Sklonost čelika API 5L X80 prema hladnim pukotinama

U radu je dan prikaz istraživanja osjetljivosti čelika API 5L X80 prema pojavi pukotina uzrokovanih vodikom. Poznato je da su čelici povišene čvrstoće skloni nastanku pukotina uzrokovanih vodikom. Prisutnost vodika u metalu zavara ili ZUT-a može dovesti do oblika pukotina poznatog kao pukotina uzrokovana vodikom (HIC). Ovaj oblik pukotina obično se naziva hladne pukotine jer nastaju na ili blizu sobne temperature nakon što se zavar ohladi. Unatoč činjenici da su vodikove pukotine proučavane više od 60 godina, još uvijek ne postoji univerzalni mehanizam nastajanja. U eksperimentalnom dijelu rada provest će se ispitivanje sklonosti čelika API 5L X80 prema hladnim pukotinama pomoću Implant testa

Application of argon-helium shielding gas mixture for TIG welding of Hastelloy C-22 nickel alloy

U ovom radu određeni su parametri TIG zavarivanja sučeljenog spoja legure nikla Hastelloy C-22 sa zaštitnom plinskom mješavinom argon – helij. U teorijskom dijelu obrađene su podjele legura nikla, njihova svojstva, otpornost na koroziju i područje primjene. Nadalje, opisani su parametri pri TIG zavarivanju i obrađen je utjecaj zaštitnog plina na geometriju zavarenog spoja i produktivnost zavarivanja. Eksperimentalni dio rada sastoji se od tri dijela. U prvom dijelu provedeno je mjerenje penetracije na probnim uzorcima od legure nikla Hastelloy C-22 korištenjem dvije vrste zaštitnih plinova, čistog argona i mješavine argon-helij. U drugom dijelu provedeno je TIG zavarivanje sučeljenog spoja legure Hastelloy C-22. U trećem dijelu rada provedeno je elektrokemijsko ispitivanje istosmjernom strujom osnovnog materijala i metala zavara s ciljem određivanja korozijske postojanosti zavarenog spoja.In this paper, the parameters for butt welding of the nickel alloy Hastelloy C-22 with TIG process with application of argon - helium shielding gas mixture are specified. In the theoretical part, nickel alloys, their properties, corrosion resistance and application area have been analyzed. Furthermore, the parameters for TIG welding are described and the effect of the shielding gas on the geometry of the welded joint and welding productivity is discussed. The experimental part of the paper consists of three parts. In the first part, the penetration test was performed on the Hastelloy C-22 nickel alloy samples using two types of shielding gases, pure argon and argon-helium mixture. In the second part, TIG welding of nickel alloy Hastelloy C-22 was carried out. In the third part, an electrochemical testing was carried out with the DC current on the parent material and the weld metal in order to determine the corrosion resistance of the Hastelloy C-22 welded joint

Analysis and Selection of the Most Favorable Energy Generating Product for the Heating Requirements of a Production Plant

Provedena je analiza i izbor najpovoljnijeg energenta za izgaranje i pretvorbu u toplinsku energiju za tehnološke potrebe, grijanje i pripremu PTV – e proizvodnog pogona u kontinentalnom klimatskom području. Analizirani energenti su: prirodni plin, bioplin, drvna sječka, peleti i ekstra lako loživo ulje. I uz 1,5 – 2,0 puta veća investicijska ulaganja u termoenergetsko postrojenje obnovljiva drvna sječka je ekološki i ekonomski najpovoljnije pogonsko gorivo za proizvodnju toplinske energije. U tom slučaju cijena 1 kWh toplinske energije je višestruko manja (3 – 7 puta) od cijene 1 kWh toplinske energije dobivene izgaranjem ostalih analiziranih pogonskih goriva. Rast jedinične cijene drvne sječke osjetljivo ne utječe na održivost i ekonomičnost cijene 1 kWh toplinske energije. Emisija štetnih plinova u okolinu je najmanja.The analysis and selection of the most favorable energy generating product for the combustion and transformation into thermal energy for technological needs, heating and preparation of consumable hot water (CHW) of a production plant in the continental climate area were carried out. The analyzed energy generating products are: natural gas, biogas, wood chips, pellets and extra light heating oil. Even with 1.5 – 2.0 times higher investments in thermal energy plant, renewable wood chips are, from the ecological and economical perspective, still the most favorable drive fuel for the production of thermal energy. In this case the price of 1kWh of thermal energy is several times lower (3 – 7 times) than the price of 1kWh of thermal energy obtained by the combustion of other analyzed drive fuels. The increase in the unit price of wood chips does not strongly affect the sustainability and cost–efficiency of the price of 1 kWh of thermal energy. The emission of harmful gases into the environment is the lowest

