Dissertations / Theses on the topic 'Metal stamping'

A blankholder is used to hold the edges of metal sheet while it is being formed by a matrix and a punch. An efficient way to design a stamping die is to integrate the blankholder plate into the die structure. This would eliminate the time and cost to manufacture blankholder plates. The integrated structure is called integrated blankholder. The main focus of this thesis is structural analysis and optimization of the integrated blankholder. The structural analysis of the integrated blankholder model (used for the production of doors of Volvo car model V70) is performed using Hypermesh and Abaqus. The FE-results were compared with the analytical calculations of the fatigue limit. To increase the stiffness and reduce the stress levels in the integrated blankholder, topology and shape optimization is performed with Optistruct. Thereafter, a CAD model is set up in Catia based on the results of optimization. Finally, structural analysis of this CAD model is performed and the results are compared with the original results. The results show reduction in stress levels by 70% and a more homogeneous stress distribution is obtained. The mass of the die is increased by 17 % and in overall, a stiffer die is obtained. Based on the simulations and results, discussion and conclusions are formulated.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2016.
The purpose of this study is the optimisation of the stamping analysis process in order to investigate the possible reasons for the part failure. (Altan & Vasquez, 2000) have conducted similar research to optimise a forming process. However, they focussed on dies for a forging process and in this study, we are looking at cold forming and this study is also different in that we are trying to reduce the number of stages while maintaining the formability. Formability is based on the dimensional conformance of the final part with additional criteria being the thinning, appearance of wrinkling, dynamic effects leading to the localisation of strain, cracking and residual stress. A numerical modelling procedure that is close enough to the real process is used to investigate the effects of changes in the frictional contact that would correspond to lubrication and also the effect of adding draw beads to the forming tools to change the frictional contact. We also investigated the effect of using a different material in terms of meeting the design requirements. Experimental results for comparison are available for certain of the stamping processes investigated that were tested in pre-production. The finite element simulation is used to account for all residual thinning, stress and strain of the multi-stage forming process to ensure optimum thickness changes of the sheet at each stage. The variations of material and manufacturing parameters are established to accurately predict the behaviour of this specific forming process. The material model required to meet physical experiments is deduced from the results of standard tensile tests and fitted to the Hill’s 48 Law for Work Hardening. The commercial packages Ls-Dyna with Dynaform and Pam-Stamp software are used for the simulation to produce 2 results for comparison.

The current work used discrete event simulation techniques to model the economics of quality within an actual automotive stamping plant. Automotive stamping is a complex, capital intensive process requiring part-specific tooling and specialised machinery. Quality control and quality improvement is difficult in the stamping environment due to the general lack of process understanding and the large number to interacting variables. These factors have prevented the widespread use of statistical process control. In this work, a model of the quality control techniques used at the Ford Geelong Stamping plant is developed and indirectly validated against results from production. To date, most discrete event models are of systems where the quality control process is clearly defined by the rules of statistical process control. However, the quality control technique used within the stamping plant is for the operator to perform a 100% visual inspection while unloading the finished panels. In the developed model, control is enacted after a cumulative count of defective items is observed, thereby approximating the operator who allows a number of defective panels to accumulate before resetting the line. Analysis of this model found that the cost sensitivity to inspection error is dependent upon the level of control and that the level of control determines line utilisation. Additional analysis of this model demonstrated that additional inspection processes would lead to more stable cost structures but these structures many not necessarily be lower cost. The model was subsequently applied to investigate the economics of quality improvement. The quality problem of panel blemishes, induced by slivers (small metal fragments), was chosen as a case stuffy. Errors of 20-30% were observed during direct validation of the cost model and it was concluded that the use of discrete event simulation models for applications requiring high accuracy would not be possible unless the production system was of low complexity. However, the model could be used to evaluate the sensitivity of input factors and investigating the effects of a number of potential improvement opportunities. Therefore, the research concluded that it is possible to use discrete event simulation to determine the quality economics of an actual stamping plant. However, limitations imposed by inability of the model to consider a number of external factors, such as continuous improvement, operator working conditions or wear and the lack of reliable quality data, result in low cost accuracy. Despite this, it still can be demonstrated that discrete event simulation has significant benefits over the alternate modelling methods.

Never before has the car industry been as challenging, interesting, and demanding as it is today. New and advanced techniques are being continuously introduced, which has led to increasing competition in an almost ever-expanding car market. As the pace and complexity heightens in the car market, manufacturing processes must advance at an equal speed. An important manufacturing process within the automotive industry, and the focus of this thesis, is sheet metal forming (SMF). Sheet metal forming is used to create door panels, structural beams, and trunk lids, among other parts, by forming sheets of metal in press lines with stamping dies. The SMF process has been simulated for the past couple of decades with finite element (FE) simulations, whereby one can predict factors such as shape, strains, thickness, springback, risk of failure, and wrinkles. A factor that most SMF simulations do not currently include is the die and press elasticity. This factor is handled manually during the die tryout phase, which is often long and expensive. The importance of accurately representing press and die elasticity in SMF simulations is the focus of this research project. The research objective is to achieve virtual tryout and improved production support through SMF simulations that consider elastic die and press deformations. Loading a die with production forces and including the deformations in SMF simulations achieves a reliable result. It is impossible to achieve accurate simulation results without including the die deformations. This thesis also describes numerical methods for optimizing and compensating tool surfaces against press and die deformations. In order for these compensations to be valid, it is imperative to accurately represent dies and presses. A method of measuring and inverse modeling the elasticity of a press table has been developed and is based on digital image correlation (DIC) measurements and structural optimization with FE software. Optimization, structural analysis, and SMF simulations together with experimental measurements have immense potential to improve simulation results and significantly reduce the lead time of stamping dies. Last but not least, improved production support and die design are other areas that can benefit from these tools.
Aldrig tidigare har bilindustrin varit så utmanande, intressant och spännande som idag. Ny och avancerad teknik introduceras i en allt snabbare takt vilket leder till ständigt ökande konkurrens på en, nästan ständigt, ökande bilmarknad. Den ständigt ökande komplexiteten ställer även krav på tillverkningsprocesserna. En viktig process, som denna licentiatuppsats fokuserar på, är pressning av plåt. Tillverkningstekniken används för att forma plåtar till dörrpaneler, strukturbalkar, motorhuvar, etc. Plåtar formas med hjälp av pressverktyg monterade i plåtformningspressar. Plåtformningsprocessen simuleras sedan ett par decennium tillbaka med Finita Element (FE) simuleringar. Man kan på så sätt prediktera form, töjningar, tjocklek, återfjädring, rynkor, risk för försträckning och sprickor m.m. En faktor som för tillfället inte inkluderas i näst intill alla plåtformningssimuleringar är elastiska press- och verktygsdeformationer. Detta hanteras istället manuellt under, den oftast långa och dyra, inprovningsfasen. Detta projekt har visat på vikten av att representera press och verktygsdeformationer i plåtformningssimuleringar. Detta demonstreras genom en analys av ett verkligt pressverktyg som belastas med produktionskrafter. Det är inte möjligt att uppnå bra simuleringsresultat utan att inkludera verktygsdeformationer i simuleringsmodellen. Uppsatsen beskriver även numeriska metoder för att optimera och kompensera verktygsytor mot press och verktygsdeformationer. För att dessa kompenseringar ska stämma är det viktigt att man representerar både verktyg och press på ett korrekt sätt. Förslag på en metod för att mäta och inversmodellera pressdeformationer har utvecklats, metoden är baserad på mätningar med DIC-systemet ARAMIS och optimering i FE-mjukvaror. Optimering, strukturanalys, och plåtformningsanalys tillsammans med experimentella mätningar har en stor potential att förbättra plåtformningssimuleringar samt reducera ledtiden för pressverktyg. Sist men inte minst, andra positiva effekter är en enklare och smidigare konstruktionsprocess och förbättrad produktionssupport.

