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  • 1.
    Andersson, Carl
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Predicting residual stresses in metal additive manufacturing by coupled finite element models2023Conference paper (Other academic)
    Abstract [en]

    Additive manufacturing (AM) is rapidly emerging as a feasible manufacturing method. The material is deposited in a layer-by-layer approach, enabling complex-shaped parts to be manufactured. However, the printed parts are typically distorted to some extent due to the residual stresses from the manufacturing stage. These residual stresses are a result of the material’s temperature fluctuations during the layer-by-layer deposition: as the material is heated, it expands, and when cooled, it shrinks. To address this issue, models have been developed capable of simulating the entire AM process. By employing modeling techniques, process optimization can be achieved by identifying suitable process parameters, eliminating the need for time-consuming trial-and-error experimentation. One of the enabling technologies to these models is the finite element method (FEM) where the deposited material and build plate is treated as a continuum discretized by finite elements (FE). This work provides an overview of the finite element models for AM and the couplings that can be made to predict the residual stresses and distortions of printed components more accurately. The coupling can be made on different scales, including the micro-, meso-, or part-scale. Micro-scale finite element models coupled with cellular automata models (FE-CA), initially developed by Gandin and Rappaz (1997), can predict the grain texture after solidification. Meso-scale models such as thermal models can predict the temperature history from the chosen scanning strategy. Subsequently, thermo-mechanical models can predict residual stresses and distortions. When it comes to predicting the distortions on a part-scale level, thermo-mechanical layer-by-layer lumping and inherent strain method can be used to reduce the computational time. The coupled thermo-mechanical FE models can be used with a physically based material model which is based on the material’s dislocation structure. For example, Lindgren et al. (2017) developed a dislocation density-based plasticity model. Here, FE-CA models can provide information about the grain orientation and grain size which are important parameters involving the strain hardening in a physically based model where the Taylor orientation factor is needed, and the Hall-Petch effect where the grain size is needed. Phase composition can be provided by a thermo-metallurgical model. Furthermore, the change in dislocation density is proportional to the plastic strain rate which is obtained from the meso- or part-scale thermo-mechanical model itself. Additionally, thermal activation can assist dislocations when passing obstacles such as precipitates or solutes, hence the prediction of an accurate temperature field is an important input to the physically based model.

    REFERENCES:

    Gandin, Ch.-A., Rappaz, M., 1997. A 3D Cellular Automaton algorithm for the prediction of dendritic grain growth. Acta Materialia. pp. 2187-2195.

    Lindgren, L.-E., Hao, Q., Wedberg, D., 2017. Improved and simplified dislocation density based plasticity model for AISI 316L. Mechanics of Materials. pp. 68-76.

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  • 2.
    Andersson, Carl
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Lundbäck, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Modeling the Evolution of Grain Texture during Solidification of Laser-Based Powder Bed Fusion Manufactured Alloy 625 Using a Cellular Automata Finite Element Model2023In: Metals, E-ISSN 2075-4701, Vol. 13, no 11, article id 1846Article in journal (Refereed)
    Abstract [en]

    The grain texture of the as-printed material evolves during the laser-based powder bed fusion (PBF-LB) process. The resulting mechanical properties are dependent on the obtained grain texture and the properties vary depending on the chosen process parameters such as scan velocity and laser power. A coupled 2D Cellular Automata and Finite Element model (2D CA-FE) is developed to predict the evolution of the grain texture during solidification of the nickel-based superalloy 625 produced by PBF-LB. The FE model predicts the temperature history of the build, and the CA model makes predictions of nucleation and grain growth based on the temperature history. The 2D CA-FE model captures the solidification behavior observed in PBF-LB such as competitive grain growth plus equiaxed and columnar grain growth. Three different nucleation densities for heterogeneous nucleation were studied, 1 × 1011, 3 × 1011, and 5 × 1011. It was found that the nucleation density 3 × 1011 gave the best result compared to existing EBSD data in the literature. With the selected nucleation density, the aspect ratio and grain size distribution of the simulated grain texture also agrees well with the observed textures from EBSD in the literature.

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  • 3.
    Andersson, Carl
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Lundbäck, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Modeling the Evolution of Grain Texture in Laser-Based Powder Bed Fusion Manufactured Alloy 6252023Conference paper (Other academic)
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  • 4.
    Azizoğlu, Yağız
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Modeling of Cold Pilgering of Stainless Steel Tubes2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cold pilgering is a complex forming process used to produce seamless tubes in terms of modeling due to the complexity in kinematic of tools, friction condition and material behavior. The process development has mostly been based on simple formulas and costly full-scale tryouts. The aim in this study is to develop validated Finite element models of cold pilgering to support design of a robust process.

    A three-dimensional thermo-mechanical Finite element models of cold pilgering has been developed in the course of the work leading to this thesis. The commercial code MSC. Marcwas used in the simulations. General 3D models are needed to be able to capture asymmetric deformation in cold pilgering. Elastic deflections of tools and roll stand were included in the model via linear and nonlinear springs that were calibrated versus experiments. A temperature dependent Chaboche type plasticity model was employed in this simulation to mimic strain hardening and softening behavior under multidirectional loading. The model parameters were optimized using multi-directional compression and uni-directional tensile tests. Heat exchange between tools and lubricant was included in the simulation via heat convection films on the surfaces. The film parameters were calibrated using experimental data. Simulation predictions for hardening, rolling force, process temperature and geometry were compared with experiments for validation purposes. The predictions showed overall good agreement with validation experiments enabling the use of this model for understanding and improving the process.

