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Optimization of mechanised metal flux cored wire welding
No full textZavarivanje kao ključna tehnologija spajanja materijala zahtijeva strogo pridržavanje
propisanih standarda i kvalifikacijskih postupaka kako bi se osigurala mehanička svojstva
zavarenih spojeva i ukupna kvaliteta proizvoda. U ovom radu bit će predstavljene i opisane
norme HRN EN ISO 15614-1 i HRN EN ISO 14732, koje se odnose na kvalifikaciju
zavarivačkog postupka (eng. WPQR – Welding Procedure Qualification Record) i
kvalifikaciju operatera za zavarivanje. Osim toga, rad će ukratko objasniti što norme
predstavljaju te koja je njihova uloga u industrijskoj praksi. Budući da norme uključuju širok
spektar tehničkih i tehnoloških zahtjeva, rad će također pružiti sažet pregled WPQR postupka,
kao i opis traktora za zavarivanje koji se koristi u cilju povećanja razine mehanizacije i
automatizacije, čak i u pojedinačnoj proizvodnji. Bit će obrađen i MCAW postupak
zavarivanja (eng. Metal-Cored Arc Welding) te dodatni materijal koji se koristi u tom
postupku, uz objašnjenja u skladu s važećim normativnim zahtjevima. U eksperimentalnom
dijelu rada prikazat će se izrada dvaju kutnih zavara oznaka A i B, uz pripremu spojeva i
izvođenje potrebnih ispitivanja prema zahtjevima norme HRN EN ISO 15614-1.Welding, as a key technology for joining materials, requires strict adherence to prescribed
standards and qualification procedures in order to ensure the mechanical properties of welded
joints and the overall quality of the product.This paper presents and describes the standards
HRN EN ISO 15614-1 and HRN EN ISO 14732, which refer to the qualification of the
welding procedure (WPQR – Welding Procedure Qualification Record) and the qualification
of welding operators. In addition, the paper briefly explains what standards are and their role
in industrial practice. Since standards encompass a wide range of technical and technological
requirements, the paper also provides an overview of the WPQR process, as well as a
description of the welding tractor used to increase the level of mechanization and automation,
even in small-scale production. The MCAW (Metal-Cored Arc Welding) process and the filler
material used in this process will also be covered, with explanations provided in accordance
with applicable normative requirements.In the experimental part of the work, the production
of two fillet welds marked A and B will be presented, along with joint preparation and the
performance of the required tests according to the requirements of the HRN EN ISO 15614-1
standard
Decision-tree-based differential diagnosis of β-thalassemia and sideropenic anemia in children
No full textMikrocitne anemije najčešći su oblik anemija u dječjoj dobi. Najčešći uzrok mikrocitne anemije jest nedostatak željeza, tj. sideropenična anemija. Značajno rjeđi uzrok mikrocitne anemije jesu talasemije. Dijagnostički model za razlikovanje tih dviju bolesti u djece samo na temelju nalaza kompletne krvne slike, prema dostupnim literaturnim podacima, nije standardiziran. Cilj istraživanja bio je odrediti matematičke indekse koji bi omogućili valjano razlikovanje tih dviju bolesti samo na temelju nalaza kompletne krvne slike, a pritom uvažavajući specifičnosti β-talasemije u naše djece.
Logističkom regresijom određene su vrijednosti krvne slike koje su najinformativnije za razlikovanje β-talasemije od sideropenične anemije. Od tih parametara kompletne krvne slike najinformativnijom se pokazao srednji volumen eritrocita (MCV). Druga dva parametra kompletne krvne slike koja najbolje služe za razdvajanje tih dviju bolesti jesu koncentracija hemoglobina (Hb) i prosječna količina hemoglobina u eritrocitu (MCH).
