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  • 1.
    Andersson, Carl
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Predicting residual stresses in metal additive manufacturing by coupled finite element models2023Konferensbidrag (Övrigt vetenskapligt)
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Lundbäck, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Modeling the Evolution of Grain Texture during Solidification of Laser-Based Powder Bed Fusion Manufactured Alloy 625 Using a Cellular Automata Finite Element Model2023Ingår i: Metals, E-ISSN 2075-4701, Vol. 13, nr 11, artikel-id 1846Artikel i tidskrift (Refereegranskat)
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Lundbäck, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Modeling the Evolution of Grain Texture in Laser-Based Powder Bed Fusion Manufactured Alloy 6252023Konferensbidrag (Övrigt vetenskapligt)
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  • 4.
    Azizoğlu, Yağız
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Modeling of Cold Pilgering of Stainless Steel Tubes2023Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Temperature and plastic strain dependent Chaboche model for 316L used in simulation of Cold PilgeringManuskript (preprint) (Övrigt vetenskapligt)
  • 6.
    Azizoğlu, Yağız
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Sjöberg, Bengt
    Alleima Sverige AB, Sweden.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Modeling of cold pilgering of stainless-steel tubes2024Ingår i: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 112, s. 112-125Artikel i tidskrift (Refereegranskat)
  • 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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. 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 Specimens2023Ingår i: Euro Powder Metallurgy 2023 (Euro PM2023) Proceedings, European Powder Metallurgy Association (EPMA) , 2023Konferensbidrag (Refereegranskat)
  • 8.
    Bemani, M.
    et al.
    Eurecat, Centre Tecnològic de Catalunya, Metal Digital Manufacturing JRU, 08242 Manresa, Spain; CIEFMA – Department of Materials Science and Engineering, EEBE, Universitat Politècnica de Catalunya, Barcelona-Tech, 08019 Barcelona, Spain; Centre for Additive Manufacturing, School of Engineering, RMIT University, Melbourne 3000, Australia.
    Parareda, S.
    Eurecat, Centre Tecnològic de Catalunya, Metal Digital Manufacturing JRU, 08242 Manresa, Spain.
    Casellas, Daniel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. Eurecat, Centre Tecnològic de Catalunya, Metal Digital Manufacturing JRU, 08242 Manresa, Spain.
    Mateo, A.
    CIEFMA – Department of Materials Science and Engineering, EEBE, Universitat Politècnica de Catalunya, Barcelona-Tech, 08019 Barcelona, Spain.
    Das, R.
    Centre for Additive Manufacturing, School of Engineering, RMIT University, Melbourne 3000, Australia.
    Molotnikov, A.
    Centre for Additive Manufacturing, School of Engineering, RMIT University, Melbourne 3000, Australia.
    Rapid fatigue evaluation of additive manufactured specimens: Application to stainless steel AISI 316L obtained by laser metal powder bed fusion2024Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 184, artikel-id 108279Artikel i tidskrift (Refereegranskat)
  • 9.
    Casellas, Daniel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. 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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    When fracture toughness becomes essential for Lightweighting: Understanding cracking behaviour in high strength sheets2022Ingår i: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Konferensbidrag (Refereegranskat)
  • 10.
    Crescenti, Marc
    et al.
    Reinforce3D, Lligallo de Lorente 3, 43870, Amposta, Spain.
    Rafols, Irene
    Eurecat Centre Tecnològic de Catalunya, Product Innovation and Multiphysics Simulation Unit, Universitat Autònoma, 23, 08290, Cerdanyola del Vallès, Spain.
    Lara, Antoni
    Eurecat Centre Tecnològic de Catalunya, Product Innovation and Multiphysics Simulation Unit, Universitat Autònoma, 23, 08290, Cerdanyola del Vallès, Spain.
    Bemani, Milad
    Eurecat Centre Tecnològic de Catalunya, Product Innovation and Multiphysics Simulation Unit, Universitat Autònoma, 23, 08290, Cerdanyola del Vallès, Spain.
    Casellas, Daniel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. Eurecat Centre Tecnològic de Catalunya, Product Innovation and Multiphysics Simulation Unit, Universitat Autònoma, 23, 08290, Cerdanyola del Vallès, Spain.
    The continuous fibre injection process (CFIP): A novel approach to lightweight design of multi-material structural components2024Ingår i: Material Forming - ESAFORM 2024 / [ed] Anna Carla Araujo; Arthur Cantarel; France Chabert; Adrian Korycki; Philippe Olivier; Fabrice Schmidt, Materials Research Forum LLC , 2024, s. 1630-1639Konferensbidrag (Refereegranskat)
    Abstract [en]

