1. Mechanisms of defect formation in Ti-6Al-4V product during re-melting of layers in selective laser meltingSnehashis Pal, Matjaž Finšgar, Radovan Hudak, Viktoria Rajtukova, Tomaž Brajlih, Nenad Gubeljak, Igor Drstvenšek, 2023, izvirni znanstveni članek Opis: Knowledge of defect formation mechanisms in the manufacturing process helps improve product quality. In this study, defect formation due to re-melting of each layer in selective laser melting of Ti-6Al-4V demonstrated the physical behavior in the manufacture of metallic parts. The re-melting strategy was based on scanning with low energy density (ED) and increased ED with various combinations of laser processing parameters. The increased EDs and their parameters, namely laser power, scanning speed, and hatch distance, were selected based on the previous research experience by the authors. The concept of selecting a low ED followed by a high ED was to reduce the spattering of the powder material during the process. The low ED caused partial sintering of the powder, while the high ED caused the melting of the material, resulting in different metallurgical properties of the manufactured parts. Densities, pore properties, porosity in the initial layers, surface morphologies, and microstructures in the defective areas of the samples were studied to determine the effects of re-melting. Advantages and disadvantages were found with respect to the range of applications of the products
Ključne besede: re-melting, pore properties, defect, surface morphology, Ti-6Al-4V, selective laser melting
Objavljeno v DKUM: 14.03.2025; Ogledov: 0; Prenosov: 1
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2. A preliminary assessment of rider/driver gaze behaviour in slovenian urban areasTomaž Tollazzi, Matej Moharić, Chiara Gruden, 2022, izvirni znanstveni članek Opis: Motorcycle riders are an increasing group of road users. The intrinsic characteristics of
powered two wheelers (PTW) allow them to be particularly flexible, both in urban and extra-urban
environments. Nevertheless, crash statistics indicate that riders involved in road accidents are highly
likely to suffer severe injuries, underlining the vulnerability of this group of road users. An element
that can greatly affect the safety of PTW users is road design, as roads are usually designed for
two-track vehicles (cars, buses, and lorries) and do not consider the needs of PTWs. Additionally,
handling a motorcycle is quite different from driving a car; thus, the behaviour of riders is different to
that of drivers. The aim of this paper is to compare how different road designs are perceived by riders
and drivers and to preliminarily assess if riders’ behaviour and attention allocation are related. For
the purpose of this research, an eye-tracking experiment was developed outdoors. Both drivers and
riders travelled along a route comprising four different road designs and various road layouts, and
the output was analysed both qualitatively and quantitatively. Although it was not possible to carry
out a statistical analysis due to the limited number of participants, the results demonstrate that there
is a difference in the gaze behaviour of drivers and riders, with the latter being far more focused on
the left-hand side of the road and concentrating on defined elements of road design. Furthermore, the
experiment demonstrated that a higher number of fixations is related to lower speeds. Finally, it was
noted that both kinds of road users focus fairly well on the carriageway, leading to the conclusion that
the indications given through road markings may be much more effective than vertical signalisation,
which has rarely been observed.
Ključne besede: road safety, powered two-wheelers (PTW), ridera, eye-tracking, gaze behavior
Objavljeno v DKUM: 13.03.2025; Ogledov: 0; Prenosov: 0
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3. Predictive modelling of weld bead geometry in wire arc additive manufacturingKristijan Šket, Miran Brezočnik, Timi Karner, Rok Belšak, Mirko Ficko, Tomaž Vuherer, Janez Gotlih, 2025, izvirni znanstveni članek Opis: This study investigates the predictive modelling of weld bead geometry in wire arc additive manufacturing (WAAM) through advanced machine learning methods. While WAAM is valued for its ability to produce large, complex metal parts with high deposition rates, precise control of the weld bead remains a critical challenge due to its influence on mechanical properties and dimensional accuracy. To address this problem, this study utilized machine learning approaches—Ridge regression, Lasso regression and Bayesian ridge regression, Random Forest and XGBoost—to predict the key weld bead characteristics, namely height, width and cross-sectional area. A Design of experiments (DOE) was used to systematically vary the welding current and travelling speed, with 3D weld bead geometries captured by laser scanning. Robust data pre-processing, including outlier detection and feature engineering, improved modelling accuracy. Among the models tested, XGBoost provided the highest prediction accuracy, emphasizing its potential for real-time control of WAAM processes. Overall, this study presents a comprehensive framework for predictive modelling and provides valuable insights for process optimization and the further development of intelligent manufacturing systems.
