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1.
Optimizacija chaboche materialnih parametrov z genetskim algoritmom
Nejc Dvoršek, 2022, master's thesis

Abstract: The basis of this thesis is research and development of a genetic algorithm for material parameters optimization. It is written in collaboration with AVL, which already has a solution for this problem, but is looking into better alternatives. Chaboche material model is a nonlinear isotropic and kinematic hardening model which can describe elasto-viscoplastic constitutive relations. Parameters of such complex nature do not have a physical interpretation in the real-world and must be defined with inverse analysis. Genetic algorithms (GA) are a promising tool to help with such tasks. They have been widely used and recognized for various optimization problems. Material data available are low cycle fatigue (LCF), creep, and tensile experiments. For each experiment a corresponding finite element model in Abaqus is prepared. Comparing experimental and simulation data is the objective function GA will try to minimize. For this reason, a corresponding fitness function was developed to score each individual. It makes use of similarity measure algorithm proposed in this paper [10]. GA was implemented in Python with Pygad library. Instead of bits, genes are represented with real-valued numbers with defined limits. Performance of developed GA was tested based on various population sizes, mutation probabilities, and crossover operators. The main parameter that impacts algorithms performance is population size. Paired with right mutation probability the algorithm can find a global minimum of described optimization problem. Making it a viable alternative to existing approach used at AVL.
Keywords: Chaboche material model, parameter optimization, genetic algorithm, finite element method
Published in DKUM: 16.12.2022; Views: 120; Downloads: 0
.pdf Full text (1,90 MB)

2.
Validation of boundary element method for assessment of weld joints accounting for notch stress
Rok Skerbiš, 2022, master's thesis

Abstract: Robust, automated mesh generation on arbitrary weld joint geometries, using finite element method (FEM) is a problematic task. It was previously discovered, that an arbitrary weld joint geometry can be parameterized inside a CAD environment [1], however when it comes to domain discretization and boundary conditions assignment, the parameterized approach becomes too demanding inside FEM. This results in long FEM model preparation times and sometimes in problems with the parametric model itself, which leads to a need for an additional numerical method - boundary element method (BEM), which overcomes this issue and is beneficial in this case. BEM is a numerical method, that in addition to other applications finds a use in the elasto-mechanic problems, where the only concern is the boundary of the considered geometric domain. Since notch stress calculations of weld joints fall into this category, their calculation can be carried out with it. Since there is not much available information on whether or not such calculations are a suitable alternative for the currently used FEM, this thesis had to be confirmed through a structured and step by step procedure. First, a notch mesh quality study has been made, then other entities followed. It was discovered that BEM is applicable to the problem and capable of calculating results with sufficient quality. Furthermore, the parameter driven approach and automated calculation provide for additional advantageous potentials.
Keywords: weld joint, boundary element method, finite element method, spatial discretization, notch stress
Published in DKUM: 02.11.2022; Views: 117; Downloads: 0
.pdf Full text (4,62 MB)

3.
Optimizacija povezovanja večpolnih ločilnih stikal z varovalko
Benjamin Juvan, 2022, undergraduate thesis

Abstract: V podjetju ETI Elektroelement d. o. o., kjer sem opravljal praktično usposabljanje, smo naleteli na problem povezovanja večpolnih ločilnih stikal z varovalko. Doslej smo za povezovanje večpolnih ločilnih stikal z varovalko uporabljali postopek orbitalnega kovičenja. Ker je trenutno zaradi svetovnih razmer težava pridobiti kovinske materiale, je bilo treba najti novo rešitev za povezovanje. Do sedaj so se za povezovanje uporabljale CuZn15 kovice in Fe zatiči. V okviru diplomske naloge smo uvedli povezovanje s plastičnimi veznimi elementi, da bi prihranili na materialu, zmanjšali normativ dela in s tem zmanjšali proizvodne stroške. Za nov sistem povezovanja smo vezne elemente namestiti v posebej za to predvidene luknje, ki ohranjajo medsebojno razdaljo. Cilj naloge je bil, da se določi najbolj učinkovita postavitev lukenj za vstavitev veznih elementov. Pri tem smo upoštevali ohranitev vseh tehničnih lastnosti izdelka, poleg tega pa je izdelek še vedno skladen s standardom IEC. Vezni elementi tudi ne vplivajo na notranji mehanizem izdelka.
Keywords: ločilna stikala, večpolna stikala, montaža, orbitalno kovičenje, optimizacija, varovalka, vezni element
Published in DKUM: 29.09.2022; Views: 105; Downloads: 0

