1. In-plane deformation behavior and the open area of rotating squares in an auxetic compound fabricPolona Dobnik-Dubrovski, Nejc Novak, Matej Borovinšek, Matej Vesenjak, Zoran Ren, 2022, izvirni znanstveni članek Opis: A conventional compound fabric was used to develop a modern, multifunctional material
with an auxetic behaviour and a tailored open area for particle filtration. Such material was produced
using traditional textile technology and laser cutting, to induce a rotating squares unit geometry. The
behaviour was investigated of three different rotating unit cell sizes. The laser slit thickness and the
length of the hinges were equal for all three-unit cells. The tensile properties, Poisson’s ratio and
auxetic behaviour of the tested samples were investigated, especially the influence of longitudinal
displacement on the fabric’s open area and the filtered particle sizes (average and maximum). Results
show that the developed compound fabric possesses an average negative Poisson’s ratio of up to
−1, depending on the applied auxetic geometry. The larger rotating cell size samples offer a higher
average negative Poisson’s ratio and a higher breaking strength due to the induced slits. The findings
highlight the usefulness of patterned cuts in conventional textile materials to develop advanced
auxetic textile materials with tailored geometrical and mechanical properties.
Ključne besede: compound textile material, auxetic structure, open area, filtration, mechanical properties, Poisson’s ratio
Objavljeno v DKUM: 25.03.2025; Ogledov: 0; Prenosov: 3
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2. Wear simulation of the conveyor belt transfer chute using the DEMTone Lerher, Žan Grum, Marko Motaln, Matej Zadravec, 2024, izvirni znanstveni članek Opis: This paper presents a wear simulation-based performance evaluation of the conveyor belt transfer chute using the DEM (Discrete Element Method). Compared to known analytical and empirical wear models, DEM simulation can significantly increase the performance of wear analysis by enabling the analysis and optimization of highly complex geometries of material handling systems such as conveyor belt transfer chutes. Only the correct design of the conveyor belt transfer chute has the potential to significantly extend its service life, resulting in considerable cost savings. Based on the parametric analysis of different angles and radius in the upper head and lower section of the transfer chute, a new geometry of the transfer chute was proposed. The wear depth of the new conveyor belt transfer chute is compared with the wear resistant and low-carbon steel of the transfer chute along with the moderate and relatively high values of the solid granules mass flow. The results show that the wear depth of the transfer chute can be significantly reduced by using the wear-resistant steel compared to the low-carbon steel, which is significantly evident in high throughput rates of the solid granules mass flow.
Ključne besede: bulk material flow, Discrete Element Method (DEM), transfer chute wear simulation, archard and relative wear, performance analysis
Objavljeno v DKUM: 10.03.2025; Ogledov: 0; Prenosov: 9
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3. Comparative analysis of a 3D printed polymer bonded magnet composed of a TPU-PA12 matrix and Nd-Fe-B atomised powder and melt spun flakes respectivelyGranit Hajra, Mihael Brunčko, Leo Gusel, Ivan Anžel, 2025, izvirni znanstveni članek Opis: The present study reports the development of new polymer bonded magnet containing a Thermoplastic Polyurethane (TPU) – Nylon (PA12) blend as the matrix material and Nd-Fe-B magnetic particles. Two composite materials were explored: one using Nd-Fe-B atomised spherical powder (ASP) and another incorporating Nd-Fe-B melt-spun flakes (MSF). The filaments were formulated by blending TPU, PA12, and one of selected type of Nd-Fe-B particles using a mixing device. The ASP and the MSF were integrated into the matrix via a precise compounding process and 3D printing was used to produce the testing specimens. The preliminary findings indicate that both formulations exhibited promising magnetic properties while maintaining the mechanical characteristics of TPU and PA12. The atomised spherical powder formulation demonstrated worse magnetic behaviour compared to the melt-spun flake formulation. ASP particles enable better fluidity of the composite material during 3D printing. However, the close-packed arrangement of these particles is the cause of much higher porosity and consequently the poorer mechanical and magnetic properties. Optimization of the processing parameters showed significant influence on the final magnetic performance and structural integrity of the printed specimens.