As part of the development process for new stamping dies, in the automotive sheet metal forming (SMF) industry, the majority of all forming operations are simulated with the Finite Element Method (FEM) before the dies are manufactured. Today, these simulations are conducted with rigid tools under the assumption that there are no tool deformations. However, research shows that tool deformations have an influence on the finished product. In real production these deformations are compensated by manual rework during the try-out. Additional reason for simulating with rigid dies is that there are non-existing simulation methods elaborated for elastic stamping dies. Also, simulation of elastic tools requires high computational power.     Since simulations today are performed with rigid stamping dies the purpose of this work is to investigate the conditions of how to conduct SMF-simulations with elastic stamping dies. The object that will be studied is a stamping die for a Volvo XC90 inner door used in a single-action press. This work is part of the development to minimize the manual rework, with the goal to compensate for tool deformations in a virtual environment.    Results for rigid stamping dies in LS-Dyna was compared to currently used AutoForm as a pre-study. A simple model was then created to find a suitable method while using elastic stamping dies. The developed method was used for an industrial size stamping die.     Since there are little amount of research performed on simulations using elastic stamping dies, elasticity and complexity were gradually introduced into the FE-model. As a first step, only the punch was included as an elastic solid. Secondly, the die was added. Finally, the entire die was simulated as elastic together with the hydraulic cushion of the press. When the FE-model worked as expected a suitable method for minimizing the simulation time with acceptable results was studied.     Comparisons of measured- and simulation results show a high correlation. To improve the results from the FE-model factors such as press deformations, advanced friction models, etc. should be included.    Conclusions from this work shows that it is possible to perform SMF-simulations with elastic stamping dies. As the computational time normally is high this work also presents a method first step to reduce the computational time with acceptable results. Comparisons between simulations with rigid and elastic stamping dies proves that there are significant differences in the outcome of the two methods.
Reduced Lead Time through Advanced Die Structure Analysis - Vinnova

Orientador: Alfredo Rocha de Faria
Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: As simulações dentro do ambiente de projeto devem prever a utilização de novas variáveis, especialmente de processos, de forma a aumentar a proximidade entre os modelos virtual e real e, com isso, aumentar a precisão das simulações. O objetivo deste trabalho foi o de estudar um modelo pelo Método dos Elementos Finitos que incluísse os efeitos da variação de espessura provenientes do processo de estampagem para a análise de vida em fadiga de um componente do sistema de exaustão automotivo. Primeiramente foi realizada a simulação do processo de estampagem, onde foi possível identificar as mudanças de espessura na geometria do componente estudado. O resultado dessa simulação foi transportado para a malha de elementos finitos, de forma que as análises posteriores, estrutural e de fadiga, considerassem os efeitos da redução e aumento da espessura local. Como base de comparação, as mesmas análises foram realizadas para a condição de espessura constante, tradicionalmente adotada durante a fase de projeto. Utilizando o modelo de Wöhler-Goodman-Miner para o cálculo do Dano acumulado e comparando com dados experimentais aquisitados em simulador veicular, os resultados cálculo de fadiga demonstraram que ambas as condições de espessura atingem vida infinita. Entretanto, após a seleção e análise de algumas regiões consideradas críticas nas simulações precedentes (estampagem e estrutural), pôde-se notar que na maior parte das regiões os valores de dano acumulado eram inferiores para a condição de espessura constante. Já a condição de espessura variável se aproximou mais ao resultado medido. Pôde-se concluir com os resultados que a variação de espessura, como efeito do processo de estampagem, desempenha um papel importante na vida do componente estudado, indicando que a utilização dos dados de processo auxilia na aproximação entre os resultados do cálculo de vida e a condição real
Abstract: The simulations within the Product Development environment must give the chance to use new variables, particularly from processes, in order to improve the correlation between the virtual and real models, and thus enhance the accuracy of the simulations. The objective of this work was to study a model by the finite element method (FEM) that includes the effects of thickness variation from stamping process for the fatigue life prediction in an automotive exhaust system component. Firstly it was carried out a simulation of the stamping process, where it was possible to identify the thickness distribution all along the geometry of selected component. Then, the result of this simulation was transported to the finite element mesh, so that further analyses, structural and fatigue, could consider the effects of reduction and increasing in local thickness. As a basis for comparison, the same analyses were performed for the homogeneous geometry (uniform thickness), which are typically taken during the design phase. Using the model proposed by Wöhler-Goodman-Miner to calculate the accumulated damage and comparing with real data acquisited from a vehicle, the calculation results of fatigue showed that both conditions (equal and unequal thickness) reached infinite life. However, after the selection and analysis of some critical regions in the previous simulations (stamping and structural), it might be noted that, in most regions, the values of accumulated damage were lower for the uniform thickness condition. Besides, for the unequal thickness condition, the results got closer to those measured in vehicle. With these results, it could be demonstrated that the unequal thickness, as a process variable, plays an important role in the component life, indicating that the use of process data helps in bringing together the results from fatigue calculation and real condition
Mestrado
Manufatura
Mestre em Engenharia Automobilistica

Working at elevated temperature has its challenges due to the high level of complexity whenthe tribosystems operate under harsh conditions, commonly resulting in an increase on thefriction and thermal softening that goes into severe adhesion, severe abrasion and materialtransfer. Despite considerable research, there is a lack of research on tribology applied to hightemperature processes.  The aim of this project is to understand the tribological behavior of tool steel sliding againstaluminum under lubrication conditions working at high temperature. Salt-based, graphite-based, and polymer-based lubricants were evaluated as they are commonly used for aluminum forming. The cleanability of the lubricants after being subjected to elevated temperatures is also studied. High temperature tribological tests were carried out in a reciprocating sliding flat-on-flat configuration for 15 seconds. Optical microscope, SEM and EDS were performed to analyze the specimens after the tribological tests. Then a cleanability study was done to evaluate the cleanability of the lubricants and the effect of temperature on the cleanability of the lubricant. The concentration of the lubricants played an important role in the lubricant’s friction stability and dispersion, particularly for the polymer-based and graphite-based lubricants. Under the tested conditions the salt-based lubricant was ineffective as it showed high and unstable friction. The 10 wt.% polymer-based lubricant concentration presented severe adhesion and material transfer from the aluminum onto the tool steel.  The effect of temperature on the cleanability of the lubricants was correlated to the temperature in which the lubricants start to degrade. Nevertheless, the best cleanability was achieved when using ethanol as a cleaning agent in combination with high pressure spraying, and wirebrush techniques. Mild and high alkaline agents had poor cleanability abilities resulting insurface damage and corrosion on the tool steel.

The competition in the car market in the world is continuously intensifying. To gain an advantage in the market while making a profit, each car manufacturer needs a strong focus on always improving in the technology development. It is not just technology of the cars that need development, but it is equally important to improve the manufacturing processes itself. In the end, this will result in more appealing products for the customer at a competitive cost. The aim and scope of this master thesis is to get a deeper understanding of the forces in the stamping die during sheet metal forming in manufacturing. By using strain gauges and microcontrollers, the forces during the entire forming process could be measured and analyzed. The relationship between the force on the pressure pins in the die and the length of the pressure pins was also investigated by adding shims on the pressure pins. A modular system using Arduino Uno with 3D-printed parts was developed to measure the forces in the blank holder during sheet metal forming. An Arduino software system and TeraTerm was found the most appropriate for collecting and organizing data from the strain gauge sensors and microcontrollers. Tests were then conducted using different settings of the press, and these showed that the forces in the blank holder were uneven. Adding shims to the pins so that they were all of equal length evened out the forces in the blank holder. Another test showed that adding more shims to only one of the pins increased the force in that pin, and that adding 0.5mm of shims to that pin more than doubled the maximum force. The system developed in this thesis can measure the forces in the blank holder during the sheet forming process at a lower speed of production. This system can also detect different force settings in the press. Lastly, it can also detect a difference in force for different pressure pin lengths.
Konkurrensen på bilmarknaden i världen intensifieras kontinuerligt. För att få en fördel påmarknaden samtidigt som de gör vinst måste varje biltillverkare ha ett starkt fokus på att alltid förbättrateknikutvecklingen. Det är inte bara bilens teknik som behöver utvecklas, utan det är lika viktigt attförbättra tillverkningsprocesserna i sig. I slutändan kommer detta att resultera i mer attraktiva produkterför kunden till ett konkurrenskraftigt pris. Syftet och omfattningen av detta examensarbete är att få en djupare förståelse av krafterna ipressverktyget under plåtformningprocessen. Genom att använda töjningsgivare och mikrokontrollerkunde krafterna under hela formningsprocessen mätas och analyseras. Förhållandet mellan kraften påmothållarpinnarna i verktyget och längden på pinnarna undersöktes också genom att lägga till shims påpinnarna. Ett modulsystem som använde Arduino Uno med 3D-printade delar utvecklades för att mätakrafterna i formen under formningsprocessen. Ett Arduino-mjukvarusystem och TeraTerm bedömdesvara det mest lämpliga för att samla in och organisera data från töjningssensorer och mikrokontroller. Tester genomfördes sedan med olika inställningar i pressen, och dessa visade att krafterna ipressverktyget var ojämna. Genom att lägga till shims på pinnarna så att de alla var lika långa utjämnadeskrafterna i pressverktyget. Ett annat test visade att genom att lägga till fler shims på endast en avmothållarpinnarna ökade kraften i pinnen. Genom att tillägg till 0,5 mm shims på den pinnen mer änfördubblade den maximala kraften. Systemet som utvecklats i denna rapport kan mäta krafterna i pressverktygets mothållarpinnarunder formningsprocessen vid en lägre produktionshastighet. Detta system kan också upptäcka olikakraftinställningar i pressen. Slutligen kan den också upptäcka skillnader i kraft vid olika längder påmothållarpinnarna.