4.
Presoja čezmejnega elementa pri svoboščinah notranjega trga EU : magistrsko delo
Mia Zemljič, 2022, master's thesis

Abstract: Magistrsko delo obravnava zahtevo po čezmejnem elementu pri svoboščinah notranjega trga. Določbe PDEU o svoboščinah notranjega trga se uporabljajo samo, če v dejanskih okoliščinah konkretne zadeve obstaja čezmejni element. Odsotnost čezmejnega elementa pomeni, da gre za povsem notranji položaj, ki je v skladu s povsem notranjim pravilom zunaj področja uporabe teh določb in posledično tudi zunaj pristojnosti Sodišča EU. Povsem notranji položaji ostajajo v pristojnosti držav članic in so v celoti podvrženi njihovemu nacionalnemu pravu. Za pravilno razumevanje pojmov čezmejnega elementa in povsem notranjih položajev je nujno poznavanje obstoječe sodne prakse Sodišča EU. Za izpolnitev zahteve po čezmejnem elementu se je tradicionalno zahtevalo dejansko čezmejno gibanje oz. dejanski čezmejni element, vendar so se negativne posledice takšnega pristopa kazale kot lažni negativi in obratna diskriminacija, ki jih je Sodišče EU v svoji novejši sodni praksi poskušalo odpraviti oz. vsaj omiliti s tem, da je s široko razlago razširilo pojem gibanja in s tem obstoj čezmejnega elementa, s tem pa hkrati omejilo primere, ko govorimo o povsem notranjih položajih, pri čemer je navedeno še posebej očitno na področju prostega gibanja oseb, ki danes ne pomeni več samo ekonomske svoboščine, saj pravo EU omogoča prosto gibanje tudi ekonomsko neaktivnim osebam, ki so varovane z določbami PDEU o državljanstvu Unije. Poleg tega pa je Sodišče EU oblikovalo tudi določene izjeme od zahteve po čezmejnem elementu in povsem notranjega pravila na področju prostega pretoka blaga in državljanstva Unije, ki omogočajo, da se pravo EU lahko uporabi tudi, kadar v dejanskih okoliščinah konkretne zadeve ne obstaja čezmejni element. Posledično je postalo vprašanje, ali neka zadeva spada na področje uporabe določb PDEU o svoboščinah notranjega trga, zelo zapleteno vprašanje, na katerega ni mogoče odgovoriti brez poznavanja obstoječe sodne prakse Sodišča EU. Logična postopkovna posledica dejstva, da povsem notranji položaji ne spadajo na področje uporabe določb PDEU o svoboščinah notranjega trga, je nepristojnost Sodišča EU na podlagi člena 267 PDEU in nedopustnost predlogov za sprejetje predhodne odločbe, ki izhajajo iz zadev, ki se nanašajo na povsem notranje položaje. Kljub temu pa je Sodišče EU večkrat odgovorilo tudi na predhodna vprašanja, ki so izhajala iz nacionalnega postopka, v katerem so bili vsi elementi omejeni na samo eno državo članico. Gre za tradicionalno zelo kaotično in nejasno področje sodne prakse Sodišča EU, pri čemer je korak v pravo smer pomenila novejša zadeva Ullens de Schooten, v kateri je Sodišče EU prvič sistematiziralo vse vrste zadev, v katerih lahko odstopi od splošnega pravila in tradicionalni trilogiji Dzodzi, Guimont, Oosthoek dodalo četrto – Libert. Zahteva po čezmejnem elementu je na prvi pogled jasen in neposreden koncept, ki logično sledi besedilu in ciljem določb PDEU o svoboščinah notranjega trga, vendar pa sodna praksa Sodišča EU kaže povsem drugačno sliko, zato so se pojavile ideje o spremembi in celo o odpravi zahteve po čezmejnem elementu.
Keywords: pravo EU, notranji trg, svoboščine notranjega trga, čezmejni element, povsem notranji položaji, sodna praksa Sodišča EU, povsem notranje pravilo, postopek predhodnega odločanja
Published in DKUM: 22.09.2022; Views: 183; Downloads: 33
.pdf Full text (836,62 KB)

