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1.
Simulation of Dual-Beam Laser Metal Deposition
Matej Kočevar, 2021, magistrsko delo

Opis: 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.
Ključne besede: Laser Metal Deposition (LMD), dual-beam process, wire-based Laser Metal Deposition (LMD-w), Finite Element Method (FEM)
Objavljeno: 23.09.2021; Ogledov: 57; Prenosov: 6
.pdf Celotno besedilo (3,37 MB)

2.
Laserski razrez pločevine v podjetju Aluminium Kety Emmi d.o.o.
Žan Strajnšak, 2021, diplomsko delo

Opis: Diplomska naloga obravnava opis in optimizacijo postopka laserskega razreza pločevin, v podjetju Aluminium Kety Emmi, d. o. o. . V tem delu je opisan razvoj laserskega razreza pločevine, nastanek laserske svetlobe, lasersko rezanje in osnovna razdelitev laserjev. Naloga obravnava korake, vse od zasnove in modeliranja izbranega obdelovanca, izbire materiala ter vse do praktične izdelave izdelka na stroju. Glavni del diplomske naloge predstavlja primerjava opazovanih parametrov obdelave pred in po posameznih optimizacijah. Te so temeljile na izbiri različnih dimenzij pločevin, ki so bile na razpolago v danem trenutku. Z opravljenimi optimizacijami smo podjetju zagotovili, da lahko kljub spremembam dimenzij pločevin na trgu, v vsakem trenutku vzamejo pločevino, ki jim v tistem trenutku najbolj ustreza. Rezultat naloge se odraža v preračunih in komentarjih, v katerih so zajeti vsi parametri obdelave in stroški, ki se pri tem pojavijo.
Ključne besede: laserski razrez pločevine, laser, optimizacija, mehanska obdelava
Objavljeno: 06.09.2021; Ogledov: 62; Prenosov: 0

3.
Analiza napak pri 3D tiskanju hiš s postopki računalniškega vida
Martin Abram, 2020, diplomsko delo

Opis: V okviru tega diplomskega dela smo se ukvarjali z analizo in proučevanjem napak, ki nastanejo v širini betonskih slojev pri 3D tiskanju hiš. Zaradi gostote materiala, vodo-cementnega faktorja, temperature in hitrosti nanašanja materiala se sloji neenakomerno nanašajo drug na drugega. Izdelali smo strojno-programski sistem s katerim izboljšamo natančnost 3D tiskanja. Razvili in implementirali smo algoritem za prepoznavo in analiziranje napak pri 3D tiskanju hiš ter android aplikacijo, ki ta algoritem uporablja. Za prepoznavanje napak smo uporabili tehnike računalniškega vida in se opirali na vizualne informacije, pridobljene s klasičnimi kamerami RGB. Rezultate smo analizirali s pomočjo predpripravljenih posnetkov tiskanja zidu v različnih pogojih. Dobljene rezultate smo primerjali z želeno vrednostjo širine sloja, izmerjena odstopanja pa smo v povratni zanki uporabili za korigiranje 3D tiskanja. Z našo rešitvijo bo gradnja oziroma "tiskanje" hiš kvalitetnejše in hitrejše, saj ne bo nepotrebnih zastojev pri ponovni obdelavi napačno izdelanega zidu. Poraba materiala bo manjša, zid pa bo bolj gladek.
Ključne besede: 3D tisk, računalniški vid, linijski laser, kamera
Objavljeno: 02.11.2020; Ogledov: 122; Prenosov: 22
.pdf Celotno besedilo (2,21 MB)

4.
Snovanje in izdelava laserskega CNC rezalnika
Tomaž Kozmus, 2020, diplomsko delo

Opis: Diplomska naloga v prvem delu vsebuje teoretično razlago delovanja laserja, v drugem delu je opisano snovanje laserskega CNC rezalnega stroja, v zadnjem delu pa so predstavljeni rezultati izgradnje tega stroja. S to diplomsko nalogo je bilo dokazano, da je možno izdelati popolnoma delujoč laserski CNC-rezalnik, pri čemer celotni stroški ne presegajo 500 €. Na koncu diplomske naloge je priložena tudi tehniška dokumentacija, ki omogoča ponovitev izdelave tega laserskega CNC-rezalnika.
Ključne besede: laserski CNC-rezalnik, laser, snovanje izdelka, diodni laser
Objavljeno: 24.09.2020; Ogledov: 219; Prenosov: 71
.pdf Celotno besedilo (3,04 MB)