Budući da granične vrijednosti izvornih indeksa koji su načinjeni za odraslu populaciju većinom ne zadovoljavaju u djece, uporabom ROC analize učinjena je optimizacija graničnih vrijednosti svih u literaturi objavljenih svjetskih indeksa i formula. Tako dobivene granične vrijednosti bolje razlikuju djecu s β-talasemijom od djece sa sideropeničnom anemijom u usporedbi s graničnim vrijednostima izvornih indeksa. Najbolji prilagođeni (optimizirani) jednostavni indeks za razlikovanje djece s β-talasemijom od djece sa sideropeničnom anemijom u Republici Hrvatskoj jest Matos-Carvalho indeks s točnošću > 90 % (91,51 %) uz uravnoteženu osjetljivost (89,94 %) i specifičnost (93,75 %). Ostali indeksi s točnošću England i Fraser > Pornprasert > Sirachainan > Telmissani MCHD > CRUISE > Alparslan > Hameed > Sargolzaie > Zaghloul II).
Složeni indeksi pokazali su također uspješnost u razlikovanju djece s β-talasemijom od djece sa sideropeničnom anemijom u Republici Hrvatskoj s točnošću 80 % (ukupno 11 indeksa i formula) upotrijebljeni su za iznalaženje novoga složenog CroCompDD indeksa (točnost 92,25 %, osjetljivost 92,72 %, specifičnost 91,67 %). Analiza grupa (engl. cluster analysis) matematičkih indeksa kao mjerilo najbolje performanse izdvojila je AUC i Youden indeks.
Uporabom metoda strojnog učenja načinjen je dijagnostički postupak s najpovoljnijim odnosom osjetljivosti i specifičnosti za te dvije bolesti. Upotrijebljena su četiri algoritma. Najboljim se pokazao JRIP s točnošću od 94,83 % s postotkom točnosti na unakrsnoj validaciji (engl. leaving one out) od 89,29 %. Sljedeći algoritam, PART, ima postotak 92,25 % s unakrsnom validacijom od 85,60 %. J48 algoritam ima postotak točnosti od 91,88 % (na unakrsnoj validaciji 88,56 %), dok Simple Cart algoritam ima točnost od 91,88 % (na unakrsnoj validaciji 87,45 %). Dobiveni rezultati omogućuju uspostavu smjernica za razlikovnu dijagnostiku mikrocitne hipokromne anemije s praktičnom primjenom u primarnoj, sekundarnoj i tercijarnoj zdravstvenoj zaštiti.Microcytic anemias are the most common form of childhood anemia. The most common cause of microcytic anemia is iron deficiency, i.e., sideropenic anemia. A significantly rarer cause of microcytic anemia is thalassemia. According to available literature data, the diagnostic model for distinguishing these two diseases in children based solely on the findings of a complete blood count is not standardized. The study aimed to determine mathematical indices that would allow a valid distinction between these two diseases only based on the findings of a complete blood count while considering the specifics of β-thalassemia in our children.
Logistic regression determined the blood count values that are most informative for distinguishing β-thalassemia from sideropenic anemia. Of these complete blood count parameters, the mean corpuscular volume (MCV) proved to be the most informative. The other two complete blood count parameters that best serve to separate these two diseases are hemoglobin concentration (Hb) and mean corpuscular hemoglobin (MCH).
Since the cut-off values of the original indices made for the adult population are mostly unsatisfactory in children, the limit values of all published world indices and formulas published in the literature were optimized using ROC analysis. The cut-off values thus distinguish children with β-thalassemia better than children with sideropenic anemia compared to the cut-off values of the original indices. The best adjusted (optimized) simple index for distinguishing children with β-thalassemia from children with sideropenic anemia in the Republic of Croatia is the Matos-Carvalho index with an accuracy of> 90% (91.51%) with balanced sensitivity (89.94%) and specificity (93.75%). Other indices with an accuracy of England and Fraser> Pornprasert> Sirachainan> Telmissani MCHD> CRUISE> Alparslan> Hameed> Sargolzaie> Zaghloul II).
Complex indices also showed success in distinguishing children with β-thalassemia from children with sideropenic anemia in the Republic of Croatia with an accuracy of <90% and ≥ 80%; Index26 with an accuracy of 82.66% with a sensitivity of 84.11% and a specificity of 80.83% (adjusted limit values) and a Janel (11T) index with standard limit values (accuracy 83.39% sensitivity, 93.39%, specificity 75.33%).
