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  • 1.
    Asnafi, Nader
    Sapa Technology, Finspång (and Vetlanda), Sweden.
    Analytical modelling of the forces and pressures required in hydropiercing2000Report (Other academic)
  • 2.
    Asnafi, Nader
    Sapa Technology, Finspång (and Vetlanda), Sweden .
    Automotive Tubular Hydroforming: Fundmentals and Industrial Practice2000Conference paper (Other academic)
  • 3.
    Asnafi, Nader
    Luleå University of Technology, Luleå, Sweden .
    Formbarhet under dragpressning, sträckpressning och bockning samt egenskaper efter formning av aluminiumplåt1988Report (Other academic)
  • 4.
    Asnafi, Nader
    Volvo Car Corporation, Göteborg (and Olofström), Sweden .
    Forming of Aluminium2002Conference paper (Other academic)
  • 5.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Hydroformability of Extra High Strength Steels in Structural Tubular Applications: an Analysis based on Literature Survey1997Report (Other academic)
  • 6.
    Asnafi, Nader
    Örebro University, School of Science and Technology.
    Innovative Lead Time and Cost Efficient Tools and Dies for Lightweight Autobody Components2016Conference paper (Other academic)
  • 7.
    Asnafi, Nader
    Volvo Car Corporation, Göteborg (and Olofström), Sweden .
    Manufacturing the car body of tomorrow2002Conference paper (Other academic)
  • 8.
    Asnafi, Nader
    Volvo Car Corporation, Göteborg (and Olofström), Sweden .
    Nya material och processer vid framtagning av lättviktskarosser2004Conference paper (Other academic)
  • 9.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden .
    On Prediction of the Yield Strength of Pressed Panels by Using the Tensile Behaviour of the Virgin Material1992Conference paper (Other academic)
  • 10.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    On Springback of Double-Curved Autobody Panels, Part I: Theoretical Treatment1996Report (Other academic)
  • 11.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    On Springback of Double-Curved Autobody Panels, Part II: Experimental Analysis1996Report (Other academic)
  • 12.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden .
    On strength, stiffness and dent resistance of car body panels1995In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 49, no 1-2, p. 13-31Article in journal (Refereed)
    Abstract [en]

    There are cases in which practitioners wish to be able to predict the properties of a panel, should they replace one material by another. In this study, the yield strength, stiffness and dent resistance of double-curvature car body panels are treated both theoretically and experimentally. The results of the investigation show that the above-mentioned properties of a pressed panel can be predicted provided that the magnitude of the principal surface strains and the magnitude of the panel radii at the panel centre are known.

  • 13.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    On Strength, Stiffness and Dent Resistance of Car Body Panels1993Report (Other academic)
  • 14.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    On Strength, Stiffness and Dent Resistance of Car Body Panels1993Conference paper (Other academic)
  • 15.
    Asnafi, Nader
    Gränges Technology, Finspång, Sweden.
    On stretch and shrink flanging of sheet aluminium by fluid forming1999In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 96, no 1-3, p. 198-214Article in journal (Refereed)
    Abstract [en]

    In this investigation, vertical stretch and shrink flanging of sheet aluminium by fluid forming are studied experimentally and theoretically. The theoretical part comprises both analytical modelling and finite-element simulations.

    The fracture limit in stretch flanging is determined by the plastic strain ratio, the strain hardening exponent, and the uniform strain. The greater the magnitude of these parameters, the greater will be the fracture limit.

    The maximum applied pressure determines the ’wrinkling’ limit in shrink flanging by fluid forming. The greater is this pressure, the greater ’wrinkling’ limit. This limit is certainly several times greater in magnitude than that in shrink flanging by conventional tools (a rigid punch and die).

