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- Nybacka, Mikael, et al.
(author)
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Project: CASTT - Centre for Automotive Systems Technologies and Testing
- 2007
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Other publication (pop. science, debate, etc.)abstract
- Through the Centre for Automotive Systems Technologies and Testing, Luleå University of Technology aims to first of all support automotive winter testing in Northern Sweden. This means to support the local automotive test entrepreneurs and through them their customers: the car manufacturers and their suppliers. To succeed in this task, the center relies on the university's areas of leading research and most importantly on the cooperation between those areas.
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| 4. |
- Andersson, Daniel C., et al.
(author)
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A Numerical Study of Material Parameter Sensitivity in the Production of Hard Metal Components Using Powder Compaction
- 2014
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In: Journal of materials engineering and performance (Print). - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 23:6, s. 2199-2208
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Journal article (peer-reviewed)abstract
- Modeling of hard metal powder inserts is analyzed based on a continuum mechanics approach. In particular, one commonly used cutting insert geometry is studied. For a given advanced constitutive description of the powder material, the material parameter space required to accurately model the mechanical behavior is determined. These findings are then compared with the corresponding parameter space that can possibly be determined from a combined numerical/experimental analysis of uniaxial die powder compaction utilizing inverse modeling. The analysis is pertinent to a particular WC/Co powder and the finite element method is used in the numerical investigations of the mechanical behavior of the cutting insert.
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| 5. |
- Andersson, Daniel C., et al.
(author)
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On the influence from punch geometry on the stress distribution at powder compaction
- 2010
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In: Powder Technology. - : Elsevier BV. - 0032-5910 .- 1873-328X. ; 202:1-3, s. 78-88
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Journal article (peer-reviewed)abstract
- A numerical analysis, using the finite element method, of the mechanical behavior at powder compaction at higher densities was performed. In this investigation the material behavior is modeled using an advanced macroscopic constitutive description initially presented by Brandt and Nilsson [1]. This material model, like many other models describing powder compaction at higher densities, includes a large number of constitutive parameters and as a result, a complete material characterization is a difficult task to perform or at least requires a large number of different experiments. A remedy to this problem is to apply inverse modeling, i.e. optimization, for determination of relevant material properties from comparatively simple experiments. It is then of course important, in order to achieve high accuracy results from the optimization procedure, that the stress fields produced during the experiments involves high gradients of stress. Adhering to simple uniaxial die compaction experiments the main parameter that can be used in order to achieve such a feature is the geometry of the punch used for load application. In the present investigation a number of punch profiles are studied and it is found that a skewed punch geometry is the most appropriate one to be used for experimental die compaction aiming at a constitutive description of the powder material based on inverse modeling. The main efforts are devoted towards an analysis based on the previously mentioned material model by Brandt and Nilsson [1] but also relevant results for another type of constitutive model will be presented. (C) 2010 Elsevier B.V. All rights reserved.
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| 6. |
- Andersson, Daniel, et al.
(author)
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Inverse modeling for parameter determination when using advanced material models to describe powder compaction
- 2010
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In: Proceedings of the World Powder Metallurgy Congress and Exhibition, World PM 2010. - : European Powder Metallurgy Association. - 9781899072194 ; , s. 77-84
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Conference paper (peer-reviewed)abstract
- In order to decrease the amount of experimental work at material characterization of powder mixtures, optimization procedures are often used. In the present study, characterization of WC/Co powders described by an advanced plasticity model is at issue. In particular, uniaxial die compaction is analyzed numerically in order to determine the correlation between material parameters, scalar and functional, and measurable information from experiments. Such information include radial (contact) pressure between powder and die walls, press force as function of indentation depth and frictional effects between powder and die walls. The commercial finite element solver LS-Dyna and the optimization module LS-OPT are used in the present investigation.
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| 7. |
- Andersson, Daniel, et al.