The CroCompDD index was compiled based on the group analysis, consisting of 6/11 best indices and formulas with adjusted cut-off values (AUC median 0.92). This index best reflects the genetic specificity of children with β- thalassemia in the Republic of Croatia (accuracy 92.25%, sensitivity 92.72%, specificity 91.67%).
A diagnostic procedure was made using machine learning methods with the most favorable relationship of susceptibility and specificity for these two diseases. Four algorithms were used. JRIP proved to be the best, with an accuracy of 94.83% with a percentage of accuracy on crossvalidation (leaving one out) of 86.35%. The J48 algorithm has an accuracy percentage of 91.88% (on cross-validation 89.29%). The following algorithm, PART, has an accuracy of 92.25% with a cross-validation score of 85.60%. The J48 algorithm has an accuracy of 91.88% (with a crossvalidation score of 88.56%), while the Simple Cart algorithm has an accuracy of 91.88% with a cross-validation score of 87.45%.The obtained results enable the establishment of guidelines for the differential diagnosis of microcytic hypochromic anemia with practical application in primary, secondary, and tertiary health care
The efficiency of the bovine intrauterine device on suppression of estrus in cow
No full textToday, the animal welfare is an important notion for the customers. In other words, it is
essential to avoid pregnant animals at the abattoirs, where important fines apply in such case.
Different methods can be used as contraception in cattle: surgical, chemical, immunological
and mechanical.
The aim of this study was to evaluate the effectiveness of the DIUB Turin® copperreleasing bovine intrauterine device (BIUD) in suppressing estrus and preventing pregnancy in
cows, as well as to assess its potential impact on uterine health.
A total of 19 animals, 18 cows and 1 heifer of various breeds received a BIUD. All
animals were issued exclusively from the Reprovet Clinic, La Brévine, Switzerland. The
devices were inserted following standard procedures and each animal was examined clinically
by ultrasound twice during the study period. Four uterine samples were sent to pathohistology
examinations to assess the possible lesions caused by the BIUD.
Results showed a high pregnancy prevention rate of 94.7 %, with only one cow
becoming pregnant, similar with the results of TURIN et al. (1996). However, estrus
suppression was observed in only 10.53 % of animals, significantly lower than the 98 %
suppression rate claimed by the commercial instruction.
Pathohistological examinations found mild to moderate localized endometrial changes
such as epithelial erosion, fibrosis, and inflammation, though no cases of uterine perforation or
pyometra were detected.
While the BIUD appears effective in preventing pregnancy its ability to suppress estrus
was not efficient. Also, its long-term impact on uterine tissue can be severe. Further
investigation is needed to evaluate correctly the risk of perforationDobrobit životinja bitan je aspekt suvremenog tržišta. U tom smislu od iznimne je
važnosti da se na liniji klanja ne pojavljuju gravidne životinje, ne samo zbog visokih kazni koje
takve slučajeve prate. U govedarstvu su nam na raspolaganju različite metode kontracepcije:
kirurške, kemijske, imunološke i mehaničke.
Cilj ovog rada bilo je istražiti učinkovitost DIUB Turin® intrauterine spirale s
otpuštajućim bakrom (BIUD) na suprimiranje estrusa (gonjenja) i spriječavanje gravidnosti u
krava kao i ocijeniti učinak iste na stijenku maternice.
BIUD je apliciran 19 grla, od čega 18 krava i jednoj junici. Sve su životinje pacijenti
klinike Reprovet Clinic, La Brevine, Švicarska. Spirale su aplicirane po standardnom postupku
te je svaka životinja klinički ultrazvučno pregledavana dva puta tijekom razdoblja provedbe
istraživanja. Četiri uzorka maternica poslana su na patohistološku pretragu kako bi se ocijenile
moguće lezije u maternici prouzrokovane spiralom.