Ključne besede: wire arc additive manufacturing, WA AM, predictive modelling, machine learning, weld bead geometry, XGBoost
Objavljeno v DKUM: 13.03.2025; Ogledov: 0; Prenosov: 0
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4. Analiza skladiščenja kemikalij v podjetju F.A MAIK d. o. o. : diplomsko deloMiha Bezjak, 2024, diplomsko delo Opis: Skladiščenje kemikalij predstavlja izziv za izvajalce skladiščnih storitev. Zaradi nevarnosti, ki jo predstavljajo manipulacije s kemikalijami, so skladiščni procesi teh snovi podvrženi strogi zakonodaji, sprejeti z namenom minimizirati tveganje za nastanek izrednih dogodkov. V primeru nesreč namreč lahko pride do hudih negativnih posledic v neposredni okolici nesreče. Zato je pri skladiščenju kemikalij ključnega pomena zagotavljanje ustreznih varovalnih sistemov in upoštevanje predpisane zakonodaje ter navodil proizvajalca kemikalij. Skladiščenje le-teh mora biti zasnovano na način, ki omogoča dober pregled in nadzor nad shranjenimi kemikalijami. Poleg podatkov o shranjenih kemikalijah je potrebno te skladiščne enote opremiti s podatki o skladiščenju, kar omogoča določitev skladiščnega mesta znotraj skladišča. Pri tem se lahko opremo na sisteme upravljanja skladišč. Sistem SQAS omogoča ocenjevanje kakovosti, varnosti, zanesljivosti in okoljske učinkovitosti logističnih procesov kemikalij ter primerjavo stanja podjetja z evropskimi standardi, ABC analiza pa nam poda oceno o učinkovitosti skladiščenja izdelkov v skladišču. V diplomskem delu smo pregledali skladiščenje kemikalij v podjetju F.A. MAIK d. o. o., določili kritične točke v procesu skladiščenja kemikalij in podali predloge za odpravo kritičnih točk.
Ključne besede: skladiščenje, kemikalije, zakonodaja, ABC analiza, analiza SQAS
Objavljeno v DKUM: 13.03.2025; Ogledov: 0; Prenosov: 7
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5. Morphological, mechanical, and in-vitro bioactivity of gelatine/collagen/hydroxyapatite based scaffolds prepared by unidirectional freeze-castingYasir Beeran Potta Thara, Tomaž Vuherer, Uroš Maver, Vanja Kokol, 2021, izvirni znanstveni članek Opis: The fabrication of biomaterials to be used in segmental bone defects, mimicking the bone's organic-inorganic architecture and mechanical properties to induce osteogenesis, persists as a key challenge. The purpose of this study was to elucidate the effect of a lightweight, morphologically graded, and multiphase self-standing scaffold structure prepared from a combination of gelatine (Gel), collagen type 1 (Col) and/or hydroxyapatite (HAP) nanoparticles by a unidirectional freeze-casting process at different temperatures (−20, −40, −60 °C), followed by carbodiimide induced cross-linking, on their in-vitro mechanical stability and bioactive properties. In addition, the rheological study of differently formulated Gel solutions has been performed to determine the effect of Col and HAP content on their microstructural arrangement, which, together with the freezing kinetic, affects Gel/Col orientation and cross-linking, and, thus, the scaffold's mechanical strength and stability. A bone-like anisotropic, interconnected, and graded porosity (from 120 to a few μm) scaffold structure with up to 30% total porosity and ~61 μm average pores' diameter is obtained by using a higher Col content (Col: Gel = 2:5) and freezing temperature (−20 °C) while forming a few μm thick close-to-parallel lamellae, separated with a 10–100 μm space when prepared at −60 °C. Such a structure influenced in-vitro stability strongly (lower swelling without weight loss), being accompanied with a ~76% increase of compression strength (to 37 kPa) and ~67% decrease of elastic modulus (to 17 kPa) when prepared with HAP and incubated in HBSS for 7 days. On the other hand, a significant reduction of both strength (~78%, to 15 kPa) and elasticity (~95%, to 5 kPa) was noted for a scaffold prepared with HAP at −60 °C, being related to faster degradation and the formation of a highly opened structure on the bottom, required to stimulate the bone ingrowth, while a more closed network structure on the top to adhere with the surrounding soft tissue. None of the scaffolds induced cytotoxicity to human bone-derived osteoblasts, even after 19 days of incubation, but rather improved their viability while promoting cells' adhesions, proliferation, and differentiation, being supported with an increased alkaline phosphatase activity and rod-like CaP formation.
