This paper investigates the possibility of using an alternative steel material EN 10250 36CrNiMo4/1.6511 (EN24 steel) in the production of shrink-fit tool holders for CNC machining centres. The ...alternative material has different thermal properties compared to the standard manufacturing material for tool holders (H13 steel), while the mechanical properties are similar. The structural and thermal stress finite element analysis together with the fatigue analysis are performed on a designed model of a tool holder with a shrink-fit clamping head and standard interface for required limiting working conditions. The application of the alternative material combined with the production process optimisation results in reductions in costs and time of producing tool holders, while adhering to all limitations and parameters prescribed by the corresponding standard. Due to higher thermal stresses during tool changes, the usage of an alternative material would be justified for processes where one type of tool is frequently used and the tool lifespan is long.
The most commonly used subsea pipeline installation method is the S-Lay method. A very important and complex task in an S-Lay installation engineering analysis is to find the optimal pipelay vessel ...installation configuration for every distinctive pipeline route section. Installation loads in the pipeline are very sensitive to small changes in the configuration of the pipeline supports during laying and other influential parameters, such as the tensioner force, stinger angle, trim and draft of the pipelay vessel. Therefore, the process of an engineering installation analysis is very demanding, and there is a need for an automated optimization process. For that purpose, installation engineering methodology criteria and requirements are formalized into a nonlinear optimization problem with mixed continuous and discrete variables. A special tailored multi-objective genetic algorithm is developed that can be adjusted to any desired combination of criteria and offshore standards’ requirements. The optimization algorithm is applied to the representative test cases. The optimization procedure efficiency and quality of the achieved solution prove that the developed genetic algorithm operators and the whole optimization approach are adequate for the presented application.
Temeljni cilj ovoga rada jest istražiti i analizirati uzroke nastanka izvanrednih događaja u željezničkom prometu. Svrha rada jest prepoznati glavne uzročnike nastanka izvanrednih događaja kako bi ...moguće korektivne akcije rezultirale maksimalnim povećanjem sigurnosti željezničkog prometa. Rezultati istraživanja temelje se na sekundarnim podacima o uzrocima nastanka izvanrednih događaja na prugama HŽ Infrastrukture za razdoblje od 2014. do 2019. godine. U radu su korištene znanstvene metode analize i sinteze, metode deskriptivne statistike te Pareto grafikon. Glavni nalaz ovoga rada upućuje na zaključak da su nesmotreno ili zlonamjerno djelovanje drugih osoba i tehnički nedostatak na infrastrukturnim podsustavima ili vozilima upravitelja infrastrukture odgovorni za 83,7 % izvanrednih događaja na prugama HŽ Infrastrukture, dakle više od svih drugih uzročnika zajedno.
The main goal of this work is to investigate and analyze the causes of extraordinary events in railway traffic. The purpose of the work is to identify the main causes of the occurrence of extraordinary events so that possible corrective actions result in a maximum increase in the safety of railway traffic. The results of the research are based on secondary data on the causes of extraordinary events on the tracks of Croatian Railway Infrastructure for the period from 2014 to 2019. Scientific methods of analysis and synthesis, methods of descriptive statistics and the Pareto chart were used in the work. The main finding of this paper points to the conclusion that reckless or malicious actions of other persons and technical defects in infrastructure subsystems or vehicles of the infrastructure manager are responsible for 83.7% of extraordinary events on the tracks of Croatian Railway Infrastructure, i.e. more than all other causes combined.
The thermal-power-plant condenser tubes, conducting cooling seawater, experienced frequent leakages, prompting the hereby presented failure analysis. Visual inspection of the corroded/ruptured tube ...segments revealed that localized corrosion may be linked to seawater sediments and thick layers of corrosion products at the tube water side. Sediments were found along the tube bottom and thick corrosion products were found adjacent to the point of contact between the baffle plates and the exterior tube walls. Underdeposit corrosion, accelerated due to sulphate-reducing bacteria, was diagnosed based on the excess sulphur found at the pit bottom using EDX, the FT-IR spectrum indicating the presence of biofilm and SEM determining the featuring corrosion products based on the biofilm. It was proposed that the corrosion initiating deposits were linked to the condenser shutdown and startup periods. Results showed that pitting corrosion occurred under the influence of biofilm microorganisms tolerant to copper. The main goal of this research was achieved by defining a systematic procedure for avoiding a shutdown of the thermal power plant.