Rezultati su pokazali visoku učinkovitost u prevenciji gravidnosti (94,7 %), sa samo
jednom gravidnom kravom što je u skladu s rezultatima TURIN i sur. (1996). Ipak, supresija
estrusa ostvarena je u samo 10,53 % životinja što je značajno niže od 98 % kako se navodi u
komercijalnoj uputi proizvođača.
Patohistološkim nalazom utvrđene su blage do umjerene, lokalizirane promjene
endometrija kao što su erozija epitela, fibroza i upala. Nalaz nije utvrdio perforacije maternične
stijenke ili pijometru.
Utvrdili smo da je BIUD učinkovit u spriječavanju gravidnosti, dok nije iskazao takovu
učinkovitost u suprimiranju estrusa (gonjenja). Također, spirala može imati ozbiljan učinak na
tkivo maternice u slučaju dugotrajnog držanja. Potrebna su daljnja istraživanja kako bismo
preciznije procijenili rizik perforacije maternice
Process improvement in wiring assembly
No full textKonstantnim unaprjeđenjima automobilske industrije, dodavanjem brojnih senzora, digitalnih zaslona u kokpit automobila i svjetskim okretom prema električnim automobilima kao načinu borbe s globalnim zatopljenjem, automobilska ožičenja postaju ključna komponenta proizvodnje automobila. Automobilska ožičenja su nezaobilazne strukture potrebne za povezivanje svih komponenata unutar automobila. Proces proizvodnje automobilskog ožičenja i kako ga unaprijediti postaje novi izazov za procesne inženjere u proizvodnji. Glavni cilj ovog rada je opisati procese u montaži automobilskog ožičenja, pokazati kako se koriste Lean alati i kako oni unaprjeđuju procese. Osim toga, definirat će se nadolazeći trendovi s naglaskom na Industriju 4.0. Sva unaprjeđenja procesa su prikazana na stvarnom primjeru u Rimac Automobili d.o.o. u prijelazu iz pojedinačne na serijsku proizvodnju.With the automotive industry constantly improving the user experience by adding numerous sensors, digital displays in car cockpits and the global turn to the electrical automobiles to combat climate changes, wiring harnesses become key components in car production. Wiring harnesses are unavoidable structures necessary for connecting all components within the car. Wiring harness assembly process and how to improve it becomes the new challenge for process manufacturing engineers. The main goal of this bachelor’s thesis is to describe processes in wiring harnesses assembly, show how lean tools are used and do they improve the process, define key performance indicators and list upcoming trends in harness assembly with an emphasis on Industry 4.0. All process improvements are shown on the real example in Rimac Automobili d.o.o. in transition from prototype to serial car production
Reliability analysis and improvement of a system for assisting the positioning of medical instruments in neurosurgery
No full textPri razvoju novih proizvoda se sve veća pozornost pridodaje aspektima pouzdanosti i sigurnosti, što je posljedica sve kraćeg trajanja razvojnih projekata uzrokovana specifičnim potrebama i konkurencijom na tržištu. Posebna pažnja na sigurnost i pouzdanost također se obraća u specifičnim tehnološkim granama, kao što je razvoj medicinskih uređaja. Stoga je cilj ovoga rada dati pregled te provesti i diskutirati različite metode za analizu pouzdanosti i sigurnosti na primjeru medicinskog robota. Prilikom izrade rada, posebna pažnja je posvećena teorijskom uvodu i opisu izabranih metoda. Metode su izabrane na temelju pregleda dostupne literature u područjima sigurnosti medicinskih uređaja. Nakon odabira metoda, svaka je predstavljena i opisana, te je prikazan postupak njihove provedbe. Prema utvrđenim postupcima, provedene su detaljne analize pouzdanosti i sigurnosti NERO sustava. Dobiveni rezultati su prikazani i opisani, te su na temelju njih provedene konstrukcijske promjene kritičnih podsustava. Svrha konstrukcijskih promjena je postizanje veće pouzdanosti i sigurnosti sustava, ali i svojevrsni zapisi znanja u obliku vodilja za daljnji konstrukcijski razvoj sustava. Prilikom provedbe navedenih postupaka, odrađene su sve pripremne radnje koje se izvode na temelju postupka odabranih metoda. Također je prije same provedbe analiza ukratko predstavljen i opisan NERO sustav, za koji su provedene analize pouzdanosti i sigurnosti.When developing new products, more and more attention is paid to reliability and safety aspects, which is a consequence of the shorter duration of development