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  • 1.
    Gustafsson, Emil
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Oldenburg, Mats
    Jansson, Anders
    Design and validation of a sheet metal shearing experimental procedure2014Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 214, nr 11, s. 2468-2477Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Throughout the industrial processes of sheet metal manufacturing and refining, shear cutting is widely used for its speed and cost advantages over competing cutting methods. Industrial shears may include some force measurement possibilities, but the force is most likely influenced by friction losses between shear tool and the point of measurement, and are in general not showing the actual force applied to the sheet. Well defined shears and accurate measurements of force and shear tool position are important for understanding the influence of shear parameters. Accurate experimental data are also necessary for calibration of numerical shear models. Here, a dedicated laboratory set-up with well defined geometry and movement in the shear, and high measurability in terms of force and geometry is designed, built and verified. Parameters important to the shear process are studied with perturbation analysis techniques and requirements on input parameter accuracy are formulated to meet experimental output demands. Input parameters in shearing are mostly geometric parameters, but also material properties and contact conditions. Based on the accuracy requirements, a symmetric experiment with internal balancing of forces is constructed to avoid guides and corresponding friction losses. Finally, the experimental procedure is validated through shearing of a medium grade steel. With the obtained experimental set-up performance, force changes as result of changes in studied input parameters are distinguishable down to a level of 1%.

  • 2.
    Gustafsson, Emil
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Oldenburg, Mats
    Jansson, Anders
    Experimental study on the effects of clearance and clamping in steel sheet metal shearing2016Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 229, s. 172-180Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shear cutting is common within several sheet metal industry processing steps, e.g. in cut to length lines, slitting lines, end cropping. Shearing is fast and cheap relative to competing cutting methods like laser and plasma cutting, but involves large forces on the equipment that increase with increased sheet material strength. Accurate shear experiments are a prerequisite to increase the knowledge of shearing parameters, improve industrial shearing, and provide data for validation of numerical shear models. Here, the two shear parameters clearance and clamp configuration, identified as important to the shear results, were studied in an experimental set-up with well defined tool movement and high measurability of tool position and force. In addition to force measurements, the sheared edge geometry was characterized. Steels of low, medium, and high strength were selected for the study. Throughout the experimental study, the shear tool penetration before fracture decreased with increased material strength. The required shear force decreased and the force attempting to separate the two shear tools increased when one side of the sheet was left unclamped and free to move. Further, the maximum shear force increased with decreased clearance. Clearance changes were small and moreover continuously measured during all shear experiments.

  • 3.
    Hansson, Sofia
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap. Sandvik Mat Technol, R&D Ctr, SE-81181 Sandviken.
    Jansson, Tomas
    Sensitivity analysis of a finite element model for the simulation of stainless steel tube extrusion2010Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 210, nr 10, s. 1386-1396Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a sensitivity analysis has been performed on a finite element model of glass-lubricated extrusion of stainless steel tubes. Fifteen model parameters, including ram speed, billet and tool temperatures, friction coefficients and heat transfer coefficients, were considered. The aim of the study was to determine the parameters that are most important for the response of the extrusion force. The relationship between the model parameters and the responses was analyzed by a calculation of two different regression models: one linear polynomial model and one model that includes interaction terms. Additional simulations were then carried out to validate the regression models. The results show that the initial billet temperature is the factor that has the strongest impact on the extrusion force within the parameter ranges studied in this work. The goodness of prediction and goodness of fit are very good for both regression models.