    The combination of different materials enables to achieve highly efficient structures in terms of lightweight and mechanical performance, as well as in terms of manufacturing costs. However, the weakest points of these structures use to be the joints. For this reason, in the last years, many studies have dealt with joining technologies for dissimilar materials. The Reinforce3D’s Continuous Fibre Injection Process (CFIP) technology delivers a unique method to join dissimilar materials. CFIP is based on injecting continuous fibers, such as carbon fibers, simultaneously with liquid resin into tubular cavities within the part. Then the resin is cured and the final composite part is obtained. This work focuses on the characterization of the mechanical properties of CFIP-made specimens and describes the potential lightweight benefits of the technology. Mechanical tests were performed under tensile and bending conditions following standardized methods. The lightweight potential is addressed by developing a representative case study by implementing finite element and topology optimization methods. The results of this case study were finally compared with a monomaterial equivalent component (aluminium) demonstrating the improvement that CFIP provides in terms of lightweight while keeping the strength.

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  • 11.
    Dalai, Biswajit
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Moretti, Marie Anna
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Åkerström, Paul
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Mechanical behavior and microstructure evolution during deformation of AA7075-T6512021Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 822, artikel-id 141615Artikel i tidskrift (Refereegranskat)
    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.

  • 12.
    Dalai, Biswajit
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Moretti, Marie Anna
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Åkerström, Paul
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Esin, V. A.
    MINES ParisTech, PSL University, Centre des Matériaux (CNRS UMR 7633), Évry, France.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    High strain rate deformation behavior of AA7075-T6512022Ingår i: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Konferensbidrag (Refereegranskat)
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  • 13.
    Dalai, Biswajit
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Moretti, Marie Anna
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Åkerström, Paul
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Esin, Vladimir A.
    Centre Des Matériaux (CNRS UMR 7633), Mines Paris, PSL University, Évry, France.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Mechanical behavior and microstructure evolution during high strain rate deformation of AA7075-T6512022Ingår i: SN Applied Sciences, ISSN 2523-3963, E-ISSN 2523-3971, Vol. 4, nr 10, artikel-id 251Artikel i tidskrift (Refereegranskat)
    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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  • 14.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. Swerim AB, Box 812, 971 25 Luleå, Sweden.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Strain Rate and Notch Radius Effects on Evaluating the Stress–Strain Relations Using the Stepwise Modeling Method2024Ingår i: Journal of Dynamic Behavior of Materials, ISSN 2199-7446, Vol. 10, s. 26-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Accurate computer simulations require the selection of suitable material models and precise prediction of their parameters. In the fields of impact engineering and plastic working, stress–strain relations that include the post-necking regime up to fracture are crucial for predicting the behavior correctly. However, obtaining suitable stress–strain relations after necking requires some form of correction and adjustment for stress and/or strain. This study applies a stepwise modeling method for post-necking characterization that only utilizes the local strain field obtained from tensile experiments to precisely measure stress–strain relations at high strain rates. The effects of the notch radius of specimens on stress–strain relations were examined to measure stress–strain relations with large strain near the stress triaxiality of 1/3. The study also discusses adequate resolution for precise stress–strain measurements. Subsequently, specimens with suitable notch radius were used to measure stress–strain relations of plate specimens of aluminum alloy 2024-T3 at high strain rates. The study also examined the effects of strain rate on the flow stress and fracture strain of aluminum alloy 2024-T3.

  • 15.
    Etikan, M. Kaan
    et al.
    Department of Civil and Architectural Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Jelagin, Denis
    Department of Civil and Architectural Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Olsson, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Partl, Manfred N.
    Department of Civil and Architectural Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Experimental and numerical analyses of crushing resistance of unbound road materials2024Ingår i: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 25, nr 1, artikel-id 2330630Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aggregate breakage in unbound pavement layers can lead to pavement distresses that affect their functionality and service life. Thus understanding the mechanics and clarifying the factors affecting materials breakage resistance are important for ensuring adequate performance of these layers. In this study, aggregate breakage in unbound granular materials (UGM) is investigated experimentally and numerically. Experimentally, aggregate breakage under uniaxial compression is examined for two UGMs prepared with the same aggregate type but different gradations. To capture the experimentally observed influence of gradation and load magnitude on aggregate breakage, a Discrete Element Method (DEM) model was developed, based on granular mechanics particle contact and failure laws. A simple procedure to identify the contact and failure law parameters from experiments is proposed. With those parameters, the model’s capability of capturing the effect of gradation and loading on the aggregate breakage in UGM is evaluated. Based on comparison with experimental findings, it is shown that the model can capture macro-scale properties of UGM, such as its deformation response under uniaxial compression, as well as the amount of aggregate breakage in the material.

