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Implementation ISO 9001 in the production of components for semiconductor industry
No full textISO 9001 je međunarodni standard sustava upravljanja kvalitetom koji organizacijama pruža okvir za postizanje izvrsnosti u kvaliteti proizvoda i usluga. Ovaj standard, objavljen od strane Međunarodne organizacije za standardizaciju (ISO), promiče princip kontinuiranog poboljšanja, fokusiranje na kupca te uspostavu jasnih i definiranih procesa. Cilj ISO 9001 je osigurati dosljednost u isporuci proizvoda i usluga, smanjenje rizika i povećanje zadovoljstva kupaca. Poluvodička industrija zahtjeva vrlo veliku preciznost tako da kontinuirano poboljšavanje i velika točnost su od velike važnosti za rad u proizvodnji komponenti za industriju poluvodiča.ISO 9001 is an international standard for quality management systems that provides organizations with a framework to achieve excellence in the quality of products and services. This standard, published by the International Organization for Standardization (ISO), promotes the principle of continuous improvement, customer focus, and the establishment of clear and defined processes. The goal of ISO 9001 is to ensure consistency in the delivery of products and services, reduce risks, and increase customer satisfaction. The semiconductor industry demands high precision, making continuous improvement and accuracy of utmost importance in this sector
Development of the annual simulation model of a solar assisted heat pump
No full textNeprestani rast energenata uzrokovan sve većom potražnjom te svjetskim krizama dovodi do
stalne potražnje za alternativnim tehnologijama grijanja. Najpoželjniji su obnovljivi izvori
energije zbog neograničenih količina te minimalnih utjecaja na okoliš i zdravlje ljudi. Tema
ovog rada odnosi se na postavljanje simulacijskog modela solarne dizalice topline kako bi se
dobio uvid u ponašanje i učinkovitost sustava solarne dizalice topline pri realnim uvjetima.
Nakon postavljene simulacije napravljena je validacija sustava na stvarnim mjerenjima
mobilne solarne dizalice topline. Prikazana je usporedba rada modela za dva grada s različitim
klimatskim uvjetima. Napravljena je godišnja simulacija s vremenskim korakom od 1 sata.
Simulacijski model je uspoređen s konvencionalnim sustavima grijanja te je dan uvid u
troškove i isplativost ugradnje sustava. Prema simulacijskom modelu za Zagreb sustav se
pokazuje neisplativ u odnosu na ostale izvore grijanja, dok su za Split dobivene vrijednosti
manje godišnje potrošnje u odnosu prema ostalim izvorima. Razlog tome su vrijednosti veće
vrijednosti godišnje ozračenosti.The continuous growth of energy consumption caused by increasing demand and global crises
leads to a constant demand for alternative heating technologies. The most desirable sources of
energy are renewable sources due to their unlimited quantities and minimal impact on the
environment and human health. The topic of present paper concerns the development of the
simulation model of a solar assisted heat pump to gain insight into the behaviour and
efficiency under real conditions. After setting up the simulation, the system was validated
with actual measurements of a mobile solar heat pump. A comparison of the model's
performance was shown for two cities with different climatic conditions. An annual
simulation was made with a time step of 1 hour. The simulation model was compared to
conventional heating systems, and insights into the costs and cost-effectiveness of installing
the system were given. According to the simulation model, the system is not cost-effective
compared to other heating sources for Zagreb, while for Split, lower annual consumption
values were obtained compared to other sources. The reason for this is higher annual radiation
values
Efficiency of numerical simulation in optimization of casting production
