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  • 101.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Validation of tool-wear simulations based on a full-scale press hardening experiment2015Ingår i: Hot Sheet Metal Forming of High-Performance Steel 5th International Conference: May 31-June 3, Toronto, Canada : Proceedings / [ed] Kurt Steinhoff; Mats Oldenburg; Braham Prakash, Auerbach: Verlag Wissenschaftliche Scripten , 2015, s. 121-128Konferensbidrag (Refereegranskat)
    Abstract [en]

    To extend the service life of stamping tools for press hardening processes, tool wear prediction gradually becomes an important topic of concern in industry. However, wear simulations based on the finite element method are mainly developed in laboratory and the lack of validation of full-scale experiments restricts the proposal of an accurate wear model. The work presented in this paper aims at validating the used wear models for stamping tools through a full-scale press hardening experiment. The wear model in conjunction with finite element (FE) simulations are dependent on contact mechanics and the corresponding wear data is obtained from laboratory tests, where the test parameters are specified in ranges that accord with the contact conditions of press hardening. The full-scale press hardening experiment producing a dog-bone shaped part is run for 200 continuous strokes. Geometry updating of the stamping tool is used to investigate the influence of shape change on the pressure occurring on the tool. The results have shown that the geometry change of the stamping tool, after producing a large number of parts, causes changes in the contact pressures and therefore affects the wear simulation. In the end, the wear simulation results are compared to the preliminary result of the full-scale press hardening.

  • 102.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of tool shape change due to wear under press hardening conditions2015Ingår i: Proceedings of The Second International Conference on Advanced High Strength Steel and Press Hardening, Singapore: World Scientific and Engineering Academy and Society, 2015, s. 580-584Konferensbidrag (Övrigt vetenskapligt)
  • 103.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Wear Observations on Uncoated Tool and Workpiece Surfaces from a Full-Scale Press Hardening Wear Test2017Ingår i: Advanced High Strength Steel and Press Hardening / [ed] Zhang, Y; Ma, M, Singapore: World Scientific, 2017, s. 433-437Konferensbidrag (Refereegranskat)
    Abstract [en]

    Tool wear in press hardening has attracted researchers' attention and recently several papers have focused on the wear observations in the laboratory tests mimicking the press hardening conditions. However, the wear observations and quantification in full-scale press hardening tests are rare in view of high costs and longtime requirements. In this work, the wear behavior in a full-scale press hardening wear test has been studied in order to understand the wear mechanisms occurring in the stamping tool. Furthermore, the wear depths in the real stamping tool were measured by using a coordinate measurement machine (CMM) that can provide the quantified wear result and serve as a base to validate the possible wear model. The present study also includes the wear observations in both the counterparts i.e., the blank (workpiece) and the stamping tool with the aim of studying the transfer material/wear particles. Two common tool steels were used in the full-scale press hardening wear test and the differences in the wear severities were observed. Since abrasion and adhesion are major wear mechanisms previously in many laboratory tests, the present study identifies the wear evolution and mechanisms on uncoated tool and workpiece surfaces in the press hardening wear test.

  • 104.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A Tribological Test under Press Hardening Conditions for Galling Research2017Ingår i: 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings / [ed] Mats Oldenburg, Braham Prakash, Kurt Steinhoff, Warrendale, PA: Association for Iron & Steel Technology, AIST , 2017, s. 453-460Konferensbidrag (Refereegranskat)
  • 105.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental Evaluation of Galling Under Press Hardening Conditions2018Ingår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, nr 3, artikel-id 93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Severe adhesion, also referred to as galling, is a critical problem in press hardening, especially in stamping tools used for hot forming of Al–Si-coated ultra-high strength steel. Galling is known to develop rapidly on the tool surface and it negatively affects the quality of the formed products. Earlier research on this topic has focused on the galling initiation. However, studies on the galling development during extended sliding and the corresponding quantitative measurement still lack depth. In the present study, a tribological test is established to study the galling development under press hardening conditions. The tribological test set-up aims to simulate extended sliding between the Al–Si-coated boron steels and the tool die material. The contact conditions in the interface are studied by a numerical model of the tribological test. The friction coefficients and material transfer are discussed taking into account the variation of the different test conditions. Using the results from the tribological tests, the galling simulation is performed in the numerical model. A geometry-updated sample based on the galling (transferred material build-up) height is simulated and the consequent pressure fluctuation is obtained in the numerical model. This contributes to the explanation of the severe transferred material accumulation during the test.