Analysis and Selection of the Most Favorable Energy Generating Product for the Heating Requirements of a Production Plant

Provedena je analiza i izbor najpovoljnijeg energenta za izgaranje i pretvorbu u toplinsku energiju za tehnološke potrebe, grijanje i pripremu PTV – e proizvodnog pogona u kontinentalnom klimatskom području. Analizirani energenti su: prirodni plin, bioplin, drvna sječka, peleti i ekstra lako loživo ulje. I uz 1,5 – 2,0 puta veća investicijska ulaganja u termoenergetsko postrojenje obnovljiva drvna sječka je ekološki i ekonomski najpovoljnije pogonsko gorivo za proizvodnju toplinske energije. U tom slučaju cijena 1 kWh toplinske energije je višestruko manja (3 – 7 puta) od cijene 1 kWh toplinske energije dobivene izgaranjem ostalih analiziranih pogonskih goriva. Rast jedinične cijene drvne sječke osjetljivo ne utječe na održivost i ekonomičnost cijene 1 kWh toplinske energije. Emisija štetnih plinova u okolinu je najmanja.The analysis and selection of the most favorable energy generating product for the combustion and transformation into thermal energy for technological needs, heating and preparation of consumable hot water (CHW) of a production plant in the continental climate area were carried out. The analyzed energy generating products are: natural gas, biogas, wood chips, pellets and extra light heating oil. Even with 1.5 – 2.0 times higher investments in thermal energy plant, renewable wood chips are, from the ecological and economical perspective, still the most favorable drive fuel for the production of thermal energy. In this case the price of 1kWh of thermal energy is several times lower (3 – 7 times) than the price of 1kWh of thermal energy obtained by the combustion of other analyzed drive fuels. The increase in the unit price of wood chips does not strongly affect the sustainability and cost–efficiency of the price of 1 kWh of thermal energy. The emission of harmful gases into the environment is the lowest

Reconstruction and development of 3D model for biaxial conventional lathes Hobbymat MD65

Prikazan je postupak rekonstrukcije konvencionalne tokarilice Hobbymat MD65 u CNC (Computer Numerical Control) stroj s dvije simultane osi ugradnjom koračnih motora tipa NEMA 23 i upravljanih PC programskim sustavom Mach3-Lathe. 3D model je izrađen u programskom alatu Solid Edge ST4 – Ordered Technology, a fotorealistički prikaz modela u programskom modulu ERA (ExplodeRenderAnimate). Na temelju dokumentacije o montaži i održavanju i mjernih skica izrađena je kompletna 2D tehnička dokumentacija stroja. U programskom alatu AutoCAD Mechanical i programskim modulima Shaft Generator i Shaft Calculation izrađen je kontrolni proračun naprezanja vratila stezne glave, a analiza naprezanja- FEA u programskom modulu Femap – Solver NX Nastran.A process of reconstruction for conventional lathes Hobbymat MD65 in CNC (Computer Numerical Control) machine with two simultaneous axes installing stepper motor type NEMA 23 and managed PC programming tool Mach3-Lathe is presented in this paper. A 3D model is created in the programming tool Solid Edge ST4 – Ordered Technology, and realistically display models is created in the programming module ERA (ExplodeRenderAnimate). Complete 2D technical documentation of the machine was made based on the documentation on the installation and maintenance of measuring and drawing. The software tool AutoCAD Mechanical and program modules Shaft Generator and Shaft Calculation are used for controlling stress calculation returned chucks and FEA stress analysis in software module Femap – Solver NX Nastran

Kliničke upute za dijagnozu, liječenje i praćenje odraslih bolesnika oboljelih od glioma središnjega živčanog sustava [Clinical guidelines for diagnosing, treating and monitoring of adult patients with gliomas of central nervous system]

Gliomas of the central nervous system are glial cell tumors that are divided in low and high grade group. Multidisciplinary approach to treatment consists of surgery, radiotherapy and chemotherapy. The type and order of treatment depend on the characteristics of the tumor and the patient. We present the clinical guidelines for diagnostic procedures, surgical treatment, oncological treatment and follow up of patients with this type of tumor in the Republic of Croatia