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  • 5.
    Azizoğlu, Yağız
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Temperature and plastic strain dependent Chaboche model for 316L used in simulation of Cold PilgeringManuscript (preprint) (Other academic)
  • 6.
    Azizoğlu, Yağız
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Sjöberg, Bengt
    Alleima Sverige AB, Sweden.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Modeling of cold pilgering of stainless-steel tubes2024In: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 112, p. 112-125Article in journal (Refereed)
  • 7.
    Bemani, M.
    et al.
    Eurecat, Centre Tecnològic de Catalunya, Metal Digital Manufacturing JRU, 08243 Manresa, Spain; CIEFMA - Department of Materials Science and Engineering, EEBE, Universitat Politècnica de Catalunya, Barcelona-Tech, 08019 Barcelona, Spain; School of Engineering, RMIT University, Melbourne 3001, Australia.
    Parareda, S.
    Eurecat, Centre Tecnològic de Catalunya, Metal Digital Manufacturing JRU, 08243 Manresa, Spain.
    Casellas, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics. Eurecat, Centre Tecnològic de Catalunya, Metal Digital Manufacturing JRU, 08243 Manresa, Spain.
    Frómeta, D.
    Eurecat, Centre Tecnològic de Catalunya, Metal Digital Manufacturing JRU, 08243 Manresa, Spain.
    Mateo, A.
    CIEFMA - Department of Materials Science and Engineering, EEBE, Universitat Politècnica de Catalunya, Barcelona-Tech, 08019 Barcelona, Spain.
    Das, R.
    School of Engineering, RMIT University, Melbourne 3001, Australia.
    Molotnikov, A.
    School of Engineering, RMIT University, Melbourne 3001, Australia.
    A Fast Method To Evaluate The Fatigue Resistance Of Additive Manufacturing Metal Specimens2023In: Euro Powder Metallurgy 2023 (Euro PM2023) Proceedings, European Powder Metallurgy Association (EPMA) , 2023Conference paper (Refereed)
  • 8.
    Casellas, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics. Eurecat, Centre Tecnològic de Catalunya, Manresa, Spain.
    Frómeta, D.
    Eurecat, Centre Tecnològic de Catalunya, Manresa, Spain.
    Parareda, S.
    Eurecat, Centre Tecnològic de Catalunya, Manresa, Spain.
    Grifé, L.
    Eurecat, Centre Tecnològic de Catalunya, Manresa, Spain.
    Tarhouni, I.
    Eurecat, Centre Tecnològic de Catalunya, Manresa, Spain.
    Sandin, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    When fracture toughness becomes essential for Lightweighting: Understanding cracking behaviour in high strength sheets2022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper (Refereed)
  • 9.
    Dalai, Biswajit
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Moretti, Marie Anna
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Åkerström, Paul
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Arvieu, Corinne
    University of Bordeaux, CNRS, Arts et Métiers Institute of Technology, Bordeaux INP, INRAE, I2M, Bordeaux, 33400, Talence, France.
    Jacquin, Dimitri
    University of Bordeaux, CNRS, Arts et Métiers Institute of Technology, Bordeaux INP, INRAE, I2M, Bordeaux, 33400, Talence, France.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Corrigendum to “Mechanical behavior and microstructure evolution during deformation of AA7075-T651” [J. Mater. Sci. Eng. A 822 (2021) 141615]2022In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 845, article id 143210Article in journal (Other academic)
  • 10.
    Dalai, Biswajit
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Moretti, Marie Anna
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Åkerström, Paul
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Arvieu, Corinne
    University of Bordeaux, CNRS, Arts et Métiers Institute of Technology, Bordeaux INP, INRAE, I2M, Bordeaux, 33400, Talence, France.
    Jacquin, Dimitri
    University of Bordeaux, CNRS, Arts et Métiers Institute of Technology, Bordeaux INP, INRAE, I2M, Bordeaux, 33400, Talence, France.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Mechanical behavior and microstructure evolution during deformation of AA7075-T6512021In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 822, article id 141615Article in journal (Refereed)
    Abstract [en]

    In view of developing a physics-based constitutive material model for AA7075-T651, the mechanical behavior and microstructure evolution of the material has been studied through compression tests using Gleeble thermo-mechanical simulator. The tests were performed at wide range of temperatures (room temperature (RT), 100, 200, 300, 400 and 500 °C) with two constant strain rates (0.01 and 1 s-1). The true stress-strain curves depicted an increase in the flow stress with increase in the strain rate and decrease in the deformation temperature, with an exception at RT. The effects of softening mechanisms, such as adiabatic heating, dissolution of precipitates, dynamic recovery (DRV) and dynamic recrystallisation (DRX), on the flow stress level, strain rate sensitivity (SRS) and temperature sensitivity over the entire range of temperatures were analyzed. Pertaining to the microstructure analysis, the intermetallic particles present in the initial as-received (AR) material were identified as (Al,Cu)6(Fe,Cu) and SiO2 with the help of back-scattered electron (BSE) imaging and energy dispersive X-ray spectroscopy (EDS). The microstructure of the material after the deformation processes were analyzed and compared with that of the AR state using inverse pole figures (IPF), grain orientation spread (GOS) and grain boundary rotation maps generated from electron back-scattered diffraction (EBSD) scans. DRV was observed for deformation at 300 °C, whereas a combination of DRV and incomplete DRX took place for 400 and 500 °C depending on the strain rate. The fraction of recrystallized grains was higher in case of deformation at higher temperature and lower strain rate. Furthermore, the difference in microstructure evolution on different surfaces of the deformed samples as well as at different locations on individual surfaces was also investigated.

  • 11.
    Dalai, Biswajit
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Moretti, Marie Anna
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Åkerström, Paul
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Esin, V. A.
    MINES ParisTech, PSL University, Centre des Matériaux (CNRS UMR 7633), Évry, France.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    High strain rate deformation behavior of AA7075-T6512022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper (Refereed)
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  • 12.
    Dalai, Biswajit
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Moretti, Marie Anna
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Åkerström, Paul
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Esin, Vladimir A.
    Centre Des Matériaux (CNRS UMR 7633), Mines Paris, PSL University, Évry, France.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Mechanical behavior and microstructure evolution during high strain rate deformation of AA7075-T6512022In: SN Applied Sciences, ISSN 2523-3963, E-ISSN 2523-3971, Vol. 4, no 10, article id 251Article in journal (Refereed)
    Abstract [en]

    The current study presents the effects of strain and temperature on the mechanical response and microstructure evolution in AA7075-T651 at high strain rates. Compression tests have been performed at room temperature (RT), 200, 300 and 400 °C using a Split-Hopkinson pressure bar (SHPB) setup with strain rates ranging between 1400 and 5300 s−1. For deformation at RT, the flow stress increases with increase in strain rate. Whereas deformation at elevated temperatures show a non-monotonous behavior of the flow stress with respect to the strain rate. This trait is attributed to the pronounced effects from the adiabatic shear bands (ASBs); namely, distorted shear bands (DSBs) and transformed shear bands (TSBs); and cracks resulting from the plastic deformation instability during hot deformation. The sequence of microstructure evolution is: inhomogeneity in the initial microstructure – DSB – TSB – crack –fracture. The feasibility of formation and growth of ASBs and cracks increases with increase in strain and temperature, neglecting any significant effect from the strain rate. During the compression tests, temperature of the material rises due to adiabatic heating. Considering a certain strain developed in the material, this adiabatic temperature rise decreases as the deformation temperature is increased. Furthermore, during individual deformation processes, the temperature rise increases with increasing strain. The adiabatic temperature leading to the formation of TSB is approximated to be 0.7 times of the melting temperature of the alloy. These results from the current study are to be used in developing a physics-based material model for the alloy.

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  • 13.
    Djebien, S.
    et al.
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
    Nohara, S.
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
    Nishida, M.
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
    Marth, Stefan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics. Swerim AB, Box 812, 971 25 Luleå, Sweden.
    Häggblad, Hans-Åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Strain Rate and Notch Radius Effects on Evaluating the Stress–Strain Relations Using the Stepwise Modeling Method2023In: Journal of Dynamic Behavior of Materials, ISSN 2199-7446Article in journal (Refereed)
  • 14.
    Fisk, Martin
    et al.
    Materials Science and Applied Mathematics, Malmö University, Malmö SE-205 06, Sweden; Division of Solid Mechanics, Lund University, P.O. Box 118, Lund SE-221 00, Sweden.
    Ristinmaa, Matti
    Division of Solid Mechanics, Lund University, P.O. Box 118, Lund SE-221 00, Sweden.
    Hultkrantz, Andreas
    AB SKF, Göteborg SE-415 50, Sweden.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Coupled electromagnetic-thermal solution strategy for induction heating of ferromagnetic materials2022In: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 111, p. 818-835Article in journal (Refereed)
    Abstract [en]

    Induction heating is used in many industrial applications to heat electrically conductive materials. The coupled electromagnetic-thermal induction heating process is non-linear in general, and for ferromagnetic materials it becomes challenging since both the electromagnetic and the thermal responses are non-linear. As a result of the existing non-linearities, simulating the induction heating process is a challenging task. In the present work, a coupled transient electromagnetic-thermal finite element solution strategy that is appropriate for modeling induction heating of ferromagnetic materials is presented. The solution strategy is based on the isothermal staggered split approach, where the electromagnetic problem is solved for fixed temperature fields and the thermal problem for fixed heat sources obtained from the electromagnetic solution. The modeling strategy and the implementation are validated against induction heating experiments at three heating rates. The computed temperatures, that reach above the Curie temperature, agree very well with the experimental results.