  • 106.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Numerical investigation of galling in a press hardening experiment with AlSi-coated workpieces2019Ingår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 99, s. 85-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Press hardened steels are commonly used as a lightweight choice for manufacturing car components because of the high ratio of strength to weight. The use of ultra-high-strength steels for the design of lightweight vehicles contributes to the reduction of emissions of carbon dioxide while maintaining passenger safety. Stamping tools used in press hardening processes suffer harsh contact conditionsin terms of dramatic temperature changes, cyclic loadings, and complex interactions between coatings and oxidation. In mass production, tool wear is an inevitable problem that increases maintenance costs. Severe adhesive wear, also called galling, substantially occurs in the stamping tool used against Al—Si-coated workpieces. The galling that takes place during press hardening not only degrades the production quality but also shortens the service life of the tool. In order to properly arrange tool maintenance and minimize galling through adjusting process parameters, engineers need to know when and where galling occurs, based on modelling of the galling in press hardening simulations. In order to implement a galling simulation for press hardening, a modified Archard wear model is employed in the present study, which is a contact-mechanics-based model. The specific wear rate in the model is calibrated by the quantitative galling measurements of a high-temperature tribometer test. The tribological test is designed to mimic the press hardening conditions, where the correlations between galling and process parameters such as temperature, pressure, and sliding distance are outlined. The galling simulation is implemented in a full-scale press hardening experiment, and the predicted galling is validated in terms of severe galling positions and galling profiles. The galling profile evolution is correlated to variations in the contact conditions. Uncertainties in the numerical model, such as the choice of penalty scaling factor and friction coefficient, are analysed with a parameter study and discussed. This study demonstrates finite element (FE) simulations involving galling prediction in press hardening so as to improve product development and production efficiency.

  • 107.
    Digby, Peter
    et al.
    Luleå tekniska universitet.
    Nilsson, L.
    Luleå tekniska universitet.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Finite element simulation of time dependent fracture and fragmentation processes in rock blasting1985Ingår i: International journal for numerical and analytical methods in geomechanics (Print), ISSN 0363-9061, E-ISSN 1096-9853, Vol. 9, nr 4, s. 317-329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two constitutive models for the simulation of fracture and fragmentation processes in rapidly loaded rocks are studied. The models were included in a wave propagation finite element code. The results obtained from the two models were compared by a study of the intensity and extent of fracturing obtained from two different configurations of explosive charge and reflecting surfaces in a plane strain problem. The evolution of the time dependent fracture pattern and fragmentation process is also presented

  • 108.
    Dini, Hoda
    et al.
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Svoboda, Ales
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Andersson, Nils-Eric
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Ghassemali, Ehsan
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Jarfors, Anders E.W.
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Optimization and validation of a dislocation density based constitutive model for as-cast Mg-9%Al-1%Zn2018Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 710, s. 17-26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dislocation density-based constitutive model, including effects of microstructure scale and temperature, was calibrated to predict flow stress of an as-cast AZ91D (Mg-9%Al-1%Zn) alloy. Tensile stress-strain data, for strain rates from 10-4 up to 10-1 s-1 and temperatures from room temperature up to 190 °C were used for model calibration. The used model accounts for the interaction of various microstructure features with dislocations and thereby on the plastic properties. It was shown that the Secondary Dendrite Arm Spacing (SDAS) size was appropriate as an initial characteristic microstructural scale input to the model. However, as strain increased the influence of subcells size and total dislocation density dominated the flow stress. The calibrated temperature-dependent parameters were validated through a correlation between microstructure and the physics of the deforming alloy. The model was validated by comparison with dislocation density obtained by using Electron Backscattered Diffraction (EBSD) technique.

  • 109.
    Domkin, K.
    et al.
    Luleå tekniska universitet.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Dislocation model for plastic hardening in sheet metal forming2001Ingår i: Simulation of Materials Processing: Theory, Methods and Applications: proceedings of the 7th International Conference on Numerical Methods in Industrial Forming Processes - NUMIFORM 2001, Toyohashi, Japan, 18 - 20 June 2001 / [ed] Ken-ichiro Mori, Lisse: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 2001Konferensbidrag (Refereegranskat)
  • 110.
    Domkin, Konstantin
    et al.
    Luleå tekniska universitet.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Segle, Peter
    Luleå tekniska universitet.
    Dislocation density based models for plastic hardening and parameter identification2003Ingår i: Computational plasticity VII: fundamentals and applications ; proceedings of the Seventh Conference on Computational plasticity / [ed] D.R.J. Owen, International Center for Numerical Methods in Engineering (CIMNE), 2003Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper the parameter identification using dislocation density based material model is studied. The model is rate-dependent and includes isotropic strainhardening/ softening as well as kinematic hardening. The model is implemented as a part of the custom toolbox for parameter identification (described in the accompanying paper) using Matlab®. A general stress-strain algorithm is used in the calculations, so the same logic can also be used when implementing the material models into a finite element code. The stressupdate algorithm of rate-dependent plasticity is chosen in the form that has the yield surface for which a so-called consistency condition exists. The amount of plasticity in a strain increment is determined by the consistency condition, whereas the internal variables history and yield stress depend on the plastic strain-rate. The paper focuses on the use of physically based material models. The dislocation density concept links the macroscopic stresses and strains to the underlying micro-structural processes of plastic deformation. The material models define evolution equations for the densities of mobile, immobile locked and immobile recoverable dislocations. The physical significance of the model parameters is highlighted. The developed toolbox is used to determine material parameters of a high-strength steel for a chosen dislocation density model fitted to the constant amplitude fully reversed strain controlled cyclic test curves. Parameter sensitivity is briefly discussed.

