| 1. |
- Ahmed, Sheikh Ali, Senior Lecturer, 1977-, et al.
(författare)
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Prediction of mechanical performance of acetylated MDF at different humid conditions
- 2020
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Ingår i: Applied Sciences. - Switzerland : MDPI. - 2076-3417. ; 10:23, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Change of relative humidity (RH) in surrounding environment can greatly affect the physical and mechanical properties of wood-based panels. Commercially produced acetylated medium density fiberboard (MDF), Medite Tricoya®, was used in this study to predict strength and stiffness under varying humid conditions by separating samples in parallel (//) and perpendicular (⊥) to the sanding directions. Thickness swelling, static moduli of elasticity (MOEstat) and rupture (MORstat), and internal bond (IB) strength were measured at three different humid conditions, i.e., dry (35% RH), standard (65% RH) and wet (85% RH). Internal bond (IB) strength was also measured after accelerated aging test. A resonance method was used to determine dynamic modulus of elasticity (MOEdyn) at the aforementioned humid conditions. Linear regression and finite element (FE) analyses were used to predict the MDF’s static bending behavior. Results showed that dimensional stability, MOEstat, MORstat and IB strength decreased significantly with an increase in RH. No reduction of IB strength was observed after 426 h of accelerated aging test. A multiple regression model was established using MOEdyn and RH values to predict MOEstat and MORstat. In both directions (// and ⊥), highly significant relationships were observed. The predicted and the measured values of MOEstat and MORstat were satisfactorily related to each other, which indicated that the developed model can be effectively used for evaluating the strength and stiffness of Medite Tricoya® MDF samples at any humid condition. Percent errors of two different simulation techniques (standard and extended FE method) showed highly efficient way of simulating the MDF structures with low fidelity.
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| 2. |
- Bagni, T., et al.
(författare)
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Modeling Results of the Quench Behavior of a Nb-Ti Canted-Cosine-Theta Corrector Magnet for LHC
- 2024
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 34:5
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Tidskriftsartikel (refereegranskat)abstract
- A newly designed superconducting magnet of the Canted-Cosine-Theta (CCT) type was developed as a result of a collaboration between Swedish universities (Uppsala and Linneaus) and Swedish industries. This magnet was designed to function as a replacement of the present LHC orbit corrector magnets, which are approaching their end of life due to the radiation load. As a result, the new CCT magnet was developed to be more radiation tolerant and to constitute a one-to-one replacement to the currently installed version, which is a 1 m long 70 mm double aperture dipole magnet. The final magnet, which is currently under construction, will be tested at FREIA laboratory at Uppsala University and generate a magnetic field of 3.3 T and an integrated field of 2.8 Tm at about 85 A. To examine the magnet quench behavior and to identify a suitable quench protection system, the 3D electro-magnetic and thermal behavior of the coil was modeled using the RAT-Raccoon software. Based on the simulation results, a Metrosil varistor was selected to protect the magnet during the test. In this article, we report the results of the numerical analysis. The magnet model is equipped with a spot heater to initialize the quench and the temperature and voltages are monitored during the avalanche effect. The simulated current decay and the hot-spot temperature are analyzed with a focus on the impact of quench-back on the magnet protection.
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| 3. |
- Ivankova, Olga, et al.
(författare)
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Static and dynamic analysis of high-rise building with consideration of two different values of subsoil stiffness coefficients
- 2017
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Ingår i: Dynamics of Civil Engineering and Transport Structures and Wind Engineering – DYN-WIND’2017. - : EDP Sciences.
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the analysis of 21-storeyed cast in-situ reinforced concrete high-rise building. Two different 3D models were created, because of two considered values of subsoil stiffness coefficient -fixed structure (alt. 1) and the structure supported by elastic soil (alt. 2). For both alternatives of foundation of structure, required analyses (static and dynamic) were done and obtained results were compared in this paper. Short description of the structure, applied loads and other input parameters are also mentioned here. The main purpose of this analysis was to provide more information to planning engineers about the behaviour of structure exposed the wind load or seismic load when different soil conditions were considered.