  • 15.
    Frómeta, D.
    et al.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència, 2, Manresa 08243, Spain.
    Parareda, S.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència, 2, Manresa 08243, Spain.
    Lara, A.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència, 2, Manresa 08243, Spain.
    Grifé, L.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència, 2, Manresa 08243, Spain.
    Tarhouni, I.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència, 2, Manresa 08243, Spain.
    Casellas, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics. Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència, 2, Manresa 08243, Spain.
    A new cracking resistance index based on fracture mechanics for high strength sheet metal ranking2021Conference paper (Refereed)
    Abstract [en]

    Driven by current safety and weight reduction policies in the automotive sector, the development of new high strength sheet metal products has experienced unprecedented growth in the last years. With the emergence of these high strength materials, new challenges related to their limited ductility and higher cracking susceptibility have also raised. Accordingly, the development of new fracture criteria accounting for the material's cracking resistance has become unavoidable. In this work, a new cracking resistance index (CRI) based on fracture mechanics is proposed to classify the crack propagation resistance (i.e. the fracture toughness) of high strength metal sheets. The index is based on the fracture energy obtained from tensile tests with sharp-notched specimens. The procedure is very fast and simple, comparable to a conventional tensile test, and it may be used as routine testing for quality control and material selection. The CRI is investigated for several advanced high strength steel (AHSS) sheets of 0.8-1.6 mm thickness with tensile strengths between 800 and 1800 MPa. The results show that the proposed index is suitable to rank high strength steel sheets according to their crack propagation resistance and it can be correlated to the material's crashworthiness and edge cracking resistance.

  • 16.
    Garcia-Llamas, Eduard
    et al.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència, 2, Manresa, Barcelona, 08243, Spain.
    Pujante, Jaume
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència, 2, Manresa, Barcelona, 08243, Spain.
    Frómeta, David
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència, 2, Manresa, Barcelona, 08243, Spain.
    Corón, David
    Gestamp, Autotech Engineering Spain Aie, Polígono Industrial Can Stela, Carrer Edison, 4, Barcelona, Sant Esteve Sesrovires, 08635, Spain.
    Galceran, Laura
    Gestamp, Autotech Engineering Spain Aie, Polígono Industrial Can Stela, Carrer Edison, 4, Barcelona, Sant Esteve Sesrovires, 08635, Spain.
    Golling, Stefan
    Gestamp R&D, Box 828, Luleå, 97 125, Sweden.
    Seijas, Carlos
    Gestamp R&D, Center China Autotech Engineering Co., Ltd, Unit 10–12, Block 21, Lane 56, Antuo Rd, Shanghai, 201805, China.
    Casellas, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Optimization of Thick 22MnB5 Sheet Steel Part Performance through Laser Tempering2023In: Metals, ISSN 2075-4701, Vol. 13, no 2, article id 396Article in journal (Refereed)
    Abstract [en]

    Press Hardening offers the possibility to obtain a wide range of mechanical properties through microstructural tailoring. This strategy has been successfully applied in thin sheet components, for instance, through differential cooling strategies. The application of these added value features to truck components implies adapting the process to the manufacture of thick sheet metal. This introduces an additional layer of complexity, but also opportunity, in a process where the final microstructure and, thus the mechanical performance is generated in the press shop. This work presents a study on optimizing the crash worthiness and impact energy absorption on a press hardened thick 22MnB5 steel sheet. Different microstructure design strategies have been studied, including ferrite-Pearlite (representative of a differential heating and austenitization strategy), in-die generated Bainite (representative of differential cooling) and Tempered Martensite (generated through laser tempering), keeping a fully hardened martensite as a reference condition. The material performance has been compared in terms of the monotonic properties, useful for anti-intrusion performance, and Essential Work of Fracture, a well-suited parameter to predict the crash failure behavior of high strength steels. The results show that laser tempering offers properties similar to Bainite-based microstructures and can be a successful replacement in components where the sheet thickness does not allow for the fine control of the in-die thermomechanical evolution.

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  • 17.
    Gonçalves, L. A.
    et al.
    Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE), Campus Norte UPC, 08034 Barcelona, Spain.
    Jiménez, S.
    Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE), Campus Norte UPC, 08034 Barcelona, Spain; Universitat Politècnica de Catalunya (UPC), Campus Norte UPC, 08034 Barcelona, Spain.
    Cornejo, A.
    Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE), Campus Norte UPC, 08034 Barcelona, Spain; Universitat Politècnica de Catalunya (UPC), Campus Norte UPC, 08034 Barcelona, Spain.
    Barbu, L. G.
    Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE), Campus Norte UPC, 08034 Barcelona, Spain; Universitat Politècnica de Catalunya (UPC), Campus Norte UPC, 08034 Barcelona, Spain.
    Parareda, S.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, 08243 Manresa, Spain.
    Casellas, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics. Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, 08243 Manresa, Spain.
    Numerical simulation of a rapid fatigue test of high Mn-TWIP steel via a high cycle fatigue constitutive law2023In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 168, article id 107444Article in journal (Refereed)
    Abstract [en]

    The generation of reliable data in the high cycle fatigue domain is crucial to support further metallurgic developments of fatigue optimized steel grades. Commonly employed for this aim, traditional standardized characterization methods are expensive and time-consuming. Thus, to circumvent these limitations, different accelerated fatigue testing methodologies have been proposed. In this work, the rapid fatigue test based on stiffness evolution is numerically reproduced using the finite element method for a specific grade of twinning-induced plasticity steel. A high cycle fatigue constitutive law grounded on the continuum damage mechanics framework is employed for this purpose. To adequately capture the material non-linear behavior observed in the experiments, a novel hardening–softening stress–strain curve for damage is proposed. The entire load history in the fatigue domain is modeled. A cycle-jump algorithm is used to improve the computational efficiency of the simulations. It is shown that a reduction of about 55% in the analysis elapsed time is reached by using this algorithm, while the result accuracy is maintained. Finally, the good agreement between numerical and experimental results, revealed by a maximum relative error smaller than 6.0%, evidences the potential of the present constitutive formulation to model the behavior of metals in the high cycle fatigue domain.

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  • 18.
    Gustafsson, David
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Effect of shear cutting on metal fatigue2024Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lightweighting of automotive and heavy-duty vehicle components is an important task that does not need any further motivation or background. It can be read in a large part of the technical papers in the field. A common approach for finding lighter solutions is to increase the material grade while decreasing the material thickness. Often in combination with design changes. For perfectly smooth components this is not an issue, but when cut edges from manufacturing processes are present the situation changes. One topic to address is that increased material grade often means increased notch and surface damage sensitivity. This has implications both on forming and fatigue. The reason for selecting a higher strength material is to allow for higher stresses in design. It has however been shown that for a given stress level the fatigue performance of a higher strength material could be worse than for a lower strength counterpart if punched holes or trimmed edges are present. This means that in the search of lower weight there is a risk of increasing stresses, and at the same time selecting a material that is less suited to handle this increase. Hence, engineers and developers are put in a position where these effects must be quantified to find the most efficient solution. This quantification is a cumbersome and expensive task, often including a considerable amount of testing. Important sources of fatigue life reduction in this context are the residual stresses in the loading direction and the surface roughness in the cut edge. This thesis aims to present an overview of metal fatigue in the context of shear cut components. Necessary knowledge regarding the shear cutting process is provided along with a description of numerical methods and considerations for process simulations. These findings are then applied to the presented papers where the first introduces a simplified approach for numerical simulation of shear cutting to obtain residual stresses. In this approach the simplification mainly lies in the failure model calibration. The second paper studies the possibility of using the obtained residual stresses together with measured values of surface roughness to quantify fatigue life reduction of shear cut specimens.  