  • 111. Domkin, Konstantin
    et al.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Troive, Lars
    Physically based material model in sheet metal forming2001Ingår i: Simulation of materials processing: theory, methods and applications : proceedings of the 7th International conference on numerical methods in industrial forming processes - NUMIFORM 2001 / [ed] Ken-ichiro Mori, Lisse: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 2001, s. 221-226Konferensbidrag (Refereegranskat)
  • 112.
    Draxler, Joar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Edberg, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Andersson, J.
    University West, Trollhättan, Sweden.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modeling and simulation of weld solidification cracking part I: A pore-based crack criterion2019Ingår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 5, s. 1489-1502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair and, if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model for computing the pressure and the thickness of the grain boundary liquid film, which are required to evaluate the crack criterion in paper 1. The third and final paper describes the application of the model to Varestraint tests of alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown.

  • 113.
    Draxler, Joar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Edberg, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Andersson, J.
    University West, Trollhättan, Sweden.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modeling and simulation of weld solidification cracking part II: A model for estimation of grain boundary liquid pressure in a columnar dendritic microstructure2019Ingår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 5, s. 1503-1519Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair, and if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model for computing the pressure and the thickness of the grain boundary liquid film, which are required to evaluate the crack criterion in paper 1. The third and final paper describes the application of the model to Varestraint tests of Alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown.

  • 114.
    Draxler, Joar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Edberg, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Andersson, Joel
    University West.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of weld solidifiation cracking in varestraint tests of alloy 7182019Ingår i: / [ed] C. Sommitsch, Gratz, 2019, Vol. 12, s. 485-504Konferensbidrag (Refereegranskat)
    Abstract [en]

    Several nickel-based superalloys are susceptible to weld solidification cracking. Numerical simulation can be a powerful tool for optimizing the welding process such that solidification cracking can be avoided. In order to simulate the cracking, a crack model inspired by the RDG model is proposed. The model is based on a crack criterion that estimates the likelihood for a preexisting pore in a grain boundary liquid film to form a crack. The criterion depends on the thickness and the liquid pressure in the grain boundary liquid film, as well as the surface tension of the pore. The thickness of the liquid film is computed from the macroscopic mechanical strain field of an FE model with a double ellipsoidal heat source. A temperature-dependent length scale is used to partition the macroscopic strain to the liquid film. The liquid pressure in the film is evaluated using a combination of Poiseuille parallel plate flow and Darcy’s law for porous flows. The Poiseuille flow is used for the part of the grain boundary liquid film that extends into the region with liquid fraction less than 0.1, while Darcy’s law is used for the rest of the liquid film that extends into the regions with liquid fraction greater than 0.1. The proposed model was calibrated and evaluated in Varestraint tests of Alloy 718. Crack location, width, and orientation were all accurately predicted by the model.

  • 115.
    Edberg, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Computational modeling of hot rolling1993Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 116.
    Edberg, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Computational modeling of hot rolling1996Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis consists of six papers on finite element simulations of the hot rolling of plates. Different friction and material models have been evaluated. The work includes both numerical simulation and experimental verification. It is shown that the constitutive model for the plate material is more important than the model for the friction between the rolled material and the rolls. It was also found that an explicit finite element method is more effective and easier to use than an implicit code. The models presented are one step towards a general and more complete computational model of flat rolling. They are not complete as they depend on a separate estimation of the roll bending. Otherwise, all three-dimensional aspects of the rolling process are included. The material models used work quite well for the simulation of the hot rolling operation. High accuracy is obtained for global quantities like rolling force and torque. A better material model would improve the prediction of the stress distribution in the rolled material. It should be able to describe the effect of rapidly changing strain rates and temperatures during deformation as well as recrystallization and thermal strains.