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  • 16.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Coupled electromagnetic-thermal solution strategy for induction heating of ferromagnetic materials2022Ingår i: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 111, s. 818-835Artikel i tidskrift (Refereegranskat)
    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.

  • 17.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. 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 ranking2021Konferensbidrag (Refereegranskat)
    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.

  • 18.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Optimization of Thick 22MnB5 Sheet Steel Part Performance through Laser Tempering2023Ingår i: Metals, ISSN 2075-4701, Vol. 13, nr 2, artikel-id 396Artikel i tidskrift (Refereegranskat)
    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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  • 19.
    Girhammar, Ulf Arne
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Belastningens betydelse vid utmattning av metaller: Seminarium vid högskolan i Luleå den 9 april 19751976Rapport (Övrigt vetenskapligt)
  • 20.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. 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 law2023Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 168, artikel-id 107444Artikel i tidskrift (Refereegranskat)
    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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  • 21.
    Grifé, Laura
    et al.
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència 2, Manresa, 08243, Spain.
    Frómeta, David
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència 2, Manresa, 08243, Spain.
    Payà, Anna
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència 2, Manresa, 08243, Spain.
    Casellas, Daniel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència 2, Manresa, 08243, Spain.
    Influence of pre-strain on fracture toughness of 3rd generation advanced high strength steels2024Ingår i: Material Forming - ESAFORM 2024 / [ed] Anna Carla Araujo; Arthur Cantarel; France Chabert; Adrian Korycki; Philippe Olivier; Fabrice Schmidt, Materials Research Forum LLC , 2024, s. 1206-1214Konferensbidrag (Refereegranskat)
    Abstract [en]

    The present work investigates the influence of pre-strain on the fracture toughness of 3rd Generation Advanced High Strength Steels (AHSS). Specifically, a Carbide Free Bainitic (CFB) and a Quenching and Partitioning (Q&P) steel have been studied, the properties of which are crucial for lightweight vehicle construction. Fracture toughness, which is a key parameter for crash performance applications, is assessed using the Essential Work of Fracture methodology. The study investigates the pre-straining states of uniaxial tension, plane strain, and equibiaxial tension in 1.5 mm Q&P and 1.4 mm CFB sheet-form steels of 1180 MPa tensile strength. Overall, Q&P steel demonstrates superior fracture toughness compared to CFB steel. Remarkably, the specific essential work of fracture (we) remains unaffected by pre-straining across different strain states. Nevertheless, pre-straining exerts a notable influence on the non-essential plastic work (βwp) due to the plastic energy consumed during pre-deformation. These results suggest that prestrain has little or no influence on the fracture properties of AHSS, which is relevant for the design and manufacturing of high crash-performance and safety-related components.

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  • 22.
    Gustafsson, David
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Effect of shear cutting on metal fatigue2024Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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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  • 23.
    Gustafsson, David
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Olsson, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    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 cutting2023Konferensbidrag (Refereegranskat)
    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.

  • 24.
    Gustafsson, David
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Parareda, S.
    Eurecat, Centre Tecnologic de Catalunya, Spain.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Olsson, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Effect Of Cutting Clearance And Sandblasting On Fatigue Of Thick CP800 Steel Sheets2022Ingår i: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Konferensbidrag (Refereegranskat)
  • 25.
    Gustafsson, David
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Parareda, Sergi
    Eurecat, Plaça de la ciència 2, 08242 Manresa; CIEFMA, EEBE, Universitat Politècnica de Catalunya-BarcelonaTech, 08019 Barcelona, Spain.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Olsson, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Effect of cutting clearance and sandblasting on fatigue of thick CP800 steel sheets for heavy-duty vehicles2022Ingår i: Hot Sheet Metal Forming of High-Performance Steel: proceedings / [ed] Mats Oldenburg; Jens Hardell; Daniel Casellas, Wissenschaftliche Scripten , 2022, s. 315-322Konferensbidrag (Refereegranskat)
    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.

