Repository of Faculty of Metallurgy University of Zagreb
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The risk assessment of the jobs in the plant of measuring transformers assembly
No full textZavršni rad sastoji se od teorijskog i analitičkog dijela. U teorijskom dijelu završnog rada prikazana je namjena i podjela mjernih transformatora te neke izvedbe mjernih transformatora koje se proizvode u firmi “KONČAR–Mjerni transformatori d.d.”. Zatim je opisana procedura procjenjivanja rizika i predstavljena matrica po kojoj će se procjena rizika provesti. Analitični dio rada započinje s analizom radnih mjesta i opasnostima s kojima se susreću u pogonu montaže mjernih transformatora. Analizirana su radna mjesta od poslovođe montaže do stolara. Provedena je procjena rizika poslova u pogonu montaže mjernih transformatora nakon koje su predstavljene mjere uklanjanja/smanjivanja utvrđenog rizika.The final paper consists of a theoretical and analytical part. In the theoretical part of the final thesis, the purpose and division of measuring transformers and some versions of measuring transformers produced by the company "Končar Instrument Transformers Inc" are presented. Then the risk assessment procedure is described and the matrix by which the risk assessment will be carried out is presented. The analytical part of the work begins with the analysis of workplaces and the dangers encountered in an instrument transformers factory. Workplaces from the assembly manager to the carpenter were analyzed. Workplaces risk assessment for the assembly plant for instrument transformers was carried out, after which the measures to remove/reduce the identified risk were presented
Biomaterijali na bazi titana
No full textU odnosu na legure na bazi kobalt-kroma i nehrđajuće čelike, titan i legure na bazi titana našle su široku primjenu u biomedi- cini, gdje se zbog svojih izvrsnih svojstava upotrebljavaju kao implantati, ali zbog visoke cijene njihove proizvodnje još uvijek nemaju širu upotrebu. Neka od bitnih svojstava su: izvrsna biokompatibilnost, dobra mehanička svojstva i oseointegracija te otpornost na koroziju. Uz predstavljanje biomedicinskih materijala koji se najčešće upotrebljavaju, ovaj članak prikazuje razvoj biomaterijala na bazi titana i njihovu biomedicinsku primjenu. Biomaterijali se obično upotrebljavaju u biomedicini za popra- vak, zamjenu ili regeneraciju tjelesnih tkiva. S obzirom na to da je poznat sve veći broj neuspjelih implantacija uzrokovanih patogenom bakterijskom infekcijom, među funkcijama koje bi se mogle dodati biomaterijalima je antibakterijsko djelovanje, koje je od velike važnosti. U novije vrijeme antibakterijske metalne legure pokazale su velik potencijal kao nova vrsta biome- dicinskog materijala
Microscopic and Mechanical Characterization of Co-Cr Dental Alloys Joined by the TIG Welding Process
No full textDue to their good mechanical and other properties, cobalt-chromium alloys (Co-Cr) are often used in prosthetic therapy. The metal structures of prosthetic works can be damaged and break, and depending on the extent of the damage, they can be re-joined. Tungsten inert gas welding (TIG) produces a high-quality weld with a composition very close to that of the base material. Therefore, in this work, six commercially available Co-Cr dental alloys were joined by TIG welding, and their mechanical properties were evaluated to determine the quality of the TIG process as a technology for joining metallic dental materials and the suitability of the Co-Cr alloys used for TIG welding. Microscopic observations were made for this purpose. Microhardness was measured using the Vickers method. The flexural strength was determined on a mechanical testing machine. The dynamic tests were carried out on a universal testing machine. The mechanical properties were determined for welded and non-welded specimens, and the results were statistically evaluated. The results show the correlation between the investigated mechanical properties and the process TIG. Indeed, characteristics of the welds have an effect on the measured properties. Considering all the results obtained, the TIG—welded I—BOND NF and Wisil M alloys showed the cleanest and most uniform weld and, accordingly, satisfactory mechanical properties, highlighting that they withstood the maximum number of cycles under dynamic load