  • 117.
    Edberg, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Three-dimensional simulation of plate rolling using different friction models1992Ingår i: Numerical methods in industrial forming processes: proceedings of the 4th International Conference on Numerical Methods in Industrial Forming Processes, Valbonne/France, 14-18 September 1992; NUMIFORM '92 / [ed] J.L. Chenot; R.D. Wood; O.C. Zienkiewicz, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1992Konferensbidrag (Refereegranskat)
  • 118.
    Edberg, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Andersson, Joel
    University West, Department of Engineering Science, 461 86 Trolhättan.
    Use of Indicators for Hot and Warm Cracking in Welded Structures2016Ingår i: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 7, s. 145-150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Weight reduction of mechanical components is becoming increasingly important as a way to provide more environment friendly production and operation of different equipment. This is true in almost any manufacturing industry, but is especially important to the aerospace industry. Casting has often been replaced by hot and cold metal working operations and welding, usually including an additional heat treatment. This gives components better material properties and provides components with less weight and cost but with increased strength and efficiency. This may even be true for rotating Ni- based superalloy components, and is enabled by welding methods. However, weld cracking of precipitation hardening Ni-based superalloys is a serious problem, both in manufacturing and overhaul since it endangers component life if cracks are allowed to propagate.

    Cracks can appear in a weld and in it's surroundings. The triggering mechanisms depend on its location and when it is nucleated. Generally saying, weld cracking in precipitation hardening Ni-based superalloys consists of two different types of cracking, hot cracking and warm cracking which may be further divided into heat affected zone (HAZ) liquation cracking, solidification cracking and strain age cracking, respectively.

    Finite element simulations of welding and heat treatment processes started in the seventies for small laboratory set-up cases and have today matured, and are now used on large-scale structures like aerospace components. But FE-based crack criteria that can predict the risk of cracking due to welding or heat treatments are rare. In a recent study both hot cracking and warm cracking have been investigated in Ni-based superalloys, and two FE-based indicators showing the risk of hot and warm cracks have been proposed. The objective of the investigation presented in this paper is to compare results from FE-simulations with experimental results from weldability tests, like the Varestraint test and the high temperature mechanical Gleeble test.

  • 119.
    Edberg, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Draxler, J.
    Comarison of two different indicators for hot cracking in welded structures2018Konferensbidrag (Refereegranskat)
  • 120.
    Edberg, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Larsson, Dan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of braking of railway wheel2003Rapport (Övrigt vetenskapligt)
    Abstract [en]

    LKAB has tried new iron ore wagons for the 30 tonnes axle load. They got problems with cracking and material removal from the rim of the wheels during the tests. Martensite, which is more prone to cracking than other microstructures, was found at these locations. The initial material microstructure is supposed to contain no martensite. The purpose of this investigation is to find whether the thermal cycle due to braking, possibly with assistance of the mechanical load, can cause martensite formation

  • 121.
    Edberg, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Efficient three-dimensional model of rolling using an explicit finite-element formulation1993Ingår i: Communications in Numerical Methods in Engineering, ISSN 1069-8299, E-ISSN 1099-0887, Vol. 9, nr 7, s. 613-627Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rolling is simulated by a three-dimensional finite-element model with elastoplastic constitutive equations. The use of an explicit finite-element formulation, instead of the more commonly used implicit formulation, has reduced the required computing time. The larger of the models used in one step towards a general and complete computational model of rolling. Results from experiments and from two and three-dimensional calculations are compared.

  • 122.
    Edberg, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Wedge rolling test1994Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 42, nr 2, s. 227-238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method for the evaluation of friction models is described. A wedge is rolled to uniform thickness, a range of reductions being investigated thereby in one experiment. Finite-element simulations are performed in order to estimate the friction parameters that can be used in the simulation of hot rolling. The influence of the material parameters and the friction parameters on the calculated results are investigated and the latter are compared with experimental results. It is shown that it is possible to separate the influence of the material parameters and the friction parameters, thus enabling the friction parameters to be evaluated from a minimum number of experiments.

  • 123.
    Edberg, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Ken-Ichiro, M.
    Shot peening simulated by two different finite element formulations1995Ingår i: Simulation of materials processing: theory, methods and applications ; proceedings of the Fifth International Conference on Numerical Methods in Industrial Forming Processes - NUMIFORM'95, Ithaca, New York, USA, 18-21 June 1995 / [ed] Shan-Fu Shen; Paul Dawson, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1995Konferensbidrag (Refereegranskat)
  • 124.
    Elfgren, Lennart
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Lundberg, Bengt
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Nilsson, Bruno
    Belastningsutrustning: En redogörelse över inköp av en servohydraulisk belastningsutrustning för provning av material och konstruktioner vid Högskolasn i Luleå1976Rapport (Refereegranskat)
    Abstract [sv]

    Servohydraulisk belastningsutrustning för 2,3 miljoner kronor upphandlades under 1975 till Högskolan i Luleå. Utrustningen består av tre drag- och tryckprovningsmaskiner (30, 200 och 300 kN), sex belastningscylindrar (130, 265 och 1000 kN), en bergmekanisk press (4500 kN), en processdator (16 kioord) samt elektronikkonsoler för styrning och registrering.

