12 results on '"Rännar, Lars-Erik"'
Search Results
2. The effect of EBM process parameters upon surface roughness
- Author
-
Klingvall Ek, Rebecca, Rännar, Lars-Erik, Bäckstöm, Mikael, and Carlsson, Peter
- Published
- 2016
- Full Text
- View/download PDF
3. Micro- to Macroroughness of Additively Manufactured Titanium Implants in Terms of Coagulation and Contact Activation.
- Author
-
Ek, Rebecca Klingvall, Hong, Jaan, Thor, Andreas, Bäckström, Mikael, and Rännar, Lars-Erik
- Subjects
DENTAL implants ,BLOOD coagulation ,PROSTHESIS design & construction ,BIOMEDICAL materials ,DENTURES ,TITANIUM ,THREE-dimensional printing - Abstract
Purpose: This study aimed to evaluate how as-built electron beam melting (EBM) surface properties affect the onset of blood coagulation. The properties of EBM-manufactured implant surfaces for placement have, until now, remained largely unexplored in literature. Implants with conventional designs and custom-made implants have been manufactured using EBM technology and later placed into the human body. Many of the conventional implants used today, such as dental implants, display modified surfaces to optimize bone ingrowth, whereas custom-made implants, by and large, have machined surfaces. However, titanium in itself demonstrates good material properties for the purpose of bone ingrowth. Materials and Methods: Specimens manufactured using EBM were selected according to their surface roughness and process parameters. EBM-produced specimens, conventional machined titanium surfaces, as well as PVC surfaces for control were evaluated using the slide chamber model. Results: A significant increase in activation was found, in all factors evaluated, between the machined samples and EBM-manufactured samples. The results show that EBM-manufactured implants with as-built surfaces augment the thrombogenic properties. Conclusion: EBM that uses Ti6Al4V powder appears to be a good manufacturing solution for load-bearing implants with bone anchorage. The as-built surfaces can be used “as is” for direct bone contact, although any surface treatment available for conventional implants can be performed on EBM-manufactured implants with a conventional design. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
4. Additive Manufacturing of a Cold‐Work Tool Steel using Electron Beam Melting.
- Author
-
Botero, Carlos, Ramsperger, Markus, Selte, Aydin, Åsvik, Kenneth, Koptyug, Andrey, Skoglund, Per, Roos, Stefan, Rännar, Lars-Erik, and Bäckström, Mikael
- Subjects
ELECTRON beam furnaces ,TOOL-steel ,TOOL manufacturing ,CARBON steel ,STEEL industry - Abstract
Metal additive manufacturing (AM) is on its way to industrialization. One of the most promising techniques within this field, electron beam melting (EBM), is nowadays used mostly for the fabrication of high‐performance Ti‐based alloy components for the aerospace and medical industry. Among the industrial applications envisioned for the future of EBM, the fabrication of high carbon steels for the tooling industry is of great interest. In this context, the process windows for dense and crack‐free specimens for a highly alloyed (Cr–Mo–V) cold‐work steel powder are presented in this article. High‐solidification rates during EBM processing lead to very fine and homogeneous microstructures. The influence of process parameters on the resulting microstructure and the chemical composition is investigated. In addition, preliminary results show very promising mechanical properties regarding the as‐built and heat‐treated microstructure of the obtained material. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
