Surface roughness modeling of CBN hard steel turning

Study in the paper investigate the influence of the cutting conditions parameters on surface roughness parameters during turning of hard steel with cubic boron nitrite cutting tool insert. For the modeling of surface roughness parameters was used central compositional design of experiment and artificial neural network as well. The values of surface roughness parameters Average mean arithmetic surface roughness (Ra) and Maximal surface roughness (Rmax) were predicted by this two-modeling methodology and determined models were then compared. The results showed that the proposed systems can significantly increase the accuracy of the product profile when compared to the conventional approaches. The results indicate that the design of experiments modeling technique and artificial neural network can be effectively used for the prediction of the surface roughness parameters of hard steel and determined significantly influential cutting conditions parameters

Utjecaj specifične veze između materijala i prevlake na tribološke i zaštitne karakteristike proizvoda

Today, parts and tools are increasingly made of composite materials. Realization of specific connection between basic material and coating is very important. The quality of coating on products, in terms of wear and resistance to destruction, has a large impact on productivity and reliability of production processes, in particular their life. In this paper, based on experimental investigations, the effect of specific relationship between the base material and coating on tribological and protective features of the product is analyzed.Danas se dijelovi i alati sve češće izrađuju iz kombiniranih materijala. Ostvarenje specifične veze između osnovnog materijala i prevlake je izuzetno značajno. Kvaliteta prevlake na proizvodima, sa aspekta habanja i otpornosti na razaranje, ima velik utjecaj na produktivnost i pouzdanost proizvodnih procesa, a osobito na njihov vijek trajanja. U radu je na temelju eksperimentalnih istraživanja analiziran utjecaj specifične veze između osnovnog materijala i prevlake na tribološke i zaštitne karakteristike proizvoda

Characterization of duplex hard coatings with additional ion implantation

In this paper, we present the results of a study of TiN thin fi lms which are deposited by a Physical Vapour Deposition (PVD) and Ion Beam Assisted Deposition (IBAD). In the present investigation the subsequent ion implantation was provided with N⁺² ions. The ion implantation was applied to enhance the mechanical properties of surface. The thin film deposition process exerts a number of eff ects such as crystallographic orientation, morphology, topography, densifi cation of the fi lms. The evolution of the microstructure from porous and columnar grains to densel packed grains is accompanied by changes in mechanical and physical properties. A variety of analytic techniques were used for characterization, such as scratch test, calo test, Scanning electron microscopy (SEM), Atomic Force Microscope (AFM), X-ray diff raction (XRD) and Energy Dispersive X-ray analysis (EDAX)

Intenzitet habanja kod različito toplinski poboljšanog nodularnog lijeva

In the paper we investigate the relationship between the wear intensity of two nodular cast irons and their heat treatment conditions. Disks tempered by austempering and isothermal procedure were used. The wear test was realized by using Pin and Disk tribometer. Measurement of the disks wear, after the contact for duration of 30 min, was done by the PQ meter. The quantity of the wear products in lubricant is determined by the PQ index. The best wear resistance posses the disk isothermally tempering with 30 minutes holding at 390 °C temperature.U ovom radu je ispitivana zavisnost između intenziteta habanja dva nodularna lijeva kao i uvjeta pri njihovoj toplinskoj obradi. Uzorci za ispitivanje nodularnog lijeva su bili poboljšani klasičnim i izotermalnim postupkom. Ispitivanje intenziteta habanja je realizirano uz pomoć Pin on Disc tribometra. Mjerenje pohabanosti diska, nakon trenja u trajanju od 30 minuta, je obavljeno na PQ metru. Količina čestica nastalih kao produkti habanja, u sredstvu za hlađenje i podmazivanje je određena PQ indexom. Najveću otpornost na habanje posjeduje disk izotermalno temperovan na 390 °C u trajanju od 30 minuta