5.
Razvoj brezvijačnega sistema spajanja kabelskih lestev
Matej Jakopanec, 2022, undergraduate thesis

Abstract: V diplomskem delu je predstavljen razvoj spojnega elementa za brezvijačni sistem spajanja kabelskih lestev, ki bo poenostavil in pospešil postopek montaže linij kabelskih lestev. V začetku smo opisali problem, postavili cilje in raziskali trg morebitnih obstoječih rešitev. Sledil je postopek konstruiranja, ki zajema faze načrtovanja, koncipiranja, snovanja in razdelave. V delu so zajeti tudi analitični preračun, numerična simulacija in primerjava pridobljenih rezultatov. Predstavljena sta tudi dva glavna postopka izdelave takšnega izdelka in njegova tehnična dokumentacija. Rezultat diplomskega dela je razvoj novega izdelka, ki na trgu še ne obstaja, ustreza ciljem naloge in je uporaben v praksi.
Keywords: razvoj izdelka, kabelska lestev, spojni element, brezvijačni sistem
Published in DKUM: 12.09.2022; Views: 124; Downloads: 0

6.
CALIBRATION OF A NEW METHOD FOR CREATING IMPERFECTIONS ON SLENDER STRUCTURES
Simon Hudales, 2022, master's thesis

Abstract: For the design of slender structures consisting of plates and tubes, such as supporting structures at cranes, buckling is beside stress and fatigue often the governing failure criteria. Stability analysis of such structures is usually performed using the GMNIA method according to DIN EN 1993. For this purpose, a suitable geometric equivalent imperfection must be applied to the structure. Buckling inherent shapes are determined for this purpose and scaled according to applicable safety concepts. Including imperfections in stability analysis can generally be relevant for the load-bearing behavior of a structure. Within this master thesis work, the influence of the initial geometric imperfection on stability behaviour is investigated. This study examines the influence, that imperfections imposed on members subjected to tensile stress have on stability behaviour. Tensile members of structures are identified and initial geometric imperfection is imposed on them in addition to critical members, that are subjected to compression stress. It is shown, that including imperfections on tensile members in stability analysis, has only a minor influence on stability behaviour and stiffness of the structure, both reducing it just slightly. Further on, investigation on boom model, that is supporting structure of the crawler crane, is made. Boom model consist of main chord members and diagonals connecting them. At the joint connection of boom and two diagonal members, one subjected to tension and one subjected to compression stress, appears area of high shear stresses. Influence of the direction, that imperfection is imposed on the diagonal member, and what is the influence on the stability behaviour and structural strength is presented in this work. Most severe case of the two chosen direction is pointed out and discussed.
Keywords: stability analysis, initial geometric imperfections, thin-walled structures, finite element method
Published in DKUM: 06.07.2022; Views: 191; Downloads: 35
.pdf Full text (5,14 MB)

7.
Comparison and implementation of thermo-mechanical fatigue damage models : magistrsko delo
Jure Vinkovič, 2021, master's thesis

Abstract: The basis of the master thesis is an in-depth and comprehensive analysis of the scientific literature on damage models of thermo-mechanical fatigue. The aim of the thesis is to investigate and determine the suitability of damage models for their application in numerical simulations of components subjected to thermo-mechanical loading with in-phase, out-of-phase or constant temperature cycles. The theoretical background of material behavior under static and dynamic loads (e.g. low-cycle fatigue, high-cycle fatigue) is presented. The work also includes an overview of damage mechanisms typical of time-temperature varying loading conditions (e.g. cyclic softening and hardening of the material, mean stress relaxation, material creep, visco-plasticity, etc.). This is followed by a structured review of several damage models of thermo-mechanical fatigue (e.g. Neu-Sehitoglu, DTMF, Coffin-Manson, Ostergren, Smith-Watson-Topper, Unified Energy Approach, etc.). An overview of the experimental tests on aluminum alloy and cast iron carried out at temperatures up to 800 °C is given. The idea of processing the raw experimental data including the calibration procedure of the thermo-mechanical fatigue damage models is schematically illustrated and described. The basic mathematical laws of constitutive material models for both material types are given. In the conclusion of the MSc thesis, the correlations of the calibrated damage models are presented, which, together with the constructive opinions, give an important message on the application of the individual damage models depending on the type of material and the loading method.
Keywords: thermo-mechanical fatigue, constitutive material model, damage model, aluminum alloy, cast iron alloy, finite element method
Published in DKUM: 03.01.2022; Views: 439; Downloads: 0