5.
Sistem za lasersko preoblikovanje optičnega vlakna
Dominik Gril, 2019, diplomsko delo

Opis: Diplomsko delo opisuje celoten postopek, zasnovo, verifikacijo in preizkušanje sistema za tanjšanje optičnega vlakna na daljših odsekih. V delu je natančno opisana zasnova mehanskih komponent uporabljenih v sistemu, ter njihova naloga in delovanje. Podrobno je opisna programska koda in grafični vmesnik za vodenje celotnega sistema. Vir za segrevanje vlakna v majhni točki je izveden s CO2 laserjem. Posebnost predstavljenega sistema je reguliranje izhodne optične moči CO2 laserja, ki je izvedeno s pomočjo kamere. Predstavljen sistem omogoča izdelavo zožitev optičnih vlaken vse do 10 μm iz različnih začetnih premerov. Prav tako smo prikazali uporabnost sistema za izdelavo krajših kosov posebnih - večjedrnih, brezjedrnih vlaken.
Ključne besede: zoženje vlakna, CO2 laser, vodenje, mikrokrmilnik, LabVIEW
Objavljeno: 25.11.2019; Ogledov: 433; Prenosov: 74
.pdf Celotno besedilo (3,51 MB)

6.
Vpliv izdelovalnih parametrov na lastnosti izdelkov iz Ti-6Al-4V, narejenih s selektivnim laserskim taljenjem in plastenje površine z bioaktivnim polimerom
Snehashis Pal, 2019, doktorska disertacija

Opis: Technological parameters included in energy density (ED) are the more powerful tools in selective laser melting (SLM) technology which can be used in the time of fabrication to regulate chemical, metallurgical, and mechanical properties of a product. The volumetric Energy Density (ED) depends on the energy input employed by the laser power, scanning speed, hatch spacing, and the layer thickness. Density, microstructure, surface morphology, dimension accuracy, strength and porosity including the number of pores, place of the pore, size of a pore shape of a pore, inclusions of pores of an SLM product depends on the processing parameters. As the powder material fusion process is done by track by track and layer by layer, the architecture of the microstructure in a product is oriented as the direction of building up too. The research has emphasized on metallurgical properties, tensile properties, and producing the non-porous products from Ti-6Al-4V alloy powder and surface modification using bioactive polymer for orthopedic application. The research has followed four steps to study the metallurgical properties and finding out the combinations of technological parameters in producing non-porous products. The purpose of the first step of the study was to examine the effects of ED on the product properties and to obtain an optimum ED as well as the optimal range of scanning speed. The second step of the study has focused on the influences of laser power. The third step of the study has investigated the effect of amounts of track overlapping and hatch spacing. Almost a zero-porosity product has been able to produce by following these three steps of the ongoing research. The fourth step has studied the metallurgical properties emphasizing on re-melting of every layer. High-density products have been found in the fourth step where a small amount of very small sized pores are present as a result of keyhole effect and gaseous bubble entrapment mainly. Four buildup orientations have been selected for each ED in the first step of the study to examine the tensile properties of the products. The best buildup orientation has been seen in longitudinally vertical tensile specimens considering tensile properties. The tensile properties have also been studied in the second and third step of the study with best build up orientation of the tensile specimens. The alterations of metallurgical and tensile properties have also been investigated after heat-treatment of the specific samples. Dimensional accuracies were also invigilated on the cubic, and tensile specimens over the studies and consequently, inaccuracies have been noticed. The fifth step of the study has observed the pore properties, adhesion properties, the compressive strength of gelatin coating manufactured using unidirectional freezing and the freeze-drying process of three different gelatin concentrations on four different surfaced Ti-6Al-4V alloy substrates. The results indicate that the coating properties depend on the substrate’s surface texture as well as the concentration of gelatin. Above 80% of porosity, interconnected and well-aligned pores of 75-200 μm have been obtained which is required to stimulate bone ingrowth histologically.
Ključne besede: selective laser melting, unidirectional freezing, fabricating parameters, porosity, microstructure, mechanical strength
Objavljeno: 01.04.2019; Ogledov: 876; Prenosov: 101
.pdf Celotno besedilo (10,52 MB)

7.
Racionalizacija postopkov izrezovanja pločevine nerjavečih jekel
Daniel Vovk, 2018, diplomsko delo

Opis: Želja po uspehu je to, kar vodi do napredka. Kljub temu da je podjetje uspešno, je vedno potrebno premisliti še o dodatni racionalizaciji proizvodnega postopka ter s tem zmanjšati proizvodne stroške, izboljšati kakovost, delovne razmere ter s tem biti na vrhu konkurence. Potrebno je dobro poznavanje proizvodnih postopkov, da lahko oblikujemo optimalni proizvodni proces. V nalogi sem se posvetil različnim rezalnim postopkom. Preučene so bile prednosti in slabosti teh postopkov. Ker prihaja v podjetju do težav pri razrezu nerjavnega jekla, sem podrobno preučil prej omenjeni material ter načine, kako bi te težave odpravili. Po preučenih prednostih in slabostih različnih rezalnih tehnik ter zahtevah po kakovosti je bilo ugotovljeno, da je za podjetje najbolj primeren nakup novega plazemskega rezalnika. Z novo sodobno tehnologijo bi odpravili veliko težav, ki jih povzroča sedanja plazma. Ker v podjetju režemo tudi nerjavna jekla, plamenski rezalnik ni primeren izbor, medtem ko laser ni primeren zaradi razreza tudi debelejših materialov.
Ključne besede: razrez, plazma, nerjaveče jeklo, laser, plamenski rezalnik, racionalizacija razreza, izboljšanje produktivnosti.
Objavljeno: 03.05.2018; Ogledov: 523; Prenosov: 122
.pdf Celotno besedilo (1,91 MB)

