Shear Bond Strength in Zirconia Veneered Ceramics Using Two Different Surface Treatments Prior Veneering

Aim of the study was to assess the effect of different surface treatments on the shear bond strength (SBS) of the veneering ceramics to zirconia core. In a shear test the influence of grinding and sandblasting of the zirconia surface on bonding were assessed. Statistical analysis was performed using SPSS statistical package (version 17.0, SPSS Inc., Chicago, IL, USA) and Microsoft Office Excel 2003 (Microsoft, Seattle, WA, USA). There was a significant difference between the groups considering shear bond strength (SBS) values, i.e. ground and sandblasted samples had significantly higher SBS values than only ground samples (mean difference=–190.67; df=10, t=–6.386, p<0.001). The results of the present study indicate that ground and sandblasted cores are superior to ground cores, allowing significantly higher surface roughness and significantly higher shear bond strength between the core and the veneering material

Međugeneracijske promjene u narcizmu

Postoji uvriježena pretpostavka starijih ljudi da su mlađi sebičniji, narcisoidniji i usmjereni na sebe. Takve pretpostavke u zadnje vrijeme promiču i mediji, nazivajući generaciju današnjih mladih Ja generacijom. Postavlja se pitanje pokazuje li svaka sljedeća generacija mladih više narcisoidnih tendencija od prethodnih generacija? Unatoč raširenom javnom mišljenju o postojanju takvih razlika, rezultati nisu jednoznačni. Naime, ne postoji očigledan trend rasta stope narcizma među mladima. Postoje određena istraživanja čiji rezultati ukazuju na više rezultate na NPI upitniku kod novijih generacija, no takvi dobiveni rezultati podvrgnuti su kritikama zbog nemogućnosti replikacije i generalizacije na cijelu populaciju mladih osoba. Nakon 2009. godine u literaturi se nalaze novi radovi koji pronalaze međugeneracijske promjene u smjeru rasta stope narcizma među mladima, što se dijelom pripisuje lošijoj ekonomskoj situaciji u svijetu. Postoji prostor za metodološka poboljšanja i u daljnjim istraživanjima o ovoj temi, s obzirom na to da su do sada uzorke većinom činili studenti u SAD-u, te bi prilikom interpretacije rezultata trebalo posvetiti više pažnje određenim facetama narcizma

Cutting performance of deep cryogenic treated and nitrided HSS cutting tool inserts

High speed steel (HSS) is a very important industrial tool material and has been constantly improved for different wear resistance applications and cutting tools, i.e. drills, milling cutters, hobs and for the cutting tools in which the economical cutting speed is too low for choosing the carbide tools. The properties of HSS depend significantly on the parameters of the conducted heat treatment. In this paper, the influence of deep cryogenic treatment in combination with nitriding of metallurgical powder metallurgy HSS on the wear resistance was measured. Additionally, the cutting performance in a single point cutting tool machinability test at the configuration of the dry low-speed turning of steel was investigated. The results showed that deep cryogenic treatment itself, and in combination with nitriding, resulted in the reduction of the wear rate. The results of the single point cutting tool machinability test showed that deep cryogenic treated and nitrided HSS inserts performed worse than the classically heat-treated inserts and deep cryogenic treated HSS inserts exhibited approximately the same flank wear as the nitrided ones

Microstructural changes in heat treatment of PM high-speed steels

Properly performed heat treatment can significantly affect final properties of high-speed steels, so the heat treatment parameters are chosen depending on the specific properties of the particular tool. Deep cryogenic treatment is carried out at a temperature of -196 °C (liquid nitrogen). By combining deep cryogenic treatments and various austenitization temperatures, which affects the volume of retained austenite, it is possible to affect the hardness and fracture toughness of tools and other steel parts. However, it may also affect the increase in wear resistance regardless of the increase in hardness. In addition, dimensional stability is achieved by transformation of residual austenite into martensite, eliminating the change in volume by 4%. This paper investigated the effect of deep cryogenic treatment on microstructures in high-speed steel produced by powder metallurgy in comparison to vacuum heat treatment

Shear Bond Strength in Zirconia Veneered Ceramics Using Two Different Surface Treatments Prior Veneering

Aim of the study was to assess the effect of different surface treatments on the shear bond strength (SBS) of the veneering ceramics to zirconia core. In a shear test the influence of grinding and sandblasting of the zirconia surface on bonding were assessed. Statistical analysis was performed using SPSS statistical package (version 17.0, SPSS Inc., Chicago, IL, USA) and Microsoft Office Excel 2003 (Microsoft, Seattle, WA, USA). There was a significant difference between the groups considering shear bond strength (SBS) values, i.e. ground and sandblasted samples had significantly higher SBS values than only ground samples (mean difference=–190.67; df=10, t=–6.386, p<0.001). The results of the present study indicate that ground and sandblasted cores are superior to ground cores, allowing significantly higher surface roughness and significantly higher shear bond strength between the core and the veneering material

SOLUTION OF STAINLESS STEEL PIPE CALIBRATION LUBRICATION PROBLEM

Sažetak Kod operacije kalibriranjem prilikom provlačenja osnovnog materijala kroz matricu akumulira se energija u rešetci osnovnog materijala. Zato pred ulje postavljamo određene zadatke kao što su dovoljno brzo odvođenje topline kako hlađenjem osnovnog materijala ne bi dolazilo do pojave pukotina, a ujedno ulje mora služiti za podmazivanje matrice. Dakle, osnovna funkcija ulja kod kalibriranja je podmazivanje matrice u cilju smanjenja trošenja te odvođenje topline zbog mogućnosti pojave pukotina.Abstract In the calibration operation while pulling the basic material through the matrix there is a great energy accumulation in the grate of the basic material. Therefore the oil has to fulfill certain requirements such as the heat conductance which should be fast enough to prevent formation of cracks while cooling of the basic material. The oil also serves for lubrication of the matrix. To conclude we can say that the basic function of the oil in the calibration process is lubricating of the matrix in order to reduce wear and the heat conductance for avoiding cracks