  • 16.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    On Stretch and Shrink Flanging of Sheet Aluminium by Fluid Forming1996Report (Other academic)
  • 17.
    Asnafi, Nader
    Industrial Development Center/Volvo Cars Body Components, Olofström, Sweden .
    On Stretch and Shrink Flanging of Sheet Aluminium by Fluid Forming1998In: Proceedings, working groups meeting - IDDRG, International Deep Drawing Research Group: Genval, Benelux, June 15 - 16, 1998, 1998Conference paper (Other academic)
  • 18.
    Asnafi, Nader
    Industrial Development Centre, Olofström, Sweden.
    On tool stresses in cold heading of fasteners1999In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 6, no 5, p. 321-335Article in journal (Refereed)
    Abstract [en]

    In this investigation, attention was focused on the tool stresses that emerge during manufacturing of fasteners. These stresses were studied both experimentally and theoretically. The theoretical part comprised finite-element simulation. This simulation showed that the zone at the die insert profile radius is so heavily loaded that plastic deformation is initiated in this region. In the experimental part, the emerging strains were measured in the region close to the interface between the die insert and the stress ring. The correspondence is good between the theoretical and experimental strains in this region. In spite of this and although 20 fasteners were cold-forged, the die insert did not fracture. Forming at production facilities showed that the die insert cracked after 9080 parts were produced. The results obtained in this investigation and the test conducted at production facilities indicate that high cycle fatigue, and not monotomic rupture, is the main cause of tool fracture in practice.

  • 19.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Springback & Fracture in V-Die Bending: A Literature Survey of Analytical Models1996Report (Other academic)
  • 20.
    Asnafi, Nader
    Gränges Technology, Finspång, Sweden.
    Springback and fracture in v-die air bending of thick stainless steel sheets2000In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 21, no 3, p. 217-236Article in journal (Refereed)
    Abstract [en]

    In this investigation, the attention is focused on the springback and fracture of thick stainless steel sheets. Nine different stainless grades and various thickness are tested. The thinnest sheet is 7.9 mm, whilst the thickest sheet is 31.3 mm. A consistent analytical model is constructed for prediction of the springback, the inner sheet radius prior to and after unloading, and the smallest die width. The springback calculated by this analytical model is in all cases smaller than that found experimentally. The correspondence between theory and practice, is however, very good, although the shift in the position of the neutral axis and thinning are neglected in the theoretical analysis. Fracture did not occur in any of the conducted bending operations. It is commonly assumed that fracture in v-die bending is related to the reduction in the cross-section area at fracture, Z, in tensile testing. Z was greater than 70% for the majority of the studied materials. It is shown that particularly the mode of fracture (fracture through shear bands or by necking) should be studied in future investigations.

  • 21.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    The Influence of In-Process Variation of Blank Holding Force on Deep-Drawability1995In: Leading-Edge Manufacturing Strategies for the Metalforming Industry, Richmond Heights, Ohio, USA: PMA , 1995, p. 965-976Conference paper (Other academic)
  • 22.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    The Influence of In-Process Variation of Blank Holding Force on Deep-Drawability1993Report (Other academic)
  • 23.
    Asnafi, Nader
    Uddeholms AB, Hagfors, Sweden.
    The tool and die materials research and innovation agenda2013In: International Heat Treatment and Surface Engineering, ISSN 1749-5148, Vol. 7, no 3, p. 101-105Article in journal (Refereed)
  • 24.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Tool Design in Cold Heading of Fasteners, Part I: Literature Survey and Analytical Modelling1995Report (Other academic)
  • 25.
    Asnafi, Nader
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Tool Design in Cold Heading of Fasteners, Part II: Finite Element Simulations and Experimental Analysis1996Report (Other academic)
  • 26.
    Asnafi, Nader
    Volvo Car Corporation, Göteborg (and Olofström), Sweden .
    Tools & Dies in Manufacturing of Car Bodies: Today and Tomorrow2004Conference paper (Other academic)
  • 27.
    Asnafi, Nader
    lnstitutet för Metallforskning, Stockholm, Sweden .
    Tube bending and hydroforming1999In: Svetsaren, a Welding Review, ISSN 0346-8577, Vol. 54, no 1-2, p. 34-35Article in journal (Refereed)
    Abstract [en]

    For the production of low-weight, high-energy absorbent and cost-effective structural automotive components, the hydroforming of aluminium extrusions is now regarded as the only method in many cases. The hydroforming of aluminium extrusions has also demonstrated significant potential in other applications.