Sheet metal working operations at elevated temperature have gained in the last years even more importance due to the possibility of producing parts characterized by high strength-to-mass ratio. In particular, the hot stamping of ultra high strength quenchenable steels is nowadays widely used in the automotive industry to produce body-in-white structural components with enhanced crash resistance and geometrical accuracy. The optimization of the process, where deformation takes place simultaneously with cooling, and of the final component performances requires the utilization of FE-based codes where the forming and quenching phases have to be represented by fully thermo-mechanical-metallurgical models. The accurate calibration of such models, in terms of material behaviour, tribology, heat transfer, phase transformation kinetics and formability, is therefore a strong requirement to gain reliable results from the numerical simulations and offer noticeable time and cost savings to product and process engineers. The main target of this PhD thesis is the development of an innovative approach based on the design of integrated experimental procedures and modelling tools in order to accurately investigate and describe both the mechanical and microstructural material properties and the interface phenomena due to the thermal and mechanical events that occur during the industrial press hardening process. To this aim, a new testing apparatus was developed to evaluate the influence of temperature and strain rate on the sheet metal elasto-plastic properties and to study the influence of applied stress and strain of the material phase transformation kinetics. Furthermore, an innovative experimental setup, based on the Nakazima concept, was designed and developed to evaluate sheet formability at elevated temperature by controlling the thermo-mechanical parameters of the test and reproducing the conditions that govern the microstructural evolution during press hardening. This equipment was utilized both to determine isothermal forming limit curves at high temperature and to perform a physical simulation of hot forming operations. Finally, a thermo-mechanical-metallurgical model was implemented in a commercial FE-code and accurately calibrated to perform fully coupled numerical simulations of the reference process. The material investigated in this work is the Al-Si pre-coated quenchenable steel 22MnB5, well known with the commercial name of USIBOR 1500P’®, and the developed approach proves to be suitable to proper evaluate high strength steels behaviour in terms of mechanical, thermal and microstructural properties, and to precisely calibrate coupled numerical models when they are applied to this innovative manufacturing technology. The work presented in this thesis has been carried out at DIMEG labs, University of Padova, Italy, from January 2005 to December 2007 under the supervision of Prof. Paolo F. Bariani.

In product development there is still potential to decrease lead times with faster and more accurate simulations. The objective of this thesis was to study whether Finite Element (FE) simulations using explicit LS-DYNA to extract reaction forces from sheet metal forming tools during forming, could be used to improve existing FE models in sheet metal forming software AutoForm.To begin with, the solid CAD-model of the stamping dies were meshed with tetrahedral elements in CATIA and imported into LS-DYNA. In combination with sheet mesh and milling surface meshes from AutoForm, an explicit model was realized. Contacts between sheet mesh and milling surface meshes used the so-called sheet forming contact. The resulting reaction forces were extracted and used in a simulation using the AutoForm software. Resulting simulation was compared to a scan of the physical sheet metal after forming.The direct transfer of reaction forces from LS-DYNA to AutoForm did however not result in the same pressure distribution in AutoForm. The AutoForm simulations using results from LS-DYNA were slightly worse than standard AutoForm simulations.Further work is needed to try and perhaps implement an implicit solution after an initial explicit solution.
Inom produktutveckling finns möjligheter att förkorta ledtider genom snabbare och mera korrekta simuleringar. Syftet med detta arbetet var att undersöka huruvida resultat från explicit LS-DYNA kunde användas för att förbättra nuvarande plåtformningssimuleringar i AutoForm.Den solida CAD-modellen av verktyget meshades med tetraediska element i CATIA och importerades till LS-PrePost, tillsammans med fräsytsmeshar och plåtmesh från AutoForm. Kontakter etablerades mellan plåt och fräsytsmeshar med så kallad sheet forming contact. Modellen löstes sedan explicit. Resulterande reaktionskrafter på plåthållare exporterades till AutoForm och implementerades där. Resulterande simulering jämfördes mot en inskannad fysisk plåt efter plåtformning.Direkt implementering av reaktionskrafter på plåthållaren i AutoForm gav resultat som avvek mer mot inskannad plåt än nuvarande simuleringsstrategi. Direkt implementering av reaktionskrafter gav heller inte en tryckfördelning som liknade den som rapporterades av LS-DYNA.Mer arbete krävs för att om möjligt implementera en implicit lösning efter en initial explicit lösning.

Orientador: Sérgio Tonini Button
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este estudo teve como finalidade avaliar a estampabilidade de chapas de aço de ultra-alta resistência mecânica (da sigla inglesa UHSS), neste caso o aço DIN 27MnCrB5-2 (nº 1.7182), para a estampagem a quente com estiramento controlado. Esse processo é conhecido por associar a alta produtividade da estampagem com o tratamento térmico de têmpera durante a conformação, o que se torna vantajoso no caso de aços UHSS, já que simultaneamente, reduz os esforços durante a conformação, praticamente elimina o efeito de retorno elástico e permite gerar produtos com limite de resistência superior a 1.500 MPa. O objetivo principal de associar a redução de espessura à estampagem a quente é de gerar uma peça que atenda aos esforços aplicados e que não apresente variações bruscas de microestrutura devidas à variação local na têmpera ou pela união de chapas que seria uma alternativa para a obtenção de seções com espessuras diferentes. Além disso, também tem-se por objetivos elevar a complexidade geométrica, diminuir o peso do componente estrutural e reduzir o custo de produção. Nesse caso, buscou-se avaliar a capacidade do material de confeccionar peças com redução de espessura variável durante a conformação a quente, por meio da análise dos limites de conformabilidade, obtidos pelo ensaio Nakazima em um modelo real e outro virtual, no caso, utilizando o software Forge 2008 ® que é baseado no método de elementos finitos. Além disso, foi confeccionado um componente com variação de espessura em sua parede, a fim de exemplificar em um modelo real a aplicação das informações obtidas no ensaio Nakazima. Ao final da análise, foi possível determinar uma faixa de deformação verdadeira segura de trabalho, válida para os diferentes estados de tensão e deformação, e verificou-se uma coerência na previsão do modelo virtual previamente calibrado com os resultados experimentais
Abstract: This study aimed to evaluate the formability of ultra-high strength steel (UHSS), in this case the DIN 27MnCrB5-2 (No. 1.7182), for hot stamping with controlled stretching. The process is known by its high productivity in stamping with simultaneous heat treatment of quenching, which is advantageous in the case of UHSS steel, since it simultaneously reduces the loads during forming, practically eliminates the "springback" effect and generates products with ultimate tensile strength exceeding 1.500 MPa. The main purpose of associating the reduction of thickness with hot stamping, is to generate a continuous structure that support the loading, or in other words, without abrupt changes in microstructure due to local variation in quenching conditions or welding of blanks which is another alternative to obtain parts with different thickness along the product. Moreover, it allows high geometric complexity, reduce component weight and reduce the cost of production. In this context, it was evaluated the capacity of the material to produce parts with variable thickness reduction during forming, by analyzing the limits of formability obtained by Nakazima test in a real and virtual model with the software Forge 2008 ® which is based in the Finite Element Method. Furthermore, it was manufactured a component with varying thickness in its wall, in order to exemplify the application of the data obtained in the Nakazima tests. After the analysis, it was determined a range of safe deformation, valid for the different states of stress and strain, also it was noticed a consistency in predicting hot formability between the virtual calibrated model and experimental results
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