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| 4. |
- Kovacikova, Janka, et al.
(författare)
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An Influence of a Shape of a Flaw on a Value of Stress on Beams
- 2016
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Ingår i: Applied Mechanics and Materials. - : Trans Tech Publications. - 1660-9336 .- 1662-7482. ; 837, s. 230-233
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Tidskriftsartikel (refereegranskat)abstract
- The main topic of this paper is finite element analysis of 4-point loaded glulam beams which contain different types of flaws. There were modeled four types of beams. First type was the beam without a flaw, second was the beam with a central crack in the middle of span located at the bottom edge of the beam, third model of beams contained also the central crack but this crack was located 20 mm above the edge and the last model contained a hole in the middle of the span as simulation of a knot. These models were performed and analyzed in ANSYS. Task was considered as two dimensional. There were compared values of stress in different types of beam's models.
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| 5. |
- Kovacikova, Janka, et al.
(författare)
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Computational and experimental analysis of timber beams with different types of flaws
- 2020
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Ingår i: Fracture and damage mechanics. - : American Institute of Physics (AIP).
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Konferensbidrag (refereegranskat)abstract
- This work was focused on the experimental testing and finite element analysis (FEA) of timber beams with and without flaws (different types of cracks and hole). The aim was analysing the effect of flaws on their load-carrying capacity. This topic is important for designers of timber constructions, since even today there is still a lack of knowledge in the field of fracture mechanics of wood. The results from experimental testing and numerical simulations were discussed in this paper. Two wood products were analysed, namely, sawn and glued laminated beams (glulam beams) and three types of flaws were considered for both products i.e. a vertical crack, an oblique crack and a circular hole. In addition for glulam beams the horizontal crack in the glue line was considered. Four-point bending test was created for experimental testing considering quasi-brittle characteristic of wood. 4 samples for each type of beam, 36 in total. XFEM (Extended Finite Element Method) was used for finite element analysis of beams with considering orthotropic-elastic properties for glulam beams were considered and The results of mechanical tests and FEA gave us an overview on how different types of flaws influence the load-carrying capacity of sawn and glulam beams and with what accuracy we can simulate cracks in wood using computational method.
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| 6. |
- Kovacikova, Janka, et al.
(författare)
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Finite element analysis of timber beams with flaws
- 2016
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Ingår i: ECCOMAS Congress 2016. - Athens : National Technical University of Athens. - 9786188284401 ; , s. 8606-8611
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Konferensbidrag (refereegranskat)abstract
- The work was focused on modelling of cracks and simulations of their propagationin timber beams. The aim was to find out the influence of flaws on load-carrying capacity. Inbeam design and beam inspection, it is necessary to determine the load-carrying capacity of abeam with flaws. There is not much information in literature about the influence of flaws onbending and shear strength of timber beams. Standards for fracture mechanics design approachfor timber structures are not easily available.The results from simulations of loaded timber beams with flaws are discussed in this paper.Two different types of timber beams were analysed. First type was a sawn timber beam andfor that four different models were analysed: first model was a beam without flaw; secondmodel was a beam with a straight central flaw; next was a beam with an oblique crack andfourth beam had a round hole in the middle of the span. Second type of beam was a gluedlaminated timber beam (glulam). For this type, five different models were analysed. First fourvariants were the same as for the solid timber beam and the fifth variant had an initial crackalong a glue line. We analysed these types of flaws, since they are the most common flaws inwood.Simulations were conducted in ABAQUS. Material properties of wood used in the modelswere retrieved from standards; C24 for solid timber and GL24c for glulam timber beams.Dimensions of beams were the same for all variants and beams were considered simply supported.For an analysis of crack propagation, linear elastic fracture mechanics was considered.Modelling fracture was conducted using the extended finite element method (XFEM).The energy approach was used for the analysis of crack propagation. Comparing results forsolid and glulam beams with and without cracks gave us an overview how different flaws influenceload-carrying capacity of the beams and under which loading failure occurs. Simulatingtimber beams is more complicated compering to steel or plastic. By understanding how tosimulate flaws in wood material it is possible to obtain reliable results with finite elementanalysis
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| 7. |
- Kovacikova, Janka, et al.