  • 28.
    Asnafi, Nader
    Luleå University of Technology, Luleå, Sweden .
    Återfjädring vid bockning längs krökta linjer1987Report (Other academic)
  • 29.
    Asnafi, Nader
    et al.
    Volvo Car Corporation, Göteborg (and Olofström), Sweden.
    Andersson, Roger
    Tubular hydroforming has arrived in Sweden: a smorgasbord of research, design, and application2001In: The Tube & Pipe Journal, Vol. 12, no 2, p. 13-17Article in journal (Refereed)
  • 30.
    Asnafi, Nader
    et al.
    Örebro University, School of Science and Technology.
    Andersson, Roger
    Persson, Martin
    Liljengren, Magnus
    Comparison of Lightweight Solutions: Low Cost Production Process for High Strength Boron Steel Components2016Conference paper (Other academic)
  • 31.
    Asnafi, Nader
    et al.
    VA Automotive AB, Hässleholm, Sweden .
    Andersson, Roger
    Duroc Special Steel, Luleå, Sweden.
    Persson, Martin
    Duroc Laser Coating, Luleå, Sweden.
    Liljengren, Magnus
    Industrial Development Center, Olofström, Sweden .
    Tailored boron steel sheet component properties by selective laser heat treatment2016Conference paper (Other academic)
    Abstract [en]

    This investigation is focused on the stamping behaviour of boron steel, the properties of which are modified by selective laser heat treatment. Both CO2 and fibre lasers are tested. By using different laser processing parameters, the hardening depth in the 1 mm thick boron steel sheet Boloc 02 is varied. Four routes are tested and verified. The forming operation (in which a so-called flexrail beam is produced) in all four routes is conducted at ambient (room) temperature. The Reference route comprises stamping of the sheet. The GridBlank route starts with selective laser heat treatment of the blank, after which the blank is allowed to cool down, moved to a hydraulic press and stamped. In the GridTube route, the blank is first stamped, after which the part is moved to a laser cell and selectively laser heat treated. The fourth route, the RapidLaser route, is similar to the GridBlank route, but a higher laser speed is used to promote higher total productivity. The GridBlank route results in the highest hardness values and the best shape accuracy. The initial sheet material exhibits a hardness of 200 HV, while the parts produced in the GridBlank route exhibit a hardness of 700 HV.

  • 32.
    Asnafi, Nader
    et al.
    Swedish Institute for Metals Research, Stockholm, Sweden .
    Ekstrand, Gunnar
    Springback and Fracture in V-Die Air Bending of Thick Stainless Steel Sheets1998Report (Other academic)
  • 33.
    Asnafi, Nader
    et al.
    Swedish Institute for Metals Research, Stockholm, Sweden .
    Gabrielson, Per
    Formability of Stainless Steel and Commercially Pure Titanium Sheets in Plate Heat Exchanger Applications1997Report (Other academic)
  • 34.
    Asnafi, Nader
    et al.
    Volvo Car Corporation, Göteborg (and Olofström), Sweden .
    Hjelm, Sven
    Scania.
    Holmgren, Björn
    Scania.
    Malmsköld, Lennart
    Saab Automobile.
    Granström, Magnus
    AB Volvo.
    Svenningstorp, Johan
    AB Volvo.
    Mellgren, Henry
    FKG.
    2015 Sustainable Manufacturing Systems Capable of Producing Innovative Environmentally Friendly and Safe Products: R&D program proposal to secure competitive vehicle and powertrain production in Sweden2008Report (Other academic)
  • 35.
    Asnafi, Nader
    et al.
    Volvo Cars Body Components, Olofström, Sweden.
    Johansson, T.
    Volvo Cars Body Components, Olofström, Sweden.
    Miralles, M.
    Volvo Cars Body Components, Olofström, Sweden.
    Ullman, A.
    Volvo Cars Body Components, Olofström, Sweden.
    Laser surface-hardening of dies for cutting, blanking or trimming of uncoated DP6002004In: Proceedings of the International Conference on Recent Advances in Manufacture and Use of Tools and Dies and Stamping of Steel Sheets / [ed] Nader Asnafi, Olofström: Vovo Cars , 2004, p. 193-214Conference paper (Refereed)
    Abstract [en]

