Dissertations / Theses on the topic 'Sheet material'

In today’s car manufacturing industry, sheet metal forming is a important process that takes preparation, which is time consuming and complex when new processes are made. When new metal grades and alloys are provided to the industry, tests are conducted to determine it’s behaviour and strengths. This gives the data for complex material models that can approximate the metal behaviour in an accurate way in a simulation environment. One of the unknown factors from tests is the friction coefficient on the sheet metal. The software Triboform is able to provide an adaptable friction coefficient model that depends on multiple simulation and user input conditions. The problems that occur when acquiring data for the material model is that testing is time consuming and the friction model has to be adjusted to give accurate results. At Volvo Cars there are two material models used with their different advantages, BBC 2005 and Vegter 2017.The purpose with this work is to compare the two material models using the Triboform friction models implemented to see if any combination provides accurate simulation results and then create recommendations for which model is best suited for different cases. Some side studies is also done with an older Vegter model, a strain rate sensitive BBC 2005 model and a Triboform model on all simulation parts.The purpose is achieved by implementing the Triboform model in Autoform and run a simulation of a Limiting Dome Height (LDH) test with both material models and compare the results with experimental data for several different materials. The data that is directly compared from the LDH test is the major and minor strain from two perpendicular sections at four different stages and also the force from the punch tool. The material models will be evaluated by how it manages to mimic the strain behaviour of the metals and how it estimates the punch force.The results point towards an improvement of the accuracy for most of the metals tested and BBC 2005 is the better model if there’s available biaxial data from tests, Vegter 2017 is decent if there’s not. However Vegter 2017 is not a good option for aluminum alloys simulations when the punch force is compared. Side study also shows that Vegter 2017 is bit of a downgrade when it comes to strain values, compared to the old Vegter.The work, in summary shows a dynamic friction model can improve the accuracy for strain predictions in the simulation process. If there’s biaxial yield data available for the metal or if it’s an aluminum alloy, BBC 2005 is the superior choice, but if only tensile tests are available for metals, Vegter 2017 is a decent choice for some cases.
I dagens bilindustri är plåtmetalformning en viktig process som kräver förberedelser som är tidskonsumerande och komplex när nya processer tillkommer. När nya metallslag kommer in till industrin, så utförs tester för att avgöra dess egenskaper och styrka. Denna testdata används till materialmodeller som kan approximera metallens beteende på ett noggrant sätt i en simuleringsmiljö. Den okända faktorn från dessa test är friktionskoefficienten på plåten. Programvaran Triboform är kapabel att göra en dynamisk friktionsmodel som beror på användar- och simuleringsdata. Problemen som uppstår vid framtagning av data är att det är tidskonsumerande och flera simuleringar måste göras för att bestämma friktionen. Volvo Cars använder sig av två modeller med olika fördelar, BBC 2005 och Vegter 2017.Syftet med detta arbete är att jämföra de två materialmodellerna med Triboform modeller implementerat för att se om de påverkar noggrannheten i simuleringar och sedan förse rekommendationer för vilken modell passar bäst för olika fall. Några sidojobb i studien som görs är en jämförelse med gamla Vegter modellen, ett test med en modell som är känslig för töjningshastighet och test med att implementera Triboform modellen på alla pressverktyg.Detta utförs med att implementera Triboform modellerna i Autoform och köra en simulering på ett LDH-test med båda materialmodeller och jämföra resultaten med experimentell data för flera olika metaller. Data som skall jämföras från LDH-testet är första och andra huvudtöjningen i två vinkelräta sektioner i fyra processsteg och stämpelkraften genom hela processen. Modellerna kommer evalueras genom hur de lyckas imitera töjningens beteende och hur den estimerar stämpelkraften.Resultaten pekar mot en förbättring när Triboform är implementerat i simuleringar för de flesta metaller som ingår i testen och BBC 2005 är den model som föredras om det finns tillgänglig biaxiel spänning data från tester, Vegter 2017 är en duglig modell om dessa data inte finns. Vegter 2017 är dock inte ett bra alternativ när det kommer till jämförelse av töjning och stämpelkraften för aluminium. Sidojobb med gamla Vegter visar att den nya Vegter 2017 inte är en direkt förbättring med hänsyn till noggrannheter av krafter och töjningar.Arbetet visar att en dynamisk friktionsmodel kan förbättra prediktering av töjningar i simuleringar. Om det finns biaxiel data för metallen eller om det gäller att simulera aluminium är BBC 2005 det bättre altermativet, om det endast finns dragprovsdata för metallen så är Vegter 2017 duglig för vissa fall.

In today's automotive industries, many different simulation programs are used to optimize parts before they come into production. This has created a market for complex material models to get the best possible approximation of reality in the simulation environment. Several industries are still using older material models that can’t give an acceptable accuracy for the materials currently in use as they are based on much simpler and older materials. The problem with material models is that there is no direct comparison between the material models which leads to several sheet metal forming companies still holding on to older models like Hill`48.   The purpose of this work is to create a comparison of sheet material models from a user perspective to be able to provide recommendations of material models. Different models will be tested for different materials and will be based on AutoForm's recommendations. AutoForm is a FEM based sheet metal forming simulation program used by large names in the automotive industry. These recommendations are Vegter2017, BBC2005 or Hill`48 for steel and Vegter2017, BBC2005 or Barlat`89 for aluminum.   This work is achieved by comparing experimental data from a Limiting Dome Height (LDH) test with a simulation of this test for all material models and then comparing the results. The data that will be compared consists of the major and minor strain in the sheet as well as the punch force. These parameters are chosen as they give an overview of the model’s applicability as well as accuracy. The test will be performed on all materials available in Volvo Cars material library to create a broader overview of all material models. The material models will also be evaluated depending on their user-friendliness by analyzing what types of data are required to perform a simulation.   The result from these tests showed that BBC 2005 should be recommended for aluminum and steel for companies that have access to biaxial data and for people who put optimization in focus. Hill`48 proved far too deviant in the results for steel and should not be used if other models are available. Vegter 2017 proved perfect for steel simulations as the result were great as well as the necessary material data can be obtained through standardized tensile tests. The result also showed that Vegter2017 should not be used for aluminum since the result was too deviant from the experimental data in aspect for both form approximation and strain magnitude. Barlat`89 gave accurate results with only data from a tensile test which makes it a preferred model when working with aluminum.   The conclusion from this work is that the choice of material model is very dependent on what conditions you have as very few industries have access to the tests required by the BBC 2005 model. Another conclusion may be drawn for Barlat`89 with aluminum and Vegter 2017 with steel as they can be preferred when working with a small timeframe as well as when few test data is available.
Inom dagens bilindustri används det många olika simuleringsprogram för att optimera delar innan de kommer ut i produktion. Detta har då skapat en marknad för komplexa material modeller för att få en så bra approximation av verkligheten som möjligt. I flera industrier använder man sig fortfarande av äldre materialmodeller som egentligen inte håller måttet för dagens material då de är baserade på simplare material. Problemet som har skapat denna situation är att det inte direkt finns en konkret jämförelse mellan materialmodellerna vilket leder till att flera plåtformnings företag fortfarande håller kvar vid äldre modeller som t e x Hill`48.   Syftet med detta arbete är att skapa en jämförelse av plåt materialmodeller från ett användarperspektiv för att kunna ge konkreta bevis till rekommendationer av materialmodeller. Olika modeller skall testas för olika material och baseras på AutoForms rekommendationer. AutoForm är ett FEM baserat plåtformningssimulerings program som används av stora namn inom bilindustrin. Dessa rekommendationer är då att köra Vegter2017, BBC2005 eller Hill`48 för stål samt att köra Vegter2017, BBC2005 eller Barlat`89 för aluminium.   Detta arbete utförs genom att jämföra experimentella data från ett Limiting Dome Height (LDH) test med en simulering av detta test för alla material modeller och sedan jämföra resultaten. Jämförelsen mellan den experimentella och simuleringsdatan kommer att involvera major och minor strain i plåten samt stämpelkraften. Dessa parametrar har valts då de ger en bra översikt över materialmodellernas applicerbarhet och noggrannhet. Testen kommer att utföras på samtliga material som finns tillgängliga i Volvo Cars materialbibliotek för att skapa en breddare syn på samtliga modellers applicerbarhet. Materialmodellerna kommer även att utvärderas beroende på deras användarvänlighet samt vilka typer av data krävs för att använda modellen.   Resultatet visade att BBC 2005 skall rekommenderas för aluminium samt stål till de företag som har tillgång till biaxiella data samt lägger optimering i fokus. Hill`48 visade sig alldeles för avvikande för stål och bör inte användas om andra modeller är tillgängliga. Vegter 2017 visade sig perfekt för stål då resultatet var bra samt att den nödvändiga materialdatan kan införskaffas genom standardiserade dragprov. Resultatet visade även att Vegter 2017 inte bör användas för aluminium då resultatet var för avvikande. Barlat`89 gav bra resultat med endast data från dragprovstest vilket ger att den är att rekommendera för aluminium.   Slutsatsen från detta arbete är att valet av materialmodell är väldigt beroende av vilka förutsättningar som finns då väldigt få industrier har tillgång till de tester som krävs för att använda BBC 2005. I större delar av industrin där minimala optimeringar inte anses som väsentliga är Barlat`89 och Vegter 2017 att föredra då detta leder till snabbare processer.

