Postojanost na trošenje i koroziju novih frikcijski postojanih materijala za automobilsku industriju

In this study, after a NiCr bond layer was deposited on a pearlitic, grey cast iron rotor disc of the kind used in a production passenger car (Toyota Corolla 1600 cc), Cr3C2-NiCr and Al2O3-TiO2powders were sprayed using High Velocity Oxygen Fuel(HVOF) and plasma spray processes, respectively. The discs were subjected to cosmetic corrosion test according to SAE J2334 test standard. Additionally, wear tests were carried out using a reciprocating wear tester by rubbing a 10 mm diameter Al2O3 ball on the specimens machined from rotor discs in salt solution. It was found that the Cr3C2-NiCr coating (HSCN) sprayed using HVOF method exhibited highest hardness and highest corrosion and wear resistances.Nakon nanošenja NiCr sloja na disk od sivog lijeva tipa koji se koristi u proizvodnji putničkog automobila (Toyota Corolla 1600 CC), Cr3C2-NiCr i Al2O3-TiO2 prašak je nanešen naštrcavanjem HVOF i plazma postupkom. Disk je izložen korozijskom ispitivanju sukladno standardu SAE J2334. Dodatno je provedeno ispitivanje na trošenje na testeru za uzajamno trošenje 10 mm zrna Al2O3 na uzorcima izrađenim iz rotacijskog diska u slanoj komori. Utvrđeno je da je Cr3C2-NiCr sloj (HSCN) naštrca HVOF postupkom pokazao veću tvrdoću i veću korozijsku postojanost i otpornost na koroziju

An alternative synthesis method for di calcium phosphate (monetite) powders from mediterranean mussel (mytilus galloprovincialis) shells

Marine species, such as corals, sea shells and nacres, attract special interest in bioceramics field for bone graft, bone cements and drug delivery applications. Most of the marine structures are made up of pure calcium carbonate (calcite or aragonite) with a very small amount of an organic matrix. In the past the most common way to transform these structures to hydroxyapatite was hydrothermal transformation method. This current work introduces a new approach for producing fine powders of calcium phosphates from Mediterranean mussel (Mytilus galloprovincialis) shells. A comparative study was carried out to investigate the differences of these powders under only hot plate heating and hot plate heating together with ultrasonic agitation while H3PO4 was added. The temperature of the hotplate was kept constant at 80 degrees C and then, H3PO4 was added drop wise into the solution for 2 hrs. The mixture was then placed into an oven at 100 degrees C for 24 hrs. They were further calcined at 800 degrees C for 3 hrs. XRD, FTIR. and ICP-MS were used to identify the structure and composition. It was found that the final powders were predominantly monetite, with some tricalcium phosphate as a secondary phase. This relatively simple and efficient method can be easily applied to produce calcium phosphate precursor powders for a range of biomedical applications

Photoluminescence and concentration quenching of Pr3+ doped BaTa2O6 phosphor

The pure and Pr3+ doped TTB-BaTa2O6 phosphors were obtained by the solid state reaction method at 1 425 °C for 20hours. X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses confirmed a single phase of BaTa2O6up to 10 mol % Pr2O36. SEM analysis also shows that BaTa2O6 grain size decreased with the increasing Pr2O36 concentration.The chemical composition of Pr3+ doped BaTa2O6 structures was confirmed by Energy Dispersive Spectroscopy(EDS) analysis. BaTa2O6:Pr3+ phosphors exhibited on a strong red emission at 620,9 nm, a green emission at 548,3 nm and a red emission at 655,2 nm. Emission intensity increased with Pr3+ doping concentration up to 1,5 mol %, then decreased due to concentration quenching

Kvantitativno određivanje mikropukotina na keramičkim premazima

In this study, composite and metallic powder is coated on steel, cast iron and aluminium surfaces using flame spray and plasma spray under atmospheric conditions. Surface morphologies have been investigated in detail using Scanning Electron Microscope (SEM). Studies using SEM have illustrated that micro-cracks occur in structures of composite and metallic coatings independently from coating and process parameters. Using segmentation through threshold techniques, amount of microcracks from the point of view quantitative analysis is computed on digital images of microcracks.U ovom radu se prikazuju premazi kompozitnog i metalnog praha nanešenog plamenim sprejem ili sprejom plazme na površinu čeličnog predmeta, predmeta od ljevanog željeza, aluminija - pod atmosferskim uvjetima. Morfologiju površina je skenirano elektronskim mikroskopom (SEM) i detalno ispitana. Studije napravljene SEM-om pokazale su da se mikropukotine pojavljuju u strukturama kompozitnih i metalnih premaza. Količina mikropukotina sa računa s točke gledišta kvantitativne analize na digitalnim slikama mikropukotina koristeći se segmentacijom pomoću tehnika praga