    In this study, the methods used to harden trim dies were at the focus. Laser surface-hardening was compared to induction- and through-hardening for small and medium-size series production. The sheet materials used were 1.2 mm thick uncoated Docol 600DP and 1.95 mm thick uncoated Docol 600DL The die materials tested were Fermo, Canmo and Sleipner. This investigation showed that the optimum laser-hardening parameters must be established for each trim die material. The trim die in laser-hardened Sleipner exhibits the smallest wear, whilst the trim die in induction-hardened Fermo displays the largest wear in the semi-industrial phase of this study. The magnitude of this largest wear is, however, very small. The trim die in induction-hardened Fermo managed 100 000 strokes without any problem. The dimensional changes after laser hardening are very small. The burr height is very small, regardless of how the trim die is hardened. In this study, two sets of production trim dies were manufactured and set up. This production trim dies are used in the manufacture of V70 B-pillar Left and Right Laser hardening resulted in a lead time reduction by 5 labour days. However, the Tool & Die unit estimates that the lead time reduction obtained with laser hardening should be around 10 days under normal conditions. The cost analysis conducted by the Tool & Die unit shows that the manufacturing costs are reduced by 6%, if laser-hardening is selected. These production trim dies are and will be monitored continuously. As this paper is being written, these dies have been subject to 50 000 strokes.

  • 36.
    Asnafi, Nader
    et al.
    Volvo Cars Body Components, Olofström, Sweden.
    Kjellsson, K.
    Volvo Cars Body Components, Olofström, Sweden.
    Johansson, T.
    Volvo Cars Body Components, Olofström, Sweden.
    Blanking, stamping and trimming die experiences at volvo cars2004In: Proceedings of the International Conference on Recent Advances in Manufacture & Use of Tools & Dies and Stamping of Steel Sheets / [ed] Nader Asnafi, Olofström: Volvo Cars , 2004, p. 263-274Conference paper (Refereed)
    Abstract [en]

    During the past years, large efforts have been made at Volvo Cars to establish a scientific and systematic approach to selection of die materials, hardening methods and surface treatments/coatings. These efforts were initiated, since both new higher strength sheet materials and new die materials with better performance were introduced. Both these higher strength sheet materials and higher performance die materials needed to be industrialized. At the same time, the die manufacturing and maintenance costs must be reduced. A relationship must also be established between the die materials, hardening methods and surface treatments/coatings selected on one side and the targeted volume sizes on the other. In this paper, some of the industrial cases studied at Volvo Cars will be presented. This study is, however, not completed yet The dies described in this paper (along with other dies) have been and will be monitored continuously. The authors have chosen to focus on the technology rather than the economy, particularly since the primary purpose of this paper is to share information with other technicians and discuss the feasibility of different technical solutions. Six blanking/trimming dies and seven stamping (forming) dies are presented in this paper.

  • 37.
    Asnafi, Nader
    et al.
    Industrial Development Centre, Olofström, Sweden.
    Langstedt, G.
    Linlan Composite AB, Staffanstorp, Sweden.
    Andersson, C.-H.
    Dept. of Prod. and Mat. Engineering, Lund Inst. Technol., P.O. B., Lund, Sweden; IFP, Swed. Inst. Fibre Poly. Res., P.O., Mölndal, Sweden.
    Östergren, N.
    Industrial Development Centre, Olofström, Sweden.
    Håkansson, T.
    Industrial Development Centre, Olofström, Sweden.
    New lightweight metal-composite-metal panel for applications in the automotive and other industries2000In: Thin-walled structures, ISSN 0263-8231, E-ISSN 1879-3223, Vol. 36, no 4, p. 289-310Article in journal (Refereed)
    Abstract [en]