Karakterizacija dupleks tvrdih prevlaka sa dodatnom ionskom primjenom

In this paper, we present the results of a study of TiN thin films which are deposited by a Physical Vapour Deposition (PVD) and Ion Beam Assisted Deposition (IBAD). In the present investigation the subsequent ion implantation was provided with N+2 ions. The ion implantation was applied to enhance the mechanical properties of surface. The thin film deposition process exerts a number of effects such as crystallographic orientation, morphology, topography, densification of the films. The evolution of the microstructure from porous and columnar grains to densel packed grains is accompanied by changes in mechanical and physical properties. A variety of analytic techniques were used for characterization, such as scratch test, calo test, Scanning electron microscopy (SEM), Atomic Force Microscope (AFM), X-ray diffraction (XRD) and Energy Dispersive X-ray analysis (EDAX).U ovom radu pretstavljaju se rezultati istraživanja TiN tankih fi lmova, nanešenih fi zičkim odlaganjem iz parne faze i te podržani ionskim snopom. U ovom istraživanju je izvršena i naknadna ionska primjena sa N+2 ionima. Ionska primjena je sprovedena radi poboljšanja mehaničkih svojstava površina. Proces nanošenja tankih fi lmova karakterizira veliki broj učinaka, kao što su: kristalografska orijentacija, morfologija, topografi ja, gustoća fi lma. Razvoj mikrostrukture od porozne i stubaste u zrnastu gusto pakovanu, se dešava uz istovremenu promjenu mehaničkih i fi zičkih svojstava. Za karakterizaciju su rabljene različite analitičke tehnike, kao što su test zaparavanja, kalo test, skenirajući elektronski mikroskop (SEM), mikroskop atomskih sila (AFM), rentgenska difrakcija X zraka (XRD) i energijska disperzivna analiza X zraka (EDAX)

Stanje površinskog sloja materijala obratka kod visokoučinskog brušenja

This paper focuses on the development of high temperatures in the cutting zone during high performance grinding. In order to identify the influence of grinding temperature on surface integrity, temperatures were measured in the workpiece surface layer under different machining conditions. Beside this, under the same conditions, the surface layer properties of the workpiece material were determined through metallographic examination. Microstructureand microhardness of the workpiece surface layer, as well as the burned surfaces and microcracks phenomena were investigated. The conducted experimental investigations allow the surface layer properties of the workpiece material in high performance grinding to be defined.U članku se ukazuje na pojavu visokih temperatura u zoni rezanja pri visokoučinskom brušenju. Da bi se ustanovio utjecaj temperature brušenja na kvalitet obrađene površine, izmjerene su temperature u površinskom sloju materijala obratka pri različitim uvjetima obrade. Ujedno je pri istim uvjetima obrade određeno stanje površinskog sloja materijala obratka metalografskim ispitivanjima. Ispitane su mikrostruktura i mikrotvrdoća površinskog sloja obratka i pojava nagorjelih površina i mikropukotina. Izvedena eksperimentalna istraživanja defi niraju stanje površinskog sloja materijala obratka kod visokoučinskog brušenja

Metodologija mjerenja karakteristika i izbor materijala elemenata tribomehaničkih sustava

Achieving the equality between the time of functional aging of mechanical systems and the time of allowed wear of the system elements is the main task of tribology. This can be reached by choosing the optimal material of elements of tribo-mehanical systems. The paper gives the results of experimental research of tribological and mechanical characteristics several pairs of material. Investigations were performed on the device with a rotating disc and static pin.Dostizanje jednakosti vjeka funkcionalnog starenja strojnih sustava i vjeka dopuštenog habanja elemenata sustava, je osnovni zadatak tribologije, koji je moguće izvesti izborom optimalnog materijala elemenata tribomehaničkog sustava. U radu se daju rezultati eksperimentalnih istraživanja triboloških i mehaničkih karakteristika više parova materijala. Istraživanja su izvedena na uređaju sa rotirajućim diskom i mirujućim pinom

Sequence variability at the internal ribosome entry site of the HCV genome in relation to therapy outcome