8.
Vpliv postopkov termičnega rezanja na lastnosti rezne površine in dobo trajanja nosilnega elementa : magistrsko delo
Kristjan Hostnik, 2021, master's thesis

Abstract: Z raziskavami v obsegu tega magistrskega dela sem želel prikazati vpliv različnih postop-kov termičnega rezanja jekla na trdoto rezne površine in na njeno hrapavost kot ključni parameter na vpliv iniciacije mikrorazpok in posledično življenjsko dobo elementa. Naloga obsega tako eksperimentalni del, kot računalniško numerično simulacijo po metodi konč-nih elementov. V eksperimentalnem delu se bom osredotočil na samo pripravo preizku-šancev za namene merjenja hrapavosti površine in trdot po višini reznega roba. Rezultati meritev hrapavosti bodo služili za pripravo numeričnega modela pojava koncentracij maksimalnih nateznih napetosti na rezni površini preizkušancev in simulacijo iniciacije razpoke kot posledice poškodbe na površini.
Keywords: termično rezanje, konstrukcijski element, doba trajanja, numerična analiza, hrapavost, trdota
Published in DKUM: 01.10.2021; Views: 407; Downloads: 27
.pdf Full text (6,41 MB)

9.
Razvoj vpenjalnega mehanizma za montažo strelnih daljnogledov : diplomsko delo
Jaka Slapnik, 2021, undergraduate thesis

Abstract: V diplomskem delu sem predstavil razvoj novega vpenjalnega mehanizma za montažo strelnih daljnogledov. V primerjavi z obstoječimi rešitvami na trgu bom izboljšal ključne lastnosti mehanizma, ki so do sedaj omejevale znižanje celotnega montažnega elementa. V teoretičnem delu bom predstavil izdelke, na katere se navezuje razvoj. V empiričnem delu pa se bom lotil analize obstoječih rešitev in patentov. S pomočjo pridobljenega znanja bom nadaljeval k dejanskemu procesu razvoja lastnega vpenjalnega mehanizma, ki vključuje zbiranje idej, konstruiranje novega mehanizma, 3D-tisk prototipa novega izdelka in trženje po konceptnih idejah.
Keywords: montažni element, vpenjalni mehanizem, razvoj izdelka, obstoječe rešitve, nove rešitve
Published in DKUM: 24.09.2021; Views: 365; Downloads: 66
.pdf Full text (3,36 MB)

10.
Simulation of Dual-Beam Laser Metal Deposition : magistrsko delo
Matej Kočevar, 2021, master's thesis

Abstract: Laser metal deposition process plays an important role in the coating and additive manufacturing of the components. Implementation of dual-beam process represents a further development and offers the advantage of laser ablation process, which provides exert force on the melt pool and increases absorption properties of the workpiece for laser light in comparison to conventional laser metal deposition processes. The main goal of the present work is to predict temperature distribution on the surface and in the cross-section during a dual-beam laser metal deposition. A better understanding of temperature distribution of the dual-beam laser metal deposition is crucial for analyzing the impact of different process parameters on the process. The prediction of temperature distribution was done using the version 6.14-6 of finite element software ABAQUS/Standard from Dassault Systèmes. The results of the simulations show that the temperature distribution in the case of dual-beam laser metal deposition can be determined with minimum deviation by utilizing the finite element analysis.
Keywords: Laser Metal Deposition (LMD), dual-beam process, wire-based Laser Metal Deposition (LMD-w), Finite Element Method (FEM)
Published in DKUM: 23.09.2021; Views: 476; Downloads: 48
.pdf Full text (3,37 MB)

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