Weight reduction is one possibility to reduce fuel consumption and emission of transportation vehicles. Sheet metals are often used in automotive and aerospace applications and therefore the weight reduction achieved by reducing the sheet metals thickness is an important contribution to weight reduction. Increasing the strength of sheet metal materials gives the opportunity to reduce the total weight while maintaining safety. To prove a maintained safety for parts with a decreased weight Finite Element (FE) simulations are commonly used. This leads to a high demand on the simulation precision of sheet metals, where an accurate prediction of the post-necking behaviour of materials is needed. Improved FE simulations are reducing time and costs during the development processes.  One application to improve the strength of sheet metals in the automotive industry is the usage of ultra high strength steels, which has constantly increased in usage during the last decades. The development of the press hardening process, where sheet metal blanks are formed and quenched simultaneously, brings new design opportunities. Using press hardening tools with zones that uses different cooling rates sheet metal parts can be produced with tailored properties, to improve their performance. Simulating materials based on the microstructure demands high precision on the plasticity modelling for high strain values.  In this thesis work a method to characterize the elasto plastic post necking behaviour of sheet metal materials, the Stepwise Modelling Method (SMM), is presented. The method uses full field measurements of the deformation field on the surface of tensile specimen. The hardening relation is modelled as a piecewise linear in a step by step procedure. The linear hardening parameter is adapted to reduce the residual between experimental and calculated tensile forces. The SMM is used to characterize the post necking behaviour of a ferritic boron steel and the results are compared with the commonly used inverse modelling method. It is shown that the stepwise modelling method characterizes the true stress, true plastic strain relation in an effective and computational efficient way. Furthermore, the SMM is used to characterize the stress state evolution during tensile testing, which is an important factor for failure and fracture modelling. This method is shown in an aerospace application for the nickel based super alloy Alloy 718.  The results shows that the stepwise modelling method is an effective and efficient alternative method to characterize the deformation and failure of sheet metals. Based on the results of this method plasticity and fracture models can be characterized in future work.

This report evaluates the influence of the die material on the cooling rate and martensitic transformation of press hardened sheets. The goal was to increase the thicknesses of sheets that can form fully martensitic microstructure when press hardened. To achieve this, a numerical- and an experimental method was used and results were compared to assess the impact of die material change. The tests were conducted with two die materials, a ductile cast iron according to standard EN‑GJS‑700‑2 and a casted steel according to standard EN 1.6220. Two sheet materials, Hardox400 and Hardox450, were press hardened and two different thicknesses were evaluated. Simulations have been designed with temperature dependent material properties based on data gathered from the literature survey. All simulations indicated an improved cooling rate over the entire temperature spectrum when changing from the iron die to the steel die.   An experimental procedure has been performed using two different dies, both planar and of approximately the same thickness. Thermocouples were used to obtain cooling curves of all sheets during quenching. Samples were taken from each sheet and the hardness, microstructure and the present phases were investigated.   The experiments concluded that the thinner sheets, when quenched, experienced an overall increase in cooling rate in the steel die compared with the iron die. A total reduction in cooling time by 37.5%-43,7% was observed over the entire temperature span. However, only the Hardox400 sheet fully formed martensite, as the cooling of the Hardox450 sheets still was not fast enough in either of the dies. For the thicker sheets, the experiments also indicated a reduction in total cooling time. The total cooling time was reduced by 23% when pressed in the steel die compared to the iron die. This improvement, however, was not observed at higher temperatures. At the critical temperature span between 800˚C and 500˚C, the sheet showed no improvements in cooling rate with the die material change. Both the hardness measurements and the microstructure evaluation of the thicker sheets indicated a pearlitic-martensitic microstructure. As both the simulations and experiments indicated similar improvements, the increase in cooling rate could be accredited to the die material change.  This concludes that the heat transfer properties of the die material affected the cooling characteristics of the process. It was also concluded that the thinner sheets experienced a reduced cooling time over the entire temperature spectrum with the die material change. The thicker sheet, however, only experienced a reduced cooling time in the lower temperature span. Thus, changing the die material did not affect the hardening of the thicker sheets. This ultimately resulted in an unsuccessful attempt to increase the possible thickness of sheets with fully martensite microstructure. The improvements observed for the thinner sheets, are however promising and could be further evaluated for another sheet material.
I denna avhandling har relationen mellan ett verktygmaterials kylningseffekt och genomhärdningsförmåga under presshärdning utvärderats, med målet att öka tjockleken på plåtmaterial som genomhärdar. För att åstadkomma detta har en numerisk undersökning och en experimentell undersökning utförts för att bedöma effekten av ett byte av verktygsmaterial. Undersökningarna utfördes med två verktygsmaterial, ett segt gjutjärn enligt standard EN‑GJS‑700‑2 och ett gjutet stål enligt standard EN 1.6220. Under testerna användes även två olika plåtmaterial, Hardox400 och Hardox450, i två olika tjocklekar. Simuleringen har utformats med relevanta temperaturberoende materialparametrar erhållna från teorin. Resultaten från simuleringarna påvisade att ett byte av verktygsmaterial gav snabbare kylning av all plåtar över hela det undersökta temperaturspannet. Den experimentella undersökningen har utförts med två olika pressverktyg, båda plana med likartad tjocklek. Temperaturgivare användes för att erhålla kylkurvor för plåtarna när de kyldes i verktygen. Hårdhet, mikrostruktur och erhållna faser undersöktes för varje plåt. Experimenten påvisade att de tunnare plåtarna kyldes snabbare i stålverktyget än i järnverktyget över hela temperaturspannet, och resulterade i 37,5%-43,7% kortare kyltider. Trots detta, var det endast Hardox400-plåten som genomhärdades, då kylningen av Hardox450-plåten inte var tillräckligt snabb i något av verktygen. Även de tjockare plåtarna uppvisade en totalt kortare kyltid. Kyltiden minskade med 23% i stålverktyget jämfört med järnverktyget. Denna förbättring observerades dock inte över hela temperaturspannet. Vid höga temperaturer kylde stålverktyget långsammare än järnverktyget. De släckta plåtarna erhöll en perlitisk/martensitisk struktur vid komplett svalning, oberoende av verktygsmaterial. Eftersom både simuleringarna och experimenten påvisade liknande förbättringar, kan den ökade kylhastigheten härledas till bytet av verktygsmaterial. Detta fastställer att värmetransportegenskaperna hos verktygsmaterialet hade en inverkan på kylningen i processen. Studien påvisade också att de tunnare plåtarna kyldes fortare över hela temperaturspannet vid materialbytet. De tjockare plåtarna uppvisade dock endast en kortare kyltid i det lägre temperaturspannet. Därmed förblev härdningen av de tjockare plåtarna opåverkad av materialbytet. Detta resulterade i att presshärdning av ökad plåttjocklek för det undersökta materialet inte lyckades. De observerade förbättringarna hos de tunnare plåtarna är dock mycket lovande och bör studeras vidare.