    A new lightweight metal-composite-metal (MCM) panel is developed. This panel consists of two layers of 0.2-mm thick stainless steel sheet with a layer of woven fabric (semi-flexible composite) in between. The stiffness and the dent resistance of this MCM-panel are compared to those of corresponding panels pressed in 1-mm thick aluminum, 0.8-mm thick carbon steel and 0.8-mm thick stainless steel sheets. Compared to the aluminum panel, the MCM-panel exhibits a slightly smaller stiffness. However, the MCM-panel displays a larger dent resistance than the aluminum and the carbon steel panels. The new panel is 46% heavier than the aluminum panel. However, it is 60% lighter than the carbon and stainless steel panels. This new panel is expected to have many applications in manufacturing of parts for car, train and bus bodies, appliances and household machines. Machine chassis and air cargo containers are other examples of products, in which the new panel can be used. Production of the new panel requires that the tools be heated. The cycle time is short, since a newly developed and patented method for ultra-rapid heating of tools has been used in this study. The production is economical, since the cycle times is short and recycled fibres can be used. The production process is not completely optimized yet. However, the conducted experiments show that the panel stiffness and dent resistance are benefitted, if the tool pressure applied during the heating is low.

  • 38.
    Asnafi, Nader
    et al.
    Swedish Institute for Metals Research, Stockholm, Sweden .
    Larsson, Mats
    On Characterization of Cold Forging Properties of Steels: a New Testing Method1994Report (Other academic)
  • 39.
    Asnafi, Nader
    et al.
    Volvo Car Corporation, Olofström, Sweden.
    Lassl, G.
    Volvo Car Corporation, Olofström, Sweden.
    Olsson, B.
    Sapa Profiles.
    Nilsson, T.
    Sapa Profiles.
    Theoretical and experimental analysis of hydropiercing2003In: SAE technical paper series, ISSN 0148-7191, article id 2884Article in journal (Refereed)
    Abstract [en]

    In this study, hydropiercing after hydroforming and prior to unloading was investigated. The primary purpose of this study was to investigate how the used hydropiercing method and the selected material and process parameters affect the hole quality. Hydropiercing inwards, hydropiercing by folding the ’scrap’ piece inwards and hydropiercing outwards were tested. The tube material was extruded AA6063-T4. The tube diameter and wall thickness were 107 mm and 2.5 mm respectively. Straight 1110-mm long tubes of this material were first hydroformed at 1300 bar and then hydropierced. Assuming that the largest (in magnitude) acceptable deflection at the hole edge is 0.2 mm, hydropiercing inwards at ≥ 1300 bar yield the best hole quality. However, the remaining scrap piece (in the tube) causes a handling problem that must be solved.

  • 40.
    Asnafi, Nader
    et al.
    Luleå University of Technology, Luleå, Sweden .
    Magnusson, Claes
    Aluminiumplåt: möjligheter att påverka formningsegenskaperna1988In: Verkstadstidningen, ISSN 0346-6434, no 9Article in journal (Refereed)
  • 41.
    Asnafi, Nader
    et al.
    Volvo Car Corporation, Olofström, Sweden.
    Nilsson, Tomas
    Sapa Profile Bending, Vetlanda, Sweden.
    Lassl, Gunnar
    Volvo Car Corporation, Göteborg, Sweden.
    Tubular hydroforming of automotive side members with extruded aluminium profiles2003In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 142, no 1, p. 93-101Article in journal (Refereed)
    Abstract [en]