Pressing and characterization of the powdered Ti-Cu mixture
No full textZbog svojih poželjnih svojstava legure titana su pronašle svoju primjenu u raznim industrijama, međutim zbog visoke cijene proizvodnje, sve se više razvijaju nove metode i tehnike proizvodnje nekih ekonomičnijih legura titana. Titan i titanske legure intenzivno se koriste u biomedicinskim primjenama zbog svoje izvrsne biokompatibilnosti i mehaničkih svojstava. Cilj ovog rada je ekonomičnim postupkom metalurgije praha kao što je miješanje u kugličnom mlinu i prešanje, proizvesti leguru Ti96Cu4 s potencijalom za biomedicinsku primjenu. Stoga će se analizirati utjecaj procesnih parametara (vrijeme miješanja i tlak kompaktiranja) na mikrostrukturne značajke legure kao bi se odredili odgovarajući parametri za postizanje homogene i kompaktne legure. Dobiveni rezultati pokazuju da je uz malu korekciju primjenjenih tehnoloških parametara kao što je vrijeme miješanja praškastih elementarnih prahova titana i bakra moguće prozvesti zadovoljavajući otpresak Ti96Cu4 legure.Due to the favorable properties of titanium alloys, they have found their application,however, due to the high cost of production, new methods and techniques for the production of more economical alloys are increasingly being developed. Titanium and titanium alloys are extensively used in biomedical applications due to their excellent biocompatibility and mechanical properties. The aim of this work is to produce a Ti96Cu4 alloy with potential for biomedical applications using an economical powder metallurgical process such as mixing in a ball mill and pressing. Therefore, the influence of the process parameters (mixing time and compaction pressure) on the microstructural characteristics of the alloy is analysed in order to determine the appropriate parameters for achieving a homogeneous and compact alloy. The obtained results show that with a small correction of the applied technological parameters, such as the mixing time of the powdered elemental titanium and copper powders, a satisfactory compact can be produced from the Ti96Cu4 alloy
Establishment of quality control at the Institute for public health of Sisak moslavina county
No full textUpravljanje kvalitetom u poslovanju je dinamična kategorija koja se mora kontinuirano usavršavati i nadopunjavati. Jedna od mogućnosti nadogradnje je i implementacija potpuno novih modela za sustave upravljanja kvalitetom. Poduzeća u suvremenom poslovanju sve veću pažnju pridaju kvaliteti. Ista praksa sve je više prisutna i u javnim institucijama. Razlog tome je što su prepoznate brojne prednosti koje proizlaze iz upravljanja kvalitetom u javnim ustanovama.
Da bi se na učinkovit način upravljalo kvalitetom, bitno je u upravljanje uključiti ISO 9001 normu, odnosno potrebno je u upravljanje kvalitetom uključiti načela koje propisuje ISO. Na taj način se može osigurati da se kontinuirano radi na poboljšanju. Jedan od načina na koji se može kvalitetno implementirati ISO 9001 je kroz potpuno upravljanje kvalitetom te kroz PDCA ciklus, odnosno kroz procesni pristup upravljanju kvalitetom i šest sigmi. Ovim pristupom poboljšava se kvaliteta svih poslovnih procesa što posljedično dovodi do većeg zadovoljstva kako vanjskih tako i unutarnjih dionika. Ovaj način uspostave kvalitete može se primijeniti i na Zavod za javno zdravstvo.Quality management in business is a dynamic category that must be continuously improved and supplemented. One of the upgrade options is the implementation of completely new models for quality management systems. Companies in modern business pay more and more attention to quality. The same practice is increasingly present in public institutions. The reason for this is that the numerous advantages resulting from quality management in public institutions have been recognised.