A Method for Testing Abrasive Wear of Aesthetic Prosthetic Materials

Trenje i trošenje zbivaju se na dodiru tvarnih površina koje su više ili manje hrapave. Tijekom abrazijskoga trošenja nastaje istiskivanje materijala prouzročenog tvrdim česticama koje prave pritisak prema površini, ili kližu duž nje (trotočkasto abrazijsko trošenje), ili pak tvrdim izbočinama (dvotočkasto abrazijsko trošenje). Zahtjevi za estetskom opskrbom grizne plohe postavljaju pred kliničara problem izbora materijala za fasetiranje. U ovome članku opisana je metoda za ispitivanje abrazijskoga tro- šenja parova zub-protetski materijal za fasetiranje. Da bi se ocijenila ta metoda ispitana su dva različita protetska materijala za fasetiranje (polimerni materijal SR Chromasit, Ivoclar i glinična keramika, Sign Ivoclar) na modificiranom Taber abrazeru, u suhim uvjetima. Dobivene su znatne razlike u tragovima trošenja na uzorcima ispitivanih materijala. Testirana metoda omogućuje ispitivanje uzoraka različitih materijala međusobno ili u paru s prirodnim zubom, pod različitim opterećenjima te s postojanjem trećeg tijela ili bez njega (hrane ili umjetne sline), što je u kliničkoj praksi vrijedan podatak pri izboru vrste konstrukcije i materijala za fasetiranje.Friction and wear occur due to the contact of surfaces which are more or less rough. During abrasive wear the extrusion of material occurs, caused by hard particles which apply pressure toward the surface or slide along it (three-body abrasive wear) or by hard protrusions (two-body abrasive wear). Because of demands to provide a satisfactory aesthetic mastication surface the clinician is faced with the problem of the choice of material for veneering. The article describes a method for testing abrasive wear of pairs of tooth-prosthetic material for veneering. In order to test the method two different prosthetic veneering materials were tested (polymer material SR Chromasit, Ivoclar and Clay ceramic, Sign-Ivoclar) on a modified Taber abraser, in dry conditions. Significant differences were determined in the wear scars on specimens of the tested materials. The method enables the testing of specimens of different materials mutually or in a pair with a natural tooth, under different loading and with or without a third body (food or artificial saliva), which in clinical practice represents valuable data during the choice of the type of construction and veneering material

Međugeneracijske promjene u narcizmu

Postoji uvriježena pretpostavka starijih ljudi da su mlađi sebičniji, narcisoidniji i usmjereni na sebe. Takve pretpostavke u zadnje vrijeme promiču i mediji, nazivajući generaciju današnjih mladih Ja generacijom. Postavlja se pitanje pokazuje li svaka sljedeća generacija mladih više narcisoidnih tendencija od prethodnih generacija? Unatoč raširenom javnom mišljenju o postojanju takvih razlika, rezultati nisu jednoznačni. Naime, ne postoji očigledan trend rasta stope narcizma među mladima. Postoje određena istraživanja čiji rezultati ukazuju na više rezultate na NPI upitniku kod novijih generacija, no takvi dobiveni rezultati podvrgnuti su kritikama zbog nemogućnosti replikacije i generalizacije na cijelu populaciju mladih osoba. Nakon 2009. godine u literaturi se nalaze novi radovi koji pronalaze međugeneracijske promjene u smjeru rasta stope narcizma među mladima, što se dijelom pripisuje lošijoj ekonomskoj situaciji u svijetu. Postoji prostor za metodološka poboljšanja i u daljnjim istraživanjima o ovoj temi, s obzirom na to da su do sada uzorke većinom činili studenti u SAD-u, te bi prilikom interpretacije rezultata trebalo posvetiti više pažnje određenim facetama narcizma

Wear of Induction Cladded Coating in the Abrasive Mass at Various Speeds and Impact Angles

The wear of induction cladded coating during motion was investigated through the abrasive mass at a speed of 1.0 to 3.0 m/s and the impact angle of abrasive particles with a worn surface of 0° to 90°. Cladding was performed by using Ni-Cr-Si-B-Fe flame spraying powder. Experimental research was carried out by using the Response Surface Method (RSM) and Central Composite Design (CCD). Analysis of variance proved that both motion speed and impact angle had significant impact on the wear of coating, both individually and interactively. Motion speed had the greatest influence, and the interaction of speed and angle had the least influence. The wear rate increased along with the motion speed increase, and the influence of the impact angle depends on the wear speed. At a speed of 1 m/s, the wear increases along with the increase of angle from 0° to 45° and then continues to decrease up to the angle of 90°. At a speed of 2 m/s, the wear increases along with the angle increase from 0° to 30° and then continues to decrease up to the angle of 90°. At a speed of 3 m/s, the wear increases along with the angle increase from 0° to 20° and then decreases as the angle increases up to 90°. Based on the statistical data processing, this research developed the mathematical model of wear in the form of quadratic polynomial that describes the influences of input variables in individual and interactive form