    Side member left and side member right, which go from bumper to bumper in a car body, were at the focus in the present study. These side members were produced using straight round (hollow with a circular cross-section) extruded aluminium profiles as tube material. The tubes were bent and hydroformed. Rotary-draw bending yielded the best result. A spread within 8mm after bending was found to be acceptable provided that the bent tube was hydroformed with a high maximum internal pressure (1300bar in this study). Pressure-assisted tool closure (hydroforming tool) should be preferred. Such a tool closure prevents formation of buckles, which may be difficult to straighten out completely during hydroforming. Planeness and parallelity of the press tables and adapters play a significant role, as far as the spread and inplaneness of hydroformed components are concerned. The hydroforming tool must be matched in the press that actually will be used. Proper evacuation (of particularly air) is essential, especially in long hydroforming tools. All cross-sections must be deformed at least 2% (average perimeter enlargement) if the hydroformed components are to exhibit a reasonable spread. The critical (fracture) cross-sections predicted by finite-element simulation corresponded to those found in practice. However, the finite-element simulation was not able to predict formation of wrinkles at the tube ends caused by excessively large strokes. Such wrinkles were obtained in practice.

  • 42.
    Asnafi, Nader
    et al.
    Volvo Car Corporation, Göteborg (and Olofström), Sweden .
    Ocklund, Johnny
    Lassl, Gunnar
    Tubular hydroforming of side members and crash beams: a study from the perspective of Volvo Cars2002In: Information Technology, Global Environment and Sheet Metal Forming: Proceedings of the 22nd Biennial Congress, 2002, p. 289-298Conference paper (Other academic)
  • 43.
    Asnafi, Nader
    et al.
    Volvo Car Components Corp./I., Olofström, Sweden.
    Skogsgårdh, A.
    Volvo Car Components Corp./I., Olofström, Sweden.
    Theoretical and experimental analysis of stroke-controlled tube hydroforming2000In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 279, no 1-2, p. 95-110Article in journal (Refereed)
    Abstract [en]

    To select tube hydroforming instead of conventional fabrication, one has to know the tube material behaviour and tribological effects during hydroforming and how the hydroforming operation itself should be controlled. The hydroforming operation is either force- or stroke-controlled. This paper deals with stroke-controlled hydroforming. Hydroforming consists of free forming and calibration. In this paper, only the so-called free forming is treated. Stroke-controlled free forming is studied theoretically and experimentally. The theoretical part consists of analytical modeling and finite-element simulations. The conducted experiments are used to show the types of errors that might occur, when the theoretically obtained loading paths are transferred to the hydroforming equipment. The forming limit curve (FLC) is normally used as an aid/instrument in component and process design (which include finite-element simulations). The present study shows that the FLC of the tube material must be determined by hydroforming, if component and process design are to rely on this instrument.

  • 44.
    Asnafi, Nader
    et al.
    Sapa Technology, Finspång (and Vetlanda), Sweden .
    Skogsgårdh, Anders
    Skåre, Thomas
    Hydroforming av rörformiga komponenter: teori och praktik2000Conference paper (Other academic)
  • 45.
    Asnafi, Nader
    et al.
    Industrial Development Center/Volvo Cars Body Components, Olofström, Sweden .
    Skogsgårdh, Anders
    Östergren, Nicklas
    Sjöstedt, Jörgen
    HYFO98: Slutrapport1998Report (Other academic)
  • 46.
    Asnafi, Nader
    et al.
    Sapa Technology, Finspång (and Vetlanda), Sweden .
    Widlund, Conny
    Håltagning vid hydroformning: material- och processparametrars inverkan på hålkvaliteten2000Report (Other academic)
  • 47.
    Babu Surreddi, Kumar
    et al.
    Dalarna University, Falun, Sweden.
    Oikonomou, Christos
    Uddeholms AB, Sweden.
    Karlsson, Patrik
    Örebro University, School of Science and Technology.
    Olsson, Mikael
    Dalarna University, Falun, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    In-situ Micro-tensile Testing of Additive Manufactured Maraging Steels in the SEM: Influence of Build Orientation, Thickness and Roughness on the Resulting Mechanical Properties2017Conference paper (Refereed)
    Abstract [en]