This master’s thesis presents a proposal for the technology of manufacturing sheet metal part, which is a part of a bicycle wall bracket. The component is made of steel sheet ČSN 11 325 with subsequent surface treatment by galvanizing. Due to the chosen method of manufacturing with a progressive stamping die, the research part is focused on the technology of shearing and bending. Technological calculations were performed for the most suitable production variant, on the basis of which a mechanical press ANDRITZ Metals with the designation KSTU 2000-20-4G-PSE was chosen. Furthermore, the design of the tool itself is presented, which is substantiated by drawing documentation. At the end of the work, a technical and economic evaluation of the produced series of 300 000 workpieces per year is calculated.

The thesis proposes a concept of manufacturing the folding meter lock. The part is made from DC01+LC steel of 0,3 mm thickness. The series size is 100 000 pcs/year. A forming in a progressive combination tool combining shearing, bending and stamping was chosen for the production, based on the analysis of possible solutions. The tool, designed on the basis of literary research of used technologies, produces the part in eleven steps exerting maximal force of 38,5 kN. The production will take place on an eccentric press LEN 40 C. The market price of 3,38 Kč for one piece was established by the technical and economic evaluation.

In the last two decades the international community has been looking for solutions to preserve the environment, and in particular the atmosphere, from the CO2 emissions through the car exhausts, considered one of the main responsible of the greenhouse effect and, therefore, of the Earth temperature increase. Rules and limits were fixed in the 1997 with the Kyoto Protocol that entered in force in 2005, by which the international community signed the legal responsibility for producing vehicles with CO2 emission limited to 95g/km to be reached in 2020. The production of cars using lightweight materials can represent an optimal solution because the lower weight means lower energy consumption. Therefore, the automotive companies are now investigating the feasibility of producing parts made of lightweight materials to replace conventional steels for the car chassis and body-in-white components, but without decreasing the passenger safety. High resistance steels and aluminium alloys have demonstrated to be the best solution thanks to their low density, high corrosion resistance and excellent stiffness-to-weight ratio. In case of use of aluminium alloy sheets and tubes, it is possible to reduce the car weight of about 15–20 % with also a consequent weight reduction of all the connected vehicle parts and therefore a substantial reduction of the pollutant exhausts. The main limit of light alloys is the poor formability and the high springback exhibited during room temperature deformation. Temperature assisted processes have proven to increase material formability: Superplastic and Quick Plastic Forming, already used for shaping aluminium sheets, have shown a relevant increase in the material formability allowing to form very complex parts but are extremely expensive due to the very long process times, therefore not applicable for mass production. On the other hand, cold and warm hydroforming processes, nowadays at the state-of-the-art for shaping hollow components, exhibit very high initial investment cost due to the high pressure of the fluid used as deformable mean and to the high tons presses needed for keeping the dies closed during the process. Moreover, a strict forming temperature limit is fixed by the fluid boil and burst temperatures, which may limit the material formability. In this research work, innovative forming processes were investigated to prove the feasibility of shaping aluminium sheets and tubes at high temperature, exceeding the limits of the already available process technologies. In particular, the Hot Stamping (HS) technology was applied to form 5xxx and 6xxx series aluminium alloys proving the capability of stamping an automotive component on a hot stamping industrial plant, and thus validating the laboratory tests results. An experimental apparatus able to work with the innovative technology of the Hot Metal Gas Forming (HMGF) process was designed and developed to form aluminium alloy tubes. In doing so, resistance heating was used as heating system and cold air in pressure was used to bulge-up the tubes during the process. The formability of different 6xxx series aluminium alloys tubes was investigated by means of free bulging tests and, afterwards, shaping component inside a die, evaluating the influence of the most important process parameters. Finally, in collaboration with an industrial company, the shaping of an aesthetic component with also the evaluation of the surface appearance was carried out demonstrating the applicability of the new process to form an industrial part.
Negli ultimi decenni, la comunità internazionale è alla continua ricerca di provvedimenti per salvaguardare l’atmosfera e l’ambiente terrestre. In campo automobilistico e dei trasporti la produzione di biossido di carbonio dai gas di scarico delle autovetture, meglio conosciuto come CO2, è ritenuto tra i maggiori responsabili del rafforzamento dell’effetto serra e dunque dell’innalzamento del clima terrestre. Per porre un concreto rimedio e regolamentare l’efficienza sul consumo medio di un autoveicolo, con il protocollo di Kyoto stipulato nel 1997 ed entrato in vigore nel 2005, la comunità internazionale si è impegnata legalmente alla produzioni di veicoli in grado di rispettare il limite di emissione di 95 g di CO2 per kilometro entro l’anno 2020. L’alleggerimento complessivo di un automobile è sicuramente tra le soluzioni più immediate per la riduzione delle particelle inquinanti, in quanto veicoli più leggeri richiedono minore forza motrice e di conseguenza minore consumo di energia. Per questo motivo le compagnie automobilistiche negli ultimi anni sono alla ricerca di materiali innovativi per sostituire l’acciaio che comunemente è impiegato per la realizzazione di telai e parti di carrozzeria, senza pregiudicare la sicurezza dei passeggeri. Gli acciai alto resistenziali ma soprattutto le leghe leggere, hanno dimostrato essere delle ottime alternative grazie alle loro proprietà di bassa densità, resistenza alla corrosione, ed ottimo rapporto rigidezza-peso. Con l’utilizzo di parti stampate ma anche di elementi tubolari in lega di alluminio il peso medio della sola scocca di una vettura può essere ridotto del 15 – 20 %, portando ad un conseguente ridimensionamento di tutte gli organi connessi ed ad una sostanziale riduzione delle emissioni dannose. La principale limitazione nella lavorazione delle leghe di alluminio è la loro scarsa attitudine a subire deformazione plastica a temperatura ambiente collegata oltretutto ad un elevato ritorno elastico. Per far fronte a questa problematica, numerosi processi innovativi utilizzanti alta temperatura sono stati o sono tuttora in fase di studio con l’obiettivo principale di incrementare la formabilità del materiale. I confermati processi di deformazione di lamiera di alluminio quali Superplastic Forming e Quick Plastic Forming, hanno dimostrato sicuramente un vantaggio in termini di formabilità riuscendo oltretutto a generare parti complesse, ma sono d’altro canto estremamente costosi e soggetti a tempi molto lunghi di processo, per cui non applicabili per produzioni in larga scala. L’idroformatura a freddo e a tiepido, invece, che rappresenta l’attuale tecnologia all’avanguardia per la sagomatura di parti cave, oltre a necessitare di elevati costi iniziali connessi alle elevate pressioni del fluido necessarie per la deformazione e alle presse ad alto tonnellaggio richieste per la chiusura degli stampi durante l’iniezione del liquido stesso, presenta severi limiti nella temperatura massima di processo. Infatti le emulsioni acqua olio generalmente impiegate come mezzo deformante risultano infiammabili al di sopra del campo tiepido per l’alluminio, limitando dunque il range termico utilizzabile per il processo e di conseguenza la formabilità del materiale. In questo lavoro di ricerca sono stati studiati processi innovativi per la produzione di componenti di alluminio in lamiera e tubolari che superassero i limiti di processo delle attuali tecnologie produttive. In particolare la tecnologia dello stampaggio a caldo (Hot Stamping), oggigiorno applicata agli acciai alto resistenziali, è stata applicata con successo su lamiere di alluminio serie 5xxx e 6xxx, e validata con test industriali eseguiti su una vera linea di stampaggio producendo un componente automobilistico. Inoltre è stato realizzato e sviluppato un prototipo in grado di operare con la tecnologia innovativa del Hot Metal Gas Forming, che utilizza gas in pressione invece di fluidi per deformare componenti tubolari al alta temperatura. Prove di formabilità su tubi di alluminio serie 6xxx, ma anche la realizzazione di componenti in stampo, hanno permesso inoltre lo studio di numerosi aspetti critici per il processo. In fine, la sagomatura di un componente industriale in collaborazione con una azienda, curando oltretutto la qualità estetica del formato, ha permesso di verificare l’applicabilità e l’efficacia di questo processo anche a livello industriale.