projects caused by specific needs and competition in the market. Special attention to safety and reliability is also paid within specific technological branches, such as the development of medical devices. Therefore, this thesis aims to provide an overview, implementation and discussion of different reliability and safety analysis methods with an example from a medical robot development project. When preparing the work, special attention was given to the theoretical introduction and description of the chosen methods. The methods were selected based on a review of the available literature in the fields of medical device safety. After selecting the methods, each is presented and described, and the procedure for their implementation is laid out. According to established procedures, detailed analyses of the NERO system's reliability and security were carried out. Finally, the obtained results are presented and described, with design changes to critical subsystems made based on them. The design changes aim to achieve higher reliability and safety of the overall system but also to record knowledge needed to guide further system development. During the implementation of the above-mentioned procedures, all preparatory actions were carried out based on the selected methods. Also, before the actual implementation of the analysis, the NERO system is briefly presented and described, for which the reliability and security analyses were carried out
The influence of emotional appeals in advertisements on social media on attracting donations
No full textNeprofitnim organizacijama nije cilj ostvarenje profita već ostvarenje općeg dobra, a za ostvarenje općeg dobra to jest ciljeva i misija, neprofitnim organizacijama su potrebna sredstva u obliku financija, volontera i proizvoda. Kako bi skupile ta sredstva, organizacije moraju primijeniti razne marketinške metode, a najdjelotvornije je oglašavanje putem društvenih medija korištenjem emocionalnih apela. Emocionalni apeli stvaraju osjećaj hitnosti za promjenom te su dizajnirani da kreiraju emocionalni odgovor na poruke prikazane emocionalnim sadržajem. U ovom radu istražuje se utjecaj emocionalnih apela u oglasima na društvenim medijima na namjeru doniranja kroz dvije ankete od kojih jedna prikazuje apel na tugu, a druga apel na ljutnju. Istraživanje je provedeno na 202 ispitanika putem anketnih upitnika u kojima se ispitivala izazvana emocija, jačina osjećaja tuge i ljutnje, namjera doniranja i visina iznosa donacije. Statističkom analizom utvrdilo se da i apel na tugu i apel na ljutnju izazivaju jake osjećaje, no unatoč tome, nije pronađena značajna razlika u namjeri doniranja između navedena dva apela.The goal of non-profit organizations is not the realization of profit, but the realization of the common good, and for the realization of the common good, that is, goals and missions, non-profit organizations need funds in the form of finances, volunteers and products. In order to raise these funds, organizations must apply various marketing methods, the most effective of which is social media advertising using emotional appeals. Emotional appeals create a sense of urgency for change and are designed to create an emotional response to messages presented with emotional content. This thesis investigates the influence of emotional appeals in social media ads and the intention to donate through two surveys, one of which shows sadness appeal, and the other anger appeal. The research was conducted on 202 respondents through questionnaires in which evoked emotions, the strength of feelings of sadness and anger, the intention to donate and the amount of the donation were examined. Through statistical analysis, it was determined that both the appeal to sadness and the appeal to anger evoke strong feelings, but despite this, no significant difference was found in the intention to donate between the two appeals
The impact of digitalization on the security of financial data in accounting