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  • 19.
    Gustafsson, David
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Olsson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Sergi, Parareda
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Manresa, 08243, Spain; CIEFMA, Universitat Politècnica de Catalunya, Barcelona, 08019, Spain.
    Ortiz-Membrado, Laia
    CIEFMA, Universitat Politècnica de Catalunya, Barcelona, 08019, Spain.
    A simplified approach for simulation of shear cutting2023Conference paper (Refereed)
    Abstract [en]

    Shear cutting, such as punching and trimming, of sheet metals is a widely used process in the automotive and heavy-duty vehicle industry due to low running costs and low cycle times. It's known that the edge properties obtained from this process has an impact both on formability and fatigue resistance of the formed part. The purpose of this contribution is to present a novel methodology for simulation of shear cutting processes taking a simplistic and phenomenological approach, resulting in an industry feasible simulation setup, simulation time and experimental workload. The task of simulating shear cutting processes includes high nonlinearities, large deformations, and crack propagation. A common approach is to use extensive material characterization to feed a material model including failure. Several specimen geometries are investigated to capture different stress states, resulting in a test and simulation matrix that could be overwhelming for industrial users. In this work it was investigated if a single tensile test and a punching test could be used for calibration of a material model including plastic flow and failure. Three different high strength materials were investigated using different cutting clearances and sheet thicknesses, one aluminium alloy and two complex phase steels. Characterization of the resulting cut edges were used for validation of the simulation results. It is shown that good agreement between simulation and experiments is achieved in terms of punch force and displacement. The main characteristics of the cut edge is also captured. Hence, using this simplified approach for simulation of shear cutting processes could reduce time to market and development cost for implementation of new materials by providing information about the process effects to a minimum of simulation and experimental effort.

  • 20.
    Gustafsson, David
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Parareda, S.
    Eurecat, Centre Tecnologic de Catalunya, Spain.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Kajberg, Jörgen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Olsson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Effect Of Cutting Clearance And Sandblasting On Fatigue Of Thick CP800 Steel Sheets2022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper (Refereed)
  • 21.
    Gustafsson, David
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Parareda, Sergi
    Eurecat, Plaça de la ciència 2, 08242 Manresa; CIEFMA, EEBE, Universitat Politècnica de Catalunya-BarcelonaTech, 08019 Barcelona, Spain.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Kajberg, Jörgen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Olsson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Effect of cutting clearance and sandblasting on fatigue of thick CP800 steel sheets for heavy-duty vehicles2022In: Hot Sheet Metal Forming of High-Performance Steel: proceedings / [ed] Mats Oldenburg; Jens Hardell; Daniel Casellas, Wissenschaftliche Scripten , 2022, p. 315-322Conference paper (Refereed)
    Abstract [en]

    Effect from manufacturing processes on fatigue properties of high-strength thick steel sheets have gained increased attention the recent years, due to new demands on the heavy-duty vehicle (HDV) industry to reduce the carbon footprint. The aim of this study is to add knowledge of the effect of shear cutting clearance on the fatigue behaviour of complex phase CP800 thick steel sheets. In addition, sandblasting and its effect on the fatigue properties are studied. Service loads are fluctuating loads acting on chassis component making fatigue an important failure mode. The fatigue strength usually follows the yield strength of the material and hence weight could in theory be saved by using steels of higher strength. However, in the presence of edge defects this relation does not necessarily hold, this leads to large safety factors of the design and under-utilization of the high-strength material. Thus, an increased knowledge about the effect from manufacturing processes on fatigue properties is important for the quest to achieve weight reduction. This is particularly true for thick sheets which, to the best of our knowledge, are less investigated than their thinner counterparts, but of high importance for the HDV development.

     

    In this paper, empirical results from fatigue testing of complex phase steel CP800, subjected to punching and trimming, are presented. Results for different cutting clearances are compared as well as the effect of sandblasting. A fast fatigue testing method called Rapid fatigue test based on stiffness evolution is utilized. The results show the improvement obtained by using sandblasting as well as illustrating the effect of different cutting clearances. These results can be used as a guidance for design and production of HDV components, where cutting clearance is set. Furthermore, the results can be used as an input for discussions whether the extra costs associated with sandblasting is motivated or not for components made from high strength, thick steel sheets.

  • 22.
    Gustafsson, David
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Parareda, Sergi
    Eurecat.
    Munier, Rémi
    ArcelorMittal Global R&D.
    Olsson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    High cycle fatigue life estimation of punched and trimmed specimens considering residual stresses and surface roughnessManuscript (preprint) (Other academic)
  • 23.
    Gustafsson, David
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Parareda, Sergi
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Manresa, 08243, Spain; Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Manresa, 08243, Spain.
    Ortiz-Membrado, Laia
    CIEFMA, Universitat Politècnica de Catalunya, Barcelona, 08019, Spain.
    Mateo, Antonio
    CIEFMA, Universitat Politècnica de Catalunya, Barcelona, 08019, Spain.
    Jiménez-Piqué, Emilio
    CIEFMA, Universitat Politècnica de Catalunya, Barcelona, 08019, Spain.
    Olsson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Simulation of metal punching and trimming using minimal experimental characterization2023In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 321, article id 118148Article in journal (Refereed)
    Abstract [en]

    This paper presents a validated finite element modeling approach for simulating shear cutting, needing a minimal amount of experimental characterization. Only one uniaxial tensile test and one force–displacement relationship from a punching experiment are needed for calibration, with maintained prediction accuracy compared to more experimentally demanding approaches. A key ingredient is the observation that the Lode angle parameter is close to zero in the fracture region, postulating that the fracture strain only depends on stress triaxiality, with one free calibration parameter. The true stress–strain behavior is provided from inverse modeling of the tensile test, whereas the fracture model is calibrated using the punching test. The model is verified for different materials by comparing force–displacement curves for punching experiments not used in the calibration. The prediction error for the intrusion is below 4%. A validation is made for two setups. The local residual stresses are measured using Focused Ion-Beam Digital Image Correlation (FIB-DIC). The simulated values are within the experimental bounds. Cut edge morphology and plastic strains obtained by nano-indentation mappings are compared to simulation results, showing a decent agreement. For trimming, the cut edge morphology prediction performance decreases at 17% cutting clearance while it is maintained over the whole range for punching. The predicted hardness values have a mean absolute percentage error below 7.5%. Finally, the effect of element size and remeshing is discussed and quantified. The minimal experimental characterization and simulation effort needed, enables an efficient optimization of the cutting process in the industry.