The in the framework of Master’s Studies developed project presents a technology- proposal for the production of a pressing tool for the manufacturing of parts from the sheet steel DD13. On the basis of a literary survey of problems of the component manufacturing through shearing, bending and the studies of heat treatment and applications of covering coat and calculation, manufacturing in the phase-shearing tool was proposed. The press GERB EDELHOFF 80 t was selected as the working device.

This master´s thesis focuses on the concept of manufacturing of carbon brush holder, made of steel S235JRG (ČSN 11 343), with thickness of 1,5 mm. In order to reduce costs, it was decided to manufacture the holder with progresive stamping tool, which combines cutting, bending and edging operations in order to achieve specific part shape. Based on relevant calculations the mechanical press LEN 63 C was chosen. The production series was set at 50 000 pieces.

KVAPIL Jan: Bending and cutting press machine for representativ part The Master´s thesis, which is developer in an undergraduate degrese in M-VSR, provides a brief overview and description of the cutting and bending technology. The thesis is carried out the calculation, which is essential for the design cutting and bending tools. Models and design are created in the software SolidWorks 2012. The Master´s thesis includes a general procedure after the award until after copy the parts on it.

Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains xxv, 222 p.; also includes graphics (some color). Includes bibliographical references (p. 185-191).

Este trabalho usa o método de determinação do coeficiente de atrito com a utilização das equações de Panknin e do ensaio de Dobramento sob Tensão (DST) para determinar o coeficiente de atrito pelas equações de Panknin foi determinada a força máxima de estampagem de copos cilíndricos dos três materiais, aço inox austenítico AISI 304, aço inox ferrítico AISI 430 e aço de baixo teor de carbono EEP, com uso de quatro lubrificantes. O valor da força máxima de estampagem foi substituída nas equações de Panknin e calculados os coeficientes de atrito. Para o ensaio de Dobramento sob Tensão foram estudadas várias equações que serviram de referência para o cálculo do coeficiente de atrito: Equação das Polias, Equação das Polias Sem Dobramento, Equação das Polias Sem Dobramento considerando os Fatores Geométricos (raio do pino e espessura da chapa), Equação de Wilson, Equação de Sniekers e Equação de Andreasen. Essas equações foram utilizadas para determinar o coeficiente de atrito com a utilização de dois lubrificantes. Os materiais de estudo foram o aço de baixo teor de carbono (EEP), aço inoxidável austenítico (AISI 304) e aço inoxidável ferrítico (AISI 430). A escolha desses materiais foi justificada pela grande quantidade de produtos estampados com esses materiais. No ensaio de DST foram utilizados corpos de prova cortados a 0°, 45° e 90° em relação à direção de laminação da chapa metálica. Nos ensaios de Dobramento sob Tensão utilizou-se uma pressão constante e uma velocidade também constante. Os resultados do coeficiente de atrito calculados pelas equações do ensaio de DST foram comparados com os resultados dos coeficientes de atrito calculados pelas equações de Panknin para validação ou não do uso das equações de Panknin para determinar o coeficiente de atrito e de referência do coeficiente de atrito destes materiais pelo Ensaio de Dobramento Sob Tensão.
This paper uses two methods for calculation of the coefficient of friction efficient, using Panknin equations and the Bending under Tension test (DST). To determine the coefficient of friction with the Panknin equations, maximum stamping strength on cylindrical cups of three materials using four lubricants was calculated. The value of maximum stamping strength was replaced in the Panknin equations to calculate the fiction coefficient. For the Bending under Tension test various equations were studied which served as reference to calculate the friction coefficient: Equation of Sheaves, Equation of Sheaves without Bending, Equation of Sheaves without Bending considering the geometric factors (radius of the pin and plate thickness), Wilson Equation, Sniekers Equation and Andreasen Equation. These equations were used to determine the friction coefficient with the use of two lubricants. The studied materials were low carbon steel, austenitic stainless steel (AISI 304) and ferritic stainless steel (AISI 430). The choice of these materials was justified by the large amount of stamped products with such materials. The Bending under Tension test was performed with specimens cut at 0°, 45° and 90° to the rolling direction of the metal sheet. The tests were made under constant pressure and constant speed. The results of friction the coefficient calculated by equations of the DST test were compared to the results of the coefficients of friction calculated by Panknin equations.