    Upphandlingsarbetet beskrivs och utrustningen presenteras.

  • 125.
    Emami, Nazanin
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Ramanenka, Dmitrij
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Enqvist, Evelina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Mechanical and thermal characterisation of novel UHMWPE-nano composite: A copmarrative study against virgin UHMWPE2012Konferensbidrag (Refereegranskat)
  • 126.
    Eman, Jesper
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Brottöjningar vid hål i ultrahöghållfast stål för olika håltagningsmetoder2007Ingår i: Svenska Mekanikdagar 2007: Program och abstracts / [ed] Niklas Davidsson; Elianne Wassvik, Luleå: Luleå tekniska universitet, 2007, s. 96-Konferensbidrag (Övrigt vetenskapligt)
  • 127.
    Eman, Jesper
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Study and characterization of localization and failure behaviour of ultra high strength steel2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In the vehicle industry there is a constant struggle to develop cars with high passive safety without increasing the fuel consumption. High passive safety requires a very rigid behaviour of the crash protecting components. Accomplishing this often leads to an increase in the weight of the components. An increase in weight results in a higher fuel consumption which is bad for the environment as well as for the economy of the car owner, therefore the manufacturers turn to new materials. One of these new materials is ultra high strength steel which is the material in focus for the present thesis. To be able to utilize all the advantages of ultra high strength steel the material behaviour must be investigated in detail. In this thesis, sheets of ultra high strength steel, which are produced by press-hardening, are investigated using a method called digital speckle photography. When using the method of digital speckle photography (DSP) a series of photographs are taken of a deforming specimen. Prior to the experiment a random pattern (speckles) has been applied to the specimen and by studying the deforming speckle pattern on the images, the deformation fields through time can be established. Within the present thesis the deformation fields up to the point of fracture have been investigated on a length scale of the order of 10e-4 meters. With length scales of this magnitude the deformation inside a localized neck can be investigated. This is done, both for a specimen shape that induces a fracture initiation at an inner point of the specimen and a specimen shape where fracture starts from the edge of a hole. These investigations show that there is a strong localization of the strain before fracture is initiated. The local strain values inside a localized neck are significantly higher than the strain values that can be observed with conventional experimental techniques involving extensometers. It is also noticed that the method used to make holes play an important role for the onset of fracture. Some methods hardly affect the material at all while others can decrease the level of local strain at the onset of fracture down to about a third of the value for unaffected material. Furthermore, a method for characterizing the material based on full-field measurements is presented. The method is a fast and simple alternative to previously used inverse modelling procedures where the material model of a finite element simulation is updated iteratively to make the simulation produce the same results as the experiment.

  • 128. Eman, Jesper
    et al.
    Sundin, Karl-Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Spatially resolved observations of strain fields at necking and fracture of anisotropic hardened steel sheet material2009Ingår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 46, nr 13, s. 2750-2756Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work plastic strain localization, also referred to as necking, of press-hardened ultra-high strength steel is observed using digital speckle correlation. The region of the neck is studied during tensile tests of specimens specially designed to facilitate strain localization at an inner point of the material, thus avoiding edge effects on localization and fracture. By using measurements with a length scale small enough to properly resolve the neck, its growth and shape can be studied. Furthermore, the anisotropy of the material is investigated by examining specimens cut out at different angles to the rolling direction. It is seen that the local fracture strain of specimens cut out along the rolling direction is approximately twice as high as it is for specimens cut out perpendicular to the rolling direction.

  • 129.
    Enqvist, Evelina
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Ramanenka, Dmitrij
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Grácio, José
    TEMA – NRD, Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal. Aveiro Institute of Nanotechnology (AIN).
    Marques, Paula
    TEMA – NRD, Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal. Aveiro Institute of Nanotechnology (AIN).
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    The effect of ball milling time and rotational speed on ultra high molecular weight polyethylene reinforced with multiwalled carbon nanotubes2016Ingår i: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 37, nr 4, s. 1128-1136Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultra high molecular weight polyethylene (UHMWPE) composites reinforced with multiwalled carbon nanotubes (MWCNT) were produced using planetary ball milling. The aim was to develop a more wear resistant composite with increased mechanical properties to be used in stress bearing joints. The manufacturing technique, using ball-milling to incorporate MWCNT into UHMWPE matrix was investigated. The effect of manufacturing parameters such as effect of ball milling time and rotational speed on final composite was analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), particle size distribution and contact angle measurements. Ball milling as mixing technique for UHMWPE based composites is not a new approach but yet, the effect of time, rotational speed, loading of milling jar and type of ball mill has not been reported properly for UHMWPE. 0.5 and 1 wt% UHMWPE/MWCNTs were manufactured at different rotational speed and mixing time. The results indicate that rotational speed rather than mixing time is important for dispersing MWCNTs