5. Additive manufacturing of 316L stainless steel by electron beam melting for nuclear fusion applications.
- Author
-
Zhong, Yuan, Rännar, Lars-Erik, Liu, Leifeng, Koptyug, Andrey, Wikman, Stefan, Olsen, Jon, Cui, Daqing, and Shen, Zhijian
- Subjects
- *
STAINLESS steel , *ELECTRON beam furnaces , *NUCLEAR fusion , *SPECIFIC gravity , *SOLID solutions , *CHEMICAL precursors , *SOLIDIFICATION , *EQUILIBRIUM - Abstract
A feasibility study was performed to fabricate ITER In-Vessel components by one of the metal additive manufacturing methods, Electron Beam Melting ® (EBM ® ). Solid specimens of SS316L with 99.8% relative density were prepared from gas atomized precursor powder granules. After the EBM ® process the phase remains as austenite and the composition has practically not been changed. The RCC-MR code used for nuclear pressure vessels provides guidelines for this study and tensile tests and Charpy-V tests were carried out at 22 °C (RT) and 250 °C (ET). This work provides the first set of mechanical and microstructure data of EBM ® SS316L for nuclear fusion applications. The mechanical testing shows that the yield strength, ductility and toughness are well above the acceptance criteria and only the ultimate tensile strength of EBM ® SS316L is below the RCC-MR code. Microstructure characterizations reveal the presence of hierarchical structures consisting of solidified melt pools, columnar grains and irregular shaped sub-grains. Lots of precipitates enriched in Cr and Mo are observed at columnar grain boundaries while no sign of element segregation is shown at the sub-grain boundaries. Such a unique microstructure forms during a non-equilibrium process, comprising rapid solidification and a gradient ‘annealing’ process due to anisotropic thermal flow of accumulated heat inside the powder granule matrix. Relations between process parameters, specimen geometry (total building time) and sub-grain structure are discussed. Defects are formed mainly due to the large layer thickness (100 μ m ) which generates insufficient bonding between a few of the adjacently formed melt pools during the process. Further studies should focus on adjusting layer thickness to improve the strength of EBM ® SS316L and optimizing total building time. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
6. Additive manufacturing of ITER first wall panel parts by two approaches: Selective laser melting and electron beam melting.
- Author
-
Zhong, Yuan, Rännar, Lars-Erik, Wikman, Stefan, Koptyug, Andrey, Liu, Leifeng, Cui, Daqing, and Shen, Zhijian
- Subjects
- *
ELECTRON beam furnaces , *THREE-dimensional printing , *FABRICATION (Manufacturing) , *MAGNETIC permeability , *MICROSTRUCTURE , *MATHEMATICAL optimization - Abstract
Fabrication of ITER First Wall (FW) Panel parts by two additive manufacturing (AM) technologies, selective laser melting (SLM) and electron beam melting (EBM), was supported by Fusion for Energy (F4E). For the first time, AM is applied to manufacture ITER In-Vessel parts with complex design. Fully dense SS316L was prepared by both SLM and EBM after developing optimized laser/electron beam parameters. Characterizations on the density, magnetic permeability, microstructure, defects and inclusions were carried out. Tensile properties, Charpy-impact properties and fatigue properties of SLM and EBM SS316L were also compared. ITER FW Panel parts were successfully fabricated by both SLM and EBM in a one-step building process. The SLM part has smoother surface, better size accuracy while the EBM part takes much less time to build. Issues with removing support structures might be solved by slightly changing the design of the internal cooling system. Further investigation of the influence of neutron irradiation on materials properties between the two AM technologies is needed. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
7. Production of customized hip stem prostheses – a comparison between conventional machining and electron beam melting (EBM).
- Author
-
Cronskär, Marie, Bäckström, Mikael, and Rännar, Lars-Erik
- Subjects
THREE-dimensional printing ,ORTHOPEDIC implants ,INDUSTRIAL applications of electron beams ,CUSTOMIZATION ,MACHINING ,RAPID prototyping ,MATERIAL fatigue - Abstract
Purpose – The purpose of this paper is to study the use of the additive manufacturing (AM) method, electron beam melting (EBM), for manufacturing of customized hip stems. The aim is to investigate EBM's feasibility and commercial potential in comparison with conventional machining, and to map out advantages and drawbacks of using EBM in this application. One part of the study concerns the influence on the fatigue properties of the material, when using the raw surface directly from the EBM machine, in parts of the implant. Design/methodology/approach – The research is based on a case study of manufacturing a batch of seven individually adapted hip stems. The stems were manufactured both with conventional machining and with EBM technology and the methods were compared according to the costs of materials, time for file preparation and manufacturing. In order to enhance bone ingrowths in the medial part of the stem, the raw surface from EBM manufacturing is used in that area and initial fatigue studies were performed, to get indications on how this surface influences the fatigue properties. Findings – The cost reduction due to using EBM in this study was 35 per cent. Fatigue tests comparing milled test bars with raw surfaced bars indicate a reduction of the fatigue limit by using the coarse surface. Originality/value – The paper presents a detailed comparison of EBM and conventional machining, not seen in earlier research. The fatigue tests of raw EBM-surfaces are interesting since the raw surface has shown to enhance bone ingrowths and therefore is suitable to use in some medical applications. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