The doctoral thesis "Innovative mathematical and numerical models for studying the deformation of shells during industrial forming processes with the Finite Element Method" aims to contribute to the development of finite element methods for the analysis of stamping processes, a problematic area with a clear industrial application. To achieve the proposed objectives, the first part of this thesis covers the solid-shell elements. This type of element is attractive for the simulation of forming processes, since any type of three-dimensional constitutive law can be formulated without the need to consider any additional conjecture. Additionally, the contact of both sides can be easily treated. This work first presents the development of a triangular prismatic solid-sheet element, for the analysis of thick and thin sheets with capacity for large deformations. This element is in total Lagrangian formulation, and uses neighboring elements to compute a field of quadratic displacements. In the original formulation, a modified right Cauchy tensor was obtained; however, in this work, the formulation is extended obtaining a modified strain gradient, which allows the concepts of push-forward and pull-back to be used. These concepts provide a mathematically consistent method for the definition of temporary derivatives of tensors and, therefore, can be used, for example, to work with elasto-plasticity. This work continues with the development of the contact formulation used, a methodology found in the bibliography on computational contact mechanics for implicit simulations. This formulation consists of an exact integration of the contact interface using mortar methods, which allows obtaining the most consistent integration possible between the integration domains, as well as the most exact possible solution. The most notable contribution of this work is the consideration of dual augmented Lagrange multipliers as an optimization method. To solve the system of equations, a semi-smooth Newton method is considered, which consists of an active set strategy, also extensible in the case of friction problems. The formulation is functional for both frictionless and friction problems, which is essential for simulating stamping processes. This frictional formulation is framed in traditional friction models, such as Coulomb friction, but the development presented can be extended to any type of friction model. The remaining necessary component for the simulation of industrial processes are the constitutive models. In this work, this is materialized in the formulation of plasticity considered. These constitutive models will be considered plasticity models for large deformations, with an arbitrary combination of creep surfaces and plastic potentials: the so-called non-associative models. To calculate the tangent tensor corresponding to these general laws, numerical implementations based on perturbation methods have been considered. Another fundamental contribution of this work is the development of techniques for adaptive remeshing, of which different approaches will be presented. On the one hand, metric-based techniques, including the level-set and Hessian approaches. These techniques are general-purpose and can be considered in both structural problems and fluid mechanics problems. On the other hand, the SPR error estimation method, more conventional than the previous ones, is presented. In this area, the contribution of this work consists in the estimation of error using the Hessian and SPR techniques for the application to numerical contact problems.
La tesis doctoral "Modelos matemáticos y numéricos innovadores para el estudio de la deformación de láminas durante los procesos de conformado industrial por el Método de los Elementos Finitos" pretende contribuir al desarrollo de métodos de elementos finitos para el análisis de procesos de estampado, un área problemática con una clara aplicación industrial. De hecho, este tipo de problemas multidisciplinares requieren el conocimiento de múltiples disciplinas, como la mecánica de medios continuos, la plasticidad, la termodinámica y los problemas de contacto, entre otros. Para alcanzar los objetivos propuestos, la primera parte de esta tesis abarca los elementos de sólido lámina. Este tipo de elemento resulta atractivo para la simulación de procesos de conformado, dado que cualquier tipo de ley constitutiva tridimensional puede ser formulada sin necesidad de considerar ninguna conjetura adicional. Además, este tipo de elementos permite realizar una descripción tridimensional del cuerpo deformable, por tanto, el contacto de ambas caras puede ser tratado fácilmente. Este trabajo presenta en primer lugar el desarrollo de un elemento de sólido-lámina prismático triangular, para el análisis de láminas gruesas y delgadas con capacidad para grandes deformaciones. Este elemento figura en formulación Lagrangiana total, y emplea los elementos vecinos para poder computar un campo de desplazamientos cuadráticos. En la formulación original, se obtenía un tensor de Cauchy derecho modificado (¯C); sin embargo, en este trabajo, la formulación se extiende obteniendo un gradiente de deformación modificado (¯F), que permite emplear los conceptos de push-forward y pull-back. Dichos conceptos proveen de un método matemáticamente consistente para la definición de derivadas temporales de tensores y, por tanto, puede ser usado, por ejemplo, para trabajar con elasto-plasticidad. El elemento se basa en tres modificaciones: (a) una aproximación clásica de deformaciones transversales de corte mixtas impuestas; (b) una aproximación de deformaciones impuestas para las Componentes en el plano tangente de la lámina; y (c) una aproximación de deformaciones impuestas mejoradas en la dirección normal a través del espesor, mediante la consideración de un grado de libertad adicional. Los objetivos son poder utilizar el elemento para la simulación de láminas sin bloquear por cortante, mejorar el comportamiento membranal del elemento en el plano tangente, eliminar el bloqueo por efecto Poisson y poder tratar materiales elasto-plásticos con un flujo plástico incompresible, así como materiales elásticos cuasi-incompresibles o materiales con flujo plástico isocórico. El elemento considera un único punto de Gauss en el plano, mientras que permite considerar un número cualquiera de puntos de integración en su eje, con el objetivo de poder considerar problemas con una significativa no linealidad en cuanto a plasticidad. Este trabajo continúa con el desarrollo de la formulación de contacto empleada, una metodología que se encuentra en la bibliografía sobre la mecánica de contacto computacional para simulaciones implícitas. Dicha formulación consiste en una integración exacta de la interfaz de contacto mediante métodos de mortero, lo que permite obtener la integración más consistente posible entre los dominios de integración, así como la solución más exacta posible. La implementación también considera varios algoritmos de optimización, como la optimización mediante penalización. La contribución más notable de este trabajo es la consideración de multiplicadores de Lagrange aumentados duales como método de optimización. Estos permiten condensar estáticamente el sistema de ecuaciones, lo que permite eliminar los multiplicadores de Lagrange de la resolución y, por lo tanto, permite la consideración de solvers iterativos. Además, la formulación ha sido adecuadamente linealizada, asegurando la convergencia cuadrática del problema. Para resolver el sistema de ecuaciones, se considera un método de Newton semi-smooth, que consiste en una estrategia de set activo, extensible también en el caso de problemas friccionales. La formulación es funcional tanto para problemas sin fricción como para problemas friccionales, lo que es esencial para la simulación de procesos de estampado. Esta formulación friccional se enmarca en los modelos de fricción tradicionales, como la fricción de Coulomb, pero el desarrollo presentado puede extenderse a cualquier tipo de modelo de fricción. Esta formulación de contacto es totalmente compatible con el elemento sólido-lámina introducido en este trabajo. El componente necesario restante para la simulación de procesos industriales son los modelos constitutivos. En este trabajo, esto se ve materializado en la formulación de plasticidad considerada. Estos modelos constitutivos se considerarán modelos de plasticidad para grandes deformaciones, con una combinación arbitraria de superficies de fluencia y potenciales plásticos: los llamados modelos no asociados. Para calcular el tensor tangente correspondiente a estas leyes generales, se han considerado implementaciones numéricas basadas en métodos de perturbación. Otra contribución fundamental de este trabajo es el desarrollo de técnicas para el remallado adaptativo, de las que se presentarán distintos enfoques. Por un lado, las técnicas basadas en métricas, incluyendo los enfoques level-set y Hessiano. Estas técnicas son de propósito general y pueden considerarse tanto en la aplicación de problemas estructurales como en problemas de mecánica de fluidos. Por otro lado, se presenta el método de estimación de errores SPR, más convencional que los anteriores. En este ámbito, la contribución de este trabajo consiste en la estimación de error mediante las técnicas de Hessiano y SPR para la aplicación a problemas de contacto numérico. Con los desarrollos previamente introducidos, estaremos en disposición de introducir los casos de aplicación centrados en el contexto de procesos de estampado. Es relevante destacar que estos ejemplos son comparados con las soluciones de referencia disponibles en la bibliografía como forma de validar los desarrollos presentados hasta este punto. El presente documento está organizado de la siguiente manera. El primer capítulo establece los objetivos y revisa la bibliografía acerca de los temas clave de este trabajo. El segundo capítulo hace una introducción de la mecánica de medios continuos y los conceptos relativos al Método de los Elementos Finitos (MEF), necesarios en los desarrollos que se presentarán en los capítulos siguientes. El tercer capítulo aborda la formulación del elemento sólido-lámina, así como del elemento de lámina sin grados de libertad de rotación que inspira el sólido-lámina desarrollado. Esta parte muestra varios ejemplos académicos que son comúnmente empleados en la bibliografía como problemas de referencia de láminas. El cuarto capítulo presenta la formulación desarrollada para la resolución de problemas de contacto numérico, consistente en una formulación implícita de integración exacta mediante métodos mortero y multiplicadores de Lagrange aumentados duales. Este capítulo incluye, asimismo, varios ejemplos comúnmente encontrados en la bibliografía, que generalmente son considerados para su validación. El quinto capítulo presenta la formulación de plasticidad empleada, incluyendo algunos detalles técnicos desde el punto de vista de la implementación, así como varios ejemplos de validación. El sexto capítulo muestra los algoritmos de remallado adaptativo desarrollados en el contexto de este trabajo, y presenta varios ejemplos, que incluyen no solo casos estructurales, sino también de mecánica de fluidos. El séptimo capítulo encapsula algunos casos de validación y aplicación para procesos de estampado. El capítulo final comprende las conclusiones, así como los trabajos que podrían continuar el presente estudio.

The aim of diploma thesis is to design technology components production orders. For a given part of the technology will be used non conventional deep drawing Wheelon method. For manufacturing lengthwise recesses and consequent cutting of shaped holes using a plasma cutting. The suitability of technological applications will be tested using the cost functions.

O processo de estampagem é influenciado por diferentes variáveis, tais como, propriedades mecânicas e rugosidade da chapa, lubrificação do blank, coeficiente de atrito entre o blank e a ferramenta, parâmetros da prensa (força relativamente constante e velocidade), bem como variações nas ferramentas de conformação (deformação elástica). Este trabalho se dedica a investigação da influência do atrito entre a ferramenta e o blank. Em particular, será investigado o desenvolvimento de padrões artificiais de rugosidade de chapas metálicas (textura de superfície). O foco do presente trabalho é o estudo, em condições industriais, da inter-relação entre topografia superficial caracterizada pelos parâmetros de rugosidade 2D e 3D e estampabilidade de chapas de aço para painéis automotivos. Diferentes texturas superficiais de chapas de aço foram analisadas em termos de estampabilidade (medido pelo deslocamento do blank durante a estampagem) e tentativamente relacionadas com os parâmetros de rugosidades (2D e 3D) obtidos na chapa antes de estampar. Algumas tendências relevantes foram estabelecidas entre estes parâmetros. Os resultados aqui apresentados estão em concordância com publicações recentes mostrando uma clara relação entre estes parâmetros e que trabalhos futuros são necessários.
The stamping process is influenced by several variables such as sheet mechanical properties and roughness, blank lubrication, friction coefficient, press parameters (press force and speed), as well as variations in the forming tools (elastic strain). This work is dedicated to study the influence of friction between the tool and the blank. In this sense, it is necessary to study the development of artificial roughness patterns of sheet metals (surface textures). The aim of this research work is to study the inter-relationship, using the surface topography characterized by 2D and 3D roughness parameters and the formability of steel sheets for automotive panels. Different surface textures of sheet metal have been evaluated in terms of formability (measured by material flow during the process stamping) and tentatively related to roughness parameters (2D and 3D) obtained in the sheet metal prior to stamping. Some relevant tendencies have been established amongst these parameters. The results presented here are in accordance with other recently published research work showing that there is a clear relationship between these parameters, and that further detailed studies are needed.