  • 130.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A modified three point bend specimen2009Ingår i: Proceedings: nternationale sur la Rupture : Ottawa, Canada, July 12 - 17, 2009 = Comptes rendus, National Resources Canada , 2009, s. 184-192Konferensbidrag (Refereegranskat)
    Abstract [en]

    Steel profiles with slightly tapered cross section sides are not uncommon in older structures. The steels are often inhomogeneous and the fracture toughness varies across the thickness. In this project, the geometry of the standard three point bend specimen (ASTM E-1820) is modified to allow full thickness testing of tapered samples. The part of the project reported here deals with the J-integral of the modified specimen. The J-integral is calculated analytically and numerically with the finite element method for a linear and a non-linear material model and different specimen cross section proportions. A simple, single test fracture toughness evaluation procedure is proposed.

  • 131.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A modified three point bend specimen2008Ingår i: Multilevel Approch to Fracture of Materials, Components and Structures: 17th European Conference on Fracture / [ed] Jaroslav Plokluda; Petr Lukás; Pavel Sandera; Ivo Dlouhý, Brno: VUTIUM , 2008, Vol. 2, s. 1932-1939Konferensbidrag (Refereegranskat)
    Abstract [en]

    Steel profiles, such as angle sections in beams and girders, with slightly tapered cross section sides are not uncommon in older structures. Further, the fracture toughness of older and inhomogeneous steels varies in general across the thickness of a sample. The thickness of a machined, standard parallel-sided specimen of a tapered sample is in practice seldom more than 60-70 % of the full sample thickness and such a specimen captures in general inferior core material only. In view of this conundrum, a modified three point bend specimen with partly tapered sides has been designed so as to accommodate tapered samples. The project includes calibration, testing and evaluation of the modified specimen. The part of the project, which is reported here, is part analytical and part numerical and aimed at calculation of the stress intensity factor for various crack lengths, taper and specimen cross section proportions.

  • 132.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A modified three point bend specimen2007Ingår i: Experimental analysis of nano and engineering materials and structures: proceedings of the 13th international conference on experimental mechanics, Alexandroupolis, Greece, July 1-6, 2007 / [ed] Emmanuel E Gdoutos, Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag, 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    Certain types of structural elements, like riveted or rolled beams and girders, etc., of older steels, often have tapered flanges and the steels themselves are as a rule mor or less inhomogeneous. The fracture toughness at in-plane loading of related structural details, has been observed to vary significantly in the thickness direction and generally increases outwardly from the mid-section part. The most common fracture toughness test specimen used for testing of samples taken from oldes steel structures, in e.g. assessment work, is the three point bend specimen. This specimen, like all standard specimen types, is plane-parallel and if machined from a tapered part it will not necessarily yield a fair estimate of the effective fracture toughness for a through crack in situations where fracture toughness varies across the thickness. In view of this, a modified three point bend specimen with partly tapered sides has been designed so as to accomodate samples with this feature. The project includes calibration , testing and evalutation of the modified specimen. The firt part of the project, which is reported here, is mainly analytical and is aimed at obtaining a first and rough estimate of the order of influence the modified geometry upon crack tip parameters.

  • 133.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A revisit to the bending problem of a thin elliptic aelotropic plate with simply supported edge and uniform lateral load2007Ingår i: Zeitschrift für Angewandte Mathematik und Physik, ISSN 0044-2275, E-ISSN 1420-9039, Vol. 58, nr 2, s. 318-329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The complex solution method of Okubo for the deflection of a thin circular aelotropic plate with simply supported edge and uniform lateral load was extended to an elliptic plate by Ohasi. In his work however several inconsistencies appear, of which at least one disqualifies a central part. From a revisit to the works of Okubo and Ohasi a new solution for the deflection of a thin elliptic aelotropic plate with simply supported edge and uniform lateral load emerged. The solution is a generalisation of Okubo's solution and is valid for any angle between material and geometric principal axes. Previously known solutions, including those for circular plates, are reproduced as special cases of the new solution and results of numerical calculations in new situations appear reasonable.

  • 134.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A three-point bend specimen with partly tapered cross-section sides2010Ingår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 77, nr 10, s. 1537-1551Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The stress intensity factor and the J-integral have been derived analytically and numerically for a modified three-point bend specimen with partly tapered sides, for various crack lengths, taper and specimen cross-section proportions, in order to allow full-thickness testing of tapered samples, common in older steel structures, to obtain a fair effective fracture toughness value for a through thickness crack in inhomogeneous materials. The stress intensity factor is obtained with the approximate analytical method of Kienzler and Herrmann, based on the concept of material forces. The J-integral is calculated numerically with a 3D finite element model for a linear elastic material and an elastic ideal-plastic material. A simple single specimen fracture toughness evaluation procedure is proposed. It is found that the effect of taper in the range encountered in practice is small, of the order of a few percent.