Aluminium alloys have been the primary material utilised for aerospace components since the 1930s. The continued requirement for weight reduction coupled with reliable performance and formability by the aerospace and automotive industries is satisfied by advanced aluminium alloys. The mechanical performance of these alloys requires numerical analysis using advanced yield criteria, such as the Leacock 2006 phenomenological yield criterion. The enhanced accuracy of this advanced yield criterion over several yield criteria including Hill 1990 has been previously reported by Leacock (2006). Constitutive equations based on the von Mises, Hill 1948, Hill 1990 and Leacock 2006 yield criteria, in combination with two non-linear hardening laws, have been implemented as a rate independent, elastoplastic user material subroutine (UMAT) within the Finite Element software PAM-STAMP 2GTM. The UMAT architecture incorporates the Associated Flow Rule and the Cutting Plane Algorithm for the integration of the elastoplastic constitutive equations. The 2024-O and 6451-T4 (Anticorodal-600 PX) aluminium alloys were characterised using uniaxial and equibiaxial tension tests. This test data formed the basis of an initial computational verification of the UMAT. A stress path specific comparison of the Finite Element results with the theoretical prediction and the experimental values showed excellent agreement. In addition, the Leacock 2006 UMAT showed favourable comparison with the theoretical and experimental uniaxial yield strengths and r-values versus the angle from the rolling direction. The Leacock 2006 UMAT was verified using two validation studies incorporating drawing and stretching modes of deformation. The Leacock 2006 UMAT provided an accurate prediction of the thickness and the punch force versus displacement in the stretching of the AA2024-T3. In particular, the Leacock 2006 UMAT exhibited the best quality of fit to the experimental major strain in the 0°, 45° and 90° orientations from the rolling direction for three depths of stretch. The Leacock 2006 UMAT also provided an earing profile prediction with an increased statistical accuracy over the Hill 1990 yield criterion of 31%, 40% and 14% for the experimental draw profiles of AA2024-0, AA6451-T4 and AA6111-T4 (NUMISHEET 2002 Benchmark A), respectively. The Leacock 2006 yield criterion has been shown to provide the best combination of earing profile and magnitude prediction over all other criteria considered with a similar minimal calibration cost.

The surface chemical properties of Sheet Molded Composite (SMC) materials, formulated to contain polyester binder, calcium carbonate filler, and glass fibers, have been investigated with emphasis on how the surface properties are related to adhesion. These surface properties, relative elemental concentratibns and their chemical states, were studied using x-ray photoelectron spectroscopy (XPS) before and after a series of surface treatments as well as after mechanical lap shear fracture tests for SMCs bonded with urethane adhesive. Surface chemical functionalities, including -C-0·R(X)/-NCOZR and -C=0 (ester carbonyl) groups, were found to promote good adhesion using urethane adhesives. These chemical functionalities_were particularly enhanced after treating the SMC surface with an isocyanate primer as well as after a solvent/abrasive surface pretreatment done with a Scotch Brite abrasive pad soaked in methylene chloride and after washing the SMC surfaces with hot aqueous chemicals at high pressures.
Master of Science

The work of this thesis centres around two related themes, the first being the characterization of the through-thickness inhomogeneity found in rolled sheet at various stages in its production. The second is involved with attempting to understand how and to what extent the existing inhomogeneity affects the correlations with the anisotropies of some physical or mechanical properties. For this, the inhomogeneity of six steels were measured.
Three were specimens removed from the sheet during the early processing of conventional grain-oriented ferrosilicon steel, one sample taken after the first cold rolling stage, another taken after the intermediate anneal, while the last was taken after the following stage, i.e. after the second cold rolling.
To contrast the extensive inhomogeneity expected in the ferrosilicon steels, the remaining three steels consisted of two continuous-annealed, interstitial-free, extra-low-carbon steels and one aluminum-killed, batch-annealed, low-carbon steel, all three of which are commercial final product, deep drawing steels.

The dimensional instability of metallic materials, following machining (or any method of material removal), is a common problem in the aerospace industry. This is because large parts have to be manufactured to very close tolerances and as much as 95% of the initial material may need to be removed. For machined, relatively complex, aerospace parts it would not be uncommon to see around 50% difference in the simulated results from the actual results, with even simple geometries showing around 19%-40% error. It is believed that a significant portion of these errors are due to a lack of: understanding of how the residual stresses redistribute following material removal; residual stress measuring capabilities; finite element (FE) modelling capabilities; knowledge of the additional residual stresses induced from the machining process (from varying cutting speeds, feed rates, tools, temperatures etc) and finally how the multiaxial residual stresses alter the shape of the part. This project improves the knowledge base of many of these topics. This work involved the development of an automated layer removal method for residual stress measurements in cold rolled sheet metal. This was needed due to the number of residual stress measurements that were required for modelling purposes. The method can determine the residual stresses in the rolling direction for cold rolled sheet material using a single strain gauge. Moreover, it is simple to set up and the total cost of the test rig and subsequent measurements is relatively low. Furthermore, in this project, a number of sheet metal aluminium parts were formed to different radii. The parts were then subsequently chemically milled in stages; the dimensional changes following each material removal being measured. This process was simulated using a commercially available FE package called PAM-STAMP. The FE results for distortion did not show good agreement when compared to the measured results; however, the residual stress measurements provided an unexpected understanding into the cause of the error. The results of the project improve the understanding of how residual stress change the shape of components and give an insight into the modelling parameters needed.

The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.

There is a need to monitor the existence and effects of damage in structural materials. Aircraft components provide a much publicized example, but the need exists in a variety of other structures, such as layered materials used in food packaging industries. While several techniques and models have been proposed for material characterization and condition monitoring of bulk materials, less attention has been devoted to thin sheets having no flexural rigidity. This study is therefore devoted to the development of a new method for acoustic Non-Destructive Testing (NDT) and material characterization of thin sheets used in food packaging materials or similar structures. A method for assessing the strength in the presence of crack of thin sheets used in food packaging is first presented using a modified Strip Yield Model (SYM). Resonance frequency measurement is then introduced and it is shown, at low frequency range (less than 2kHz), that a change in the physical properties such as a reduction in stiffness resulting from the onset of cracks or loosening of a connection causes detectable changes in the modal properties, specifically the resonance frequency. This observation leads to the implementation of a simple method for damage severity assessment on sheet materials, supported by a new theory illustrating the feasibility of the detection of inhomogeneity in form of added mass, as well as damage severity assessment, using a measurement of the frequency shift. A relationship is then established between the resonance frequency and the material’s elastic property, which yields a new modality for sheet materials remote characterization. The result of this study is the groundwork of a low-frequency vibration-based method with remote acoustic excitation and laser detection, for nondestructive testing and material characterization of sheet materials. The work also enhances the feasibility of the testing and condition monitoring of real structures in their operating environment, rather than laboratory tests of representative structures. The sensitivity of the new experimental approach used is liable to improvement while being high because the frequency measurement is one of the most accurate measurements in physics and metrology.