No full textGrey cast iron is frequently used in industry, due to good thermal conductivity, low price and good mechanical properties. Chemical properties and solidification conditions have significant influence on microstructure and mechanical properties development. Most common use of grey cast iron is in automotive industry and heating elements. The application in the casting of thinwalled castings requires careful elaboration of the technological casting process parameters due to the curving tendency and the burns appearance. Advantage of numerical simulations is in effective and fast calculation of pouring and solidification of castings. Economical advantage lays in fast change of more different product variations in short time. Experimental part of this paper has several versions of numerical simulation of casting process. First one is the original geometry, which has been used in regular casting process of thin-walled castings framework for fireplace doors. Other versions with optimizing geometry of the castings have been elaborated. Pouring process of all casting versions of EN GJL-200 quality was performed followed by investigation of casting quality and process parameters interaction. The influence of clamp position, ingates size and temperature distribution during casting solidification on microstructure development, hardness and tensile strength of grey cast iron EN GJL-200 casting samples was determined and compared with the results obtained by numerical simulation
Razvoj legura s prisjetljivošću oblika na bazi bakra u okviru znanstveno-istraživačkih projekata na Metalurškom fakultetu Sveučilišta u Zagrebu
No full textU ovom pregledu prikazan je dio znanstvenih istraživanja pri razvoju legura s prisjetljivošću oblika (engl. Shape Memory Alloy, SMA) na bazi bakra na Metalurškom fakultetu Sveučilišta u Zagrebu u razdoblju od 2006. do 2022. godine u suradnji s brojnim visokoškolskim i znanstvenim institucijama u regiji. Istraživane su sljedeće legure SMA: CuAlNi, CuAlMn, itd. Provedeno je f izikalno modeliranje uključujući numeričku simulaciju razvoja mikrostrukture i toplinsku analizu tih legura. Legure SMA rađene su u lučnoj, visokofrekventnoj i indukcijskim pećima pomoću tri različite tehnologije lijevanja: brzo skrućivanje, lijevanje u metalne i/ili grafitne kokile te kontinuirano lijevanje u šipke. Nakon toga odabrane legure su toplo i hladno valjane. Provedena je toplinska obrada (austenitizacija uz naknadno gašenje u vodi i žarenje) i karakterizacija funkcionalnih svojstava legura SMA u različitim stanjima. Za karakterizaciju, osim ispitivanja mehaničkih svojstava, primijenjene su brojne visokosofisticirane metode: optička mikroskopija (OM), pretražna (SEM) i transmisijska elektronska mikroskopija (TEM), energetsko disperzijska-spektroskopija (EDS), pretražna diferencijalna kalorimetrija (DSC), dinamičko-mehanička analiza (DMA), rendgenska difrakcija (XRD), elektrokemijska impedancijska spektroskopija (EIS) itd. Već pri lijevanju kod pojedinih legura SMA, a posebice nakon toplinske obrade austenitizacijom uz naknadno gašenje u vodi, utvrđena je martenzitna mikrostruktura koja je osnovni preduvjet za svojstvo prisjetljivosti oblika. Na temelju provedenih istraživanja po većini parametara (plastičnost, korozijska otpornost itd.) može se zaključiti da su se najbolje pokazale legure CuAlMn. Kao rezultat provedenih istraživanja na legurama SMA, prema podatcima iz baze CROSBI (na dan 23. prosinca 2022.), istraživački tim objavio je 33 rada u časopisima (od kojih su 23 rada u časopisima indeksiranim u bazi podataka Web of Science), 74 rada u zbornicima međunarodnih konferencija, 18 sažetaka u zbornicima konferencija te pet ostalih radova. Također, obranjena je jedna doktorska disertacija te je izrađeno i obranjeno 12 završnih i 25 diplomskih radova u području tehničkih znanosti iz znanstvenih polja metalurgije i kemijskog inženjerstva
Comparison of different testing machine control in static tensile testing during cold deformation
No full textStatic tensile tests were performed during the application of different types of loading rates during cold deformation on aluminum - magnesium alloy. The influence of different types of loading rates and different testing machine control on the distribution of temperature changes and deformations during the cold deformation of aluminum - magnesium alloys was analysed and compared. The analysis of the distribution of temperature changes and deformations of the conducted tests was carried out using the methods of thermography and digital image correlation. The tests showed that different testing machine control, during static tensile testing, affects the distribution of temperature changes and deformations during the cold deformation of the aluminum magnesium alloy