  • 24.
    Hammarberg, Samuel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    A Study on Sandwich Structures: Development, Mechanical Characterization and Numerical Modeling2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Legislative demands force the automotive industry to reduce greenhouse gas (GHG) emissions. At the same time, crashworthiness must not be compromised. A ve-hicle’s GHG emissions, such as carbon dioxide, is dependent on its fuel consump-tion. Lowering the vehicle weight, reducing fuel consumption, will therefor reduce emissions. Thus, high performance lightweight materials and structures are on demand. Several methods for achieving high-performance lightweight components are available. One of the most successful approaches has been replacing mild steels with press-hardened steels, e.g. ultra high strength steels (UHSS). In the press-hardening process, a low-alloyed boron steel blank is austenitized followed by simultaneously forming and cooling. By controlling cooling rates, a martensitic microstructure can be obtained, resulting in components with superior properties compared to mild steels. Other methods of achieving lightweight components in-clude the usage of sandwich structures where stiff skins are bonded to a low-density core. In the present thesis, several types of sandwich structures are studied both numerically and experimentally. A UHSS sandwich with a bidirectionlly corru-gated core, intended for stiffness application, is manufactured and evaluated in three-point bending. Finite element models are utilized to recreate the three-point bend test. A large amount of finite elements are required for precise discretization of the core. The number of finite elements are reduced by replacing the sandwich with an homogeneous, equivalent model with input data obtained from analyzing representative volume elements (RVEs) of the core, subjected to periodic and ho-mogeneous boundary conditions. Good agreement is found between experiments and finite element models. A UHSS sandwich with a partly perforated core is evaluated numerically for energy absorption applications. Several hole configu-rations for the core are evaluated with respect to specific energy absorption. A fracture criterion is utilized for the sandwich skins. Computational time is re-duced by homogenization of the core using a stress-resultant based constitutive model. It is found that the sandwich concept allows for an increase in specific energy absorption and that the computational time can be reduced while still be-ing able to predict energy absorption. An experimental methodology is developed for mechanical characterization of micro-sandwich materials. Tools are developed for loading the micro-sandwich in out-of-plane tension and shear, where digital image correlation is used for measuring displacements fields and fracture of the micro-sandwich core. Statistical methods are adopted for analyzing the variation in the mechanical properties of the micro-sandwich from which statistical means may be obtained. The experimental data is used as input for constitutive models, simulating the micro-sandwich material subjected to peeling, using a T-peel test. The numerical models are validated against experiments, found to agree within one standard deviation, suggesting that the experimental methodology produces robust data.The present work has thus presented methods, further increasing the usability of UHSS with regard to lightweighting, and explored how such components may be simulated numerically with adequate accuracy and reasonable computation time. Furthermore, the present thesis contributes by presenting methods for character-izing micro-sandwich materials, including statistical methods for analyzing scatter in mechanical properties, and how such sandwich materials may be modeled, tak-ing elasto-plasticity and damage into account. These results opens up possibilities for further development and optimization of lightweight constructions.

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  • 25.
    Hammarberg, Samuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Kajberg, Jörgen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Larsson, Simon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Moshfegh, Ramin
    Lamera AB, Odhners gata 17, 42130 Västra Frölunda, Sweden.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Calibration of orthotropic plasticity- and damage models for micro-sandwich materials2022In: SN Applied Sciences, ISSN 2523-3963, E-ISSN 2523-3971, Vol. 4, no 6, article id 182Article in journal (Refereed)
    Abstract [en]

    Sandwich structures are commonly used to increase bending-stiffness without significantly increasing weight. In particular, micro-sandwich materials have been developed with the automotive industry in mind, being thin and formable. In the present work, it is investigated if micro-sandwich materials may be modeled using commercially available material models, accounting for both elasto-plasticity and fracture. A methodology for calibration of both the constitutive- and the damage model of micro-sandwich materials is presented. To validate the models, an experimental T-peel test is performed on the micro-sandwich material and compared with the numerical models. The models are found to be in agreement with the experimental data, being able to recreate the force response as well as the fracture of the micro-sandwich core.

  • 26.
    Hammarberg, Samuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Kajberg, Jörgen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Larsson, Simon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Moshfegh, Ramin
    Lamera AB, A Odhners Gata 17, 421 30 Västra Frölunda, Sweden.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Novel Methodology for Experimental Characterization of Micro-Sandwich Materials2021In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 14, no 16, article id 4396Article in journal (Refereed)
    Abstract [en]

    Lightweight components are in demand from the automotive industry, due to legislation regulating greenhouse gas emissions, e.g., CO2. Traditionally, lightweighting has been done by replacing mild steels with ultra-high strength steel. The development of micro-sandwich materials has received increasing attention due to their formability and potential for replacing steel sheets in automotive bodies. A fundamental requirement for micro-sandwich materials to gain significant market share within the automotive industry is the possibility to simulate manufacturing of components, e.g., cold forming. Thus, reliable methods for characterizing the mechanical properties of the micro-sandwich materials, and in particular their cores, are necessary. In the present work, a novel method for obtaining the out-of-plane properties of micro-sandwich cores is presented. In particular, the out-of-plane properties, i.e., transverse tension/compression and out-of-plane shear are characterized. Test tools are designed and developed for subjecting micro-sandwich specimens to the desired loading conditions and digital image correlation is used to qualitatively analyze displacement fields and fracture of the core. A variation of the response from the material tests is observed, analyzed using statistical methods, i.e., the Weibull distribution. It is found that the suggested method produces reliable and repeatable results, providing a better understanding of micro-sandwich materials. The results produced in the present work may be used as input data for constitutive models, but also for validation of numerical models.

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  • 27.
    Hassila, Carl-Johan
    et al.
    Uppsala Universitet, Uppsala University.
    Malmelöv, Andreas
    Luleå University of Technology.
    Andersson, Carl
    Luleå University of Technology.
    Hektor, Johan
    Malmö Universitet, Malmö University.
    Fisk, Martin
    Malmö Universitet, Malmö University.
    Wiklund, Urban
    Uppsala Universitet, Uppsala University.
    Lundbäck, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Influence of scan strategy on residual stresses in laser powder bed fusion manufactured alloy 718: Modeling an experimentsManuscript (preprint) (Other academic)
  • 28.
    Hassila, C.-J.
    et al.
    Department of Materials Science and Engineering, Division of Applied Materials Science, Uppsala University, Uppsala, Sweden.
    Malmelöv, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Andersson, Carl
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Hektor, J.
    Department of Materials Science and Applied Mathematics, Malmö University, Malmö, Sweden.
    Fisk, M.
    Department of Materials Science and Applied Mathematics, Malmö University, Malmö, Sweden; Department of Construction Sciences, Division of Solid Mechanics, Lund University, Lund, Sweden.
    Wiklund, U.
    Department of Materials Science and Engineering, Division of Applied Materials Science, Uppsala University, Uppsala, Sweden.
    Lundbäck, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Influence of Scanning Strategy on Residual Stresses in Laser Powder Bed Fusion Manufactured Alloy 718: Modelling and Experiments2022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper (Refereed)
  • 29.
    Jelagin, Denis
    et al.
    Department of Civil and Architectural Engineering, KTH – Royal Institute of Technology, Stockholm, Sweden.
    Olsson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Raab, Christiane
    Concrete and Asphalt, Empa, Swiss Federal Laboratories for Material Science and Technology, Duebendorf, Switzerland.
    Partl, Manfred N.
    PaRRC Partl Road Research Consulting, Oeschgen, Switzerland.
    Experimental and numerical modelling of shear bonding between asphalt layers2023In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 24, no S1, p. 176-191Article in journal (Refereed)
    Abstract [en]

    Interlayers in asphalt pavements are potential structural damage initiators. In order to better understand the quantitative role of interlayer parameters, such as surface roughness, binder type, binder content and loading type on interlayer shear strength, this paper focuses on the effects of particle interlock and contact conditions on interlayer strength through experimental and numerical modelling. Experimentally, interlayer shear box strength tests on a model material consisting of stiff binder blended with steel balls are performed with and without normal force confinement. A Discrete Element method model of the test is developed using measurements of the model material for calibrating the contact law and for validating the model. It is shown that this model captures adequately the measured force-displacement response of the specimens. It is thus a feasible starting point for numerically and experimentally studying the role of binder and tack coat regarding interlayer shear strength of real asphalt layers.

