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  • 1.
    Andreasson, Eskil
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Lindström, Tommy
    Lunds Universitet, SWE.
    Käck, Britta
    Altair Engineering AB, SWE.
    Malmberg, Christoffer
    Saab AB, SWE.
    Asp, Ann Magret
    Tetra Pak AB, SWE.
    Simulation of thin aluminium-foil in the packaging industry2017In: AIP Conference Proceedings / [ed] Brabazon D.,Ul Ahad I.,Naher S., American Institute of Physics Inc. , 2017, Vol. 1896, article id 160014Conference paper (Refereed)
    Abstract [en]

    This work present an approach of how to account for the anisotropic mechanical material behaviour in the simulation models of the thin aluminium foil layer (≈10 μm) used in the Packaging Industry. Furthermore, the experimental results from uniaxial tensile tests are parameterised into an analytical expression and the slope of the hardening subsequently extended way beyond the experimental data points. This in order to accommodate the locally high stresses present in the experiments at the neck formation. An analytical expression, denominated Ramberg-Osgood, is used to describe the non-linear mechanical behaviour. Moreover it is possible with a direct method to translate the experimental uniaxial tensile test results into useful numerical material model parameters in Abaqus™. In addition to this the extended material behaviour including the plastic flow i.e. hardening, valid after onset of localisation, the described procedure can also capture the microscopic events, i.e. geometrical thinning, ongoing in the deformation of the aluminium foil. This method has earlier successfully been applied by Petri Mäkelä for paperboard material [1]. The engineering sound and parameterised description of the mechanical material behaviour facilitates an efficient categorisation of different aluminium foil alloys and aid the identification of the correct anisotropic (RD/TD/45°) mechanical material behaviour derived from the physical testing. © 2017 Author(s).

  • 2.
    Devotta, Ashwin Morris
    et al.
    Sandvik Coromant Sverige AB, SWE.
    Sivaprasad, Palla Venkata
    Sandvik Materials Technology, SWE.
    Beno, Tomas
    Högskolan Väst, SWE.
    Eynian, Mahdi
    Högskolan Väst, SWE.
    Hjertig, Kjell
    Högskolan Väst, SWE.
    Magnevall, Martin
    Lundblad, Mikael
    Sandvik Coromant Sverige AB, SWE.
    A modified johnson-cook model for ferritic-pearlitic steel in dynamic strain aging regime2019In: Metals, ISSN 2075-4701, Vol. 9, no 5, article id 528Article in journal (Refereed)
    Abstract [en]

    In this study, the flow stress behavior of ferritic-pearlitic steel (C45E steel) is investigated through isothermal compression testing at different strain rates (1 s-1, 5 s-1, and 60 s-1) and temperatures ranging from 200 to 700 °C. The stress-strain curves obtained from experimental testing were post-processed to obtain true stress-true plastic strain curves. To fit the experimental data to well-known material models, Johnson-Cook (J-C) model was investigated and found to have a poor fit. Analysis of the flow stress as a function of temperature and strain rate showed that among other deformation mechanisms dynamic strain aging mechanism was active between the temperature range 200 and 400 °C for varying strain rates and J-C model is unable to capture this phenomenon. This lead to the need to modify the J-C model for the material under investigation. Therefore, the original J-C model parameters A, B and n are modified using the polynomial equation to capture its dependence on temperature and strain rate. The results show the ability of the modified J-C model to describe the flow behavior satisfactorily while dynamic strain aging was operative. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

  • 3.
    Falk, Johannes
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Fracture prediction of stretched shear cut edges in sheets made of Dual-Phase steel2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Dual-Phase (DP) steels, part of the group of Advanced High Strength Steels (AHSS), are used by car manufactures due to its large strength to weight ratio. The high strength of the DP steel does have a negative impact on the formability during sheet metal forming and stretch forming, e.g. fractures often appear in shear cut edges during forming of blanks made of DP steel.

     

    The main objective with this thesis is to develop a new punch for Volvo Cars that concentrates the strain to the sheared edges of a test specimen made from different types of DP steel. This is done to be able to measure and obtain maximum fracture strain during stretch forming tests in a press. The newly developed test method is called CTEST (Concentrated Trim Edge Strain Test).