  • 135.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    An overview of older structural steel and their properties2011Ingår i: International Workshop Strengthening of Steel Bridges: Topics of relevance for the BRIFAG project / [ed] Peter Collin; Mattias Nilsson; Milan Veljkovic, Luleå: Luleå tekniska universitet, 2011Konferensbidrag (Refereegranskat)
  • 136.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Att konstruera med stål : läromedel för konstruktörer: Modul 8, Utmattning2006Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 137.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Att konstruera med stål : läromedel för konstruktörer: Modul 9, Brottmekanik2006Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 138.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Decomposition of Eshelby's energy momentum tensor and application to path and domain independent integrals for the crack extension force of a plane circular crack in Mode III loadiing2007Ingår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 144, nr 1-2, s. 215-225Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vanishing divergence of Eshelby's energy momentum tensor allows formulation of path or domain independent integral expresssions of the crack extension force. In this work, a decomposition scheme of this tensor is presented, which results in zero divergence decomposed parts that allow formulation of expressions yielding the Mode I, II and III crack tip parameters J and K, with particular emphasis on Mode III, at present. By using the Mode III decomposed part of Eshelby's tensor and the virtual crack extension method, a path and a domain independent integral, both new, for the crack extension force of a plane cirular crack in axi-symmetric Mode III loading, are derived as examples of applicatioin.

  • 139.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Materialteknisk provning av konstruktionsstål från järnvägsbro över Åby älv2014Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Brottmekanisk provning, dragprovning och slagprovning av konstruktionsstål från undre ramstång i huvudfackverk, från långbalk och från tvärbalk i den nedmonterade järnvägsbron över Åby älv, uppförd 1951.

  • 140.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    On the point-wise J-value of axisymmetric plane cracks1998Ingår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 91, nr 3, s. L31-L36Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    A point-wise value of the J-integral for a radially expanding plane axisymmetric crack, which is path independent an yields the energy release rate, has been derived from Eshelby's energy momentum tensor taken in cylindrical coordinates. In particular the area integral in the expression for J by Carpenter et al. has not been found to be zero, as recently advanced by Jonsson and Nilsson, but in agreement with results of others, e.g. Bergkvist and Lan Huong

  • 141.
    Eriksson, Kjell
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    The support reaction of a simply supported and uniformly loaded thin circular aeolotropic plate2008Ingår i: Journal of applied mechanics, ISSN 0021-8936, E-ISSN 1528-9036, Vol. 75, nr 2, s. 10021-10028Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A previous analytical solution of the deflection of a thin circular aeolotropic plate, with simply supported edge and uniform lateral load, has been used to derive approximate series expressions for the plate support reaction, which are directly applicable in practice. The support reaction, which has been calculated for some typical anisotropic materials of varying degree of anisotropy, varies significantly along the plate perimeter and strongly anisotropic materials require in general a higher order series solution. Certain solution constants of previous deflection approximations were not found to harmonize and are therefore recalculated.

  • 142. Eriksson, Magnus
    et al.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Berggren, C.
    Nobel Biocare AB.
    Andersson, M.
    Nobel Biocare AB.
    Holmersson, R.
    Nobel Biocare AB.
    Carlström, E.
    Swedish Ceramic Institute, PO Box 5403, SE-402 29 Göteborg.
    New semi-isostatic high velocity compaction method to prepare titanium dental copings2004Ingår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 47, nr 4, s. 335-342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new method to prepare titanium dental copings from titanium powder was tested, involving high velocity compaction and various elastic forms, which were used to achieve a semi-isostatic effect during the impact. The tooth preparation die (mandrel) and the powder were placed inside an elastic form. The impact struck the elastic form, and the powder was compacted against the tooth preparation die. Several different elastomers were tested to find the best one. Cross-sections of the powder bodies were studied for density variations. The soft, flexible elastomer worked best to compact the powder. The highest densification could be focused closest to the mandrel where the coping should be milled out. The density in the highest density areas could locally reach 98-99%. If the method with elastic forms could be optimised to give as high a density as without elastic forms, a lower shrinkage and possible deformation of the copings could be reached.

  • 143. Eriksson, Magnus
    et al.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Finite element forming simulations in the development of high strength tubular components2001Ingår i: International Journal of Engineering Simulation, ISSN 1468-1137, Vol. 2, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Light weight structures with high structural performance are one of the most important goals for automotive and transportation applications. One manufacturing technology, aiming to enable low weight design, is the combined forming and quenching of tubular thin-walled profiles of high strength steel. For optimal utilisation of this technology it is necessary to simulate and analyse the processes involved in a fast and efficient way. In this work, experiments of high temperature bending of thin walled profiles are performed and the forming response force is compared with results from finite element simulations. The analysed forming is modelled as a constant temperature forming and the material data for the specified temperature is evaluated from experiments and literature. The simulations and experiments are conducted to study the ability of the finite element model to predict high temperature forming characteristics and simulate the influence of profile and tool geometry. The need for further improvements and developments in the simulation technology is however identified. This work is part of a research project LOWHIPS (Low Weight High Performance Steel structures) aiming to obtain new knowledge concerning the involved forming and quenching processes and how they will affect the performance of the product.