  • 26.
    Gustafsson, David
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Parareda, Sergi
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Manresa, 08243, Spain.
    Munier, Rémi
    ArcelorMittal Global R&D - BP 30320, Maizières-lès-Metz Cedex, F-57283, France.
    Olsson, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    High cycle fatigue life estimation of punched and trimmed specimens considering residual stresses and surface roughness2024Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 186, artikel-id 108384Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shear cutting processes have a detrimental effect on fatigue of high strength metal components. The effect tends to increase with material grade, counteracting the task of reducing weight in chassis components using higher strength materials. Base material fatigue data are often available, but assessment of components with cut edges often require additional costly and time-consuming testing. This paper provides a methodology for estimation of fatigue life reduction by using residual stresses obtained from process simulations, and measured surface roughness in the cut edge. A stress relaxation criterion is applied to handle reduction of the initial local residual stresses. Two complex phase steels and one aluminum alloy are studied for validating the approach. Polished fatigue data is reduced to estimate S–N curves of trimmed and punched specimens at different load ratios. Good agreement between the model and test results are found for all cases. The needed data for the predictions are only a high cycle S–N relationship for polished material, uniaxial tensile properties, and the cut edge fracture surface residual stress and roughness without any parameter fitting, making it a convenient tool for estimating the reduction in fatigue life and for parameter studies.

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  • 27.
    Gustafsson, David
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Simulation of metal punching and trimming using minimal experimental characterization2023Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 321, artikel-id 118148Artikel i tidskrift (Refereegranskat)
    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.

  • 28.
    Hammarberg, Samuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    A Study on Sandwich Structures: Development, Mechanical Characterization and Numerical Modeling2021Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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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  • 29.
    Hammarberg, Samuel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Moshfegh, Ramin
    Lamera AB, Odhners gata 17, 42130 Västra Frölunda, Sweden.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Calibration of orthotropic plasticity- and damage models for micro-sandwich materials2022Ingår i: SN Applied Sciences, ISSN 2523-3963, E-ISSN 2523-3971, Vol. 4, nr 6, artikel-id 182Artikel i tidskrift (Refereegranskat)
    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.

  • 30.
    Hammarberg, Samuel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Moshfegh, Ramin
    Lamera AB, A Odhners Gata 17, 421 30 Västra Frölunda, Sweden.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Novel Methodology for Experimental Characterization of Micro-Sandwich Materials2021Ingår i: Materials, E-ISSN 1996-1944, Vol. 14, nr 16, artikel-id 4396Artikel i tidskrift (Refereegranskat)
    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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  • 31.
    Hassila, Carl-Johan
    et al.
    Uppsala Universitet, Uppsala University.
    Malmelöv, Andreas
    Luleå tekniska universitet.
    Andersson, Carl
    Luleå tekniska universitet.
    Hektor, Johan
    Malmö Universitet, Malmö University.
    Fisk, Martin
    Malmö Universitet, Malmö University.
    Wiklund, Urban
    Uppsala Universitet, Uppsala University.
    Lundbäck, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Influence of scan strategy on residual stresses in laser powder bed fusion manufactured alloy 718: Modeling an experimentsManuskript (preprint) (Övrigt vetenskapligt)
  • 32.
    Hassila, C.-J.
    et al.
    Department of Materials Science and Engineering, Division of Applied Materials Science, Uppsala University, Uppsala, Sweden.
    Malmelöv, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Andersson, Carl
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Influence of Scanning Strategy on Residual Stresses in Laser Powder Bed Fusion Manufactured Alloy 718: Modelling and Experiments2022Ingår i: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Konferensbidrag (Refereegranskat)
  • 33.
    Jelagin, Denis
    et al.
    Department of Civil and Architectural Engineering, KTH – Royal Institute of Technology, Stockholm, Sweden.
    Olsson, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    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 layers2023Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 24, nr S1, s. 176-191Artikel i tidskrift (Refereegranskat)
    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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  • 34.
    Jonsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Towards energy-based fracture modelling for crashworthiness applications2024Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The automotive industry is currently adapting to progessively more stringent emission and safety regulations imposed by governmental agencies. This introduces significant design difficulties due to the conflicting nature of passenger safety in automotive manufacturing, namely that increased crashworthiness generally leads to heavier vehicles, which in turn leads to more severe crashes. Significant industry effort to introduce lightweight materials into automotive Body-in-White (BIW) design has thus been introduced in recent years to reduce curb weight while improving crashworthiness. Third generation Advanced High Strength Steels (3rd-gen AHSS) and new generations of press hardening steels (PHS) has emerged as cost-effective and natural substitutes in the safety critical crush zones of the vehicle. The limited ductility of these higher strength materials can however make them more prone to cracking, which in turn make reliable deformation behaviour difficult in a crash event. Thus, predicting cracks in the material and its resistance to further propagate them are essential in evaluating crash performance of a design. Fracture toughness measured within the frame of fracture mechanics using the Essential Work of Fracture (EWF) has shown to correlate well with AHSS crashworthiness for steel sheets, making it an interesting parameter for further study in this area. EWF is however strain rate dependent, and most available EWF testing for AHSS is still performed using quasi-static loading rates, conditions completely different from common high-speed crash scenarios. Furthermore, since full-scale testing is a costly endeavor, numerical modelling is used in Computer Aided Engineering (CAE) to test designs before proceeding with a physical prototype. To promote the use of new high strength steel grades in the industry, reliable and properly characterised material models are thus necessary. These models then need to be validated with component experiments to ensure that the models are accurate enough. This is usually done using crash box components in an axial compression or three-point bending setup because of their similarity to real structural components used in crash zones. In this work, EWF at the higher loading rates common in crash scenarios is further investigated to contribute additional data regarding strain rate dependence of fracture toughness measured within the frame of fracture mechanics for AHSS sheets. Furthermore, the crashworthiness of dynamically loaded axially compressed AHSS and PHS crash boxes are evaluated both experimentally using full-field measurements and numerically using a commercially available damage model. The high-speed photography allow for a more efficient component crashworthiness evaluation with fewer components due to the possibility to track crack initiations and their propagation during the deformation. The results from the commercial damage model show that although the prediction of the first cracks is decent, the damage evolution is not captured accurately. These results show the need for further development of economically feasible (shell) damage models that take propagation energy into account in crash simulations. This would also help promote the use of fracture toughness in the automotive industry.