8.
Simulating various terrestrial and UAV LiDAR scanning configurations for understory forest structure modelling
Marina Hämmerle, Niko Lukač, K.-C. Chen, Zsófia Koma, C.-K. Wang, K. Anders, B. Höfle, 2017, objavljeni znanstveni prispevek na konferenci

Opis: Information about the 3D structure of understory vegetation is of high relevance in forestry research and management (e.g., for complete biomass estimations). However, it has been hardly investigated systematically with state-of-the-art methods such as static terrestrial laser scanning (TLS) or laser scanning from unmanned aerial vehicle platforms (ULS). A prominent challenge for scanning forests is posed by occlusion, calling for proper TLS scan position or ULS flight line configurations in order to achieve an accurate representation of understory vegetation. The aim of our study is to examine the effect of TLS or ULS scanning strategies on (1) the height of individual understory trees and (2) understory canopy height raster models. We simulate full-waveform TLS and ULS point clouds of a virtual forest plot captured from various combinations of max. 12 TLS scan positions or 3 ULS flight lines. The accuracy of the respective datasets is evaluated with reference values given by the virtually scanned 3D triangle mesh tree models. TLS tree height underestimations range up to 1.84 m (15.30 % of tree height) for single TLS scan positions, but combining three scan positions reduces the underestimation to maximum 0.31 m (2.41 %). Combining ULS flight lines also results in improved tree height representation, with a maximum underestimation of 0.24 m (2.15 %). The presented simulation approach offers a complementary source of information for efficient planning of field campaigns aiming at understory vegetation modelling.
Ključne besede: forest structure, understory, laser scanning simulation, full waveform, 3D point cloud analysis, field campaign planning
Objavljeno: 09.10.2017; Ogledov: 954; Prenosov: 298
.pdf Celotno besedilo (3,71 MB)
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9.
A benchmark of lidar-based single tree detection methods using heterogeneous forest data from the alpine space
Lothar Eysn, Markus Hollaus, Eva Lindberg, Frédéric Berger, Jean-Matthieu Monnet, Michele Dalponte, Milan Kobal, Marco Antonio Pellegrini, Emanuele Lingua, Domen Mongus, Norbert Pfeifer, 2015, izvirni znanstveni članek

Opis: In this study, eight airborne laser scanning (ALS)-based single tree detection methods are benchmarked and investigated. The methods were applied to a unique dataset originating from different regions of the Alpine Space covering different study areas, forest types, and structures. This is the first benchmark ever performed for different forests within the Alps. The evaluation of the detection results was carried out in a reproducible way by automatically matching them to precise in situ forest inventory data using a restricted nearest neighbor detection approach. Quantitative statistical parameters such as percentages of correctly matched trees and omission and commission errors are presented. The proposed automated matching procedure presented herein shows an overall accuracy of 97%. Method based analysis, investigations per forest type, and an overall benchmark performance are presented. The best matching rate was obtained for single-layered coniferous forests. Dominated trees were challenging for all methods. The overall performance shows a matching rate of 47%, which is comparable to results of other benchmarks performed in the past. The study provides new insight regarding the potential and limits of tree detection with ALS and underlines some key aspects regarding the choice of method when performing single tree detection for the various forest types encountered in alpine regions.
Ključne besede: single tree extraction, airborne laser scanning, forest inventory, comparative testing, co-registration, mountain forests, Alpine space, matching
Objavljeno: 21.06.2017; Ogledov: 540; Prenosov: 304
.pdf Celotno besedilo (13,97 MB)
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10.
The action of a laser on an aluminium target
Višnja Henč-Bartolič, Tonica Bončina, Suzana Jakovljević, Davor Pipić, Franc Zupanič, 2008, izvirni znanstveni članek

Opis: A nitrogen laser beam (337 nm, 6 ns (FWHM), (3.2 [plus minus] 0.2) mJ) was focused with a quartz lens (f = 100 mm) onto an aluminium target in air at normal pressure. The laser irradiation and plasma explosion caused a modification to the Al surface and the deposition of a thin film (droplets) onto a glassy carbon plate. The irradiated target and the deposited material were studied with a scanning electron microscope (SEM) and a focused-ion-beam (FIB) device. A crater surrounded by a rim was produced on the spot of maximum irradiation on the aluminium target. The crater, very deep in comparison to its width and thickness, was presumably caused by the Kelvin-Helmholtz and the Rayleigh-Taylor instabilities. The temperatures of the electron and the massive particles were explained.
Ključne besede: aluminium, laser ablation, thin film deposition, instabilities, temperatures
Objavljeno: 23.03.2017; Ogledov: 665; Prenosov: 74
.pdf Celotno besedilo (324,07 KB)
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