In this paper fatigue for professional soldier caused by
active physical activity and endurance limits is investigated. The resulting workload is one of indicators of how training, preparedness and ...other acquired work skills can contribute to the human body being a large working “machine”. Ergometry test was conducted and field test for
soldier fitness condition and energy expenditure was measured regarding
the level of body’s metabolism. Field test consisted of three runs on a
polygon of 10 km and different workloads, the energy consumption was monitored. Work load was compared with Occupational Safety and Health law acts. The results showed difference in workload conditions and hart rate which allowed to determine rest spots and safety in training conditions.
U ovom radu istražuje se umor profesionalnog vojnika uzrokovan aktivnom fizičkom aktivnošću i ograničenjima izdržljivosti. Rezultat radnog opterećenja jedan je od pokazatelja kako obuka, pripremljenost i druge stečene radne vještine mogu pridonijeti ljudskom tijelu kao velikom radnom „stroju“. Provedeno je ergometrijsko ispitivanje i terenski test za kondicijsko stanje vojnika i potrošnja energije mjereno je s obzirom na razinu metabolizma u tijelu. Terensko ispitivanje sastojalo se od staza na poligonu od 10 km i različitih opterećenja, a praćena je i potrošnja energije. Radno opterećenje uspoređeno je sa zakonima o zaštiti na radu. Rezultati su pokazali razliku u uvjetima radnog opterećenja i brzini vrtnje, što je omogućilo određivanje mjesta odmora i sigurnosti u uvjetima treninga.U ovom radu istražuje se umor profesionalnog vojnika uzrokovan aktivnom fizičkom aktivnošću i ograničenjima izdržljivosti. Rezultat radnog opterećenja jedan je od pokazatelja kako obuka, pripremljenost i druge stečene radne vještine mogu pridonijeti ljudskom tijelu kao velikom radnom „stroju“. Provedeno je ergometrijsko ispitivanje i terenski test za kondicijsko stanje vojnika i potrošnja energije mjereno je s obzirom na razinu metabolizma u tijelu. Terensko ispitivanje sastojalo se od staza na poligonu od 10 km i različitih opterećenja, a praćena je i potrošnja energije. Radno opterećenje uspoređeno je sa zakonima o zaštiti na radu. Rezultati su pokazali razliku u uvjetima radnog opterećenja i brzini vrtnje, što je omogućilo određivanje mjesta odmora i sigurnosti u uvjetima treninga.
Shape memory alloys (SMAs) are smart materials with unique properties of superelasticity and shape memory effect. These properties are the consequence of thermoelastic martensitic transformation, ...which can occur under thermal or mechanical deformation. Cu-Al-Ag alloys have high temperatures of martensite transformation, unlike other SMAs, which makes them suitable for use in specific applications. In this paper, Cu10Al-1Ag alloy was prepared by melting pure metals in an electric arc furnace and casting the melt in a cylindrical mold. The microstructure of the as-cast and quenched material was determined by optical microscopy (OM) and scanning electron microscopy (SEM) equipped with energy dispersive analysis (EDS). X-ray diffraction (XRD) analysis was performed to identify crystal phases in the microstructure, while transformation temperatures were determined by differential scanning calorimetry (DSC). The hardness of Cu-Al-Ag SMA was also determined with a microhardness tester. The results showed partially formed martensite in the as-cast state, and fully formed martensite structure, 18R-type, in the quenched Cu-10Al-1Ag alloy. Keywords shape memory alloys, Cu-Al-Ag alloys, microstructure, phase transformations, martensite
SAŽETAK: Temeljni cilj ovoga rada jest istražiti stanje sigurnosti na radu u Republici Hrvatskoj. Ukupan broj ozljeda na radu i broj smrtno stradalih na radu predmetom se analize pomoću metode ...deskriptivne statistike za razdoblje od 1996. do 2016. godine. Posebna pozornost posvećuje se istraživanju korelacije između broja ozljeda na radu, broja smrtno stradalih i kretanja bruto domaćeg proizvoda, ukupne zaposlenosti i zaposlenosti po pojedinim gospodarskim djelatnostima. Dobiveni rezultati istraživanja omogućit će sagledavanje osnovnih trendova sigurnosti na radu u Republici Hrvatskoj te detektiranje onih gospodarskih grana u kojima kretanje zaposlenosti determinira ukupan broj ozljeda na radu. Rezultati istraživanja temelje se na metodama deskriptivne statistike i statističkoj metodi korelacijske analize.
