Cracking of an Aircraft Wheel Rim Made From Al-Alloy 2014-T6

Generally failures of different aircraft components and parts are revealed and examined by the use of non-destructive examination methods. In further detailed explanation and interpretation of failures optical and scanning electron microscopy are used. This paper deals with a problem of a crack on aircraft wheel rim made from aluminium alloy 2014-T6.The crack was observed during regular control by the maintenance unit for non-destructive examination of the Slovenian air carrier Adria Airways. The crack on the rim of an aircraft wheel investigated was a typical fatigue crack. At same time a numerous pits were found which served as stress concentrations on the rim surface

Pucanje naplatka avionskog kotača izrađenog od Al-slitine 2014-T6

Generally failures of different aircraft components and parts are revealed and examined by the use of non-destructive examination methods. In further detailed explanation and interpretation of failures optical and scanning electron microscopy are used. This paper deals with a problem of a crack on aircraft wheel rim made from aluminium alloy 2014-T6.The crack was observed during regular control by the maintenance unit for non-destructive examination of the Slovenian air carrier Adria Airways. The crack on the rim of an aircraft wheel investigated was a typical fatigue crack. At same time a numerous pits were found which served as stress concentrations on the rim surface.Oštećenja različitih dijelova i komponenti aviona otkrivena su i ispitivana primjenom nedestruktivnih metoda ispitivanja. Za detaljna objašnjavanja i interpretaciju oštećenja korištene su metode optičke i pretražne elektronske mikroskopije. Ovaj se članak bavi problemom pukotine na naplatku avionskog kotača izrađenog od aluminijeve slitine 2014-T6. Pukotina je zapažena za vrijeme redovite kontrole od strane slovenskog zračnog prijevoznika Adria Airways. Ispitivanja su pokazala, da je zapažena pukotina na naplatku avionskog kotača bila tipična umorna pukotina. Također je utvrđeno, da brojna oštećenja u obliku rupica pronađena na površini naplatka djeluju kao koncentratori naprezanja

Nastajanje niobij karbonitridnog eutektika u konstrukcijskom čeliku

The reduction of area in the through thickness direction is an essential mechanical property of thick steel heavy plates. By a routine control, a very small through thickness reduction of area was found for tensile specimen of a 90 mm plate. Careful investigations of the fracture and section of specimens cut from the as solidified continuously cast 250mmthick slab showed that the cause was the presence of coarse particles of niobium carbonitride as constituent of the quasi eutectic Fe-Nb(C, N) that form because of the centerline segregation of niobium.Kontrakcija u smjeru debljine je vrlo važno mehaničko svojstvo debelih limova od konstrukcijskih čelika. Pri rutinskoj kontroli svojstava čelika utvrđena je ispitivanjem na razvlačenje na uzorku lima debljine 90 mm, vrlo mala kontrakcija u smjeru debljine lima. Ispitivanja prijelomne površine i presjeka uzoraka izrezanih iz kontinuirano odlivenog 250 mm debelog slaba pokazala su da je uzrok tome prisutnost grubih čestica niobijevih karbonitrida u kvazieutektiku Fe-Nb(C, N) koji je nastao zbog središnjih segregacija niobija

Nastajanje niobij karbonitridnog eutektika u konstrukcijskom čeliku

The reduction of area in the through thickness direction is an essential mechanical property of thick steel heavy plates. By a routine control, a very small through thickness reduction of area was found for tensile specimen of a 90 mm plate. Careful investigations of the fracture and section of specimens cut from the as solidified continuously cast 250mmthick slab showed that the cause was the presence of coarse particles of niobium carbonitride as constituent of the quasi eutectic Fe-Nb(C, N) that form because of the centerline segregation of niobium.Kontrakcija u smjeru debljine je vrlo važno mehaničko svojstvo debelih limova od konstrukcijskih čelika. Pri rutinskoj kontroli svojstava čelika utvrđena je ispitivanjem na razvlačenje na uzorku lima debljine 90 mm, vrlo mala kontrakcija u smjeru debljine lima. Ispitivanja prijelomne površine i presjeka uzoraka izrezanih iz kontinuirano odlivenog 250 mm debelog slaba pokazala su da je uzrok tome prisutnost grubih čestica niobijevih karbonitrida u kvazieutektiku Fe-Nb(C, N) koji je nastao zbog središnjih segregacija niobija

Has private participation in water and sewerage improved coverage? - empirical evidence from Latin America