Ključne besede: biomimetic scaffolds, rheology, unidirectional freeze-casting, morphology, compression properties, bioactivity
Objavljeno v DKUM: 10.03.2025; Ogledov: 0; Prenosov: 2
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6. In-depth analysis of fatal motorcycle accidents—case study in SloveniaTomaž Tollazzi, Laura Brigita Parežnik, Chiara Gruden, Marko Renčelj, 2025, izvirni znanstveni članek Opis: Motorcyclists remain a disproportionately large group of vulnerable road users, with fatality rates significantly higher than that in other road groups. Additionally, fatal accidents involving motorcyclists have a more slowly decreasing trend in comparison to that of other road users, while the number of this kind of users is growing fast. For all these reasons, there is a need to understand what the key factors leading to fatal accidents are in order to identify the possible measures to minimize the accidents themselves or at least their consequences. This would permit, indeed, to positively impact the road traffic system, leading to the creation of the safest road traffic system possible, as it is the goal of the Sustainable Safety approach. The aim of this study is to dive into the mentioned problem, analyzing fatal motorcycle accidents in Slovenia over a decade, highlighting the key factors contributing to these incidents. By integrating data from four databases, the study evaluated accident trends, infrastructural elements, and rider behavior through a multi-stage analysis. Firstly, data were collected from four national, up-to-date databases that contain information about road accidents themselves, the road infrastructure, additional police data, and media descriptions. After merging this information into one comprehensive database, where each row represents all the data available for one accident, a general analysis of accidents’ trends over the considered 10-year period was developed, considering at first all fatal road accidents, then deepening it to accidents caused by a motorcyclist, and finally to single-vehicle accidents. A statistical analysis followed, aimed at identifying a statistical correlation between the accidents and the factors leading to them. The results of the first accident analysis indicated that excessive speed, incorrect driving direction, and overtaking maneuvers are the primary causes of fatal accidents, especially on non-urban roads preferred by motorcyclists. Single-vehicle accidents frequently involve collisions with roadside objects, including safety barriers and poles, underscoring the need for targeted infrastructural improvements. The following correlation analysis revealed that a total of seven factors were statistically significant: three human factors (age, gender, experience)—which were the ones with the strongest correlations—one infrastructural factor (pavement width), and three factors belonging to external conditions (accident type, cause, and location). Of these, four were positively correlated to the causer, while three, i.e., pavement width, causes, and road location, were negatively correlated. This study provides a foundation for future research on less severe accidents and proactive risk behavior analysis, aiming to improve motorcyclist safety comprehensively.
Ključne besede: motorcycle safety, fatal accidents, road infrastructure, rider behavior
Objavljeno v DKUM: 10.03.2025; Ogledov: 0; Prenosov: 4
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7. Distributed energy resource operation analysis using discrete event-simulationBojan Rupnik, Dušan Kragelj, Simona Šinko, Tomaž Kramberger, 2020, izvirni znanstveni članek Opis: This paper presents a discrete-event simulation (DES) approach for simulation of distributed energy resources (DER). The DES approach provides means to adapt the energy workloads of the system according to any variations of demands that can occur due to temperature regulation requirements or operational demands. Along with a basic model based on a concrete DER configuration, additional models are presented and analysed in order to demonstrate the adaptability of the DES approach to analyse alternative configurations. The models were tested on historical energy consumption data in order to provide the expected workloads and costs. Models are capable to predict the amount of three different energies and cost for the company based on the inside and outside temperatures.