SUMMARY: The basic objective of this paper is to investigate the state of work safety in the Republic of Croatia. The total number of injuries at work and the number of fatalities at work were analyzed using the method of descriptive statistics for the period 1996 - 2016. Special attention is paid to the correlation between the number of injuries at work, the number of fatalities and the movement of gross domestic product, total employment and employment by individual economic activities. The results of the research will provide an overview of the basic labor safety trends in the Republic of Croatia and the identification of those industries in which employment trends determine the total number of injuries at work. The results of the research are based on the methods of descriptive statistics and the statistical method of correlation analysis.
Provedeno je terensko mjerenje buke i zvučne izolacije u radnom i životnom okolišu na stambeno-poslovnoj novoizgrađenoj zgradi u Pazinu u ulici M. Belušića prema Zakonu o zaštiti od buke NN br. ...30/09, Pravilniku o zaštiti radnika od izloženosti buci na radu NN br. 46/08, Pravilniku o najvišim dopuštenim razinama buke u sredini u kojoj ljudi rade i borave NN br. 145/04. Mjerenje buke izvršeno je zvukomjerom Brüel
& Kjaer 2250 te se zvuk, odnosno bijeli šum, reproducirao pomoću uređaja toptalica (5 čekića na bregastoj osovini). Zvuk se mjerio u prijamnoj i u predajnoj sobi kako bi se odredio indeks zvučne izolacije Rw. Nakon analize i obrade podataka dobiveni rezultati uspoređeni su s važećim propisima. U radu su objašnjeni osnovni pojmovi vezani uz opis, mjerenja i utvrđivanja akustičkih parametara te posljedice dugotrajnog utjecaja izlaganja prekomjernim razinama buke kod čovjeka. Pri tome dane
su i smjernice te preporuke za zaštitu od buke.
In this paper field measurement of environmental noise is conducted in working and living environment in the residential and commercial new building in Pazin, street M. Belušić under the Noise Protection Official
Gazette No.30 / 09, the regulations on the protection of workers from exposure to noise at work official national gazette nr. 46/08, regulations on maximum permissible noise levels in areas where people work and live, official national gazette nr. 145/04. Noise measurements were performed by sound-level meter SLM Brüel & Kjaer 2250 and sound
or white noise were reproduced by the device for generating sound source Tapping machine (5 hammers in line on a camshaft). Sound is measured in the receiver and in the transmitter room to determine the index of sound insulation Rw. After analyzing and processing obtained results a comparison with the current regulations was made. The paper explains the basic concepts related to the description, measurement and determination of acoustic parameters and the effects on humans caused by
prolonged exposure to excessive noise levels. In doing so some guidelines for noise protection are mentioned.
The basic objective of this paper is to investigate the state of work safety in the Republic of Croatia. The total number of injuries at work and the number of fatalities at work were analyzed using ...the method of descriptive statistics for the period 1996 - 2016. Special attention is paid to the correlation between the number of injuries at work, the number of fatalities and the movement of gross domestic product, total employment and employment by individual economic activities. The results of the research will provide an overview of the basic labor safety trends in the Republic of Croatia and the identification of those industries in which employment trends determine the total number of injuries at work. The results of the research are based on the methods of descriptive statistics and the statistical method of correlation analysis.
U radu je provedeno istraživanje transporta cisterne pri prijevozu opasne tvari s fokusom na opasnost od prevrtanja, te taktički pristup gašenju požara takvog incidenta. Kao ključan dokument u ...prijevozu opasnih tvari cestom, sporazum ADR je konzultiran uz analizu vijeka trajanja vozila za transport u Republici Hrvatskoj. Analizirani su glavni uzroci nepravilnosti na tehničkim pregledima vozila za prijevoz opasnih tvari. Prikazana je i procedura koja se obavlja pri prijevozu opasnog tereta - benzina na Hrvatskim autocestama uz pomoć karti rizika, odabira sigurnih ruta. Temeljem odabranog prijevoza opasne tvari dane preporuke za vatrogasnu taktiku u slučaju incidenta.
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