Ključne besede: bonded magnets, Nd-Fe-B melt spun flakes, Nd-Fe-B atomised powders, material extrusion, additive manufacturing, fused specimen fabrication
Objavljeno v DKUM: 08.01.2025; Ogledov: 0; Prenosov: 9
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4. Information communication technology and supply chain efficiency in manufacturing SMES in Bulawayo Province in ZimbabweSithokozile Bafana, Simba Mutsvangwa, Felix Chari, 2024, izvirni znanstveni članek Opis: There has been a global plummeting trend of failure in most manufacturing Small and Medium Enterprises (SMEs) due to purported supply chain inefficiency. It is imperative for clothing manufacturing SMEs in developing nations like Zimbabwe, with reference to Bulawayo Province, which lacks digitization to integrate Information and Communication Technology (ICT) solutions into their supply chain operations to improving efficiency and maintain competitiveness in the global market. Thus, the purpose of the study was to evaluate ICT and supply chain efficiency in the clothing manufacturing SMEs in Bulawayo Province. Employing the pragmatic approach, data were collected using semi-structured questionnaires from a sample of 107 from a total population of 147 that were triangulated with 15 interviews from clothing manufacturing SMEs in Bulawayo. A simple linear regression analysis through Ordinary Least Squares was conducted to test the relationship between ICT and supply chain efficiency. The results show that ICT has a positive and statistically significant effect on cost performance, agility and delivery performance in Bulawayo clothing manufacturing SMEs. By prioritizing ICT adoption, managers can achieve better cost management, increased responsiveness to market demands, and enhanced delivery capabilities. It is recommended that clothing manufacturing SMEs in Bulawayo should embrace the ICT. Further studies should examine the relationship between ICT and supply chain efficiency in manufacturing SMEs across different industries and nations.
Ključne besede: information and communication technology, supply chain efficiency, SMEs (small and medium enterprises), material requirement planning
Objavljeno v DKUM: 17.12.2024; Ogledov: 0; Prenosov: 5
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5. Izboljšava embalaže vratic električnih omaric v izbranem podjetju : diplomsko deloMitja Zagoranski, 2024, diplomsko delo Opis: V diplomski nalogi z naslovom Izboljšava embalaže vratic električnih omaric smo se osredotočili na iskanje embalaže, ki bi nudila večjo zaščito izdelkom med transportom, omogočala enostavnejšo manipulacijo s polizdelki na odvzemnem mestu ter optimizirala tovorni prostor, s čimer bi omogočili transport večje količine izdelkov.
Za namene diplomskega dela smo v začetku naloge povzeli že znana teoretična izhodišča in stališča s področja embalaže. Glavne ugotovitve naše raziskave kažejo, da lahko z uporabo kompaktnejše embalaže zmanjšamo poškodbe polizdelkov, kar posledično znižuje stroške zaradi odpisov poškodovanih izdelkov. Predlagana embalaža bi prav tako zagotavljala večjo varnost zaposlenih, saj prihaja pri manipulaciji izdelkov občasno do poškodb zaradi slabe zaščite polizdelkov v trenutni embalaži. Z uvedbo nove embalaže bi podjetje omogočilo transport večje količine vrat in povečalo izkoristek prostora na tovornem vozilu. Izpostaviti je treba tudi možnost večkratne uporabe nove embalaže, ki je obstojnejša kot embalaža podjetja, ki jo trenutno uporabljajo.
V zaključku diplomskega dela smo povzeli priporočila podjetju, ki bi lahko vpeljalo uporabo nove embalaže ter preverilo, ali se stroški transporta, odpadnega materiala in odpisanih izdelkov zmanjšajo ob uporabi nove embalaže skozi daljše časovno obdobje.
Ključne besede: embalaža, električna omarica, odpadni material, karton, reciklaža
Objavljeno v DKUM: 12.12.2024; Ogledov: 0; Prenosov: 23
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6. Analiza procesa zajemanja in praznjenja elevatorja s korci z uporabo numeričnega orodja Ansys RockyMihael Arčan, 2024, diplomsko delo Opis: Pri transportu materiala v vertikalni ali poševni smeri se v praksi pogosto uporabljajo elevatorji, ki omogočajo učinkovito transport različnih vrst razsutega tovora. V okviru diplomskega dela smo obravnavali transport izbranega elevatorja s korci ter izvedli simulacije v numeričnem orodju Ansys Rocky. S pomočjo orodja smo analizirali različne oblike korcev. Zanimalo nas je, kako oblika korca vpliva na zmogljivost elevatorja, pretoke po zajemanju, pretoke v povratni veji ter obrabo korcev. Iz simulacij smo ugotovili, da se je pri našem elevatorju s korci najbolj obrabljal plitek korec. Plitek korec je imel najboljšo zmogljivost in je edini dosegel zahtevano zmogljivost.