Doutoramento em Engenharia Mecânica
With the development of full-field measurements methods, recent material parameters identification strategies call upon the use of heterogeneous tests. The inhomogeneous strain fields developed during these tests lead to a more complete mechanical characterization of the sheet metals, allowing the substantial reduction of the number of tests in the experimental database needed for material parameters identification purposes. In the present work, an innovative design optimization process for the development of heterogeneous tests is presented. The main goal is the design of a mechanical test able to characterize the material behavior of thin metallic sheets under several stress and strain paths and amplitudes. To achieve this aim, the study was carried out with a virtual material, though derived from experimental data. An indicator of the mechanical interest of the test was proposed, and was used in an optimization procedure to design both the boundary conditions and the sample shape. On the one hand, the virtual behavior of a mild steel was characterized using a complex phenomenological model composed by the Yld2004-18p anisotropic yield criterion combined with a mixed isotropic-kinematic hardening law and a macroscopic rupture criterion. An efficient material parameters identification process based on finite element model updating type was implemented and the identified parameters set was validated by performing a deep drawing test leading either to full drawing or rupture of the blank. On the other hand, an indicator which rates the strain field of the experiment by quantifying the mechanical information of the test was formulated. The relevance of the indicator was stressed out by the numerical analysis of already known classical as well as heterogeneous tests and the results obtained were validated by a material parameter sensitivity study. Two different optimization approaches were used for designing the heterogeneous test, namely (i) a one-step procedure designing both specimen shape and loading path by using a tool and (ii) a sequential incremental technique designing the specimen shape and the loading path of the specimen considering local displacements. The results obtained revealed that the optimization approach proposed was very promising for designing a single experiment able to fully characterize the several strain paths and amplitudes encountered in sheet metal forming processes.
Devido ao desenvolvimento de métodos de medição global, recentes estratégias de identificação de parâmetros de material baseiam-se na informação obtida em testes mecânicos heterogéneos. Os campos de deformação desenvolvidos por estes testes permitem uma melhor caracterização mecânica de chapas metálicas, o que possibilita reduzir consideravelmente o número de testes mecânicos necessários num processo de identificação de parâmetros de modelos constitutivos complexos. No presente trabalho, uma metodologia de design recorrendo a optimização para desenvolver testes mecânicos heterógenos é apresentada. O seu principal objectivo consistiu na concepção de um teste mecânico capaz de caracterizar o comportamento mecânico de chapas metálicas para vários estados de tensão e deformação. Para isso, este estudo foi realizado considerando um material virtual obtido a partir de dados experimentais. Além disso, um indicador capaz de caracterizar testes mecânicos foi proposto para ser posteriormente utilizado na metodologia de optimização. Por um lado, o comportamento virtual de um aço macio foi caracterizado através de um modelo fenomenológico complexo composto pelo critério de plasticidade anisotrópico Yld2004-18p, combinado com uma lei de encruamento mista e com um critério macroscópico de ruptura. Para esta caracterização mecânica, um processo eficiente de identificação de parâmetros foi desenvolvido e o conjunto de parâmetros identificado foi validado comparando resultados experimentais e numéricos do processo de embutidura de um copo cilíndrico. Por outro lado, um indicador quantitativo para avaliar a informação do campo de deformação de testes mecânicos foi formulado e a sua performance foi avaliada através da análise numérica tanto de testes mecânicos clássicos como de testes heterogéneos. Relativamente à metodologia de optimização, duas abordagens diferentes foram consideradas para a concepção do teste mecânico heterógeno. A primeira abordagem consistiu num procedimento de etapa única projectando a forma do provete e o carregamento através da utilização de uma ferramenta. A segunda abordagem consistiu numa técnica incremental de varias etapas projectando a forma do provete e o caminho de deformação através da aplicação de carregamento por deslocamentos locais. Os resultados obtidos revelaram que a metodologia de optimização proposta permite a concepção de testes mecânicos capazes de caracterizar toda a gama de estados de deformação e níveis de deformação normalmente observados nos processos de conformação de chapas metálicas.
Grâce au développement des méthodes de mesure de champs, de nouvelles stratégies d’identification de paramètres matériau de lois de comportement mécanique sont proposées, fondées sur l’utilisation d’essais mécaniques hétérogènes. Les champs de déformation hétérogènes développés au cours de ces essais permettent une meilleure caractérisation du comportement mécanique des tôles métalliques et, par conséquent, de réduire considérablement le nombre d’essais nécessaires pour identifier les paramètres matériau de modèles phénoménologiques complexes. Mais comment concevoir ces essais? Dans ce travail, une méthodologie d’optimisation pour le développement d’essais mécaniques hétérogènes est présentée. L’objectif principal est la conception, par analyse inverse et en proposant un indicateur représentatif des états de déformation, d’un essai capable de caractériser le comportement mécanique des tôles métalliques pour plusieurs états de contrainte et déformation. Pour cela, cette étude a été réalisée en considérant un matériau virtuel (acier doux sous forme de tôle mince), obtenu à partir de données expérimentales. En outre, un indicateur qui caractérise les essais mécaniques a été proposé pour être utilisé dans la méthodologie d’optimisation. D’un côté, le comportement mécanique de l’acier doux a été représenté avec un modèle phénoménologique complexe composé du critère anisotrope de plasticité Yld2004-18p, combiné à une loi d’écrouissage mixte et un critère macroscopique de rupture. Pour cette loi de comportement, un procédé d’identification des paramètres du matériau a été développé et le jeu de paramètres identifiés a été validé en comparant des résultats expérimentaux et numériques de l’emboutissage d’un godet cylindrique. D’un autre côté, un indicateur quantitatif pour évaluer l’information du champ de déformation des essais mécaniques a été formulé et sa pertinence a été évaluée à travers l’analyse numérique d’essais classiques et hétérogènes de la littérature. Concernant la méthodologie d’optimisation, deux approches différentes ont été considérées pour la conception de l’essai mécanique hétérogène. La première approche est fondée sur une procédure en une seule étape, où l’optimisation de la forme de l’éprouvette et des conditions aux limites, imposées par un outil, a été effectuée. La seconde approche est fondée sur une technique incrémentale en plusieurs étapes, en optimisant la forme de l’éprouvette et le chemin de déformation, par l’application des déplacements locaux. Les résultats obtenus sont comparés et un essai est retenu pour identifier les paramètres matériau, en utilisant le matériau virtuel comme référence, afin d’illustrer la pertinence de la démarche.

The Caribbean steelpan is a pitched percussion instrument that originated in Trinidad and Tobago during the Second World War. Despite several research initiatives to improve the making of this relatively new instrument, several areas remain unaddressed. This thesis presents new approaches to help improve the making of the instrument. These approaches are situated in the production, vibration and material aspect of the steelpan. A novel sheet forming technology termed Incremental Sheet Forming (ISF) is applied to the production of miniature steelpan dishes. The thickness distribution in the wall of the ISF dishes is compared to the wall thickness distribution in a traditionally formed steelpan dish and a wheeled dish. Unlike traditional forming and wheeling, ISF produces stretching in only a portion of the walls of the formed dishes. Multi-pass ISF is used to extend the stretched zone but this extension is minimal. A break even analysis is also applied to investigate the fiscal viability of ISF application to the production of miniature and full size steelpan dishes. The application of ISF to steelpan making is found to be commercially profitable but could be jeopardised by the tuning stage of the steelpan making process. A preliminary study on the effect of impact on tone stability is conducted on a pair of notes on a fullsize steelpan and detuning is found more likely to occur by repeated impact of the note at its centre. Mode confinement in test-pans is also investigated. ISF is used to produce miniature test-pans with test-notes that are geometrically identical to notes on full size pans. It is possible to confine modes by varying the curvature of the bowl surrounding the test-note. The number of localised modes in the test-note increases as the radius of curvature of the surrounding bowl increases. The natural frequency of the first confined mode in the test-notes is sensitive to material springback in ISF and the mechanism of confinement appears to be due to the change in geometry that occurs between the flat test-note region and the bowl wall. This control of mode confinement may find use in future efforts to completely or partially automate the steelpan making process. Material damping and mechanical properties in low-carbon steel used to produce steelpans are researched. Damping and mechanical properties are extracted from low-carbon steel that is subjected to identical stages to the steelpan production process. Material damping trends suggest that an annealing temperature between 300°C and 400°C would be appropriate for the heat treatment of steelpans. Air-cooled and water-quenched low-carbon specimens exhibit comparable damping trends. Hardness increases in cold formed low-carbon specimens is attributed to strain hardening and not strain ageing. Investigation of damping trends and mechanical properties in ultra low bake-hardenable and interstitial-free steels reveals that a wider range of low-carbon steels may be suitable for steelpan making.

A steel slitting process is simulated using FEM (Finite Element Method) in order to see potential defects along the edge in a steel sheet after it has been cut. The model's results were compared to microscope images of the steel sheet in order to verify accuracy. The purpose is conceptual and to find a model that successfully simulates a steel cutting process and (hopefully) how the edge depends on different parameters. The model developed seems to achieve this task, and a more thorough calibration of the model could result in (more) optimal parameters for the machine to use.