  • 144. Eriksson, Magnus
    et al.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Finite element modelling of tubular beams subjected to high temperature forming2000Ingår i: 3rd ESAFORM Conference on Material Forming, Inst. of steam and gas turbines, RWTH , 2000Konferensbidrag (Refereegranskat)
  • 145. Eriksson, Magnus
    et al.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Numerical and experimental investigation of the spray cooling process for sheet metal components2002Ingår i: Proceedings CD of the Fifth World Congress on Computational Mechanics, Vienna, Austria, July 7 - 12, 2002, Vienna: Vienna University of Technology , 2002Konferensbidrag (Refereegranskat)
  • 146. Eriksson, Magnus
    et al.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Somani, M.C.
    University of Oulu.
    Karjalainen, L.P.
    University of Oulu.
    Testing and evaluation of material data for analysis of forming and hardening of boron steel components2002Ingår i: Modelling and Simulation in Materials Science and Engineering, ISSN 0965-0393, E-ISSN 1361-651X, Vol. 10, nr 3, s. 277-294Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Finite element modelling and simulation is becoming an increasingly important tool in the development process for structural automotive components, manufactured using thermo-mechanical forming techniques. Accurate and reliable analysis of coupled thermo-mechanical processes requires efficient simulation tools as well as good quality and relevant material data, usually obtained by experimental testing of the mechanical and thermal properties. The work present in this paper concerns methods for obtaining and evaluating the mechanical properties, required for modelling the high-temperature forming of a high-strength boron-alloyed steel. The material data was obtained from high temperature compression tests and dilatometric measurements made using a Gleeble 1500 thermo-mechanical simulator. Two examples of finite element simulations using the data obtained are also presented. The first example is an isothermal finite element simulation of a thin-walled tubular beam subjected to high-temperature bending. The predicted press force showed acceptable agreement with experimental results in the initial part of the process. In the second example, a cylindrical specimen compressed during continuous cooling was simulated, and the press force and radial displacement were compared with experimental results. Again the simulations showed acceptable agreement with experimental results but indicated the need for further improvements in the simulation technology and methods used for material parameter evaluation.

  • 147. Federzoni, L.
    et al.
    Riedel, H.
    Coube, O.
    Oldenburg, Mats
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gethin, D.
    State of the art review - Comparison of computer models representing powder compaction process.1999Ingår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 42, nr 4, s. 301-311Artikel i tidskrift (Refereegranskat)
  • 148.
    Fisk, Martin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    FEM simulering av induktionsvärmningsprocess2007Ingår i: Svenska Mekanikdagar 2007: Program och abstracts / [ed] Niklas Davidsson; Elianne Wassvik, Luleå: Luleå tekniska universitet, 2007, s. 85-Konferensbidrag (Övrigt vetenskapligt)
  • 149.
    Fisk, Martin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling of induction heat treatment in a manufacturing chain2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Due to increased competitiveness in the aerospace industry, deeper knowledge of the manufacturing process is needed. It is, for example, known that the microstructure is important for the performance of the components. In order to make a cost effective prediction of a product's final shape and mechanical properties, modelling of the various processes in a manufacturing chain is of interest. The finite element method is the best and most common tool used for this purpose.The main route for manufacturing of structural components in aero engines are either forging, casting or fabrication. During these steps, manufacturing defects such as cracks or voids can occur. Repair welding is then necessary. However, welding changes the microstructure of the material. In order to restore the microstructure, and reduce welding residual stresses an heat treatment of the component is necessary. The heat treatment is usually performed by placing the component in a furnace, i.e. a global heat treatment, although it is only a local region that needs to be restored. One method to perform a local heat treatment is by induction heating.The possibility to replace global heat treatment with local using induction heating has been evaluated in the project, both numerically using the finite element method as well as with validation experiments. Finite element models has also been used in order to simulate induction heating in the manufacturing process chain of stainless steel tubes.The aim of this work has been to simulate a process chain consisting of repair welding and local heat treatment with induction heating. It is then possible to predict deformations as well the residual stress state and the change in microstructure. For this has a material model been developed. It is a dislocation density based flow stress model in which precipitate hardening for alloy 718 is taken into account.

  • 150.
    Fisk, Martin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of induction heating in manufacturing2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
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  • text
  • asciidoc
  • rtf