     

    The tests are performed with DP steel specimens with three different qualities of the shear cut edges; fine cut, medium cut and worn cut. DP steels tested are DP600GI, DP600UC and DP800GI from three different suppliers. 10 different types of DP steels are tested in this study with different thickness. Thickness of specimens tested are 1 mm, 1.1 mm, 1.5 mm and 2 mm and all specimens tested have a lengthwise (RD) rolling direction.

     

    The quality of the sheared cut edge has a great impact to the formability and maximum fracture strain of the specimen. A specimen with a fine cut endures higher fracture strain than medium cut and a worn cut for all types of DP steel with different thickness. A 1 mm thick specimen endures a lower fracture strain than 1.5 mm and 2 mm specimen for all cut qualities.

     

    Further, the impact of the orientation of the burr zone of a shear cut edge is studied. With the burr zone facing upwards from the CTEST punch the formability of the specimens is decreased compared to a burr zone facing downwards, especially for a worn cut specimen with micro cracks and imperfections in the edge surface.

     

    ARAMIS Digital Image Correlation (DIC) system is used to analyze the specimen edges during press experiments. The ARAMIS results unveil that several small fractures appear in the sheared edges of a specimen just before the specimens split into two pieces. This phenomenon was seen for specimen with worn and medium shear cut qualities.

     

    Finite Element (FE) simulations of the CTEST is performed in AutoForm to determine maximum values of the true strain for the three different cut qualities. The simulation in AutoForm does show a slightly higher value of the force and press depth than the value from the press test before maximum fracture strain in reached. The small fractures seen in ARAMIS just before the specimen split into two pieces cannot be seen in the simulation in AutoForm.

  • 4.
    Karlsson, Hampus
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Karlsson, Anton
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Konceptutveckling av en caterpillar med inriktning på kvalitet: En utvecklingsprocess2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When transporting a sea cable, what is commonly called a caterpillar is used, but the most common said is a cable tensioner. These machines can be found in a flurry of different variants, where there are a multitude of competitors, which applies demands to having an extremely distinctive machine. Therefore  from  a  market  analysis  it  have  been  identified  that  a  lack  of  quality  regarding  the machines are a factor. A poor quality shortage that usually occurs in hard weather conditions, but this is something that should not happen as it may lead to machine breakdown.

    Semcon AB in Karlskrona constructs and then collaborates with Ronneby Svets & Smide, who manufacture cable carousels, armrests and other equipment for the cable industry but not the cable tensioner that are ordered separately by external companies. This is the background to why the project is created because Semcon sees a need to eliminate this bottleneck and also expand their product portfolio for customer recovery. The aim it therefore, together with Semcon, develop a new concept for a completely  new cable tensioner with given preferences, rough drawing and selection of qualitative features for the machine in order to be competitive with its future overall solution for the cable industry.   

    To find a solution to the described problem, a product development process has been followed to establish  structure.  The  process  include  a  planning,  concept  development,  design  and  detailed development phase. From the first phase, a wide understanding of how the complex machine works and where its deficiencies may be. Even hidden customer needs in form of interviews with cable manufacturers in Karlskrona and with industries that handle sea cable were conducted to get a broader spectrum. The needs are transformed into specifications to generate concepts based on the rankings of the measurably formulated specifications. Followed up by an evaluation where the best concepts were taken to the design phase and detailed development. All design calculations have been made, either by hand or with computer-based programs.  

    The work has resulted in an innovative concept of a whole cable tensioner with all key components, rough drawing, together with a new thinking solution regarding the contact face between the cable and the machine, developed through experiments and theory studies. As this project is very broad, the overall project has been divided into two master thesis works and all electronics are handles by  an  electrical/automation  company.  Therefore,  for  a  broader  understanding  and  information about functionality, reference is made to the second project “Konceptutveckling kring funktionerna hos en kabeldragare” authored by Anton Hansson.  

    It is extremely important to mention that the outcome of this project is intended to be a concept for a new innovative cable tensioner. This means that with future work on the concept, which includes  continued  depth  of  calculation  and  further  contact  with  suppliers,  can  provide  an opportunity  to  manufacture  the  generated  concept.  Another  development  area  Semcon  must proceed with is to review the safety routines of the machine. The authors of this report believe that a highly competitive solution has been presented, and that work contributes to a strong foundation for  the  development  of  transporting  sea  cable  technology  in  the  future  with  the  help  of  this innovative concept.