Grâce au développement des méthodes de mesure de champs, de nouvelles stratégies d’identification de paramètres matériau de lois de comportement mécanique sont proposées, fondées sur l’utilisation d’essais mécaniques hétérogènes. Les champs de déformation hétérogènes développés au cours de ces essais permettent une meilleure caractérisation du comportement mécanique des tôles métalliques et, par conséquent, de réduire considérablement le nombre d’essais nécessaires pour identifier les paramètres matériau de modèles phénoménologiques complexes. Mais comment concevoir ces essais? Dans ce travail, une méthodologie d’optimisation pour le développement d’essais mécaniques hétérogènes est présentée. L’objectif principal est la conception, par analyse inverse et en proposant un indicateur représentatif des états de déformation, d’un essai capable de caractériser le comportement mécanique des tôles métalliques pour plusieurs états de contrainte et déformation. Pour cela, cette étude a été réalisée en considérant un matériau virtuel (acier doux sous forme de tôle mince), obtenu à partir de données expérimentales. En outre, un indicateur qui caractérise les essais mécaniques a été proposé pour être utilisé dans la méthodologie d’optimisation. D’un côté, le comportement mécanique de l’acier doux a été représenté avec un modèle phénoménologique complexe composé du critère anisotrope de plasticité Yld2004-18p, combiné à une loi d’écrouissage mixte et un critère macroscopique de rupture. Pour cette loi de comportement, un procédé d’identification des paramètres du matériau a été développé et le jeu de paramètres identifiés a été validé en comparant des résultats expérimentaux et numériques de l’emboutissage d’un godet cylindrique. D’un autre côté, un indicateur quantitatif pour évaluer l’information du champ de déformation des essais mécaniques a été formulé et sa pertinence a été évaluée à travers l’analyse numérique d’essais classiques et hétérogènes de la littérature. Concernant la méthodologie d’optimisation, deux approches différentes ont été considérées pour la conception de l’essai mécanique hétérogène. La première approche est fondée sur une procédure en une seule étape, où l’optimisation de la forme de l’éprouvette et des conditions aux limites, imposées par un outil, a été effectuée. La seconde approche est fondée sur une technique incrémentale en plusieurs étapes, en optimisant la forme de l’éprouvette et le chemin de déformation, par l’application des déplacements locaux. Les résultats obtenus sont comparés et un essai est retenu pour identifier les paramètres matériau, en utilisant le matériau virtuel comme référence, afin d’illustrer la pertinence de la démarche
With the development of full-field measurements methods, recent material parameters identification strategies call upon the use of heterogeneous tests. The inhomogeneous strain fields developed during these tests lead to a more complete mechanical characterization of the sheet metals, allowing the substantial reduction of the number of tests in the experimental database needed for material parameters identification purposes. In the present work, an innovative design optimization process for the development of heterogeneous tests is presented. The main goal is the design of a mechanical test able to characterize the material behavior of thin metallic sheets under several stress and strain paths and amplitudes. To achieve this aim, the study was carried out with a virtual material, though derived from experimental data. An indicator of the mechanical interest of the test was proposed, and was used in an optimization procedure to design both the boundary conditions and the sample shape. On the one hand, the virtual behavior of a mild steel was characterized using a complex phenomenological model composed by the Yld2004-18p anisotropic yield criterion combined with a mixed isotropic-kinematic hardening law and a macroscopic rupture criterion. An efficient material parameters identification process based on finite element model updating type was implemented and the identified parameters set was validated by performing a deep drawing test leading either to full drawing or rupture of the blank. On the other hand, an indicator which rates the strain field of the experiment by quantifying the mechanical information of the test was formulated. The relevance of the indicator was stressed out by the numerical analysis of already known classical as well as heterogeneous tests and the results obtained were validated by a material parameter sensitivity study. Two different optimization approaches were used for designing the heterogeneous test, namely (i) a one-step procedure designing both specimen shape and loading path by using a tool and (ii) a sequential incremental technique designing the specimen shape and the loading path of the specimen considering local displacements. The results obtained revealed that the optimization approach proposed was very promising for designing a single experiment able to fully characterize the several strain paths and amplitudes encountered in sheet metal forming processes

A formação de professores de Física e de Química, nomeadamente a formação académica no que concerne às áreas da Segurança e da Gestão de Laboratórios, é reduzida. Partindo desta realidade, e com a ambição de minimizar essa lacuna e auxiliar o desempenho dos professores, pretende-se produzir uma compilação legislativa essencial/fundamental nos laboratórios escolares complementada com o respetivo manual de segurança. Este trabalho consiste, assim, na compilação da legislação e do tipo de materiais a utilizar na construção e apetrechamento dos laboratórios, assim como das normas de segurança aplicadas. A consulta detalhada da legislação aplicada aos laboratórios escolares possibilita o bom funcionamento de um laboratório. Após a compilação das normas, da legislação e do tipo de materiais aplicados, elabora-se o manual tendo em atenção o que se conhece sobre laboratórios de Química e de Física; ABSTRACT: The training for teachers of Physics and Chemistry, in particular, academic education, with regard to the areas of Laboratory Security and Management, is quite limited. Based on this reality and aiming at minimizing this gap and assisting the teachers' performance, we intend to produce an essential legislative compilation for school laboratories complemented with its safety manual. Thus, the bulk of this work is the compilation of the legislation and the type of materials used in the construction and equipping of laboratories, as well as the safety standards applied. A detailed consultation on the legislation allows school laboratories the proper functioning. After the compilation of the rules, laws and types of materials used, the manual will be put into practice taking into account the Portuguese reality concerning the laboratories of Chemistry and Physics.

The project, developed under the terms of engineering studies of the M-STG Manufacturing Technology branch, presents the analytical assessment of the cutting surface of the metal sheet by two most commonly used modern technologies of cutting, which is the laser beam division and the exact cutting. The evaluation of this area was mainly focused on the level of the penetration of the zinc surface layer in the area of the given cutting. With the help of modern methods of electron microscopy, these values of penetration were then estabilished for each technology. The analysis itself was preceded by literary studies of all individual parts participating in this experiment.

Studien har genomförts på ett antal stålplåtar från olika kulturhistoriska byggnader. När kulturhistoriskt värdefulla byggnader ska renoveras måste detta göras med så god kunskap som möjligt om byggnadens olika delar och de värden dessa representerar. Det problem som studien har ämnat att lösa har varit en bristande kunskap om historiska stålplåtar. Studien har därför utförts för att bidra med kunskap som kan användas när gamla byggnader ska renoveras.För att uppnå syftet att bidra med kunskap som kan vägleda renovering av kulturhistoriska byggnader har studiens mål varit att undersöka hur de olika plåtarna tillverkats och vilka resultat de processerna har fått.Detta har genomförts genom att utföra en metallografi på samtliga prover för att undersöka deras mikrostrukturer och få en förståelse för materialen. Även en kemisk analys av materialens innehåll har gjorts genom en optisk emissions spektroskopi.De resultat som hämtades från plåtarna visade hur stor skillnad det var mellan olika tillverkningsmetoder och deras konsekvenser. Genom att ha sett den mångfald av egenskaper som fanns bland plåtarna har slutsatserna dragits att det finns ett värde i att respektera de äldre materialen.Genom att vara medveten om att det kan finnas stora skillnader i materialen kan valet av plåt göras på ett bättre sätt. Under studiens gång blev det även uppenbart hur mycket historia som fanns lagrad i de gamla plåtarna som är viktig att ta vara på.
The study has been conducted on a number of steel plates from different buildings of cultural and historical value. When old, cultural buildings are to be renovated, it must be done with as much knowledge as possible about the different parts of the building and the values that they represent. The problem that the study has aimed to solve has been an inadequate level of knowledge in regards to historical steel plates. Because of this, the study has been conducted to contribute with knowledge that could be used when old buildings are to be renovated.To achieve the purpose of contributing knowledge to guide renovations of culturally and historically valuable buildings, the goal of the study has been to analyze how the different plates have been made and what the results of those processes were.This has been carried out by conducting a metallography on all of the samples to analyze their microstructures and to gain an understanding of the materials. A chemical analysis has also been conducted on the contents of the materials by using optical emission spectroscopy.The results showed how big of a difference there was between different manufacturing methods and their consequences. By discovering the diversity of the properties of the plates the conclusion has been drawn that there is value in respecting the values of the older materials.By being conscious of how large the difference is between different types of steel sheets, better decisions can be made during choice of steel sheet, and it is more obvious how much history that is stored within the old plates.

Abstract

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.

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.

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.

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.