No full textDigitalizacija je transformirala računovodstvenu profesiju uvođenjem naprednih softverskih rješenja, automatiziranih procesa i pohrane podataka u digitalnom obliku. Iako digitalna transformacija donosi brojne prednosti poput veće učinkovitosti, preciznosti i dostupnosti informacija, ona istovremeno otvara prostor za nove sigurnosne izazove. Financijski podaci, kao osjetljiv i ključan resurs svake organizacije, izloženi su rizicima poput kibernetičkih napada, neovlaštenog pristupa i gubitka integriteta. U radu se analizira kako digitalizacija utječe na sigurnost financijskih informacija, koje tehnologije i softverska rješenja doprinose zaštiti podataka te koja je uloga računovodstvenih stručnjaka u uspostavljanju sigurnosne prakse. Također se razmatraju regulatorni okviri poput GDPR-a i nacionalnih propisa te se naglašava važnost kombinacije tehnoloških, organizacijskih i pravnih mjera za cjelovitu zaštitu podataka u digitalnom okruženju.Digitalization has transformed the accounting profession through the introduction of advanced software solutions, automated processes, and the digital storage of data. While digital transformation offers numerous advantages such as increased efficiency, accuracy, and information accessibility, it also introduces new security challenges. Financial data, as a sensitive and critical resource for any organization, is exposed to risks such as cyberattacks, unauthorized access, and loss of data integrity. This paper analyzes the impact of digitalization on the security of financial information, explores the technologies and software solutions that contribute to data protection, and highlights the role of accounting professionals in establishing effective security practices. Furthermore, it discusses regulatory frameworks such as the GDPR and national legislation, emphasizing the importance of combining technological, organizational, and legal measures for comprehensive data protection in a digital environment
Synthesis of polymer surfactant in green organic solvent
No full textProvedena je sinteza polimerne površinski aktivne tvari u zelenom organskom otapalu metilnom esteru masnih kiselina (biodizelu), uz različite masene udjele prijenosnika rasta lanca. Korišteni monomeri podrazumijevaju dimetilaminoetil-metakrilat (DMAEMA), metil-metakrilat (MMA), dodecil-metakrilat (DDMA) i oktadecil-metakrilat (ODMA). Konverzija reakcije određena je pomoću nuklearne magnetske rezonancije, a postignute su vrlo visoke vrijednosti (> 96 %). Kromatografijom isključenja po veličini dobivena je raspodjela molekulske mase koja potvrđuje nastanak sve većeg broja polimernih molekula manje molekulske mase povećanjem masenog udjela prijenosnika rasta lanca. Kinematičke viskoznosti polimernih otopina i čistog biodizela dobivenog iz uljane repice, izmjerene putem viskozimetra, ukazuju na to kako dodatak sintetiziranih polimernih površinski aktivnih tvari u čisti biodizel dovodi do porasta u njihovim vrijednostima što je korisno za poboljšanje mazivosti. Toplinska svojstva otopina polimera u zelenom organskom otapalu, karakterizirana su pomoću razlikovne pretražne kalorimetrije. Utvrđeno je kako povećanje masenog udjela prijenosnika rasta lanca i smanjenje molekulske mase polimera uzrokuje povišenje temperature pri kojoj počinje kristalizacija. Vrijednosti niskotemperaturnih svojstava, odnosno tecišta i maglišta, imala su gotovo nepromjenjive vrijednosti, unatoč promjeni masenog udjela polimera i molekulske mase polimera. Iznosi faktora trenja, određeni korištenjem reometra, pokazuju prvotni nagli pad vrijednosti pri niskim brzinama klizanja, potom nagli rast povećanjem brzine klizanja i naposljetku oscilirajuće vrijednosti.Synthesis of a polymeric surfactant was conducted in a green organic solvent of methyl ester fatty acids, with various mass fractions of chain transfer agents. Used monomers include dimethylaminoethyl methacrylate (DMAEMA), methyl methacrylate (MMA), dodecyl methacrylate (DDMA) and octadecyl methacrylate (ODMA). Conversion of the reaction was determined by using nuclear magnetic resonance spectroscopy, obtaining extremely high values (> 96 %). Size exclusion chromatography revealed the molecular weight distribution, confirming the formation of an increasing number of polymer molecules with lower molecular weights as the mass fraction of the chain transfer agent was increased. The kinematic viscosities of polymer solutions and pure biodiesel derived from rapeseed, measured using a viscometer, indicate that the addition of synthesized polymeric surfactants to pure biodiesel leads to an increase in their values, which is beneficial for improving lubricity. Thermal properties of polymer solutions in green organic solvent were