    Selective laser melting (SLM) is frequently used additive manufacturing technique capable of producing various complex parts including thin-wall sections. However the surface roughness is a limiting factor in thin sections produced by SLM process when strength is the main criterion. In this study, the influence of build orientation, thickness and roughness on the resulting mechanical properties of as-built test samples was investigated. Various thin sheets of EN 1.2709 maraging steel built in horizontal and vertical orientations produced by SLM were investigated using in-situ micro-tensile testing in a scanning electron microscope. The mechanical strength and deformation mechanisms were analyzed and explained based on thickness and build orientation. Increased ductility was observed in thicker samples as well as in the horizontal build samples. The results illustrate the potential of the in-situ test technique and aspects important to consider in design guidelines for thin AM structures.

  • 48.
    bergman, martin
    Örebro University, School of Science and Technology.
    Sinnenas Rum - Ytor för bastumiljö2010Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report handles the development of a graphic manual and a physical mood-board with specific number of surfaces for the sauna manufacturing company Tylö® AB in Halmstad. The reader will have a general understanding of how the semantic of a product affects its users, and how this affects the product's performance on the market. The project is based on a fairly unused method, which basically is used for; seize a target group specific feeling about a specific product to make it more optimized. In this project, it was more about the development of specific structures on surfaces, which eventually came to lead to a number of specially selected materials and surfaces for the company Tylö ® AB. The materials, together with special surfaces, probably come to create a more elegant feeling in their upcoming concepts. The method that was used to achieve the target is called Kansei Engineering.

  • 49.
    Berns, H.
    et al.
    Institut für Werkstofle, Ruhr-Universität Bochum, Bochum, Germany .
    Melander, A.
    lnstitutet för Metallforskning, Stockholm, Sweden .
    Weichert, D.
    Laboratoire de Mécanique de Lille, Lille, France .
    Asnafi, Nader
    lnstitutet för Metallforskning, Stockholm, Sweden .
    Broeckmann, C.
    Institut für Werkstofle, Ruhr-Universität Bochum, Bochum, Germany .
    Gross-Weege, A.
    Laboratoire de Mécanique de Lille, Lille, France .
    A new material for cold forging tools1998In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 11, no 3, p. 166-180Article in journal (Refereed)
    Abstract [en]

    A new tool material for cold forging applications was developed using numerical simulation techniques (FEM) for the design and a powder metallurgical route (HIP) for the production. The basic idea was to find an optimized microstructure of the two phase material by simulating different distributions of hard particles within the metal matrix. On the micro-scale, loading was applied by a field of deformations which was obtained by a macroscopical simulation of a particular cold forming process in bolt making. A new double dispersion microstructure was found to show the best resistance against crack propagation. Specimens were produced by hot isostatic pressing. Afterwards the new material was tested in the laboratory. Wear resistance and bending strength of the double dispersive material are comparable to a standard dispersion material with the same volume fraction of particles, but fracture toughness is increased by about 30%. Testing the new material in bolt making showed that the life time of the tool is increased by a factor of 8.

  • 50.
    Ekengren, Jens
    Karlstads universitet, Avdelningen för maskin- och materialteknik.
    Estimating inclusion content in high performance steels2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Non-metallic inclusions in steel pose a major problem for the fatigue resistance, especially regarding fatigue at very long lives corresponding to low cyclic stress levels, as well as being detrimental to material toughness and polishability.

    The largest inclusions are quite rare, which makes conventional detection methods timeconsuming if reliable results are to be obtained. Based on surface scanning using light or electron microscopes, these methods provide results that have to be converted to reflect the statistical volume distribution of inclusions.

    Very high cycle fatigue (in the order of 109 cycles or more) using ultrasonic fatigue at 20 kHz has been found efficient at finding the largest inclusions in volumes of about 300 mm3 per specimen. The inclusions found at the fatigue initiation site can then been used to estimate the distribution of large inclusions using extreme value statistics.

    In this work, a new method for estimating the volume distribution of large inclusions is presented as well as a suggested ranking variable based on the volume distribution.