The electronic market is continually moving towards higher power densities. As a result, the demand on the cooling is increasing. Focus has to be put on the whole thermal management chain, from the component to be cooled to the ambient. Thermal interface materials are used to efficiently transfer heat between two mating surfaces or in some cases across larger gaps. There are several different thermal interface materials with various application areas, advantages and disadvantages. This study aimed to evaluate thermal and mechanical properties of graphite sheets and graphite gap pads. The work was done in cooperation with Ericsson AB. A test rig based on the ASTM D5470 standard was used to measure the thermal resistance and thermal conductivity of the materials at different pressures. It was found that several graphite sheets and gap pads performed better than the materials used in Ericsson’s products today. According to the tests, the thermal resistance could be reduced by about 50 % for the graphite sheets and 90 % for the graphite gap pads. That was also verified by placing the materials in a radio unit and comparing the results with a reference test. Both thermal values and mechanical values were better than for the reference materials. However, the long term reliability of graphite gap pads could be an issue and needs to be examined further.
Elektronikbranschen rör sig mot högre elektriska effektertätheter, det vill säga högre effekt per volymenhet. Som en följd av detta ökar också efterfrågan på god kylning. Kylningen måste hanteras på alla nivåer, från komponenten som ska kylas, ända ut till omgivningen. Termiska interface material (TIM) används för att förbättra värmeöverföringen mellan två ytor i kontakt med varandra eller för att leda värmen över större gap. Det finns flera olika TIM med olika tillämpningsområden, fördelar och nackdelar. Denna studie gick ut på att utvärdera termiska och mekaniska egenskaper hos grafitfilmer och så kallade ”graphite gap pads” då de används som TIM. Projektet gjordes i sammarbete med Ericsson AB. En testuppställning baserat på ASTM D5470-standarden användes för att utvärdera värmeledningsförmågan och den termiska resistansen hos de olika materialen vid olika trycknivåer. Resultaten visade att flera grafitfilmer och ”gap pads” presterade bättre än materialen som används Ericssons produkter idag. Enligt testerna skulle den termiska resistansen kunna minskas med 50 % för grafitfilmerna och 90 % för ”gap padsen”. Materialens fördelaktiga egenskaper verifierades i en radioenhet där temperaturerna kunde sänkas i jämförelse med ett referenstest med standard-TIM. De nya materialen var mjukare än referensmaterialen och skulle därför inte orsaka några mekaniska problem vid användning.  Den långsiktiga tillförlitligheten för grafitbaserade ”gap pads” måste dock undersökas vidare eftersom de elektriskt ledande materialen skulle kunna skapa kortslutningar på kretskorten.

Fibre-to-board is a simulation model developed at Stora Enso Research Centre Karlstad. Within this model isotropic hand sheet properties are used as input data for prediction of the final multi ply board properties. In order to improve and verify the calculations from simulations in Fibre-to-board so that these will correspond better with the results from the measurements on the paper/board machine, it was requested at RCK to investigate the possibility to optimize the input data to the model.

Standardized hand sheet forming always results in sheets with properties far away from those produced on a machine. Therefore the aim with this Master thesis was to modify the laboratory procedure to receive hand sheets with properties closer to machine sheets. To achieve this, it was investigated how different parameters affect the sheet properties and if the hand sheet making process could be improved.

When freely dried sheets were investigated it was found that sheets pressed with a wire clothing between the blotting paper and the hand sheet were less cockled than sheets pressed against only blotting papers. These sheets also tend to have a higher density. The cockling i.e. as a result from shrinkage was also reduced when the sheets were dried between slightly weighted wire clothing. Neither wire clothing nor orientated blotting papers during pressing eliminate the influence of anisotropic blotters on the shrinkage for isotropic hand sheets.

It was also examined how the fine material influences sheet properties. The results showed that an increase in fines content result in higher shrinkage, higher density, increased TSI, more cockling and decreased air permeability.

Different pressing loads and an increased density did not have much influence on the shrinkage. The density for freely dried sheets increased with higher load, but the results did not reach machine sheet densities, when the laboratory platen press was used. It might be difficult to receive freely dried hand sheets with higher densities. This is because fibres in freely dried sheets tend to relax after pressing, which will influence the density. Another press than the platen press used in these studies might compensate this matter. An increased pressing load resulted in less cockled sheets.

The basis weight did not seem to have that large affect on the shrinkage when using machine chest furnish, therefore the basis weight on hand sheets used as input data to the simulation model Fibre-to-board might not be that important.

It was studied how different plies and SW/CTMP pulp in a mixture affect the shrinkage. The results showed that the shrinkage increased with a higher SW content. It was also found that there is a linear relation between the total shrinkage of a SW/CTMP pulp mixture and the shrinkage for each individual pulp.

In order to verify the Fibre-to-board model a simulation finally was performed. Furnishes and CD profiles of board were collected from a particular board machine within the Stora Enso Group. Properties from hand sheets made of furnishes were used as input data and the machine CD profiles were used as references. The CD TSI value corresponded with the value received from measurements on the machine board, but the MD TSI value did not. The shrinkage calculated on machine sheets did not coincide with the shrinkage from the simulation in Fibre-to-board.

There are insecurities in the results from shrinkage measurement on the board CD profile due to the lack of width measurement during the process, which complicates the validation of the Fibre-to-board model.

Fibre to board är en simulerings modell framtagen vid Stora Enso Research Centre Karlstad. Modellen används för att prediktera krympning och styrkeegenskaper hos en bestämd kartongbana. Indata till modellen hämtas ifrån isotropa laboratorieark. För att förbättra och verifiera erhållna resultat från simuleringsmodellen så att de korresponderar bättre med värden från kartongmaskinen fanns det ett önskemål från RCK om att undersöka möjligheten att optimera indata till modellen.

Laboratoriearktillverkning enligt standard resulterar alltid i ark med egenskaper som ligger långt från maskin arkens. Därför är syftet med detta examensarbete att modifiera arktillverkningsmetoden så att laboratorieark med egenskaper närmare de för maskinark kan erhållas. För att lyckas med detta undersöktes det hur olika parametrar påverkar pappersegenskaperna och om tillverkningsmetoden kunde förbättras.

Vid undersökning av fritorkade ark upptäcktes att ark som pressats med viraduk mellan läskark och laboratorieark blev mindre buckliga än ark som pressats med enbart läskark. Dessa ark hade också en något högre densitet. Buckligheten som är en följd av krympningen reducerades också när arken torkades mellan viraduk under lätt belastning. Läskarkens inverkan på de isotropa arken kunde inte elimineras genom att använda viraduk vid pressning, inte heller genom att växla läskarken så att deras MD riktning orienterades olika.

Även finmaterialets inverkan på pappersegenskaperna undersöktes. Resultaten visade att ett ökat finmaterial innehåll ger ökad krympning, högre densitet, ökat dragstyvhetsindex, buckligare ark och en minskad luft permeabilitet.

Det visade sig att olika presstryck ger arken en högre densitet men krympningen påverkades inte märkbart. Densitet i samma nivå som på maskinark kunde däremot inte erhållas med laboratorieplanpress. Detta kan bero på att fibrerna i fritorkade ark relaxerar efter pressning, vilket ger en lägre densitet. För att kunna få högre densitet kanske en annan press än den planpress som användes i dessa studier kan införas. Det kunde även konstateras att ett ökat presstryck ger mindre buckliga ark.

I dessa studier, där ark tillverkades av färdiga skiktblandningar från maskinkar, hade inte ytvikten på arken någon större inverkan på krympningen. Detta tyder på att ytvikten på arken som används som indata inte har så stor inverkan vid simulering i modellen Fibre-to-board.

Det undersöktes även hur skikten i ett två-skikts ark och en blandning av LF/CTMP massa påverkar krympningen. Resultaten visade att krympningen ökar med en högre andel LF och att det finns ett linjärt samband mellan den totala krympningen för en blandning av LF/CTMP massa och krympningen för de enskilda massorna.

För att kunna verifiera beräkningsmodellen Fibre-to-board utfördes slutligen en simulering. Skiktblandningar och tvärsprofiler från kartong togs ut från en specifik pappers maskin inom Stora Enso koncernen. Egenskaperna på laboratorieark gjorda av skiktblandningarna användes som indata till simuleringsprogrammet och kartongprofilerna från pappersmaskinen användes som referens. Dragstyvhetsindex i CD stämde bra överens med de mätningar som gjordes på maskinarken, men dragstyvhetsindex i MD skiljde sig. Krympningen som beräknades på maskinarken överensstämde inte med det simulerade resultatet. Det förekommer en osäkerhet i krympmätningarna som gjordes på kartong profilerna, då det idag inte förekommer någon mätutrustning på pappersmaskinen, som bestämmer bredden mellan press- och torkpartiet. Detta komplicerar valideringen av Fibre-to-board modellen.

