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- Harrysson, Magnus, et al.
(författare)
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Spatial representation of evolving anisotropy at large strains
- 2007
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 44:10, s. 3514-3532
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Tidskriftsartikel (refereegranskat)abstract
- A phenomenological model for evolving anisotropy at large strains is presented. The model is formulated using spatial quantities and the anisotropic properties of the material is modeled by including structural variables. Evolution of anisotropy is accounted for by introducing substructural deformation gradients which are linear maps similar to the usual deformation gradient. The evolution of the substructural deformation gradients is governed by the substructural plastic velocity gradients in a manner similar to that for the continuum. Certain topics related to the numerical implementation are discussed and a simple integration scheme for the local constitutive equations is developed. To demonstrate the capabilities of the model it is implemented into a finite element code. Two numerical examples are considered: deformation of uniform plate with circular hole and the drawing of a cup. In the two examples it is assumed that initial cubic material symmetry applies to both the elastic and plastic behavior. To be specific, a polyconvex Helmholtz free energy function together with a yield function of quadratic type is adopted.
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| 4. |
- Harrysson, Anders, et al.
(författare)
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Large strain elasto-plastic model of paper and corrugated board
- 2008
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 45, s. 3334-3352
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Tidskriftsartikel (refereegranskat)abstract
- An anisotropic elasto-plastic constitutive model of paper material is presented. It is formulated in a spatial setting in which anisotropic properties are accounted for by use of structural variables. A multiplicative split of the deformation gradient is employed to introduce plasticity. A similar approach is used to model the plastic deformation of the substructure. The yield surface adopted is based on the Tsai-Wu failure criterion, used previously to model failure of paper material. A non-associated plasticity theory is employed to calibrate the model to experimental data. It turns out that a multi-axial loading situation is needed to calibrate the model and here a biaxial tension test is audited. The model was implemented into a finite element environment and the creasing process of a corrugated board panel is investigated.
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| 5. |
- Harrysson, Fredrik, et al.
(författare)
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Dual antenna terminals in an indoor scenario
- 2006
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Ingår i: [Host publication title missing]. - 1550-2252. ; 6, s. 2737-2741
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Konferensbidrag (refereegranskat)abstract
- The performance of two different dual antenna hand-held test mobile terminals has been investigated in a realistic indoor office environment and scenario, with respect to antenna performance, diversity combining and Shannon MIMO channel capacity. Measurements of a 2times2 MIMO channel at 1877.5 MHz (narrowband) were performed using a dual-polarized base station antenna. Analyses show that diversity gains, using ideal selection combining and maximum ratio combining, between 0.7 and 4.6 dB was achieved at the 10% outage probability level. Ideal dual-side beamforming (single branch) gives up to 3.3 dB capacity gain compared to single antenna systems at SNR less than 10 dB, however, decreases with rising SNR. Dual branch MIMO capacity gain is only significant at higher SNR above 10 dB. In addition, horizontal polarization at the base station was found to outperform vertical polarization in this scenario
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| 6. |
- Harrysson, Fredrik, et al.
(författare)
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Efficient experimental evaluation of a MIMO handset with user influence
- 2010
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 9:2, s. 853-863
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Tidskriftsartikel (refereegranskat)abstract
- The immediate environment of handset antennas, including the casings and the users holding the handsets, has a strong impact on the radio channel in mobile communication. In this paper we investigate a composite channel method that synthetically combines double-directional measurements of the userless propagation channel with measured super-antenna patterns, i.e., patterns of the combined antenna-casing-user arrangement. We experimentally evaluate the method by comparing results (power, capacity, and eigenvalue distribution) obtained from this composite method with direct measurements in the same environment. The measurements were done in two static 8 × 4 MIMO scenarios at 2.6 GHz, with the user indoors and the base station located outdoors and indoors, respectively. A realistic user phantom together with a “smart-phone” handset mock-up with four antenna elements was used, and different configurations and orientations were tested. The method gives statistical distributions of the MIMO eigenvalues, that are close to the measured. By using the composite method, we found that the user, apart from introducing hand and body loss that mainly decreases the SNR of the channel, slightly increases the correlation between the fading at the antenna elements.
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| 7. |
- Harrysson, Fredrik, et al.
(författare)
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Evaluation of user hand and body impact on multiple antenna handset
- 2010
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Ingår i: [Host publication title missing]. - 1522-3965 .- 1947-1491. - 9781424449675
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Konferensbidrag (refereegranskat)abstract
- From our experimental investigation of multiple-antenna performance and user impact of a realistic mobile terminal setup, we find that apart from the important loss of efficiency due to the user hand, the impact on the individual antennna elements and the directional impact of the user body shadowing have quite small influence on the diversity and capacity performance. It is found that the top and bottom placement of antennas within the handset case are the most efficient to be used with up to two antenna elements. There are, however, significant diversity and capacity gain that can be explored by using four distributed antennas even if only two radio chains are available through hybrid selection and combining schemes. It was also found that the practical method of choosing antennas based on signal power for 2 branch MIMO with 4 available handset antennas, performs well compared to the optimal solution.
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| 8. |
- Harrysson, Fredrik, et al.
(författare)
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The composite channel method : Efficient experimental evaluation of a realistic MIMO terminal in the presence of a human body
- 2008
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Ingår i: 2008 IEEE 67th Vehicular Technology Conference-Spring, VTC. - 1550-2252. - 9781424416455 ; , s. 473-477
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Konferensbidrag (refereegranskat)abstract
- The immediate environment of the transmit (TX) and receive (RX) antennas, including the antenna casings and the users holding the antennas, has a strong impact on the propagation channel and thus on wireless systems. In this paper we experimentally evaluate a method that synthetically combines double-directional measurements of the propagation channel (without the user influence) with measured antenna patterns of antennas-plus-users, by comparing obtained sample results with direct measurements in the same environment. The measurements are done for a static microcell 8×4 MIMO scenario at 2.6 GHz. A realistic user phantom was used together with a test terminal prototype with four antenna elements, and a number of different configurations and orientations of the phantom were tested. In average over all test cases, the mean signal power deviation between composite channel method and measurements was well within 1 dB. The composite method shows 6% higher terminal antenna correlation but similar statistical distributions as the measured. The differences between the model and measurements for the strongest eigenvalue (relevant for MRC combining) was found to be within 1 dB above 10% outage level. Relative deviations in the ergodic MIMO capacity were smaller than 10%.
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| 10. |
- Karlsson, Joakim, 1984-, et al.
(författare)
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Thickness dependency of mechanical properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
- 2024
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Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810.
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Tidskriftsartikel (refereegranskat)abstract
- Metal powder bed additive manufacturing technologies, such as the Electron Beam Melting process, facilitate a high degree of geometric flexibility and have been demonstrated as useful production techniques for metallic parts. However, the EBM process is typically associated with lower resolutions and higher surface roughness compared to similar laser-based powder bed metal processes. In part, this difference is related to the larger powder size distribution and thicker layers normally use As part of an effort to improve the resolution and surface roughness of EBM fabricated components, this study investigates the feasibility of fabricating components with a smaller powder size fraction and layer thickness (similar to laser based processes). The surface morphology, microstructure and tensile properties of the produced samples were evaluated. The findings indicate that microstructure is dependent on wall-thickness and that, for thin walled structures, tensile properties can become dominated by variations in surface roughness.
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