In order to effectively manage quality, it is necessary to include the ISO 9001 standard in management, that is, it is necessary to include the principles prescribed by ISO in quality management. In this way, it can be ensured that there is continuous improvement. One of the ways in which ISO 9001 can be effectively implemented is through complete quality management and through the PDCA cycle, that is, through a process approach to quality management and six sigma. This approach improves the quality of all business processes, which consequently leads to greater satisfaction of both external and internal stakeholders. This method of establishing quality can also be applied by the Institute of Public Health
Plastic instabilities during processing of AlMg alloy
No full textDuring the plastic deformation of most metallic materials, the normal material flow takes place in part of the material, which we call deformation zone. There are some exceptions in certain alloys where process of plastic deformation is unstable and there is inhomogeneous plastic flow at certain parameters of plastic processing. Examples of such instabilities are the inhomogeneous plastic deformations such as Lűders bands and the Portevin-Le Chatelier effect, which appear in the form of deformation bands. Instabilities like these cause problems during metal processing into final products. The focus of this research was to determining the type of instability in received AlMg alloy. Visualization of material flow, displacement and deformation measurement during the static tensile test was performed using the DIC method. From results of tensile tests, repetitive serrations on the stress-strain curve during plastic deformation were observed. DIC analysis showed inhomogeneous deformation during the test, which lead to reasonable assumption that the observed instability was Portevin-Le Chatelier effect. To investigate the mechanisms of deformation, microstructures were recorded on samples before, during and after propagation by PLC band. Structural analysis showed that the deformation takes place through the movement of dislocations, which is indicated by their increased density at the PLC front and behind front after it passes
PLC Effect at Different Types of Loading During Static Tensile Testing of Aluminium Alloys
No full textAluminium and aluminium alloys are indispensable materials nowadays, widely used in various constructions. It is known that some aluminium alloys, such as Al-Mg, show inhomogeneous, localized deformation phenomena at certain temperatures and strain rates. This is known in the literature as the appearance of Portevin-Le Chatelier lines, or short the PLCeffect. The Portevin-Le Chatelier effect contributes to the reduction of material ductility and leaves surface defects on the final products. The study of this phenomenon was carried out using a static tensile test and the digital image correlation method. The influence of using a constant increase of stress on the phenomenon itself was studied in comparison to the classical control of the testing machine with a constant crosshead speed. The results of the study show that the phenomenon persists regardless of the type of control and no significant changes were observed at used testing parameters. Regardless of the deformation parameters, PLC lines form throughout the whole duration of the plastic deformation until the specimen breaks
An Analysis of the Metal Connection Using Metallographic Investigation
No full textPistons are mainly made of Al-Si alloys. The first piston channel’s highly loaded diesel engines use a ring carrier. In this case, two different materials (aluminum alloy and austenitic cast iron) must establish an excellent metallic bond (intermetallic bonding layer). If no intermetallic bonding layer is formed, the first piston ring carriers will separate, and the engine will fail. This research is aimed at analyzing the formation of the intermetallic bonding layer. The manuscript presents an analysis of the formation of the metal connection between a piston and a ring carrier. The metallographic investigation combined an optical microscope with SEM/EDS to analyze the quality of the metal connection. The test results show the formation of the metal connection between the two materials of different qualities
Analysis of the densification of a biomedical titanium alloy produced by powder metallurgy
No full textTitanium as a raw material for production is very expensive due to its high price and the complex production process. One of the successful alternatives for the production of titanium alloys and final products is powder metallurgy technology. In this work, a Ti-20Zr alloy for biomedical applications was produced using the powder metallurgy process. The density values determined for the compacts depend on the compression pressure. Namely, the compressibility of the powder mixture increases with increasing compaction pressure. A higher sintering temperature as well as a longer sintering time are more favourable to obtain higher values for the sintered density. Similarly, the compression coefficient is lower for samples compacted at higher pressure, while its value increases with increasing sintering temperature. The volume change in the volume of the sample is more pronounced after sintering at higher temperature and shorter time
Adsorption of Cu(II) ions by means of foundry waste
No full textThis article deals with the analysis of the adsorptive properties of the waste produced during the shot blasting of castings in foundries. During this process, particles of moulding mixture and scale that remained on the surface of the casting after removal from the mould are removed. Since this waste contains particles of moulding mixture (SiO2, carbon, ...) and scale (i.e. iron oxides), which as individual components are known as satisfactory adsorbents, its adsorption properties towards Cu(II) ions in aqueous solution were investigated. The obtained results show that the investigated waste has a significant adsorption capacity for binding Cu(II) ions