Ključne besede: cost, discrete-event simulation, distributed energy resources, energy efficiency, hospitals, logistics
Objavljeno v DKUM: 10.03.2025; Ogledov: 0; Prenosov: 2
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8. CAE artificial neural network applied to the design of incrementally launched prestressed concrete bridgesTomaž Goričan, Milan Kuhta, Iztok Peruš, 2025, izvirni znanstveni članek Opis: Bridges are typically designed by reputable, specialized engineering and design companies with years of experience. In these firms, experienced engineers share and pass on their knowledge to younger colleagues. However, when these experts retire, some of the knowledge is lost forever. As a subset of artificial intelligence methods, artificial neural networks (ANNs) can solve the problem of acquiring, transferring, and preserving specialized expert knowledge. This article describes the possible application of CAE ANN to acquire knowledge and to assist in the design of incrementally launched prestressed concrete bridges. Therefore, multidimensional graphs in the form of iso-curves of equal values were created, allowing practicing engineers to understand complex relationships between design parameters. The graphs also contain information about the reliability of the results, which is defined by an estimated parameter. The general rule is that results based on a larger number of actual data points are more reliable. Finally, an ANN BD assistant is proposed as an application that assists engineers and designers in the early stages of design and/or established engineers and designers in variant studies and design parameter optimization.
Ključne besede: artificial neural networks, bridge design, incremental launching method, expert knowledge, reliability of predictions, prestressed concrete bridges
Objavljeno v DKUM: 10.03.2025; Ogledov: 0; Prenosov: 5
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9. Varivost novejših toplotno odpornih materialov in njihova uporaba v termoenergetskih objektih : diplomsko deloLuka Ferlež, 2024, diplomsko delo Opis: V diplomski nalogi smo analizirali vplive parametrov varjenja na kakovost zvara, pri varjenju temperaturno odpornega jekla X10CrVMoNb9-1 (P91).Izvedli smo mobilne in laboratorijske meritve trdote (po Vickersu) v osnovnem materialu in v varu, izvedeli smo tudi natezni preizkus preko vara. Meritve smo izvedeli na štirih vzorcih, ki so bili iz proizvodnje izločeni, zaradi neustreznih trdot in pomanjkljivega nadzora nad samim varjenjem. Pridobljene rezultate smo primerjali s tistimi zapisanimi v pristojnih standardih. V diplomski nalogi pa smo tudi analizirali vplive temperature in časa na odpornost jekla P91 proti lezenju, ter vpliv toplotne obdelave pred in po varjenju.
Ključne besede: jeklo X10CrVMoNb9-1, parametri varjenja, trdota, natezni preizkus, odpornost proti lezenju, TVP, toplotna obdelava
Objavljeno v DKUM: 06.03.2025; Ogledov: 0; Prenosov: 4
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10. Zasnova in izdelava cnc stroja za lasersko graviranjeDavid Fridrih, 2025, diplomsko delo Opis: Pred izdelavo stroja za lasersko graviranje je bilo potrebno izbrati želeno obliko in konstrukcijo. Izdelali smo osnovno skico, nato je sledila izdelava CAD modela. Ta model nam je omogočal preverjanje skladnosti raznih komponent med sabo.
Vse plastične komponente stroja smo izdelali s pomočjo 3D tiska, pogonsko os pa s struženjem. Vse ostale komponente smo kupili (vijake, motorje, elektroniko).
Stroj se giblje po X- in Y-osi, po Z-osi pa ga je mogoče nastavljati samo ročno. Glavni gibanji stroja se ne opravljata po vodilih, temveč se voziček vozi s kolesi po utoru profila. Gibanje se opravlja preko motorjev na jermena. Za to sta uporabljena dva motorja, ki ju krmili krmilnik na zadnji strani ohišja. Stroj mora biti med obratovanjem ves čas priključen na računalnik.
Ključne besede: CNC stroj, CAD model, lasersko graviranje, 3D tisk
Objavljeno v DKUM: 04.03.2025; Ogledov: 0; Prenosov: 19
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