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  • 30.
    Jonsson, Simon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Kajberg, Jörgen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Impact crash tests of high-strength steels using 3D high-speed digital image correlation and finite element analysis2022In: 8th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: May 30th - June 2nd, 2022, Barcelona, Spain / [ed] Mats Oldenburg, Jens Hardell, Daniel Casellas, Auerbach: Verlag Wissenschaftliche Scripten , 2022, p. 119-126Conference paper (Other academic)
    Abstract [en]

    The automotive industry is currently adapting to a new reality, where anthropogenic emissions need to decrease significantly. To meet present and future demands of vehicle design, press harden-ing techniques to produce complex geometries with high strength and ductility as well as good precision are of great interest. New generations of hot forming steels enable both further weight reductions by using thinner sheets as well as better crash performance due to its ability to improve the structural integrity of the body-in-white. To promote the use of these new steel grades, it is important to study their performance using well-instrumented lab scale test of full-scale compo-nents. Since these tests are often time consuming and expensive, calibrating constitutive models with tensile specimens and using finite element analysis is a more cost-effective alternative. How-ever, these calibrated models should be validated against full-scale experiments to verify their effectiveness in predicting the material behaviour in complex crash environments. In this paper, a high-speed 3D digital image correlation experiment is performed on a crash box under axial com-pression. The material is a hot forming steel grade with a specified tensile strength of 1000 MPa. The axial crash tests are modelled based on a visco-plastic model calibrated by high-speed tensile tests. The computed results in terms of force response and obtained deformations agree well with the corresponding measurements.

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  • 31.
    Jonsson, Simon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Kajberg, Jörgen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Impact crash tests using high-speed 3D digital image correlation2022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper (Refereed)
    Download full text (pdf)
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  • 32.
    Jonsson, Simon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Kajberg, Jörgen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Evaluation of Crashworthiness Using High-Speed Imaging, 3D Digital Image Correlation, and Finite Element Analysis2023In: Metals, E-ISSN 2075-4701, Vol. 13, no 11, article id 1834Article in journal (Refereed)
    Abstract [en]

    To promote the use of newhigh-strengthmaterials in the automotive industry, the evaluation of crashworthiness is essential, both in terms of finite element (FE) analysis aswell as validation experiments. Thiswork proposes an approach to address the crash performance through high-speed imaging combined with 3D digital image correlation (3D-DIC). By tracking the deformation of the component continuously, cracks can be identified and coupled to the load and intrusion history of the experiment. The so-called crash index (CI) and its decreasing rate (CIDR) can then be estimated using only one single (or a few) component, instead of a set of components with different levels of intrusion and crushing. Crash boxes were axially and dynamically compressed to evaluate the crashworthiness of TRIP-aided bainite ferrite steel and press-hardenable steel. Acalibrated rate-dependent constitutivemodel, and a phenomenological damage model were used to simulate the crash box testing. The absorbed energy, the plastic deformation, and the CIDR were evaluated and compared to the experimentally counterparts. When applying the proposed method to evaluate the CIDR, a good agreement was found when using CI:s reported by other authors using large sets of crash boxes. The FE analyses showed a fairly good agreement with some underestimation in terms of energy absorptions. The crack formation was overestimated resulting in too high a predicted CIDR. It is concluded that the proposed method to evaluate the crashworthiness is promising. To improve the modelling accuracy, better prediction of the crack formation is needed and the introduction of the intrinsic material property, fracture toughness, is suggested for future investigations and model improvements.

  • 33.
    Jonsén, Pär
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Westerberg, Lars-GöranLuleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.Larsson, SimonLuleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.Olsson, ErikLuleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Svenska Mekanikdagar 20222022Conference proceedings (editor) (Refereed)
  • 34.
    Lara, A.
    et al.
    Eurecat, Centre Tecnològic de Catalunya, Plaça de la Ciència, 2, Manresa 08243, Spain.
    Frometa, D.
    Eurecat, Centre Tecnològic de Catalunya, Plaça de la Ciència, 2, Manresa 08243, Spain.
    Parareda, S.
    Eurecat, Centre Tecnològic de Catalunya, Plaça de la Ciència, 2, Manresa 08243, Spain.
    Casellas, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics. Eurecat, Centre Tecnològic de Catalunya, Plaça de la Ciència, 2, Manresa 08243, Spain.
    Larour, P.
    voestalpine Stahl GmbH, voestalpine-Straße 3, 4020 Linz, Austria.
    Hinterdorfer, J.
    voestalpine Stahl GmbH, voestalpine-Straße 3, 4020 Linz, Austria.
    Atzema, E.
    Tata Steel, P.O. Box 10.000, 1970 CA IJmuiden, The Netherlands.
    Heuse, M.
    Faurecia Autositze GmbH, Garbsener Landstraße 7, 30419 Hannover, Germany.
    Sheared edge formability characterization of cold-rolled advanced high strength steels for automotive applications2022In: IOP Conference Series: Materials Science and Engineering / [ed] Sandrine Thuillier, Vincent Grolleau, Hervé Laurent, Institute of Physics (IOP), 2022, Vol. 1238, article id 012029Conference paper (Refereed)
    Abstract [en]

    Edge cracking has become a limiting factor in the use of some advanced high strength steels (AHSS) for high-performance automotive applications. This fact has motivated the development of a multitude of experimental tests for edge formability prediction over the last years. In this sense, the Hole Expansion Test (HET) according to ISO16630 has been established in the automotive industry as a standard procedure for edge cracking sensitivity ranking. However, whereas it may be useful for rapid material screening, the results are often not accurate and reliable enough. Consequently, alternative methods based on Digital Image Correlation (DIC) have been proposed aimed at improving the prediction of edge cracking occurrence during forming and obtaining useful strain data that can be implemented in forming simulations. This paper explores the applicability of different DIC-based methods, such as Half-Specimen Dome Tests, Sheared Edge Tensile Tests, and KWI hole expansion tests with a flat nosed punch, for characterizing the edge formability of three cold-rolled AHSS sheets. The results obtained from the different testing methods are compared and validated with a laboratory-scale demonstrator. Finally, the limitations and advantages of the different methods are discussed.

  • 35.
    Larsson, Fredrik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    A Testing Methodology for Hot Rolled High Strength Steels Under Warm Forming Conditions2022In: Hot Sheet Metal Forming of High-Performance Steel: proceedings / [ed] Mats Oldenburg; Jens Hardell; Daniel Casellas, Wissenschaftliche Scripten , 2022, p. 411-418Conference paper (Refereed)
    Abstract [en]

    For the reduction of the environmental footprint of Heavy-Duty vehicles (HDV), lighter chassiscomponents can be considered. A lighter HDV chassis gives the opportunity of lower fuel consumption, increased payloads, and savings of material resources. One way of achieving this, is to reduce thicknesses of components in combination of using higher strength steels. For the aim of forming UHSS into complex geometries the need to characterize thick sheet metal at elevated temperatures arises. This work aims at expanding earlier research of characterization of thinner sheet metal and create a testing methodology for tensile tests of 7 mm thick steel sheets at elevated temperatures. An experimental methodology for evaluating high strength steel under warm conditions have been developed and demonstrated. A Digital Image Correlation system is used to extract strain fields for all three testing temperatures. This together with an automatized induction system pre-defined temperature cycles are applied. When the desired Hollomon-Jaffe constant is obtained the tensile test is executed. The methodology shows promising results with good repeatability of stress-strain curves. The methodology shows good stability and are promising for future development and investigations of high strength steels under warm forming conditions.