Hot stamping of aluminium alloys allows for increased formability, decreased springback and the possibility of integrating age-hardening heat treatments into the process. However, it can be challenging due to the occurrence of material transfer of aluminium onto the tool, as aluminium is prone to adhesion even at low temperatures. Hence, lubrication is always necessary when forming aluminium, but lubricants can still fail, leading to direct interaction between tool and workpiece and thus material transfer. This phenomenon reduces the efficiency of the process, as interruptions are necessary for the refurbishment of the tools. Understanding of how material transfer takes place is important in order to find new or improved solutions, in terms of lubrication and surface engineering, to prevent adhesion. Nevertheless, current research in high temperature tribology of aluminium, mainly in terms of material transfer mechanisms, is very limited, as many of the works focus on lubricated conditions and do not look into the fundamental interactions between aluminium alloys and tool steels. In this context, the aim of this work is to investigate the mechanisms behind the occurrence of aluminium alloy transfer onto tool steel during sliding at high temperature and in dry conditions. A hot-strip drawing tribometer was used to perform tests at room temperature, 300°C, 400°C, and 500°C, directly after solubilizing the aluminium alloy at 520°C. Two different topographies for the tool steel were used: ground and polished. Material transfer characterization was performed mainly through scanning electron microscopy. It was found that grinding marks (ground tool steel) and carbides (polished tool steel) act as initiation sites for the transfer to occur. Temperature plays a role on the growth mechanisms of the transfer films during sliding, as thermal softening of the aluminium alloy is the dominant factor in determining the growth direction of the transfer layers. A growth towards the trailing edge (shearing and smearing of the transferred aluminium) or a growth towards the leading edge (build-up of transferred aluminium, leading to a thicker and more localized transfer material).

Hot stamping and cold die quenching has been developed in forming complex shaped structural components of metals. This study is the first attempt to develop unified viscoplastic damage constitutive equations for the prediction of formability of metals under hot stamping conditions. In order to achieve the aim of this study, test facilities and methods need to be established to obtain experimental formability data of metals under hot stamping conditions. The research work is concerned with four aspects: thermo-mechanical properties of an alloy under hot stamping conditions, feasibility study of a novel biaxial testing system for hot stamping applications, formability tests by cruciform specimens under hot stamping conditions, and developed material models for formability evaluation and prediction. Hot tensile tests were performed at various temperatures and strain rates after heating and cooling processes to study the thermo-mechanical properties of AA6082 under hot stamping conditions. An error analysis of the proposed strain measurement method was carried out using an FE model coupled with thermo-electrical and thermo-mechanical conditions. The viscoplastic deformation behaviour of AA6082 was analysed in terms of temperature and strain rate dependence based on the experimental results. A viscoplastic damage constitutive model was developed to describe the thermo-mechanical response of the metal, material constants in which were calibrated from the hot tensile test results. A novel biaxial testing system was developed, patented and used for formability tests of AA6082 under hot stamping conditions after the feasibility study of this new testing method. Three heating and cooling strategies were proposed to investigate the temperature and strain distributions in a type of cruciform specimen. The dimensions of cruciform specimens adopted for the determination of forming limit under various strain paths were designed and optimised based on the selective heating and cooling method. Formability tests of AA6082 were conducted at various temperatures and strain rates after the heating and cooling processes. Two unified multi-axial viscoplastic constitutive models were developed and determined from the formability test results of AA6082 for the prediction of forming limit of alloys under hot stamping conditions. This research, for the first time, enabled formability data to be generated and forming limits to be predicted under hot stamping conditions. The technique has been verified for a particular aluminium alloy and can be applied to other metals under hot stamping conditions.

Orientador: Aneirson Francisco da Silva
Resumo: A Estampagem a Frio é um processo de conformação plástica de chapas metálicas, que possibilita, por meio de ferramentas específicas, obter componentes com boas propriedades mecânicas, geometrias e espessuras variadas, diferentes especificações de materiais e com boa vantagem econômica. A multiplicidade destas variáveis gera a necessidade de utilização de técnicas estatísticas e de simulação numérica, que suportem a sua análise e adequada tomada de decisão na elaboração do projeto das ferramentas de conformação. Este trabalho foi desenvolvido em uma empresa brasileira multinacional de grande porte que atua no setor de autopeças, em seu departamento de engenharia de projetos de ferramentas, com o propósito de reduzir o estiramento e a ocorrência de trincas em uma travessa de 6,8 [mm] de aço LNE 380. A metodologia proposta obtém os valores dos fatores de entrada e sua influência na variável resposta com o uso de técnicas de Delineamento de Experimentos (DOE) e simulação pelo método de Elementos Finitos (FE). Uma Função Empírica é desenvolvida a partir desses dados, com o uso da técnica de regressão, obtendo-se a variável resposta y (espessura na região crítica), em função dos fatores influentes xi do processo. Com a Otimização via Simulação Monte Carlo (OvSMC) insere-se a incerteza nos coeficientes desta Função Empírica, sendo esta a principal contribuição deste trabalho, pois é o que ocorre, por via de regra, na prática com problemas experimentais. Simulando-se por FE as ferram... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre

碩士
國立高雄第一科技大學
機械與自動化工程所
96
This research studies the effects of process parameters on the spring back phenomenon in sheet metal stamping and bend allowance in order to improve the part quality. To reduce the spring back, the finite element analysis software, Dynaform is utilized to study the spring back phenomenon in the U-bending stamping process. Also, the Taguchi method is used to find the optimal combination of U-bending stamping parameters. Meanwhile, experiments are conducted to verify the simulation results. As for improving the accuracy of the neutral-plane correction coefficient for the bend allowance, both simulation and experimental analysis are conducted so that a more precise estimate of the bend allowance can be obtained.

"March 2003."
Thesis (Ph.D.)--Chinese University of Hong Kong, 2003.
Includes bibliographical references (p. 183-193).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.