characterized by the usage of differential scanning calorimetry. It was found that an increase in the mass fraction of the chain transfer agent and a decrease in the molecular weight of the polymer lead to a rise in the temperature at which crystallization begins. The values of low-temperature properties, namely the pour and cloud points, remained nearly unchanged despite variations in the mass fraction of polymers and molecular weight of polymers. The coefficients of friction, determined by using a rheometer, show an initial sharp decrease in values at low sliding speeds that are followed by a sharp increase with increasing sliding speed and finally values that oscillate
Modular approach toward procedure development of central beam weldment assembly on electric railcar
No full textU ovom radu prikazana je procedura zavarivanja čelične konstrukcije sklopa srednje grede. U
uvodnom dijelu rada je predstavljen sklop srednje grede kao dio konstrukcije elektromotornog
vlaka tvrtke Končar – Električna vozila. Zatim je predstavljena tvrtka ZM-Vikom čija je obveza
proizvesti cjelokupnu konstrukciju modula elektromotornog vlaka. Opisana je tehnologija
zavarivanja sklopa kroz opis nelegiranog konstrukcijskog čelika S355, MAG postupka
zavarivanja te žice za zavarivanje. Prikazan je način definiranja procesa zavarivanja, a samim
time i proizvodnje čelične konstrukcije, u skladu s normom HRN EN 15085: Željeznički sustav
-- Zavarivanje željezničkih vozila i sastavnih dijelova. U eksperimentalnom dijelu rada
osmišljena je procedura zavarivanja sklopa srednje grede korištenjem modularnog pristupa
prilikom analize procesa izrade konstrukcije uz dokumentiranje procesa izrade koji se izvršava
korištenjem naprava za sastavljanje i zavarivanje. Podjelom procesa zavarivanja u više koraka
rada uz definiranje svih radnji kojima se proces zavarivanja provjerava i potvrđuje razvijena je
procedura koja nailazi na prihvaćanje. Na temelju razvijene procedure osmišljen je koncept
radnih procedura primjenjiv za analizu procesa zavarivanja i načina njegova provođenja.
Naposlijetku je iznesen zaključak rada.In this paper, the welding procedure of the steel structure of the central beam assembly is presented. In the introductory part of the paper, the central beam assembly is presented as part of the design of the Končar – Električna vozila electric train. Then, the company ZM-Vikom was presented, whose obligation is to produce the entire design of the electric train module. The welding technology of the assembly is described through the description of non-alloy structural steel S355, MAG welding process and welding wire. The method of defining the welding process, and thus the production of steel structures, in accordance with the standard HRN EN 15085: Railway system - Welding of railway vehicles and components is presented. In the experimental part of the paper, the welding procedure of the central beam assembly was designed using a modular approach when analyzing the design process with documenting the manufacturing process performed using assembly and welding devices. By dividing the welding process into several steps of work with the definition of all actions by which the welding process is checked and confirmed, a procedure has been developed that is accepted. Based on the developed procedure, the concept of working procedures applicable to the analysis of the welding process and the manner of its implementation has been developed. Finally, the conclusion of the paper was presented
CAD predložak za pojedine faze proizvodnje vijaka za beton
No full textConcrete screw anchors are well-known fasteners used in industries such as construction, automotive or nuclear. Among cold forming’s different methods, the ones mainly used for producing screw anchors are extrusion and upsetting. Screws must consistently meet the given requirements and perform the way they are meant to in different environments, and that's the task for which multi-stage cold forming is a suitable choice. Multi-stage cold forming is a widely used forming process for efficient and fast mass-production of simple and complex parts with great mechanical properties. Benefits to this forming process are negligible loss of material, good dimensional control, great surface finish, improved strength, and reproducibility. However, the forming sequence must be carefully