Microhardness dependence of Ti-Zr alloys on time and temperature of sintering
No full textCommonly used metallic biomaterials are titanium and its alloys, cobalt-based alloys and 316L stainless steel. Titanium alloys are reference materials in biomedical applications due to their desirable properties such as excellent mechanical properties and good biocompatibility. Since presence of different metals can significantly alter the properties of titanium it is usually alloyed with other metals, including the zirconium. In this work Ti-20Zr was prepared by powder metallurgy by mixing the powders in a ball mill and sintering in a tube furnace under argon atmosphere. Microscopic analysis with the light microscope showed that the porosity decreased with increasing temperature and sintering time. Scanning electron microanalysis with energy-dispersive spectrometry showed the two-phase microstructure of the sintered alloy. Microhardness was determined by Vickers method. A longer sintering time and a higher sintering temperature resulted in higher microhardness values
Microstructural analysis of CuAlMn alloy with shape memory effect
No full textU ovom radu provedena je mikrostrukturna analiza CuAlMn legure kemijskog sastava Cu – 8,2% Al – 8,3% Mn (mas %). Dobivena legura s prisjetljivosti oblika podvrgnuta je postupku kovanja i toplinske obrade. Toplinska obrada šipke nakon kovanja promjera 13 – 14 mm sastojala se od žarenja 870 °C/20 minuta uz hlađenje u pijesku i od žarenja na 870 °C/20 minuta uz hlađenje u vodi. Mikrostrukturna analiza lijevanog stanja CuAlMn legure provedena je optičkom i pretražnom elektronskom mikroskopijom te energetsko disperzijskom spektroskopijom. Nakon kovanja i toplinske obrade mikrostrukturna analiza provedena je optičkom mikroskopijom. Rezultati su pokazali kako je mikrostruktura CuAlMn legure žarene na 870 °C/20´ i hlađene u pijesku krupnozrnata dvofazna (α+β), dok je mikrostruktura CuAlMn legure žarene na 870 °C/20´ i hlađene u vodi krupnozrnata martenzitna mikrostruktura. Putem optičke mikroskopije primjećene su pukotine u CuAlMn leguri. Ispitivanje makrotvrdoće provedeno je Brinell-ovom metodom, a rezultati pokazuju niže vrijednosti makrotvrdoće pri hlađenju u vodi za razliku od hlađenja u pijesku.In this work, a microstructural analysis of CuAlMn alloy with chemical composition Cu - 8.2% Al - 8.3% Mn (wt.%) was performed. The resulting shape memory alloy was subjected to a forging and heat treatment process. The heat treatment of the bar after forging with a diameter of 13 – 14 mm consisted of annealing at 870 °C/20 minutes with cooling in sand and of annealing at 870 °C/20 minutes with cooling in water. Microstructural analysis of the as cast state of CuAlMn alloy was performed by optical and scanning electron microscopy and energy dispersive spectroscopy. After forging and heat treatment, microstructural analysis was performed by optical microscopy. The results showed that the microstructure of CuAlMn alloy annealed at 870 °C/20´ and cooled in sand has a large grained two phases (α+β), while the microstructure of CuAlMn alloy annealed at 870 °C /20´ and cooled in water was a large grained martensitic microstructure. Cracks in the CuAlMn alloy were observed by optical microscopy. The macrohardness test was performed by the Brinell method, and the results show lower values of macrohardness during cooling in water unlike cooling in sand
Testing of tool steel on resistance to local corrosion in 3,5% NaCl medium
No full textU ovom radu provedena su elektrokemijska i metalografska ispitivanja na alatnom čeliku za hladni i topli rad te na čeliku za cementiranje, a sve u svrhu dobivanja korozijskih parametara i zaključka koji od ispitanih uzoraka je otporniji na lokalnu pitting koroziju. Elektrokemijska ispitivanja su izvedena u mediju 3,5 % NaCl, a zasnivala su se na provođenju cikličke anodne polarizacije u području potencijala od -2000 mV do 200 mV vs SCE i povratno. Rezultati istraživanja su pokazali da su sva tri uzorka podložna pitting koroziji, ali se najlošijim pokazao uzorak alatnog čelika za cementiranje X19NiCrMo4 kod kojeg je registriran najniži pitting potencijal. Najboljim se pokazao uzorak alatnog čelika za topli rad oznake W600, kod kojeg je registriran najviši pitting potencijal.