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  • 36.
    Larsson, Fredrik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    High Temperature Characterization of 7 mm UHSS2022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper (Refereed)
  • 37.
    Larsson, Simon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Particle-Based Methods for Modeling Granular Materials2022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå: Luleå tekniska universitet, 2022Conference paper (Refereed)
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  • 38.
    Larsson, Simon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Rodriguez Prieto, Juan Manuel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials. Mechanical Engineering Department, EAFIT University, Medellín, Colombia.
    Gustafsson, Gustaf
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Häggblad, Hans-Åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    The particle finite element method for transient granular material flow: modelling and validation2021In: Computational Particle Mechanics, ISSN 2196-4378, Vol. 8, no 1, p. 135-155Article in journal (Refereed)
    Abstract [en]

    The prediction of transient granular material flow is of fundamental industrial importance. The potential of using numerical methods in system design for increasing the operating efficiency of industrial processes involving granular material flow is huge. In the present study, a numerical tool for modelling dense transient granular material flow is presented and validated against experiments. The granular materials are modelled as continuous materials using two different constitutive models. The choice of constitutive models is made with the aim to predict the mechanical behaviour of a granular material during the transition from stationary to flowing and back to stationary state. The particle finite element method (PFEM) is employed as a numerical tool to simulate the transient granular material flow. Use of the PFEM enables a robust treatment of large deformations and free surfaces. The fundamental problem of collapsing rectangular columns of granular material is studied experimentally employing a novel approach for in-plane velocity measurements by digital image correlation. The proposed numerical model is used to simulate the experimentally studied column collapses. The model prediction of the in-plane velocity field during the collapse agrees well with experiments.

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  • 39.
    Larsson, Simon
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Rodríguez Prieto, Juan Manuel
    Mechanical Engineering Department, EAFIT University, Medellín, Colombia.
    Heiskari, Hannu
    Metso Outotec – Research Center, Pori, Finland.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    A Multi-Physics Approach for Modelling of Stirred Media Mills2021Conference paper (Refereed)
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  • 40.
    Latorre, Nuria
    et al.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Polymeric and Composite Processes, Av. Universitat Autònoma, 23 – 08290 Cerdanyola del Vallès, Spain; AMADE, Polytechnic School, University of Girona, Av. Universitat de Girona, 4. 17003 Girona, Spain .
    Casellas, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics. Eurecat, Centre Tecnològic de Catalunya, Unit of Polymeric and Composite Processes, Av. Universitat Autònoma, 23 – 08290 Cerdanyola del Vallès, Spain.
    Costa, Josep
    AMADE, Polytechnic School, University of Girona, Av. Universitat de Girona, 4. 17003 Girona, Spain.
    A mechanical interlocking joint between sheet metal and carbon fibre reinforced polymers through punching2023In: IOP Conference Series: Materials Science and Engineering / [ed] Nader Asnafi, Lars-Erik Lindgren, Institute of Physics (IOP), 2023, Vol. 1284, article id 012001Conference paper (Refereed)
    Abstract [en]

    The joint between different lightweight materials plays a significant role in multi-material design of structural components for the automotive industry, aiming to reduce the vehicle's weight without compromising performance or safety. Yet, conventional mechanical joining technologies between metals and Carbon Fibre Reinforced Polymers (CFRP) result in either a hole being drilled in the composite material, leading to damages which reduce the load bearing capacity, or the weight of the part being increased due to the incorporation of fasteners. At the same time, alternative mechanical joining methodologies involve complex and costly processing, hindering their industrial application. This work presents a new, simple, cost-efficient and non-weight penalizing mechanical joining technology between a metal sheet and fibre reinforced polymer prepregs consisting of a single-step punching process. In this process, the metallic sheet is completely perforated, while the prepreg is not. The punch pushes the carbon fibres through the metallic hole, with no, or minimal fibre breakage, generating a mechanical interlock. The shear strength and the absorbed energy of the co-cured joint increase with the incorporation of the mechanical interlocking joint.

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  • 41.
    Latorre, Núria
    et al.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Polymeric and Composite Processes, Av. Universitat Autònoma 23, 08290 Cerdanyola del Vallès, Spain; AMADE, Polytechnic School, University of Girona, Av. Universitat de Girona, 4. 17003 Girona, Spain.
    Casellas, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics. Eurecat, Centre Tecnològic de Catalunya, Unit of Polymeric and Composite Processes, Av. Universitat Autònoma 23, 08290 Cerdanyola del Vallès, Spain.
    Costa, Josep
    AMADE, Polytechnic School, University of Girona, Av. Universitat de Girona, 4. 17003 Girona, Spain.
    A punching process to join metal sheets and fibre reinforced polymer composites by mechanical interlocking2023In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 175, article id 107744Article in journal (Refereed)
    Abstract [en]

    In the multi-material lightweight design of structural components for the automotive industry, the joint between different materials plays a significant role in reducing vehicle weight without compromising performance or safety. Conventional technologies to mechanically join metals and carbon fibre reinforced polymers result in either drilling a hole in the composite material or increasing the weight of the part because of the fasteners employed. This work presents a new, simple, cost-efficient and non-weight penalizing mechanical joining technology for metal sheets and fibre reinforced polymer prepregs. It consists of a single-step punching process where the metallic sheet is completely perforated, but the prepreg is not. The punch pushes the carbon fibres through the hole in the metal sheet with no or minimal fibre breakage, generating a mechanical interlock which, in turn, increases the shear strength and absorbed energy of the co-cured joint.

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  • 42.
    Lindroos, Matti
    et al.
    Integrated Computational Materials Engineering, VTT Technical Research Centre of Finland Ltd., Finland.
    Andersson, Tom
    Integrated Computational Materials Engineering, VTT Technical Research Centre of Finland Ltd., Finland.
    Laukkanen, Anssi
    Integrated Computational Materials Engineering, VTT Technical Research Centre of Finland Ltd., Finland.
    Suarez, Laura
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Kajberg, Jörgen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Terva, Juuso
    Metso Outotec Finland Oy, Finland.
    Kallio, Marke
    Metso Outotec Finland Oy, Finland.
    Micromechanical and multi-scale modeling of manganese containing slag comminution in the design of energy efficient secondary raw material beneficiation processes2021In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 170, article id 106995Article in journal (Refereed)
    Abstract [en]

    Efficient separation of valuable metals from various slags is of great interest for the industry to effectively utilize valuable raw materials. Present work focuses on modeling the deformation and damage behavior of manganese containing slag materials at the microstructural level, which dictates the macroscopic material behavior and allows one to investigate possibilities to perform metal separation after comminution of the slags. The model includes finite element micromechanical description of the material behavior and slag microstructure. Computational micromodels are constructed based on direct input characterization data and statistically representative synthetic models. The damage model treats brittleness and ductility of the material together with phase specific material behavior, all relevant to comminution of the slag. Finally, a simplified jaw crusher simulation accounts for freeing materials, assisting the evaluation of empirical random breakage, all together with a microstructural particle study which is analyzed against micromechanical modeling. Crystal plasticity level simulations of surface deformation and hardening in jaw crusher are presented to couple macroscale crushing events with microscale deformation of wear parts. The work overall presents a workflow and proposes a methodology how digitalization and multi-scale material modeling can contribute to the development of efficient comminution means for hard to process secondary raw materials.