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  • 35.
    Jonsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Frómeta, David
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials.
    Grifé, Laura
    Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials.
    Larsson, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Studying the rate-dependence of Essential Work of Fracture in press hardening steels2024Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The automotive industry is currently in a paradigm shift transferring the fleet over from internal combustion vehicles to battery electric vehicles (BEV). This introduces new challenges when designing the Body-In-White (BIW) since it is essential to protect the heavy and energy-dense battery in a crash scenario. Press hardening steels (PHS) have emerged as an excellent choice when designing crash safety parts due to their high-strength and forming flexibility. It is however crucial to evaluate the crash performance of the selected materials before producing parts. Component testing is cumbersome, and it is difficult to separate material behaviour from other influences such as spot welds. Fracture toughness measured in the frame of fracture mechanics using the Essential Work of Fracture (EWF) has emerged as an interesting tool to rationalise crash performance of steel sheet designs. The EWF has previously been shown to increase, sometimes substantially, with increasing strain rate, but the cause of this is still largely unknown. For high strain rates, adiabatic heating can have a significant effect on the mechanical and fracture properties, especially for steel grades with metastable austenite. However, the rate dependence is still evident for press hardened martensitic steel grades. In this work, quasi-static and high-speed EWF experiments are performed on two PHS grades designed for anti-intrusion and energy absorption, respectively. The thermals are monitored using infrared thermography to study the adiabatic heating and thus the thermal environment in the FPZ during EWF at high-loading rates. The results are compared and discussed.

  • 36.
    Jonsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Impact crash tests of high-strength steels using 3D high-speed digital image correlation and finite element analysis2022Ingår i: 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, s. 119-126Konferensbidrag (Övrigt vetenskapligt)
    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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  • 37.
    Jonsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Impact crash tests using high-speed 3D digital image correlation2022Ingår i: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Konferensbidrag (Refereegranskat)
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  • 38.
    Jonsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Evaluation of Crashworthiness Using High-Speed Imaging, 3D Digital Image Correlation, and Finite Element Analysis2023Ingår i: Metals, E-ISSN 2075-4701, Vol. 13, nr 11, artikel-id 1834Artikel i tidskrift (Refereegranskat)
    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.

  • 39.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Westerberg, Lars-GöranLuleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.Larsson, SimonLuleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.Olsson, ErikLuleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Svenska Mekanikdagar 20222022Proceedings (redaktörskap) (Refereegranskat)
  • 40.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. 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 applications2022Ingår i: IOP Conference Series: Materials Science and Engineering / [ed] Sandrine Thuillier, Vincent Grolleau, Hervé Laurent, Institute of Physics (IOP), 2022, Vol. 1238, artikel-id 012029Konferensbidrag (Refereegranskat)
    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.