Ključne besede: elevator s korci, metoda diskretnih elementov, sipki material, numerično orodje
Objavljeno v DKUM: 22.10.2024; Ogledov: 0; Prenosov: 25
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7. Imobilizacija encimov na visoko porozne polimerne nosilce : magistrsko deloLara Berložnik, 2024, magistrsko delo Opis: Namen magistrskega dela je bil razviti učinkovite postopke za sintezo poroznih polimernih materialov v različnih oblikah, kot so monoliti in zrna. Monolitne materiale smo pripravili s polimerizacijo v masi in s polimerizacijo zunanje faze emulzij z visokim deležem notranje faze, medtem ko smo zrna sintetizirali s suspenzijsko polimerizacijo. Zrna smo nato uporabili kot nosilce za imobilizacijo encimov.
Najprej smo sintetizirali monolitne poli(glicidil metakrilat-ko-etilen glikol dimetakrilatne) materiale s polimerizacijo v masi, pri čemer smo uporabili različne deleže porogenega topila, ki so variirali med 0 in 200 vol. % glede na volumen monomerov. Produkt je bil krhek material, pri čemer se je z nižjimi deleži porogena tvoril material z neporozno morfologijo, z višjimi deleži pa t.i. cvetačna morfologija. S polimerizacijo zunanje faze emulzij z visokim deležem notranje faze, inducirano termično ali s fotopolimerizacijo ter uporabo zamreževala v deležih od 5 mol % do 25 mol %, smo pridobili monolitne materiale s celično morfologijo. Pore v teh materialih so bile raznolike tako po obliki kot po velikosti. Materiale smo karakterizirali z vrstičnim elektronskim mikroskopom za določitev morfologije,FTIR spektroskopijo in elementno analizo za določitev kemijske sestave ter porozimetrijo za določitev porazdelitve velikosti por in specifične površine.
Sintetizirana in okarakterizirana poli(glicidil metakrilat-ko-etilen glikol dimetakrilatna) zrna smo uporabili kot nosilce za imobilizacijo encima lipaze iz Candida cylindracea. Imobilizacijo encima smo izvedli na poroznih in neporoznih zrnih, tako z uporabo distančnika in mrežnega zamreževalca kot brez njiju. Imobilizacija je bila uspešna v vseh primerih, pri čemer je bila nekoliko bolj učinkovita ob uporabi distančnika in mrežnega zamreževalca, kar smo potrdili s testno reakcijo hidrolize 4-nitrofenil butirata. Učinkovitost vezave encima smo preverjali z določanjem koncentracije proteina pred in po imobilizaciji z Bradfordovo metodo.