  • 5.
    R Lacno, Jeronimo
    Blekinge Institute of Technology. Höganäs AB.
    Förbättrad korrosionmetod för Höganäs AB lödningslegeringar2017Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    This report summarizes and compares two different corrosion methods, Höganäs internal corrosion test and a corrosion test according to VDA 230-214. The goal has been to develop a new method that solves Höganäs problems with repeatability with these two tests as a background. By carefully studying the process of brazing, acid preparation, corrosion testing for 4 weeks and the microstructure testing process on the brazed joint, you have managed to get a quantitative result.

    The improvement of the internal corrosion method was chosen to be based on the sulfuric acid and preparing acid solutions by controlling the pH value between an aggressive and a less aggressive value. It was also chosen to compare two products that has the same corrosion properties, Brazelet F300 and Brazelet Ni613. The difference between F300 and Ni613 is that the F300 contains iron and less nickel. Previous investigations have been made to compare these products but have shown different results.

    This investigation has led to a method of quantifying the corrosion resistance of the different brazing instead of only visually judging whether the corrosion resistance is good or bad. This method will be used for future work to investigate other acids.

  • 6.
    Sigvant, Mats
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Pilthammar, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Hol, Jeroen
    TriboForm Engineering, NLD.
    Wiebenga, J. H.
    TriboForm Engineering, NLD.
    Chezan, T.
    Tata Steel, NLD.
    Carleer, Bart
    AutoForm Engineering, DEU.
    Van Den Boogaard, A. H.
    University of Twente, NLD.
    Friction and lubrication modeling in sheet metal forming simulations of a Volvo XC90 inner door2016In: IOP Conference Series: Materials Science and Engineering, 2016, Vol. 159, no 1, article id 012021Conference paper (Refereed)
    Abstract [en]

    The quality of sheet metal formed parts is strongly dependent on the tribology, friction and lubrication conditions that are acting in the actual production process. Although friction is of key importance, it is currently not considered in detail in stamping simulations. This paper presents a selection of results considering friction and lubrication modeling in sheet metal forming simulations of the Volvo XC90 right rear door inner. For this purpose, the TriboForm software is used in combination with the AutoForm software. Validation of the simulation results is performed using door inner parts taken from the press line in a full-scale production run. The results demonstrate the improved prediction accuracy of stamping simulations by accounting for accurate friction and lubrication conditions, and the strong influence of friction conditions on both the part quality and the overall production stability. © Published under licence by IOP Publishing Ltd.

  • 7.
    Tabourot, Laurent
    et al.
    Universite Savoie Mont Blanc, FRA.
    Charleux, Ludovic
    Universite Savoie Mont Blanc, FRA.
    Balland, Pascale
    Universite Savoie Mont Blanc, FRA.
    Sène, Ndèye Awa
    Universite Cheikh Anta Diop, SEN.
    Andreasson, Eskil
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Experimental characterization and microstructure linked modeling of mechanical behavior of ultra-thin aluminum foils used in packaging2018In: PROCEEDINGS OF 21ST INTERNATIONAL ESAFORM CONFERENCE ON MATERIAL FORMING (ESAFORM 2018), American Institute of Physics Inc. , 2018, Vol. 1960, article id UNSP 170016Conference paper (Refereed)
    Abstract [en]

    This paper is based on the hypothesis that introducing distribution of mechanical properties is beneficial for modeling all kinds of mechanical behavior, even of ordinary metallic materials. To bring proof of its admissibility, it has to be first shown that modeling based on this assertion is able to efficiently describe standard mechanical behavior of materials. Searching for typical study case, it has been assessed that at a low scale, yield stresses could be strongly distributed in ultrathin aluminum foils used in packaging industry, offering opportunities to identifying their distribution and showing its role on the mechanical properties. Considering initially reduced modeling allow to establish a valuable connection between the hardening curve and the distribution of local yield stresses. This serves for finding initial value of distribution parameters in a more sophisticated identification procedure. With finally limited number of representative classes of local yield stresses, concretely 3 is enough, it is shown that a 3D finite element simulation involving limited numbers of elements returns realistic behavior of an ultrathin aluminum foil exerted to tensile test, in reference to experimental results. This gives way to large possibilities in modeling in order to give back complex experimental evidence. © 2018 Author(s).

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