8. Microstructural and Mechanical Evaluation of a Cr-Mo-V Cold-Work Tool Steel Produced via Electron Beam Melting (EBM).
- Author
-
Botero, Carlos Alberto, Şelte, Aydın, Ramsperger, Markus, Maistro, Giulio, Koptyug, Andrey, Bäckström, Mikael, Sjöström, William, and Rännar, Lars-Erik
- Subjects
ELECTRON beam furnaces ,TOOL-steel ,COLD working of steel ,HEAT treatment ,ISOSTATIC pressing ,POWDER metallurgy - Abstract
In this work, a highly alloyed cold work tool steel, Uddeholm Vanadis 4 Extra, was manufactured via the electron beam melting (EBM) technique. The corresponding material microstructure and carbide precipitation behavior as well as the microstructural changes after heat treatment were characterized, and key mechanical properties were investigated. In the as-built condition, the microstructure consists of a discontinuous network of very fine primary Mo- and V-rich carbides dispersed in an auto-tempered martensite matrix together with ≈15% of retained austenite. Adjusted heat treatment procedures allowed optimizing the microstructure by the elimination of Mo-rich carbides and the precipitation of fine and different sized V-rich carbides, along with a decrease in the retained austenite content below 2%. Hardness response, compressive strength, and abrasive wear properties of the EBM-manufactured material are similar or superior to its as-HIP forged counterparts manufactured using traditional powder metallurgy route. In the material as built by EBM, an impact toughness of 16–17 J was achieved. Hot isostatic pressing (HIP) was applied in order to further increase ductility and to investigate its impact upon the microstructure and properties of the material. After HIPing with optimized protocols, the ductility increased over 20 J. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
9. Micro- and macro-structural heterogeneities in 316L stainless steel prepared by electron-beam melting.
- Author
-
Olsén, Jon, Shen, Zhijian, Liu, Leifeng, Koptyug, Andrey, and Rännar, Lars-Erik
- Subjects
- *
ELECTRON beams , *STAINLESS steel , *CRYSTAL grain boundaries , *MOLYBDENUM , *MICROHARDNESS , *AGGLOMERATION (Materials) - Abstract
This is a study of the micro- and macrostructural variations in samples of stainless steel with the overall composition of the grade 316L, produced using electron beam melting. Electron beam melting is one of the processing methods under consideration for manufacturing some of the International Thermo- Nuclear Experimental Reactor In-Vessel components. Therefore further studies of the homogeneity of the material were conducted. Electron beam melting results in a complicated thermal history of the manufactured part giving a significant impact on the microstructure. A cellular structure that is often observed in samples prepared by selective laser melting was found in the top layers of the specimens. Further down, the structure changed until the cellular structure was almost non-existing, and the grain boundaries had become more pronounced. This revelation of a heterogeneous structure throughout the entire part is crucial for large-scale industrial applications like the Thermo- Nuclear Experimental Reactor to make sure that it is understood that the properties of the material might not be the same at every point, as well as to assure that the correct post-treatment is done. It is also exposed that a significant part of this change is due to molybdenum redistribution inside the sample when it diffuses from the cell boundaries into the cells, and into bigger agglomerates in the grain boundaries. This diffusion seems not to affect the microhardness of the samples. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
10. Fabrication of multiple-layered gradient cellular metal scaffold via electron beam melting for segmental bone reconstruction.