Ključne besede: poliHIPE material, HIP emulzija, suspenzijska polimerizacija, imobilizacija encima, Lipaza Candida Cylindracea
Objavljeno v DKUM: 04.10.2024; Ogledov: 0; Prenosov: 37
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8. Izračun nabavne cene materiala v izbranem proizvodnem podjetjuNatalija Gaberc, 2024, diplomsko delo Opis: Delo diplomskega projekta prikazuje izračun nabavne cene materiala (komponent) v izbranem proizvodnem podjetju. Namen je prikazati, kako izbrano podjetje izračunava nabavno ceno materialov (komponent), ki jih potrebuje za svoje poslovanje, to je proizvodnjo proizvodov. V delu po uvodni kratki predstavitvi vsebin v zvezi s stroški, kalkulacijami in na splošno še nabavo predstavimo izračunavanje nabavnih cen materialov (komponent), ki so potrebni za proizvodnjo avtomobilskega praga. Avtomobilski prag je namreč sestavljen iz večih komponent, med drugim tudi komponente iz aluminija in neravnega jekla. Ker gre za surovini, katerima se nabavna cena pogosto spreminja, smo tudi na kratko predstavili, kako je ta cena sestavljena, ko podjetje z dobavitelji sklepa dogovore glede nabavnih cen. V delu diplomskega projekta je postavljena hipoteza, da ima proizvodno podjetje organizirane notranje procese pri nabavi materiala (komponent) v podjetju tako, da lahko na podlagi teh procesov računovodstvo natančno izračuna nabavno ceno posameznega nabavljenega materiala (komponent). To hipotezo smo potrdili, saj ima proučevano proizvodno podjetje takšne nabavne funkcije in pravila, ki računovodstvu priskrbujejo vse potrebne podatke za izračunavanje nabavnih cen posameznega materiala (komponent) in skupaj stroškovno ceno avtomobilskega praga. V delu diplomskega projekta smo tudi predstavili, kako se podjetje sooča z dogodki, ki lahko višajo nabavno oz. stroškovno ceno našega končnega proučevanega izdelka (avtomobilski prag). V delu diplomskega projekta smo prikazali tudi, kako izbrano podjetje računalniško obdela postopek od naročila do nabave, ki se zaključi s prejetim računom.
Ključne besede: nabava, nabavna cena, izračun nabavne cene, strošek, material, stroškovna cena proizvoda
Objavljeno v DKUM: 25.09.2024; Ogledov: 0; Prenosov: 20
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9. Finite element analysis of titanium foam in mechanical response for dental applicationSnehashis Pal, Igor Drstvenšek, 2021, izvirni znanstveni članek Opis: Metals with certain porosity are a new class of materials with extremely low density and a unique combination of excellent mechanical, thermal, electrical, and biocompatible properties. Absorption of impact and shock energy, dust and fluid filtration, construction materials, and most importantly, biocompatible implants are all potential applications for metallic foams. An orthopaedic implant made of metallic foam can provide an open-cell structure that allows for the ingrowth of new bone tissue and the transport of body fluids. Due to its strong biocompatibility and stable fixation between the implant and human bone, titanium foam has recently received much attention as an implant material. Finite element modelling is a suitable method to obtain an efficiently designed implant. Accurate finite element analyses depend on the precision before implementation as well as the functionality of the material properties employed. Since the mechanical performances of titanium foam and solid titanium are different, a constitutive model for porous metal is required. The model of Deshpande and Fleck in the finite element analysis software ABAQUS is used to describe the compressive and flexural deformation properties of titanium foam with 63.5% porosity. The finite element simulation results were compared with the practical mechanical properties obtained by compression testing of the foam. Finally, the material modelling was used to investigate the stress distributions on the dental implant system.
Ključne besede: finite element analysis, ABAQUS, titanium foam, sintering, dental implant, material modeling, mechanical properties, bending, compressing
Objavljeno v DKUM: 25.09.2024; Ogledov: 0; Prenosov: 5
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10. Suitability of test procedures for determining the compatibility of seal materials with ionic hydraulic fluidsDarko Lovrec, Vito Tič, 2024, izvirni znanstveni članek Opis: The compatibility of seal materials with the working fluid is crucial for the flawless, energysaving, environmentally sustainable, and safe operation of any technical system. This is especially
true for hydraulic systems operating under high operating pressure. The problem of materials
compatibility comes into play when either a new type of seal material or a new type of fluid comes
into use. The paper discusses the research findings regarding material compatibility testing of new
high-tech ionic hydraulic fluids with commonly used seal materials. Due to the completely different
chemical composition of these new fluids compared to the classical mineral-based oil, for these fluids,
there are no standardized testing procedures. In these cases, we can only lean on the Standards
that apply to classical fluids, which can lead to incorrect results. In the forefront of the paper is the
discrepancy between the results obtained by the standardized test, and the test under real operating
conditions. FKM, an excellent material for seals, proved to be the most suitable in the case of using
ionic hydraulic fluid, according to a standardized test. However, it failed in the comparison test
under real operating conditions, as the cylinder leaked. NBR seals proved to be a better solution.
Ključne besede: ionic hydraulic fluids, seal material compatibility, static and dynamic test, comparison of results, differences, test suitability
Objavljeno v DKUM: 10.09.2024; Ogledov: 59; Prenosov: 31
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