Ng Yiu Ming.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (leaves 110-114).
Abstracts in English and Chinese.
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Diagnosis concept based on thermal energy distribution --- p.6
Chapter 1.1.1 --- A cup drawing example --- p.8
Chapter 1.2 --- Need for 3D infrared thermal distribution measurement --- p.10
Chapter 1.3 --- Outline of the Thesis --- p.11
Chapter 2. --- Approach --- p.15
Chapter 2.1 --- Similarity and extreme temperature analysis --- p.15
Chapter 2.2 --- Thermodynamics for FEA in sheet metal stamping --- p.17
Chapter 2.3 --- Acquisition of 3D thermal distribution --- p.20
Chapter 3. --- Implementation of the Diagnosis System --- p.23
Chapter 3.1 --- Thermograph acquisition --- p.23
Chapter 3.2 --- Diagnosis system setup --- p.24
Chapter 3.3 --- Perspective camera model --- p.25
Chapter 3.4 --- System calibration --- p.27
Chapter 3.4.1 --- LEDs calibration board --- p.27
Chapter 3.4.2 --- Net-and-board calibration box --- p.29
Chapter 3.5 --- Reconstruction algorithm --- p.33
Chapter 3.6 --- Summary --- p.37
Chapter 4. --- Consistency from Different Viewpoints --- p.38
Chapter 4.1 --- Summary --- p.42
Chapter 5. --- Visual Reconstruction of Objects --- p.44
Chapter 5.1 --- Visual camera calibration --- p.45
Chapter 5.2 --- Results --- p.49
Chapter 5.2.1 --- "Cartoon model ""SiuSun""" --- p.49
Chapter 5.2.2 --- Stamping disc --- p.51
Chapter 5.3 --- Summary --- p.53
Chapter 6. --- Thermal Distribution Reconstruction of Stamping Workpieces --- p.54
Chapter 6.1 --- Infrared camera calibration --- p.54
Chapter 6.2 --- Results --- p.57
Chapter 6.2.1 --- Air conditioner cap --- p.57
Chapter 6.2.2 --- Deep drawing cup --- p.59
Chapter 6.2.3 --- Stamping cylinder from KS Factory --- p.61
Chapter 6.3 --- Summary --- p.65
Chapter 7. --- Infrared Camera on a Robotic Arm --- p.66
Chapter 7.1 --- Robotic arm system setup --- p.67
Chapter 7.2 --- System calibration --- p.68
Chapter 7.3 --- Results --- p.77
Chapter 7.3.1 --- Image sequence from horizontal viewpoints --- p.77
Chapter 7.3.2 --- Image sequence from inclined viewpoints --- p.80
Chapter 7.3.3 --- Image sequence from arbitrary viewpoints --- p.83
Chapter 7.4 --- Comparison of the three different viewpoints --- p.85
Chapter 7.5 --- Summary --- p.87
Chapter 8. --- Compensation of Temperature Fade-out Problem --- p.88
Chapter 8.1 --- Causes of temperature fade-out --- p.88
Chapter 8.2 --- Solutions --- p.90
Chapter 8.3 --- Summary --- p.91
Chapter 9. --- Other Applications --- p.92
Chapter 9.1 --- Automotive industry --- p.92
Chapter 9.1.1 --- Background --- p.93
Chapter 9.1.2 --- Experiment and result --- p.94
Chapter 9.2 --- General heat transfer analysis --- p.97
Chapter 9.3 --- Summary --- p.98
Chapter 10. --- Conclusions --- p.99
Chapter 10.1 --- Summary --- p.99
Chapter 10.2 --- Future work --- p.104
Chapter A. --- Transformation Matrices of the System --- p.106
Bibliography --- p.110

碩士
國立臺灣大學
機械工程學研究所
97
Based on KBE(Knowledge-based Engineering) methodology, a design automation system for automobile sheet metal stamping die is proposed. The system integrates the feature recognition, process planning and die structure design, and the surface, feature, process and die structure data will be stored in the database. There are two goals to be achieved: one is assisting enterprises with preserving tacit knowledge of die design and promoting knowledge management; the other is accelerating the die design by automation. To represent the feature of sheet metal and the process of stamping die, this paper defines the feature protocol and process protocol. A sheet metal comparison algorithm based on the feature protocol is proposed, retrieving the similar design case more efficiently. The KBE system was implemented by Java language and embedded　Spring Solid System for STEP file importing. The CATIA CAD platform was applied for the construction of die CAD model. Using of CATIA CAD model template is constructed the die template database. An architecture transforming process data into die model is also proposed. This paper also presentes the research method for connecting Java and CATIA platform, for connecting the bridge between KBE and CAD platform.

碩士
臺灣大學
機械工程學研究所
98
Base on the methodology of knowledge-based expert systems, a CAPP(computer-aided process planning) system for automobile sheet metal is constructed. This system use rule-based reasoning to analyze the data of feature recognition, to provide the information of processes like the direction and the location of mechanisms. This system also use KBE (Knowledge-based Engineering) system to manage those information data. The principle of stamping die design is the manufacturing processes of automobile sheet metal. According to the physical laws of forming sheet metal, the process can be decided. But the knowledge rules are complicated and manifold. Most of them are the tacit knowledge or experience. The CAPP system stores those rules to the database systematically and parametrically. The user can modify the data flexibly. The rule-based reasoning engine is building on the relation between feature and process rule. This paper define the process protocol and feature protocol to represent the feature of sheet metal and the process of stamping die. The process of die design case by case is stored in database for reusing the similar design case. The CAPP system was implemented by Java language and embedded into the Spring Solid System for surface model. Use the surface model to recognize features as the input of CAPP system. The output is using VB bridge transfer the pass process protocol on Design Guide System that based on CATIA platform. CAPP system also use CATIA Power Copy function to build the standard part template library, and decide the location of mechanisms to provided the solid model designing of stamping die.

碩士
國立臺灣大學
機械工程學研究所
100
There are various factors make some contributions to the cost estimation of stamping die for automobile sheet metal, including designing and manufacturing, management and sale. If a system can store the parameters and find the rule of estimating the cost of each process, it can reach the goal of convenient and efficient cost estimation which is a vital key to increase competition in this industrialized society. In this research, the main goal is to establish the cost architectures and rules based on the design specifications, statistics and modified by collected knowledge from the experts. We use the CAD file of sheet metal and the process planning as the input, obtain the geometrical information of the sheet metal, the type of cam and the length of the knife, and calculate the cost of material, standard parts, milling, engraving, designing, trial plus indirect cost as the output. The system provides the interface to modify the parameters concerning the cost estimation and in this way users can find the most suitable parameters to estimate the cost. Keywords: cost estimation, stamping die, automobile sheet metals

A real-time dynamic feedback control system is developed. An improved PID algorithm, called the integral separated piecewise PID scheme, is used in the control system. This algorithm is able to limit the contribution of the integral component in the PID calculation to avoid integral windup. In addition, it could use different PID parameters to adapt to different segments within one punch motion cycle. Hence, the error of the punch motion, either resulting from the machine assembly or from the machine dynamics, can be compensated by tuning the velocity of the servomotor. This is a unique feature of the new press that ensures its accuracy.
Based on the novel structure, the detailed design is then carried out, which includes the mechanical design, kinematics and inverse kinematics analysis, static force analysis, parametric design and the other related designs. A calibration method based on the experiment and computer simulation is proposed for the new press, which is also useful for the parallel mechanisms. Cooperated with Guangdong Metal Forming Machine Works Co. Ltd., a 250 KN prototype has been built and tested.
In order to ensure the desirable performance, dynamic control is necessary. The thesis uses two dynamic modeling methods to study the dynamics of the press. One is the kineto-static method. It is also called D'Alembert principle which rearranges Newton's second law and transfers a dynamic problem to an equivalent static problem by adding the inertial forces and inertial torques onto the system. The model can then be analyzed easily and exactly as a static system subjected to the inertial forces and torques and the external forces. The other method is the Lagrangian method which derives the dynamic model from the energy perspective. Based on the model, the dynamics of the press is studied by means of computer simulation and is validated experimentally.
In this thesis, a controllable hybrid mechanical metal forming press is developed, which is driven by a CSM with a flywheel and a servomotor. From a mechanism point of view, it is a closed-loop 2-DOF parallel planar five-bar mechanism with four resolute joints and one prismatic joint. Thanks to the usage of the servomotor, the punch motion of the new press can be controlled by tuning the velocity of the servomotor. Accordingly, desired punch motions for different stamping processes can be obtained. In other words, the new press is flexible and controllable like the servo mechanical press and the hydraulic press. Moreover, the CSM with flywheel provides the main power during the stamping operation, and hence, it is energy efficient. In addition, it is not expensive to build, as it uses only a small servomotor.
Metal forming is one of the oldest production processes and yet, is still one of the most commonly used processes today. Everyday, millions of parts are produced by metal forming ranging from battery caps to automobile body panels. Therefore, even a small improvement may add to significant corporative gain.
The thesis also describes the trajectory planning method for the press, which is based on the combination of the inverse kinematics and cubic spline interpolation. The trajectory is optimized under multiple constraints on velocity, acceleration and jerk of the servomotor. It guarantees the new press is controllable and energy efficient.
Two typical stamping processes, drawing and forging, are taken as examples for the operations of the new press. The results of the simulation and the experiment match well. Based on the simulation and experiments, it is found that the CSM provides the main power for the metal forming operations, while the servomotor is mainly responsible for overcoming the inertia forces to realize the desired punch motion. The experiments show that the new press is energy efficient, fast, controllable and inexpensive to build. It combines the advantages of both mechanical press and hydraulic press and has a good performance. It is expected the new press will have a great potential for the metal forming industry. (Abstract shortened by UMI.)
He, Kai.
"February 2008."
Adviser: Ruxu Du.
Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1902.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2008.
Includes bibliographical references (p. 147-149).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.