Rezultati elektrokemijskih ispitivanja se podudaraju s metalografskim ispitivanjima jer su na površini uzorka W600 nakon korozije u kloridnom mediju vidljivi tek početci pitting korozije u obliku djelomičnih nakupina korozijskih produkata, dok je uzorak čelika za cementiranje oznake X19NiCrMo4 bio u potpunosti prekriven korozijskim produktima, što znači da je od tri ispitana alatna čelika najpodložniji pitting koroziji čelik za cementiranje te se isti ne preporučuje za korištenje u uvjetima gdje dolazi u kontakt s kloridnim ionima. Za vrlo nizak pitting potencijal i posljedično tome izrazitu pitting koroziju odgovorna je martenzitna mikrostruktura alatnog čelika za cementiranje. S druge strane alatni čelik oznake W600 je pokazao bolju korozijsku otpornost zbog sitnijeg zrna i ujednačene raspodjele karbida.In this paper, electrochemical and metallographic tests were performed on tool steel for cold and hot work and on steel for cementation, all with the purpose of obtaining corrosion parameters and concluding which of the tested samples is more resistant to local pitting corrosion. Electrochemical tests were performed in a medium of 3.5% NaCl, and were based on conducting cyclic anodic polarization in the potential range from -2000 mV to 200 mV vs SCE and vice versa. The results of the research showed that all three samples are subject to pitting corrosion, but the worst was the cementing tool steel sample X19NiCrMo4, which registered the lowest pitting potential. The W600 tool steel sample for hot work proved to be the best, with the highest pitting potential.
The results of the electrochemical tests coincide with the metallographic tests, because after corrosion in the chloride medium only the beginnings of pitting corrosion are visible on the surface of the W600 sample in the form of partial accumulations of corrosion products, while the X19NiCrMo4 cementing steel sample was completely covered with corrosion products, which means that of the three tested tool steels, cementing steel is the most susceptible to pitting corrosion and is not recommended for use in conditions where it comes into contact with chloride ions. The martensitic microstructure of cementing tool steel is responsible for the very low pitting potential and, consequently, pronounced pitting corrosion. On the other hand, the W600 tool steel showed better corrosion resistance due to its finer grain and uniform carbide distribution
Characterization of immobilized titanium (iv) oxide photocatalyst on basalt fibers
No full textRazvojem analitičkih metoda dolazi se do spoznaje da mikroonečišćujuće tvari uvelike utječu kako na biljni i životinjski svijet tako i na ljude. Za pročišćavanje voda od mikroonečišćujućih tvari u svijetu se koristi aktivni ugljen čija uporaba zahtjeva procese regeneracije radi slabljenja njegovog djelovanja. Posljednjih nekoliko godina intenzivno se radi na pronalaženju novih metoda pročišćavanja vode ali i zraka od ove vrste onečišćenja. Napredne oksidacijske metode pokazuju veliki potencijal, a kao jedna od njih se ističe fotokataliza uz uporabu titan(IV) oksida kao fotokatalizatora. Kako bi se poboljšala fotokatalitička svojstva koriste se različiti kemijski elementi i nosači. U ovom radu bit će ispitan utjecaj bazaltnih i staklenih vlakana kao nosača katalizatora TiO2 na razgradnju salicilne kiseline.The development of analytical methods leads to the realization that micropollutants greatly affect both plant and animal life as well as humans. Activated carbon is used worldwide to purify water from micropollutants, the use of which requires regeneration processes to weaken its effect. In the last few years, intensive work has been done to find new methods of purifying water and air from this type of pollution. Advanced oxidation methods show great potential, and photocatalysis with the use of titanium(IV) oxide as a photocatalyst stands out as one of them. In order to improve the photocatalytic properties, different chemical elements and carriers are used. In this work, the influence of basalt and glass fibers as TiO2 catalyst carriers on the decomposition of salicylic acid will be examined
Analytical approach to crack tip plasticity of dental CoCrMo alloy
No full textIn this paper, a thin infinite plate of CoCrMo alloy with a straight crack was loaded perpendicularly to the crack plane. CoCrMo alloys are due to their suitable mechanical and corrosion properties widely used for dental applications. The importance of good mechanical properties is reflected in ensuring the functional and technical durability of dental appliances. The intention of this paper is to use a mathematical approach in analyzing a thin infinite plate with a straight crack to the rather complex occurrences within the cohesive zones around the crack tips. The dependence of plastic zone magnitude around the crack tip on an external load of dental CoCrMo alloy plate was considered in this paper. Static tensile tests were carried out to determine the mechanical properties of dental CoCrMo alloy. At plastic deformation, the dental CoCrMo alloy is nonlinearly hardened in accordance with the Ramberg-Osgood equation which parameters were determined using a least-squares method from experimental data. The application of the Dugdale model the plastic zone magnitude around the crack tip was determined. The stress intensity coefficient from the cohesive stresses was calculated using Green functions. The analytical methods, assuming a small plastic zone around a crack tip, were used in the analysis. The results were obtained by means of a commercial software package and presented in the form of diagrams