Infrared detector technologies have been developing each day. Thermal detectors take great attention in commercial applications due to their low power consumption and low costs. The active material selection and the deposition of the material are highly important performance effective factors for microbolometer detector applications. In that sense, developing vanadium oxide (VOx) microbolometer active material by sol-gel method might be feasible approach to achieve good performance microbolometer detectors. In this study, vanadium oxide thin films are prepared by sol-gel method is deposited on silicon or silicon nitride wafers as active material by spin coating. The films are annealed under different hydrogen concentration of H2/N2 environments at 410

Introduction: A mercury fact sheet that contains essential information and can be clearly understood by majority of adults is needed. In Fiscal Year 2009, EPA responded to more releases related to mercury than any other release. Since 2003, EPA has responded to more than 200 mercury releases. The American Association of Poison Control Centers estimate more than 50,000 people have been exposed to mercury vapors from 2003 to 2008, and 19,000 mercury cleanups have occurred from 2006 to 2008. Purpose: To determine what information needs to be included in a mercury fact sheet and how it should be created to inform adults who may be important in preventing and limiting exposure during accidental mercury release in the United States. Methods: The Flesch-Kincaid Grade Level Formula Data and the Suitability Assessment of Materials (SAM) tool were used to determine readability and appropriateness of twelve fact sheets related to elemental mercury. Length of fact sheets and illustration coverage percentage were also assessed. In addition, surveys were performed with four people who were involved in response to mercury releases in 2007 to 2009. The information they provided was also summarized to determine important elements that should be included in the fact sheets. Results: Information in a fact sheet should include the background of mercury, procedures in the event of a release, and ways to prevent releases. Based on the Flesch-Kincaid Grade Level, the literacy levels required to comprehend the 12 facts sheets was 11.4 on average. The majority of adults cannot comprehend the twelve fact sheets evaluated. Based on the evaluation of the material using SAM, none of the fact sheets scored higher than adequate with SAM. Only two fact sheets were written on one page and none of the fact sheets used relevant, simple illustrations with captions. Discussion: An effective mercury fact sheet needs to be about one page long and focuses on background, procedures, and prevention of exposure during a mercury release. Information obtained from interviews found that people focused the majority of their attention on the first page only. The fact sheet needs to be written at a sixth grade reading and to be able to receive a superior rating when assessed with SAM. This will ensure that the fact sheet is readable and comprehendible by the majority of adults and include the necessary information that the public must know regarding mercury. A new fact sheet was developed and assessed using both Flesch-Kincaid level and SAM and was found to have a 6.6 reading grade level and received a superior score under SAM. This fact sheet will be used by EPA along with the existing more comprehensive fact sheets at state agencies, and poison control centers for future releases and will be given to schools to educate and prevent future releases.

Unconventional technologies and their continual development brings along new possibilities in the manufacturing process. The submitted project is focused on solving problems in the procession of sheet metals in the manufacture of special parts of roller and conveyor chains. In the assessment of the technology of components, laser cutting was evaluated as the most optimal technology. With this goal, there was a public tender in terms of the purchase of a new machine designed for the manufacturing operations of the company of RETEZY Vamberk. This company ranks among the most major manufacturers of conveyor, roller and special chains in Europe.

Thesis (Ph. D. of Philosophy)--University of Western Sydney, Hawkesbury, 1997.
"A thesis submitted to the School of Agriculture and Rural Development, Faculty of Agriculture and Horticulture, University of Western Sydney Hawkesbury, in part fulfilment of the requirements for the Degree of Doctor of Philosophy." Includes bibliographical references (p. 236-267).

The main purpose of this project is to investigate different tool steels in terms of their ability to withstand material transfer buildup, so-called galling, occurring in SMF (sheet metal forming) operations. The ability to withstand galling is vital to optimize cost-effectiveness and increase the work tool’s effective operational time. This investigation studies four different tool steels, including a TiN-coating, with the intention of evaluating the microstructures, chemical composition and hardness effect on galling resistance in dry conditions using a slider-on-flatsurface (SOFS) tribo-tester which measures the coefficient of friction during sliding.

An OP (optical profilometer) was used to measure the size and geometry of lump growth on the tool and damage on the work sheet. A scanning electron microscope (SEM) was used to identify the interacting tribological mechanisms exhibited at different stages during the slide. The SEM figures confirmed three different types of characteristic patterns exhibited in the tracks after tribo- testing which were categorized as mild adhesive, abrasive and severe adhesive damage.

A SEM figure that illustrates a ragged contact surface and an obvious change in the sheet materials plastic behavior is in this report regarded as a sign of severe adhesive contact, the characteristics could possibly be explained by local high temperature and high pressure followed by a sudden pressure drop and creation of hardened welds or solders between the two surfaces which increase the frictional input needed for further advancement. Friction coefficients observed in the initial 100% mild adhesive stage were, μ=0,22-0,26 succeeded by abrasive SEM characteristics often in association with mild adhesive contact and friction values between μ=0,25-0,4 which where sometimes followed by severe adhesive SEM characteristics in 100% of the contact zone with friction values between μ=0,34- 0,9 respectively. The tool material that performed best according to the friction detection criteria was Sv21 closely followed by Sleipner (TiN coated) and Va40 (HRC 63.3). Unfortunately was the friction criteria, a significant raise in friction for defining a sliding length to galling, not adequate for dry conditions due to immediate material transfer succeeded by cyclic changes between partial or 100% abrasive+mild adhesive and severe adhesive contact. The mechanism that change abrasive wear in association with mild adhesive contact, (moderate friction input), to sever adhesive wear, (higher friction input), is dependent on lump shape (lump geometry) and can appear at comparably low speeds 0,04-0,08 [m/s] and low friction energy input (μ=0,34), the magnitude of the change in friction is therefore not always significant and hardly detectable on the friction graph. This was quite unexpected but could be explained by concentration of friction energy rater than the absolute amount. The problem with using friction graphs for galling evaluation was increased even further when a very small lump size and low corresponding rate of material transfer to the tool surface caused a sustainable high raise in friction (μ≈0,3→0,6) on a TiN-coated tool steel called Sleipner.

A hardly detectable or similar friction raise for Sv21 and Va40 showed much larger corresponding lump size and rate of material transfer. This means that friction graphs demonstrate a clear problem with quantifying lump size [m3] and rate of  material transfer [m3/s]. Another phenomenon called stick slip behavior, material transfer and lump growth followed by a sudden decrease in lump size and transfer of material back to the work sheet, is also not possible to detect on a friction graph. Because a drop in friction can easily be a change in contact temperature and lump attack angle due to a growing lump and not a decreasing lump.

 

The conclusion, a friction graph is not suited for galling evaluation and ranking in dry SOFS conditions. A ranking should primarily be based on dimensional OP measurements of the cross section of formed tracks and scratches or preferably by repeated OP measurements of the tool surface during a single test, the last revel the exact lump growth history and true lump growth even in the sliding direction.

 

