Iskanje po katalogu digitalne knjižnice

Opis: Iron losses represent a crucial factor in the design process of electrical machines. For this reason, it is important to consider adequate hysteresis behavior within models which predict iron losses. A promising hysteresis description is the static hysteresis model developed by the G2Elab research group. It proposes a unique approach of modelling magnetization curves inside the major loop based on the so-called unit differential reversal curves (uDRCs). This work focuses on modelling of the uDRCs. We analyzed the accuracy and identification approaches of several uDRC models, where we compared the established model with simplified solutions with less parameters. Further, we analyzed the impact of individual models regarding identification convergence. Finally, we highlighted which simplified models give the best trade-off between the ease and stability of identification process of parameters, and the accuracy of the hysteresis model.
Ključne besede: static hysteresis model, iron loss, loss surface model, magnetic material, mathematical modelling
Objavljeno v DKUM: 26.01.2024; Ogledov: 214; Prenosov: 23
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Opis: In the global market, the casting industry recorded a growth trend for ductile iron last year. Ductile iron is used due to its excellent mechanical properties, machinability and castability. The microstructure of nodular cast iron consists of a metal matrix and graphite extruded in the form of beads and nodules. In recent years, the production of ductile iron castings has increased significantly for parts for heavy transport vehicles and containers for permanent disposal of nuclear waste, and it is expected that this trend of expansion will continue for at least the next twenty years. When poured in sand moulds, the quality of products can not be reached. There can be defects on the raw surface and/or on the machining surface, as well as hidden defects inside the material. For casting products, defects can be detected on raw and machining surfaces and inside material defects by carrying out a visual inspection. The results of the inspection depend on the inspection method used. In general, basic methods of cutting or milling inspection are used in the casting industry, which means that products are classified in terms of whether or not they meet the drawing specification(s). The authors of this paper focused on the hidden defects inside ductile iron material, which can be detected by carrying out a cutting or milling inspection or through an X-ray inspection. Huge amounts of energy and energy sources are used in the production of nodular cast iron, which creates a negative environmental footprint. Therefore, by being preventively rational and through appropriate control procedures it is possible to significantly reduce the carbon footprint.
Ključne besede: carbon footprint, ductile iron, X-ray inspection, cutting inspection, hidden mistakes, defects, porosity, inclusion, green energy, reduced production of energy, decrease in production emissions
Objavljeno v DKUM: 26.10.2023; Ogledov: 373; Prenosov: 6
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Opis: Reaction-formed $MnZn$ ferrite was prepared and the decrease in shrinkage after sintering due to the volume expansion accompanying iron oxidation was studied. Green compacts consisting of the milled raw oxides $Fe_2O_3$, $Mn_3O_4$, $ZnO$ and metallic iron powder were sintered at 1350 °C in air. During the first hold at 800 °C, $Fe$ was oxidized to $\alpha-Fe_2O_3$ and $Zn$ ferrite was formed. Above 1300 °C the reaction bonding was completed and $MnZn$ ferrite, exhibiting a relatively low shrinkage, was formed. The chemical reactions involved during reaction bonding were associated with a volume expansion and porosity formation, compensating for the shrinkage on sintering. Intensive milling decreases the porosity after sintering but induces the oxidation of iron, and partially removes the shrinkage compensation caused by the presence of metallic iron.
Ključne besede: reaction-forming, $MnZn$ ferrite, inorganic technology, ferrite ceramics, reaction bonded ceramics, sintering, iron oxides, iron
Objavljeno v DKUM: 25.08.2017; Ogledov: 1182; Prenosov: 112
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Opis: The ▫$Li_1.746Nd_4.494FeO_9.493$▫ (LNF) ternary phase, located in the ▫$Li_2O$▫-rich part of the ▫$Li_2O-Nd_2O_3-Fe_2O_3$▫ system, crystallizes with a cubic unit cell of dimension and the space group Im3m. Refinement on F resulted in R=1.9%. The structure is comprised of a network of corners, edges and faces sharing the coordination polyhedra of neodymium. In between this skeleton the regular octahedra of oxygen-coordinated iron and trigonal prisms of lithium are located. The Mössbauer spectra revealed the presence of ▫$Fe^3+$▫, ▫$Fe^4+$▫ and ▫$Fe^5+$▫ ions distributed on two symmetry-independent lattice positions.
Ključne besede: crystal structure, ternary compounds, single-crystal X-ray diffraction, Mössbauer spectroscopy, iron oxidation state, kristalna struktura, ternarne spojine, rentgenska difrakcija, Mössbauerjeva spektroskopija, rentgenska strukturna analiza
Objavljeno v DKUM: 01.06.2012; Ogledov: 2701; Prenosov: 47
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Opis: This paper analyses the impact of armature slotting and magnetically nonlinearand anisotropic iron core on the trajectories of a kinematically controlled linear synchronous reluctance motor (LSRM). A new magnetically nonlinear dynamic two-axis LSRM model is introduced in order to perform the analysis. The magnetic nonlinearities and slotting effects are accounted for by the current and position-dependent characteristics of flux linkages.
Ključne besede: devices motors, reluctance synchronous motor, iron core model
Objavljeno v DKUM: 31.05.2012; Ogledov: 2702; Prenosov: 107
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