Different types of interferon are widely used to treat hepatitis C virus (HCV) infection. Results obtained in vitro suggest that interferon inhibits internal ribosome entry site (IRES)-mediated translation of the HCV genome. To elucidate the possible effect of the nucleotide sequence of IRES on therapy outcome, we compared HCV isolates from patients with sustained response and non-response to interferon/ribavirin combination therapy. In 56 analyzed HCV isolates, nucleotide changes appeared strictly in the stem-loop IIIb region, the stem part from 243 nt to 248 nt, and the polypyrimidine-II region. The natural sequence variability of IRES in isolates of genotype 3a was significantly higher than in isolates of genotype 1b (p < 0.05). The average number of nucleotide changes in genotype 3a correlated with response to therapy (p < 0.05).Interferonska terapija se danas najčešće koristi u lečenju infekcije virusom hepatitisa tipa C (HCV). In vitro rezultati su pokazali da interferoninhibira translaciju kod ovog virusa preko interakcije sa delom genoma koji učestvuje u inicijaciji translacije tzv. 'unutrašnje ribozomalno ulazno mesto' (IRES). U ovom radu smo ispitivali nukleotidne izmene u IRES-u kod izolata HCV-a dobijenih iz seruma osoba koje su primale kombinovanu terapiju interferon/ribavirin. U analiziranoj grupi od 56 HCV izolata, nukleotidne izmene su utvrđene u: IIIb petlji, regiji između 243 nt i 248 nt i polipirimidin-II regiji. Utvrđena varijabilnost IRES-a kod izolata genotipa 3a značajno je veća u poređenju sa izolatima genotipa 1b (p < 0.05). Prosečan broj nukleotidnih izmena kod izolata genotipa 3a je u korelaciji sa odgovorom na primenjenu terapiju (p < 0.05).Projekat ministarstva br. 143010 i 14301

Effect of acute experimental aluminum poisoning on hematologic parameters

Having in mind the presence of aluminum in industry, as well as in households, we wanted to define changes in the number of erythrocytes and aluminum content in the plasma and erythrocytes following acute aluminum poisoning under experimental conditions. The experiment involved gerbils which received intraperitoneally aluminum chloride solution at a dose of 3.7g per kg of body mass. The experimental group was sacrificed after 24, 48, 72 and 96 hours from the beginning of the experiment by cardiac punction or by abdominal artery punction. The control group was treated with saline, only. The number of erythrocytes and hemoglobin concentration were considerably reduced with respect to the control group, most likely as the result of cell membrane changes and reduced life cycle of erythrocytes. During the experiment, aluminum content in the plasma was increased in the first and second day of the experiment, it started to decline on the third day, while on the fourth day it returned to its original value, which proves again the existence of a special mechanism of "clearance" of aluminum in plasma

Sequence variability at the internal ribosome entry site of the HCV genome in relation to therapy outcome

Different types of interferon are widely used to treat hepatitis C virus (HCV) infection. Results obtained in vitro suggest that interferon inhibits internal ribosome entry site (IRES)-mediated translation of the HCV genome. To elucidate the possible effect of the nucleotide sequence of IRES on therapy outcome, we compared HCV isolates from patients with sustained response and non-response to interferon/ribavirin combination therapy. In 56 analyzed HCV isolates, nucleotide changes appeared strictly in the stem-loop IIIb region, the stem part from 243 nt to 248 nt, and the polypyrimidine-II region. The natural sequence variability of IRES in isolates of genotype 3a was significantly higher than in isolates of genotype 1b (p < 0.05). The average number of nucleotide changes in genotype 3a correlated with response to therapy (p < 0.05).Interferonska terapija se danas najčešće koristi u lečenju infekcije virusom hepatitisa tipa C (HCV). In vitro rezultati su pokazali da interferoninhibira translaciju kod ovog virusa preko interakcije sa delom genoma koji učestvuje u inicijaciji translacije tzv. 'unutrašnje ribozomalno ulazno mesto' (IRES). U ovom radu smo ispitivali nukleotidne izmene u IRES-u kod izolata HCV-a dobijenih iz seruma osoba koje su primale kombinovanu terapiju interferon/ribavirin. U analiziranoj grupi od 56 HCV izolata, nukleotidne izmene su utvrđene u: IIIb petlji, regiji između 243 nt i 248 nt i polipirimidin-II regiji. Utvrđena varijabilnost IRES-a kod izolata genotipa 3a značajno je veća u poređenju sa izolatima genotipa 1b (p < 0.05). Prosečan broj nukleotidnih izmena kod izolata genotipa 3a je u korelaciji sa odgovorom na primenjenu terapiju (p < 0.05).Projekat ministarstva br. 143010 i 14301