Introducing private sector participation (PSP) into the water and sewerage sectors in developing countries is difficult and controversial. Empirical studies on its effects are scant and generally inconclusive. Case studies tend to find improvements in the sector following privatization, but they suffer from selection bias, and it is difficult to generalize from their results. To explore empirically the effects of PSP on coverage, we assemble a new dataset of connections to water and sewerage services at the city, and province level, based on household surveys in Argentina, Bolivia, and Brazil. The household surveys, conducted over a number of years, allow us to compile data, before and after the introduction of PSP, as well as from similar (control) regions that never privatized at all. Our analysis reveals that, in general, connection rates to piped water and sewerage, improved following the introduction of PSP, consistent with the case study literature. We also find, however, that connection rates similarly improved in the control regions, suggesting that PSP, per se, may not have been responsible for those improvements. On the other hand, connection rates for the poorest households also tended to increase in the regions with PSP, and in the control regions, suggesting that-in terms of connections at least-PSP did not harm the poor.Environmental Economics&Policies,Decentralization,Health Economics&Finance,Water Conservation,Water and Industry,Town Water Supply and Sanitation,Health Economics&Finance,Environmental Economics&Policies,Water Supply and Sanitation Governance and Institutions,Water and Industry

Analiza međupovršine eksplozijski zavarenih ploča iz niskougljičnog čelika i titana

On the basis of experimentally obtained data, it was established that a very thin layer of a melt is generated at the explosive welding of two metals at the bond interface within which impurities flow at the bond during melting. Rapid cooling after the collision generates an alloy of different structure and very small grains of an average thickness approximately 1 to 2 mm. The generation of such an amorphous layer in the bond area has been noticed with various metal combinations and represents a fundamental mechanism of explosive welding of metals. Using the metallographic analysis, the development of the vortices which were formed by the explosive welding of low-carbon steel and titanium plates is described in the paper.Na osnovi eksperimentalnih rezultata utvrđeno je da pri eksplozijskom zavarivanju dvaju metala na međupovršini spoja nastaje veoma tanki sloj rastaljenog metala unutar kojeg dolazi do istjecanja nečistoća tijekom taljenja. Velika brzina hlađenja nakon sudara dovodi do nastanka sitnozrnate legure drugačije strukture s proječnom veličinom od 1 do 2 mm. Zapaženo nastajanje amorfnog sloja na području spoja kod različitih kombinacija metalnih materijala predstavlja temeljni mehanizam eksplozijskog zavarivanja metala. Primjenom rezultata metalografske analize u radu je opisan razvoj vrtloga koji su nastali eksplozijskim zavarivanjem ploča iz niskougljičnog čelika i titana

Učinkovitost i kvaliteta indukcijskog zagrijavanja i kaljenja osovina startera dizel motora

Presented work discusses a complex process of inductive heating and quenching of carbon steel planetary shafts for diesel engine starters. On the measurements base of temperature fields on the surface of the planetary shafts by thermographic camera and theoretical knowledge, a mathematical model for temperature conditions determination in the shaft during the entire process of heating and quenching was carried out. On the basis of developed mathematical model a computer program was developed, and used for analyses and induction hardening process optimization of planetary shafts.U ovom se radu raspravlja o složenom procesu indukcijskog zagrijavanja i kaljenja osovina iz ugljičnog čelika za pokretanje dizelskih motora. Na temelju rezultata mjerenja temperaturnih polja na površini osovina termografskom kamerom i teorijskih spoznaja, razvijen je matematički model temperaturnih uvjeta tijekom procesa zagrijavanja i kaljenja osovina. Na temelju postavljenog matematičkog modela razvijen je računalni program koji je korišten za analizu i optimizaciju procesa zagrijavanja osovina

Development of banded microstructure in 34CrNiMo6 steel

In this paper the development of a banded microstructure in hot-rolled 34CrNiMo6 steel which consisted of bainitic and martensitic bands is explained. The chemical compositions of the bands were measured with energy dispersive x-ray spectroscopy (EDS), which showed that the martensitic bands contained more alloying elements (Mn, Cr, Mo, Si) than bainitic bands. By using Oberhoffer reagent, the segregations of phosphorus were also revealed. These phosphorus segregations coincided with the positive segregations of the alloying elements. The continuous cooling transformation (CCT) diagrams of steel were calculated. They confirmed the formation of martensite in positive segregations and the formation of bainite in negative segregations

Structural and thermodynamic analysis of whiskers on the surface of grey cast iron

The paper focuses, first, on the characterization of the whiskers on the surface of grey cast iron and second, it gives an explanation of whiskers growth based on thermodynamic calculations. The whiskers were observed on the surface of hot plates for the electric stove after black-oxide-coating (blackening) performed the furnace at 650°C in order to produce a protective layer mainly of magnetite (Fe3O4). However, the whiskers caused brown spots on dark grey surface and thus, the surface was aesthetically damaged. The investigations confirmed that whiskers are of hematite (Fe2O3); however, the thermodynamic calculations present that hematite may be formed as a result of the oxidation of magnetite if the partial pressure of oxygen is increased during the blackening