- Author
-
Surmeneva, Maria A., Surmenev, Roman A., Chudinova, Ekaterina A., Koptioug, Andrei, Tkachev, Mikhail S., Gorodzha, Svetlana N., and Rännar, Lars-Erik
- Subjects
- *
TITANIUM alloys , *ELECTRIC double layer , *ELECTRON beam furnaces , *TRAUMATIC bone defects , *TISSUE engineering , *BONE surgery , *MICROFABRICATION - Abstract
The triple- and double-layered mesh Ti-based alloy scaffolds were successfully fabricated using electron beam melting (EBM). In this study Ti-based alloy cylindrical scaffolds with different 3D architectures intended for the segmental bone defect treatment were systematically compared. All lattice-like scaffolds were additively manufactured using EBM technology from Ti6Al4V to mimic the structures of human trabecular bone. Cylindrically-shaped lattice scaffolds (outer diameter of 15 mm and length of 35 mm) of five different types were designed and manufactured. Four types were tubular with inner hole diameter of 5 mm and two lattice layers of different density. Fifth type was cylindrical with three lattice layers of different density. In all samples outer lattice layer was most dense, and inner layers- least dense. Mechanical properties of scaffolds were determined by conducting uniaxial compression testing. The strain-stress curves for all samples with gradient porosities showed considerable ductility. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
11. Damage-induced failure analysis of additively manufactured lattice materials under uniaxial and multiaxial tension.
- Author
-
Molavitabrizi, Danial, Bengtsson, Rhodel, Botero, Carlos, Rännar, Lars-Erik, and Mahmoud Mousavi, S.
- Subjects
- *
DIGITAL image correlation , *ELECTRON beam furnaces , *FAILURE analysis , *STRESS-strain curves , *MECHANICAL failures , *DAMAGE models - Abstract
Mechanical behavior of additively manufactured lattice materials has been mainly investigated under uniaxial compression, while their performance under uniaxial and multiaxial tension are yet to be understood. To address this gap, a generic elastoplastic homogenization scheme with continuum damage model is developed, and three different lattice materials, namely cubic, modified face-center cubic and body-center cubic, are analyzed under uniaxial, biaxial and triaxial tension. The influence of micro-architecture on the material's failure behavior as well as its macroscopic mechanical performance is thoroughly discussed. For validation, a set of uniaxial tensile experiments are conducted on functionally graded cubic lattice samples that are additively manufactured using Electron Beam Melting (EBM) process. Digital image correlation technique is employed to obtain the macroscopic stress–strain curves, and manufacturing imperfections are inspected using light omitting microscopy. It turns out that the behavior of as-built samples could substantially differ from numerical predictions. Thus, a defect-informed numerical model is employed to accommodate the effect of imperfections. The outcome is in a very good agreement with experimental data, indicating that with proper input data, the developed scheme can accurately predict the mechanical and failure behavior of a given lattice material. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
12. Compositionally-tailored steel-based materials manufactured by electron beam melting using blended pre-alloyed powders.
- Author
-
Koptyug, Andrey, Popov, Vladimir V., Botero Vega, Carlos Alberto, Jiménez-Piqué, Emilio, Katz-Demyanetz, Alexander, Rännar, Lars-Erik, and Bäckström, Mikael
- Subjects
- *
ELECTRON beam deposition , *IRON powder , *PLASMA sprayed coatings , *ELECTRON beams , *LASER deposition , *MATERIALS , *POWDERS , *BEAM steering - Abstract
The paper presents the prospects of additive manufacturing (AM) in metal, using the powder bed fusion (PBF) method Electron Beam Melting (EBM) in fabrication specific steel-based alloys for different applications. The proposed approach includes manufacturing of metals from blended pre-alloyed powders for achieving in situ alloying and the material microstructure tailoring by controlling electron beam energy deposition rate EBM tests were conducted with the blends of 316L stainless steel and Colferoloys 103 and 139, corrosion- and abrasion-resistant iron based materials commonly used for plasma spray coating. Thorough microstructure analysis of the manufactured sample was carried out using electron microscopy and measurements of microhardness and elastic modulus was carried out using nanoindentation. It is concluded that implementation of blended powder pathway in PBF AM allows to widen the scope of available materials through diminishing the dependence on the availability of pre-alloyed powders. Together with beam energy steering this pathway also allows for an effective sample microstructure control at different dimensional scales, resulting in components with unique properties. Therefore, the implementation of 'blended powder pathway' in PBF AM provides a possibility of manufacturing components with the composite-like and homogeneous zones allowing for the microstructure control and effectively adding a "4th dimension" to "3D printing". Image 1 [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.