  • 43.
    Lindwall, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Ericsson, Anders
    ivision of Solid Mechanics, Lund University, Box 118, SE-221 00, Lund, Sweden.
    Marattukalam, Jithin James
    Department of Physics and Astronomy, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.
    Hassila, Carl Johan
    Department of Materials Science and Engineering, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden.
    Karlsson, Dennis
    Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden; Sandvik Materials Technology, SE-811 81, Sandviken, Sweden.
    Sahlberg, Martin
    Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.
    Fisk, Martin
    Division of Solid Mechanics, Lund University, Box 118, SE-221 00, Lund, Sweden; Materials Science and Applied Mathematics, Malmö University, SE-205 06, Malmö, Sweden.
    Lundbäck, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Simulation of phase evolution in a Zr-based glass forming alloy during multiple laser remelting2022In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 16, p. 1165-1178Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing by laser-based powder bed fusion is a promising technique for bulk metallic glass production. But, reheating by deposition of subsequent layers may cause local crystallisation of the alloy. To investigate the crystalline phase evolution during laser scanning of a Zr-based metallic glass-forming alloy, a simulation strategy based on the finite element method and the classical nucleation theory has been developed and compared with experimental results from multiple laser remelting of a single-track. Multiple laser remelting of a single-track demonstrates the crystallisation behaviour by the influence of thermal history in the reheated material. Scanning electron microscopy and transmission electron microscopy reveals the crystalline phase evolution in the heat affected zone after each laser scan. A trend can be observed where repeated remelting results in an increased crystalline volume fraction with larger crystals in the heat affected zone, both in simulation and experiment. A gradient of cluster number density and mean radius can also be predicted by the model, with good correlation to the experiments. Prediction of crystallisation, as presented in this work, can be a useful tool to aid the development of process parameters during additive manufacturing for bulk metallic glass formation.

  • 44.
    Lindwall, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Lundbäck, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Marattukalam, Jithin James
    Department of Physics, Materials Physics, Uppsala University, P.O. Box 530, 75121 Uppsala, Sweden.
    Ericsson, Anders
    Division of Solid Mechanics, Lund University, P.O. Box 118, 22100 Lund, Sweden.
    Virtual Development of Process Parameters for Bulk Metallic Glass Formation in Laser-Based Powder Bed Fusion2022In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 15, no 2, article id 450Article in journal (Refereed)
    Abstract [en]

    The development of process parameters and scanning strategies for bulk metallic glass formation during additive manufacturing is time-consuming and costly. It typically involves trials with varying settings and destructive testing to evaluate the final phase structure of the experimental samples. In this study, we present an alternative method by modelling to predict the influence of the process parameters on the crystalline phase evolution during laser-based powder bed fusion (PBF-LB). The methodology is demonstrated by performing simulations, varying the following parameters: laser power, hatch spacing and hatch length. The results are compared in terms of crystalline volume fraction, crystal number density and mean crystal radius after scanning five consecutive layers. The result from the simulation shows an identical trend for the predicted crystalline phase fraction compared to the experimental estimates. It is shown that a low laser power, large hatch spacing and long hatch lengths are beneficial for glass formation during PBF-LB. The absolute values show an offset though, over-predicted by the numerical model. The method can indicate favourable parameter settings and be a complementary tool in the development of scanning strategies and processing parameters for additive manufacturing of bulk metallic glass.

  • 45.
    Lundholm, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    On the relationship between microstructure, process parameters and mechanical properties of boron steels2023Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The continuous development of the press hardening technology has led to stronger, lighter and more environmentally friendly components. Utilising the varying properties of boron steel at different temperatures enables great design freedom, while also attaining high strength in the final component. This is achieved by heating the initial material to an austenitic state, where it has good formability, followed by forming and quenching using pressing tools. However, in order to simulate this thermo-mechanical process the microstructure evolution must be understood. Research has been performed using various initial material states, evaluating possible effects on the final mechanical properties. Studies have also been performed to evaluate the grain growth during austenitisation. The influence of the initial material and the evolution of the austenite morphology during austenitisation has previously been less researched compared to other parts of the process.

    In this work, samples from commercially available materials have been heat treated to create test specimens, which subsequently have been used for mechanical testing and microstructure analysis. Digital image correlation was used to determine local fracture strains and anisotropic properties during plastic deformation. Samples were also heat treated using varying process parameters in order to study the grain growth during austenitisation. It was found that if hot rolled, cold rolled and soft annealed cold rolled samples were compared after hardening, their mechanical properties only exhibited minor variations. However, all samples displayed anisotropic properties during plastic deformation. There is therefore some microstructural trace from the production which is unaffected by soft annealing, austenitisation and subsequent quenching. The grain growth observed during the austenitisation was consistent within a temperature range not exceeding 930 ◦C. Using data retrieved from isothermal experiments a model could be fitted which described the growth using the temperature and current grain size. At 960 ◦C the microstructure was irregular, with large single grains and considerable variations in the average grain size within the same sample. The bending performance was not affected in a major way by the austenitisation temperature.

    The lack of variation of the mechanical properties due to the initial microstructure or parent austenite grain size is a testament to the robustness of the process. It should be noted however, that all samples were rapidly quenched. If the microstructure is formed through diffusion dependent phase transformations, the final mechanical properties could be more sensitive to process parameters. Further research is needed to fully understand the microstructural evolution and thus the mechanical properties where a more general thermal cycle can be used.

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  • 46.
    Lundholm, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Akerström, Paul
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Forouzan, Farnoosh
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sala, R.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Numerical Modelling of the Mechanical Properties of Press Hardened Boron Steels2022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper (Refereed)
  • 47.
    Lundholm, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Kajberg, Jörgen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Åkerström, Paul
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Influence of the initial material microstructure on the tensile properties after austenitisation and quenching of boron steelsManuscript (preprint) (Other academic)
  • 48.
    Lundholm, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Maissara, Khalifa
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Åkerström, Paul
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    The influence of austenitisation conditions on grain growth and the bending performance of boron steelManuscript (preprint) (Other academic)
  • 49.
    Lundkvist, A.
    et al.
    Department of Engineering Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Larsson, P.-L.
    Department of Engineering Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Olsson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    Structural and Mechanical Simulation of Anegative Electrode Active Layer in Lithium-Ionbatteries using Discrete Element Modelling2022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper (Refereed)
  • 50.
    Lundkvist, Axel
    et al.
    Department of Engineering Mechanics, Unit of Solid Mechanics, Royal Institute of Technology – KTH, Teknikringen 8, 100 44 Stockholm, Sweden.
    Larsson, Per-Lennart
    Department of Engineering Mechanics, Unit of Solid Mechanics, Royal Institute of Technology – KTH, Teknikringen 8, 100 44 Stockholm, Sweden.
    Olsson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.
    A discrete element analysis of the mechanical behaviour of a lithium-ion battery electrode active layer2023In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 425, article id 118574Article in journal (Refereed)
    Abstract [en]

    Lithium-ion batteries experience charge capacity loss during their lifecycle caused by mechanical phenomena. In this study, a discrete element method (DEM) simulation model, to link the local mechanical behaviour in the positive electrode active layer to its global mechanical properties, was developed. DEM is a suitable method to use as the electrode active layer has a granular structure and the model includes contact formulations for the active particles and the binder domain. Simulations of the calendering process and the measurement of the active layer's global mechanical properties is possible with the framework. The model developed can capture the pressure sensitivity of the active layer, which has been observed in experiments.

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