designed by highly experienced die designers, and it requires both their experienced judgment and the implementation of established design rules. The development of such sequences is being improved through the years. Since one specific screw is designed in a couple of variations, to reduce the total design time, engineers have implemented CAD templates for automatically generating the forming stages for different screw lengths. The final product’s dimensions, tools, and machine parameters are given as an input, and the template outputs the forming part’s dimensions through the stages for different screw sizes and lengths. The template for hexagonal head screw anchors had issues with replicating the part’s dimensions from the machine, i.e., the actual formed stages were not following the computer-generated ones. The initially assumed root causes for the dimension differences were that the volume distribution between the screw’s head and body are not the same for all stages. Likewise, the effects of some machine parameters, such as different ejector positions, were previously not thoroughly examined. Therefore, the main objective of this thesis is to have a better understanding of the volume distribution between the screw’s head and body through the stages, and of the forming process itself. For these reasons, an analysis of the semi-finished screw billets through the stages using precise measurements and numerical analysis is necessary. The effects of different ejector positions were observed on the measurements, and further tested in a numerical analysis tool Deform2D. The necessary adjustments to the template are finally implemented, and the modified template is tested. The modified template had smaller differences to the real parts in comparison to the initial one.Betonski sidreni vijci su dobro poznati spojni elementi korišteni u industrijama kao što su građevinska, automobilna i nuklearna. Između različitih metoda hladnog oblikovanja, one koje se najviše koriste za proizvodnju betonskih vijaka su ekstruzija i sabijanje. Vijci moraju redovito zadovoljavati različite zahtjeve koji se na njih postavljaju i to u različitim okruženjima, a da bi se to postiglo, idealan proces proizvodnje je hladno oblikovanje. Hladno oblikovanje u više faza je često korišteni proces oblikovanja za efikasnu i brzu masovnu proizvodnju jednostavnih i kompleksnih dijelova s odličnim mehaničkim svojstvima. Prednosti ovog procesa su zanemarivi gubitak materijala, dimenzijska točnost, dobra kvaliteta površine, poboljšana čvrstoća i ponovljivost. Međutim, redoslijed operacija mora biti pažljivo oblikovan od strane iskusnih konstruktora alata i zahtjeva njihovu iskustvenu procjenu, kao i implementaciju općih pravila deformiranja. Takvi redoslijedi operacija se poboljšavaju kroz godine. S obzirom da jedan vijak ima nekoliko varijacija veličine, inženjeri su implementirali CAD predloške za automatsko generiranje redoslijeda operacija za različite dužine i veličine vijaka s ciljem smanjenja ukupnog vremena procesa dizajna. Dimenzije gotovog proizvoda i parametri alata i strojeva unose se u predložak, koji onda stvara redoslijed sa svim dimenzijama kroz različite faze, za različite veličine i dužine vijaka. Jedan predložak koji generira vijke sa šesterokutnom glavom nije dobro replicirao dimenzije stvarnog proizvoda, tj. dimenzije na proizvedenim dijelovima nisu u potpunosti odgovarale dimenzijama na predlošku. Inicijalno pretpostavljeni uzroci tog problema su nejednaka distribucija volumena između glave i tijela vijka kroz faze na stvarnim uzorcima. Nadalje, efekti podešavanja nekih parametara strojeva, kao što su pozicije izbacivača, nisu prethodno bile detaljnije ispitane. S obzirom na to, glavni cilj ovog rada je formiranje boljeg razumijevanja distribucije volumena između glave i tijela vijka kroz faze, ali i samog proizvodnog procesa. Iz tih razloga, potrebna je analiza pojedinih poluproizvoda vijaka kroz proizvodne faze uz pomoć preciznih mjerenja uzoraka i numeričke analize. Efekti različitih pozicija izbacivača su prepoznati pomoću mjerenja, i dodatno ispitani uz pomoć alata za numeričku analizu Deform2D. Potrebne promjene na predlošku su u konačnici implementirane, a promijenjeni predložak je ispitan. Novi predložak je imao manje razlike između stvarnih vrijednosti i onih u predlošku u odnosu na inicijalni