(author)
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Parameter Sensitivity at Advanced Constitutive Modeling of Powder Materials
- 2009
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In: Proceedings of the Euro International Powder Metallurgy Congress and Exhibition, Euro PM 2009. - : European Powder Metallurgy Association (EPMA). - 9781899072088 ; , s. 293-298
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Conference paper (peer-reviewed)abstract
- Dry pressing powder compaction is analyzed using the finite element method (FEM) and in particular then the explicit commercial FEM program LS-DYNA. The aim is then to determine the sensitivity of mechanical local and global parameters with respect to different constitutive as well as geometrical variables. A very advanced constitutive description (not available as standard in commercial FEM packages but implemented into LS-DYNA for the present investigation) is used in the numerical analysis, Brandt and Nilsson [1], and the results are particularly helpful for a forthcoming inverse analysis where it is crucial, for reasons of efficiency, to reduce the number of variables in the optimization procedure aiming at a accurate description of the mechanical behavior of the powder material. It should be clearly stated that the geometrical parameters to be investigated include different possible press geometries to be used for experimental verification of the results.
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| 9. |
- DAWODY, JAZAER, 1959, et al.
(author)
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An integrated system for energy-efficient exhaust aftertreatment for heavy-duty vehicles
- 2015
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In: Renewable Energy in the Service of Mankind. - Cham : Springer International Publishing. - 9783319177779 - 9783319177762 ; 1, s. 133-143
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Book chapter (other academic/artistic)abstract
- © Springer International Publishing Switzerland 2015. This chapter presents a unique system approach applied in a joint academic- industrial research programme, E4 Mistra, to attain the goals of high energy efficiency and low emissions in an exhaust aftertreatment system for heavy-duty vehicles. The high energy efficiency is achieved by heat recuperation, onboard hydrogen production for NOx reduction, and by finding new solutions for making the aftertreatment system active at low exhaust temperatures. To reach low particulate emissions, a mechanical filter using a sintered metal powder is developed and coated with catalytic material to improve the soot oxidation efficiency. Low NOx emissions are achieved by an efficient NOx reduction catalyst. The integrated E4 Mistra system comprises four technological advances: thermoelectric (TE) materials for heat recuperation, catalytic reduction of NOx over innovative catalyst substrates using either the onboard diesel or biodiesel, H2 from a high-efficiency fuel reformer, and particulate filtration over a porous metal filter. The TE materials are used in a TE generator (TEG) which converts thermal energy into electricity. The TEG is used to recuperate heat from the exhaust-gas recirculation (EGR) circuit of heavy-duty trucks and is expected to generate ~1 kW electric power from 20 kW heat in the exhaust gas. The TEG is integrated in a plate heat exchanger (HEX) designed particularly for this application. Apart from the knowledge and experiences in TEG and heat exchange technologies, a thorough fluid dynamics and TE analysis are performed in this project to understand the governing processes and optimize the system accordingly. The components of the E4 Mistra system are explained in the chapter in addition to test results, which show the system's capacity for H2 production, NOx conversion, particulate matter filtration and soot oxidation, and finally electric power generation via heat recuperation from the exhaust gas using the developed TEG-HEX system.
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| 10. |
- Fredriksson, Per, et al.
(author)
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Wedge indentation of thin films modelled by strain gradient plasticity
- 2008
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In: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 45:21, s. 5556-5566
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Journal article (peer-reviewed)abstract
- A plane strain study of wedge indentation of a thin film on a substrate is performed. The film is modelled with the strain gradient plasticity theory by Gudmundson [Gudmundson, P., 2004. A unified treatment of strain gradient plasticity. journal of the Mechanics and Physics of Solids 52, 1379-1406] and analysed using finite element simulations. Several trends that have been experimentally observed elsewhere are captured in the predictions of the mechanical behaviour of the thin film. Such trends include increased hardness at shallow depths due to gradient effects as well as increased hardness at larger depths due to the influence of the substrate. In between, a plateau is found which is observed to scale linearly with the material length scale parameter. It is shown that the degree of hardening of the material has a strong influence on the substrate effect, where a high hardening modulus gives a larger impact on this effect. Furthermore, pile-up deformation dominated by plasticity at small values of the internal length scale parameter is turned into sink-in deformation where plasticity is suppressed for larger values of the length scale parameter. Finally, it is demonstrated that the effect of substrate compliance has a significant effect on the hardness predictions if the effective stiffness of the substrate is of the same order as the stiffness of the film.
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