civilingenjörsexamen

Numerische Prozessanalysen werden heute standardmäßig zur virtuellen Prozessabsicherung der Herstellung umgeformter Blechformteile eingesetzt. Die dabei notwendige hohe Prognosegüte kann nur mit einer hinreichend präzisen Materialmodellierung realisiert werden. Ein wesentlicher Aspekt ist dabei die Modellierung des Fließverhaltens und der Werkstoffanisotropie. Zur Charakterisierung des Werkstoffverhaltens existieren zahlreiche Versuchs- und Auswertestrategien; diese werden aufgrund des hohen Versuchs- und Rechenaufwands in der industriellen Anwendung jedoch nur vereinzelt eingesetzt. Im Rahmen dieser Arbeit wird eine neuentwickelte halbanalytische Methode zur Charakterisierung von Fließortkurven sowie der Folgefließortkurven vorgestellt. Dazu wurde eine Spannungsanalyse auf Messdaten einer digitalen Bildkorrelation sowie ein Schnittlinienansatz zur Berechnung innerer Kräfte entwickelt. Durch Bilanzierung dieser inneren Schnittkräfte mit gemessenen äußeren Prüfkräften werden Parameter eines gewählten Materialmodells in einer inversen Analyse identifiziert. Die Methode zur Parameteridentifikation wurde zunächst an synthetischen und anschließend an realen Experimenten untersucht. Es wurde eine sequentielle Identifikationsstrategie aufgestellt, die an den Blechwerkstoffen DX54, DP600 sowie AA5182 untersucht wurde. Abschließend wurde die Methode mithilfe von Validierungsversuchen hinsichtlich der identifizierten Materialantworten überprüft.:Inhaltsverzeichnis I Symbolverzeichnis IV Abkürzungen und Begriffe VIII 1 Einleitung 1 2 Stand der Technik 3 2.1 Grundlagen zur Umformung von Blechwerkstoffen 3 2.1.1 Umformprozesse zur Herstellung von Blechformteilen 3 2.1.2 Anforderungen bei der Herstellung von Blechbauteilen 4 2.2 Numerische Prozessauslegung von Blechumformoperationen 5 2.2.1 Anwendung der FEM als Hilfsmittel in der Prozessauslegung 5 2.2.2 Kritische Punkte der numerischen Prozessauslegung 7 2.3 Werkstoffverhalten und Materialmodellierung 8 2.3.1 Kenngrößen zur Beschreibung großer Deformation 8 2.3.2 Grundlagen zur Beschreibung elastoplastischen Materialverhaltens 9 2.3.3 Beschreibung der Verfestigungsregel in Materialmodellen 11 2.3.4 Modellierung anisotroper Fließortkurven 12 2.3.5 Modellierung der Fließortkurvenentwicklung 18 2.3.6 Zusammenfassende Hinweise zu den Fließkriterien 25 2.4 Kennwertermittlung und Werkstoffcharakterisierung 26 2.4.1 Experimentelle Methoden und analytische Verfahren zur Fließortkurvenermittlung 26 2.4.2 Erweiterte Messtechnik zur Identifikation von Fließortkurven 33 2.4.3 Inverse Strategien zur Identifikation von Fließortkurven 36 2.5 Zusammenfassung zum Stand der Technik 43 3 Zielsetzung und Vorgehensweise 45 3.1 Zielsetzung 45 3.2 Vorgehensweise 45 4 Experimentelle Versuchsdurchführung 47 4.1 Versuchsaufbau und Messtechnik 47 4.2 Prüfverfahren zur Werkstoffprüfung 48 4.2.1 Zugversuch 49 4.2.2 Kerbzugversuch 49 4.2.3 Scherzugversuch 49 4.2.4 Biaxialer Zugversuch 50 4.3 Wahl der Versuchswerkstoffe 51 4.3.1 Kaltgewalzter Tiefziehstahl DX54 51 4.3.2 Kaltgewalzter Dualphasenstahl DP600 52 4.3.3 Aluminiumknetlegierung AA5182 52 4.4 Messergebnisse aus den Werkstoffprüfungen 53 4.5 Zusammenfassung zur Versuchsdurchführung 55 5 Entwicklung einer halbanalytischen Methode zur Parameteridentifikation 56 5.1 Spannungsanalyse 56 5.1.1 Spannungsrichtung 57 5.1.2 Spannungszuwachs 58 5.1.3 Elastische Kompensation 59 5.2 Schnittkraftermittlung 60 5.3 Inverse Analyse 62 5.4 Zusammenfassende Darstellung der Entwicklung 64 6 Validierung der Methode an virtuellen Experimenten 67 6.1 Virtuelle Versuche 67 6.2 Validierung der Spannungsanalyse 68 6.2.1 Vorgehensweise zur Prüfung der Spannungsanalyse 69 6.2.2 Ergebnisse der Überprüfung der Spannungsanalyse 70 6.3 Validierung der Schnittkraftermittlung 76 6.4 Sensitivität der Materialantwort gegenüber den Materialparametern 80 6.4.1 Einfluss variierender Fließkurvenapproximationen 80 6.4.2 Einfluss variierender Fließortkurven 82 6.5 Diskussion zur Wahl geeigneter Schnittlinien 88 6.6 Fehlerbetrachtung 89
Numerical process analysis is widely used today for the virtual process validation of the production of formed sheet metal parts. In this context, sufficiently precise material modeling is essential, especially for the flow behavior and the material anisotropy. Numerous test and evaluation strategies are known for the material characterization. However, these strategies are only used occasionally in industrial applications due to high experimental and computational costs. In the context of this work, a newly developed semi-analytical method for the characterization of yield locus curves and subsequent yield locus curves is presented. For this purpose, a stress analysis based on digital image correlation data and a cutting-line approach for internal forces computation was developed. By balancing these internal cutting forces with measured external test forces, parameters of a material model are identified in an inverse analysis. The method for parameter identification was first examined on synthetic and subsequently on real experiments. A sequential identification strategy was set up and examined on the sheet metal materials DX54, DP600 and AA5182. Finally, the method was checked using validation tests with regard to the identified material responses.:Inhaltsverzeichnis I Symbolverzeichnis IV Abkürzungen und Begriffe VIII 1 Einleitung 1 2 Stand der Technik 3 2.1 Grundlagen zur Umformung von Blechwerkstoffen 3 2.1.1 Umformprozesse zur Herstellung von Blechformteilen 3 2.1.2 Anforderungen bei der Herstellung von Blechbauteilen 4 2.2 Numerische Prozessauslegung von Blechumformoperationen 5 2.2.1 Anwendung der FEM als Hilfsmittel in der Prozessauslegung 5 2.2.2 Kritische Punkte der numerischen Prozessauslegung 7 2.3 Werkstoffverhalten und Materialmodellierung 8 2.3.1 Kenngrößen zur Beschreibung großer Deformation 8 2.3.2 Grundlagen zur Beschreibung elastoplastischen Materialverhaltens 9 2.3.3 Beschreibung der Verfestigungsregel in Materialmodellen 11 2.3.4 Modellierung anisotroper Fließortkurven 12 2.3.5 Modellierung der Fließortkurvenentwicklung 18 2.3.6 Zusammenfassende Hinweise zu den Fließkriterien 25 2.4 Kennwertermittlung und Werkstoffcharakterisierung 26 2.4.1 Experimentelle Methoden und analytische Verfahren zur Fließortkurvenermittlung 26 2.4.2 Erweiterte Messtechnik zur Identifikation von Fließortkurven 33 2.4.3 Inverse Strategien zur Identifikation von Fließortkurven 36 2.5 Zusammenfassung zum Stand der Technik 43 3 Zielsetzung und Vorgehensweise 45 3.1 Zielsetzung 45 3.2 Vorgehensweise 45 4 Experimentelle Versuchsdurchführung 47 4.1 Versuchsaufbau und Messtechnik 47 4.2 Prüfverfahren zur Werkstoffprüfung 48 4.2.1 Zugversuch 49 4.2.2 Kerbzugversuch 49 4.2.3 Scherzugversuch 49 4.2.4 Biaxialer Zugversuch 50 4.3 Wahl der Versuchswerkstoffe 51 4.3.1 Kaltgewalzter Tiefziehstahl DX54 51 4.3.2 Kaltgewalzter Dualphasenstahl DP600 52 4.3.3 Aluminiumknetlegierung AA5182 52 4.4 Messergebnisse aus den Werkstoffprüfungen 53 4.5 Zusammenfassung zur Versuchsdurchführung 55 5 Entwicklung einer halbanalytischen Methode zur Parameteridentifikation 56 5.1 Spannungsanalyse 56 5.1.1 Spannungsrichtung 57 5.1.2 Spannungszuwachs 58 5.1.3 Elastische Kompensation 59 5.2 Schnittkraftermittlung 60 5.3 Inverse Analyse 62 5.4 Zusammenfassende Darstellung der Entwicklung 64 6 Validierung der Methode an virtuellen Experimenten 67 6.1 Virtuelle Versuche 67 6.2 Validierung der Spannungsanalyse 68 6.2.1 Vorgehensweise zur Prüfung der Spannungsanalyse 69 6.2.2 Ergebnisse der Überprüfung der Spannungsanalyse 70 6.3 Validierung der Schnittkraftermittlung 76 6.4 Sensitivität der Materialantwort gegenüber den Materialparametern 80 6.4.1 Einfluss variierender Fließkurvenapproximationen 80 6.4.2 Einfluss variierender Fließortkurven 82 6.5 Diskussion zur Wahl geeigneter Schnittlinien 88 6.6 Fehlerbetrachtung 89