  • 41.
    Larsson, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    A Testing Methodology for Hot Rolled High Strength Steels Under Warm Forming Conditions2022Ingår i: Hot Sheet Metal Forming of High-Performance Steel: proceedings / [ed] Mats Oldenburg; Jens Hardell; Daniel Casellas, Wissenschaftliche Scripten , 2022, s. 411-418Konferensbidrag (Refereegranskat)
    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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  • 42.
    Larsson, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    High Temperature Characterization of 7 mm UHSS2022Ingår i: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Konferensbidrag (Refereegranskat)
  • 43.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Particle-Based Methods for Modeling Granular Materials2022Ingår i: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå: Luleå tekniska universitet, 2022Konferensbidrag (Refereegranskat)
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  • 44.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Rodriguez Prieto, Juan Manuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. Mechanical Engineering Department, EAFIT University, Medellín, Colombia.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    The particle finite element method for transient granular material flow: modelling and validation2021Ingår i: Computational Particle Mechanics, ISSN 2196-4378, Vol. 8, nr 1, s. 135-155Artikel i tidskrift (Refereegranskat)
    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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  • 45.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Rodríguez Prieto, Juan Manuel
    Mechanical Engineering Department, EAFIT University, Medellín, Colombia.
    Heiskari, Hannu
    Metso Outotec – Research Center, Pori, Finland.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    A Multi-Physics Approach for Modelling of Stirred Media Mills2021Konferensbidrag (Refereegranskat)
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  • 46.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. 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 punching2023Ingår i: IOP Conference Series: Materials Science and Engineering / [ed] Nader Asnafi, Lars-Erik Lindgren, Institute of Physics (IOP), 2023, Vol. 1284, artikel-id 012001Konferensbidrag (Refereegranskat)
    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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  • 47.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. 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 interlocking2023Ingår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 175, artikel-id 107744Artikel i tidskrift (Refereegranskat)
    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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  • 48.
    Latorre, Núria
    et al.
    Eurecat, Technological Centre of Catalonia, Parc Tecnològic del Vallès, Av. Universitat Autònoma, 23 –, 08290, Cerdanyola del Vallès, Spain; AMADE Research Group, Polytechnic School, University of Girona, Campus Montilivi s/n, E-17003, Girona, Spain.
    Casellas, Daniel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära. Eurecat, Technological Centre of Catalonia, Parc Tecnològic del Vallès, Av. Universitat Autònoma, 23 –, 08290, Cerdanyola del Vallès, Spain.
    Costa, Josep
    AMADE Research Group, Polytechnic School, University of Girona, Campus Montilivi s/n, E-17003, Girona, Spain.
    Garcia-Llamas, Eduard
    Eurecat, Technological Centre of Catalonia, Parc Tecnològic del Vallès, Av. Universitat Autònoma, 23 –, 08290, Cerdanyola del Vallès, Spain.
    Pujante, Jaume
    Eurecat, Technological Centre of Catalonia, Parc Tecnològic del Vallès, Av. Universitat Autònoma, 23 –, 08290, Cerdanyola del Vallès, Spain.
    Forming of mechanically interlocked aluminium and carbon fibre reinforced polymer parts with complex geometry2024Ingår i: Material Forming - ESAFORM 2024 / [ed] Anna Carla Araujo; Arthur Cantarel; France Chabert; Adrian Korycki; Philippe Olivier; Fabrice Schmidt, Materials Research Forum LLC , 2024, s. 1640-1649Konferensbidrag (Refereegranskat)
    Abstract [en]

    Forming of aluminium-CFRP hybrid structures into complex shapes is key to decrease environmental impact in automotive industry. However, challenges such as preserving joint integrity after forming operations must be assessed. Therefore, the authors of this work have cold stamped hybrid aluminium-CFRP panels into omega shaped profiles with and without a mechanical interlocking joining technology. The effect of lubricant application, of the CFRP positioning (inside or outside the omega profile), and of the number of mechanical joints were studied. It was concluded that it is possible to cold stamp aluminium-CFRP prepreg panels even with mechanical joints into complex profiles when lubricant is used. Moreover, the position of the CFRP prepreg has a strong impact on the flange springback of the stamped part.

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  • 49.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Kajberg, Jörgen
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    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 processes2021Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 170, artikel-id 106995Artikel i tidskrift (Refereegranskat)
    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.

  • 50.
    Lindwall, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Hållfasthetslära.
    Simulation of phase evolution in a Zr-based glass forming alloy during multiple laser remelting2022Ingår i: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 16, s. 1165-1178Artikel i tidskrift (Refereegranskat)
    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.

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