(författare)
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Mechanical properties of fiberboard composite bonded with polymer matrixcomputed by mean-field homogenization methods
- 2021
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Ingår i: 25th International Congress of Theoretical and Applied Mechanics, August 22-27, 2021. - Milano, Italy. - 9788365550316 ; , s. 1984-1985
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Nowadays, the design of composite materials considering sustainability and the environmental impact of the production is conspicuous. Therefore, in this work, we focus on investigating the mechanical behaviour and structure of a new green wood-based fibrous composite material bonded with a novel polymer matrix. The constitutive prediction models employing the material and structure design approaches simultaneously are proposed here to describe the material's microstructure. The goal is speeding up trials and reducing experiments expenses by replacing tests with computer simulations. Additionally, the relationship between material behaviour and structure is established and will be later used to generate Representative Volume Elements (RVEs) for finite element analysis (FEA).
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| 8. |
- Pepitone, K., et al.
(författare)
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Design and Fabrication of a Canted-Cosine-Theta Double Aperture Orbit Corrector Dipole for the LHC
- 2023
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515 .- 2378-7074. ; 33:5
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Tidskriftsartikel (refereegranskat)abstract
- A prototype CCT dipole magnet developed by a collaboration between Swedish universities, Swedish industry and CERN will be tested at Uppsala University. This 1 m long double-aperture magnet can provide a field strength of 3.3 T at 85 A in a 70 mm aperture with an integrated field of 2.8 Tm. It is intended to replace the current LHC orbit corrector magnets which are reaching the end of their expected life due to the radiation load. The new magnet is designed to handle the radiation dose of the upgrade to the high-luminosity LHC, which will deliver about ten times the current radiation dose. It must therefore be more resistant to radiation and meet strict requirements in terms of electrical insulation while matching the original field quality and self-protective capability, mechanical volume, and maximum excitation current. This paper will present the latest of the design and manufacturing work, including the results of simulations of the mechanical field and the mechanical stress. Details of the various tests performed before machining the parts are also presented.
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| 9. |
- Pepitone, Kevin, Dr, 1988-, et al.
(författare)
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Design of a Canted-Cosine-Theta Orbit Corrector for the High Luminosity LHC
- 2022
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 32:6
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Tidskriftsartikel (refereegranskat)abstract
- The High Luminosity LHC requires dipole orbit correctors grouped in double aperture magnet assemblies. They provide a field of 3.1 T at 100 A in an aperture of 70 mm. The current standard design is a classical cosine-theta layout made with ribbon cable. However, the electric insulation of this cable is not radiation-resistant enough to withstand the radiation load expected in the coming years of LHC operation. A new design, based on a cable with polyimide insulator, that can replace the existing orbit correctors, is needed. The challenge is to design a magnet that fits directly into the existing positions and that can operate with the same busbars, passive quench protection, and power supplies. The new orbit corrector design meets high requirements on the field quality while keeping within the same mechanical volume and maximum excitation current. A collaboration of Swedish universities and Swedish industry has been formed for the development and production of a prototype magnet following a concurrent engineering methodology to reduce the time needed to produce a CCT magnet. The magnet has a 1 m long CCT dipole layout consisting of two coils. The superconductor is a commercially available 0.33 mm wire with polyimide insulation in a 6-around-1 cable. The channels in the coil formers, that determine the CCT layout, allow for 2 x 5 cable layers. A total of 70 windings makes that the coil current can be kept below 100 A. We will present the detailed design and preliminary quench simulations.
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