø15 mm). Two different geometric forms were applied: Cone Frustum and Pyramid Frustum, both with radial profile of vertical walls. In all, 15 different SPIF experiments were performed. The experiments were carried out in a machine dedicated to the process, able to acquire the values of Force (FX, FY e FZ) during the tests. With the realization of SPIF experiments, it was possible to elaborate the Fracture Forming Line – FFL of Brass C-268 sheet, In the three thicknesses investigated, Where the results indicate higher values of true strain (1 vs 2), when compared to the FLC values. Additionally, the FFL of the three sheet thicknesses analyzed, indicate the values of the highest true deformations (1) very close, evidencing in this case, that the decrease of Vertical Increment (∆Z) is more relevant for the forming than the increase in sheet thickness. The Cone Frustum and Pyramid Frustum geometries presented tolerable geometric discrepancies in relation to the projected profile, more different from each other, influenced by different springback of each geometry. However, their fractures presented the same behavior, meridional direction propagation. The SPIF experiments performed with the forming tool with Ø10mm provided the greatest depths. The final thickness (s1) measurement near the fractured regions, proved the measured values did not exceed the respective values resulting from the mathematical expression Sine Law, and also, that the lower the initial thickness (s0) of sheet, lower the variation of the measured and calculated values. Analysis of Forces (FX, FY e FZ) resulting from the SPIF process, show that the larger the Vertical Increment (∆Z), larger the initial thickness (s0) of the sheet, and larger diameter (DT) of the forming tool, larger will be the necessary forces in SPIF. In addition, it was possible to determine the values of Friction (µ), obtained in function of the SPIF Forces (FX, FY e FZ).

Nowadays FE-simulations for sheet metal forming process are used to reduce the tryout phase in automotive industries. But the complex forming simulation processes are very challenging. One of the challenges is to create an FE-model which can be used to analyze the effects of cushion motion on the forming process. This thesis is focused on creating an FE model for two dies single cushion sheet metal forming press which can be used to analyze the effects of cushion motion on the contact pressure between the stamping tools and blanks. Using LS-PrePost a model with rigid stamping tools and cushion was created where the two blanks were of different thicknesses. After the model creation LS-DYNA was used for the simulations. The results showed that the cushion is moving in all DOFs and due to this movements, uneven contact pressure distribution is seen on the blanks and stamping tools.