    Results from fatigue fractography and area scanning methods are compared to the endurance limit at 109 cycles for a number of batches from two high performance steels.

    In addition, the extreme value distributions of fatigue initiating inclusions in six high performace steels, produced by different routes, are presented. It is shown that all modes of the Generalized Extreme Values distribution can be found in different materials. This result shows that the assumption of mode I distribution, also known as Gumbel or Largest Extreme Value distribution, must be substantiated.

    List of papers
    1. Relating gigacycle fatigue to other methods in evaluating the inclusion distribution of a H13 tool steel
    Open this publication in new window or tab >>Relating gigacycle fatigue to other methods in evaluating the inclusion distribution of a H13 tool steel
    2007 (English)In: Fourth International Conference on Very High Cycle Fatigue (VHCF-4) / [ed] John E. Allison, J. Wayne Jones, James M. Larsen & Robert O. Ritchie, TMS (The Minerals, Metals & Materials Society) , 2007, p. 45-50Conference paper, Published paper (Refereed)
    Abstract [en]

    Inclusions play a crucial role for the fatigue properties of high strength steel, but to find the largest inclusions by microscopy measurements large areas have to be examined.In this study ultrasonic gigacycle staircase fatigue testing has been used to find large inclusions in an H13 tool steel. The inclusions have been examined in SEM and their size distribution modeled using methods from extreme value statistics. The inclusion distribution obtained from the fatigue crack surfaces is compared to distributions acquired by microscopy study of cross sections as well as ultrasound immersion tank measurements and to the corresponding staircase fatigue data via the Murakami √Area model.It is shown that the fatigue method more effectively finds large inclusions than the other methods. It is also shown that the correlation between predictions of inclusion sizes by the √Area model from stress levels and fatigue initiating inclusions is weak forthis material.

    Place, publisher, year, edition, pages
    TMS (The Minerals, Metals & Materials Society), 2007
    Keyword
    non-metallic inclusion, steel, gigacycle fatigue
    National Category
    Materials Engineering
    Research subject
    Materials Engineering
    Identifiers
    urn:nbn:se:oru:diva-39905 (URN)978-0-87339-704-9 (ISBN)
    Conference
    Fourth International Conference on Very High Cycle Fatigue (VHCF-4)
    Available from: 2009-02-05 Created: 2014-12-19 Last updated: 2017-10-17Bibliographically approved
    2. Detecting large inclusions in steels: evaluating methods
    Open this publication in new window or tab >>Detecting large inclusions in steels: evaluating methods
    (English)Manuscript (preprint) (Other academic)
    National Category
    Metallurgy and Metallic Materials
    Identifiers
    urn:nbn:se:oru:diva-40114 (URN)
    Available from: 2015-01-02 Created: 2015-01-02 Last updated: 2017-10-17Bibliographically approved
    3. Extreme value distributions of inclusions in six steels
    Open this publication in new window or tab >>Extreme value distributions of inclusions in six steels
    (English)Manuscript (preprint) (Other academic)
    National Category
    Metallurgy and Metallic Materials
    Identifiers
    urn:nbn:se:oru:diva-40117 (URN)
    Available from: 2015-01-02 Created: 2015-01-02 Last updated: 2017-10-17Bibliographically approved
    4. Finding non-metallic inclusions in clean steel
    Open this publication in new window or tab >>Finding non-metallic inclusions in clean steel
    2008 (English)Report (Other academic)
    Place, publisher, year, edition, pages
    Karlstad: Karlstads universitet, 2008
    Series
    Karlstad University Studies, ISSN 1403-8099 ; 2008:51
    National Category
    Materials Engineering
    Research subject
    Materials Engineering
    Identifiers
    urn:nbn:se:oru:diva-39895 (URN)978-91-7063-208-2 (ISBN)
    Available from: 2009-02-05 Created: 2014-12-19 Last updated: 2017-10-17Bibliographically approved
123 1 - 50 of 101
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