  • 4.
    Lindgren, Michael
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Cold roll forming of a U-channel made of high strength steel2007Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 186, nr 1-3, s. 77-81Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cold roll forming is a bending process where the bending occurs gradually in several forming steps from an undeformed strip to a finished profile. The process is very interesting for the sheet metal industry due to the high speed in which the profile can be produced. High strength steel has, in recent years, become more common in cold roll forming. These materials have advantages but also disadvantages that affect the design of the process. Simple models in literature [K.F. Chiang, Cold roll forming, ME Thesis, University of Auckland, August 1984] predict that the longitudinal peak membrane strain in the flange of a profile is independent of the material properties. However, Ingvarsson [L. Ingvarsson, F¨orenklad teori f¨or rullforming av element¨ar v-profil, j¨amf¨orelse mellan normalt och h¨ogh°allfast st°al, VAMP 15- rullforming 23 april 2001] compared mild and ultra high strength in a roll forming experiment and the conclusion was that the material properties will affect the finished profile. This paper is a fundamental study performed in order to understand the observation by Ingvarsson [L. Ingvarsson, F¨orenklad teori f¨or rullforming av element¨ar v-profil, j¨amf¨orelse mellan normalt och h¨ogh°allfast st°al, VAMP 15- rullforming 23 april 2001]. The objectives of this study are to investigate the change in the longitudinal peak membrane strain at the flange edge and the deformation length when the yield strength increases. These are important since they can be used to determine the number of forming steps and the distance between them when designing the cold roll forming machine. The result from the simulations show that the longitudinal peak membrane strain decreases and the deformation length increases when the yield strength is increased.

  • 5.
    Lindgren, Michael
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialvetenskap.
    Bexell, Ulf
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Wikström, Lars
    Roll forming of partially heated cold rolled stainless steel2009Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 209, nr 7, s. 3117-3124Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Today you will find roll formed details in many different products, for example buildings, household appliances and vehicles. The industry, in order to save weight, tends to use more and more high strength steel. The disadvantage with these materials is that they can be difficult to form due to reduced ductility. A way to increase the ductility in the forming areas is by partially heat the steel. It is shown that partial heating substantially increases the ductility of high strength steel and make it possible to roll form large bend angles. When roll forming, the material will work hardening almost to the as-received condition in the outer and inner radius of the roll formed profile. Furthermore, the heating power decides the bend angle obtained. Finally, the mechanical properties after heating and roll forming are discussed.

  • 6.
    Michael, Lindgren
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Experimental investigations of the roll load and roll torque when high strength steel is roll formed2007Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 191, nr 1-3, s. 44-47Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The cold roll forming process is a highly efficient process used to produce profiles for many applications, for example vehicles, buildings, domestic machines, etc. Therefore, its market share is increasing every year. Many of the above products are already today made of high strength steel and the usage of these materials will likely continue to increase. The objectives of this project are to find howthe roll load and roll torque are influenced by the yield strength of the material. Full-scale experiments have been performed. U-channels made of different materials from mild to ultra high strength steels have been formed. The roll torque is measured during the process using a torque sensor mounted between the tool and the power transmission. Used power is also calculated with help of the motor current. The roll load is measured with load cells mounted on both side of the roll forming tool. The experimental result will increase the understanding of the specific conditions for roll forming steels with increasing yield strength. The result can be used to support the roll machine designer to choose machine elements and power unit for these applications. Furthermore, the result can also be compared with finite element simulations in order to improve and validate simulation models.

  • 7.
    Zhou, Nian
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Peng, R. L.
    Pettersson, R.
    Surface integrity of 2304 duplex stainless steel after different grinding operations2016Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 229, s. 294-304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface integrity has significant effect on service performance of a component. In this study, the evolution of the surface and sub-surface changes induced by grinding duplex stainless steel (DSS) 2304 was studied with regard to the residual stress, the microstructure, surface roughness and surface defects. The results provide insights into the effect of abrasive grit size, grinding force and lubrication on the surface integrity. The abrasive grit size was found to have the largest influence. Surface defects, a highly deformed surface layer and the generation of tensile residual stresses along the grinding direction have been found to be the main types of damage induced by the grinding operation. Residual stresses induced by mechanical effects dominate over thermal effects in this study. The results obtained can be used to understand the contribution of surface condition and residual stress on failure of duplex stainless steels in service by fatigue or stress corrosion cracking.

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