121 1 Technical Cooperation Officer, Overseas Development Administration

In San Javier, Bolivia, with a system of dairy ranching where cows are Bilked once per day while raising a calf, it was shown that the grazing of a forage reserve of the legumes Macrotyloma axillare cv Archer and Glycine wightii cvTinaroo raised milk production by 11-20Z. The leguminous protein reserve also consistently increased the butterfat content of the milk by an average of 0.4 percentage points. It was calculated that coring the 5 aunties of the dry season from April to August' one hectare of reserved legume pasture in conjunction with 3 hectares of grass could provide about 50% more grazing than 4 hectares of unimproved grass. Suitable dry season stocking rates for good levels of production without problems of overgrazing are about 1.2 and 0.8 cows per hectare respectively for the protein reserve system and the unimproved traditional pasture

Ispitivanje premaza primjenjenih na diskove kočnica na dva uloška za disk-kočnicu

While braking, according to the severity of it, thermal, metallurgical, constructive and tribological occurrences emerge on the brake disc-pad interface. In this study, NiCr was sprayed as bonding layer onto the discs, one of which was coated with Al2O3-TiO2 by plasma spray and the other was coated with NiCr-Cr3C2 by High Velocity Oxygen Fuel (HVOF). In addition, the discs were tested with inertia dynamometer according to SAE’s J2522 testing procedure. The measurements showed that although the pads of the coated discs were exposed to higher braking temperatures, friction coefficient of the disc coated with NiCr- Cr3C2 was obtained 6 % higher compared to the original disc.Pri kočenju, zbog jačine, dolazi do termalnih, metalurških, konstruktivnih i triboloških pojava na sučelju uloška za disk kočnice. U ovoj analizi, na diskove je poprskan NiCr kao vezni sloj, od kojih je jedan disk premazan plazma sprejem Al2O3-TiO2, a drugi je premazan s NiCr- Cr3C2 pod visokim kisikovim tlakom (VKT). Osim toga, diskovi su testirani dinamometrom inercije prema postupku testiranja SAE J2522. Mjerenja su pokazala da iako su ulošci premazanih diskova bili izloženi visokim temperaturama kočenja, dobiven je 6 % viši koeficijent trenja diska premazanog s NiCr-Cr3C2 u usporedbi s originalnim diskom

Getting lost in a story: how narrative engagement emerges from narrative perspective and individual differences in alexithymia

The present research examines how narrative engagement, or the extent to which people immerse themselves into the world of a story, varies as a function of narrative perspective and individual differences in alexithymia. The authors hypothesised that narrative engagement would be higher when people assume a first-person (rather than third-person) perspective and for people lower (rather than higher) on alexithymia. In an online study (N = 541) and a lab study (N = 55), participants with varying levels of alexithymia read first- and/or third-person narrated texts and then rated their narrative engagement. As expected, first-person stories evoked more narrative engagement than third-person stories, and global alexithymia was negatively correlated with narrative engagement. Narrative perspective did not interact with cognitive facets of alexithymia (i.e. difficulties identifying, verbalising, and understanding feelings). However, narrative perspective did interact with affective facets of alexithymia (i.e. emotionalising and fantasising): First-person (rather than third-person) stories elicited more narrative engagement at lower levels of affective alexithymia, but not at higher levels of affective alexithymia. The interaction effect was significant in Study 1; the interaction was significant in Study 2 after controlling for trait absorption. Together, these findings suggest that alexithymia is linked to difficulties in mentally simulating narrative worlds.Pathways through Adolescenc

Modeling of the Direct Current Generator Including the Magnetic Saturation and Temperature Effects

En este artículo se propone la inclusión del efecto de la temperatura sobre la resistencia de campo al modelo del generador de corriente directa DC1A valido para estudios de estabilidad. Se parte del modelo lineal del generador, luego se incluye el efecto de la saturación magnética y por último el cambio en la resistencia de campo debido a la temperatura producida por la corriente de campo. La metodología aplicada para validar el modelo es la comparación de resultados experimentales y simulaciones de los modelos. La comparación visual de los resultados simulados con resultados experimentales muestra el acierto del modelo propuesto, puesto que presenta el menor error de los modelos comparados. El acierto del modelo propuesto se observa a través del índice Suma Normalizada de Errores Cuadráticos Modificada igual a 3.8979%.In this paper the inclusion of temperature effect on the field resistance on the direct current generator model DC1A, which is valid to stability studies is proposed. First, the linear generator model is presented, after the effect of magnetic saturation and the change in the resistance value due to temperature produced by the field current are included. The comparison of experimental results and model simulations to validate the model is used. A direct current generator model which is a better representation of the generator is obtained. Visual comparison between simulations and experimental results shows the success of the proposed model, because it presents the lowest error of the compared models. The accuracy of the proposed model is observed via Modified Normalized Sum of Squared Errors index equal to 3.8979%

Effect of heat treatment on the wear and corrosion behaviors of a gray cast iron coated with a COLMONOY 88 alloy deposited by high velocity oxygen fuel (HVOF) thermal spray

The present work has been conducted in order to determine the influence of heat treatment on the wear and corrosion behaviours of a gray cast iron substrate coated with a Ni base coating deposited by HVOF thermal spray. The wear resistance of the coatings was obtained using a reciprocating wear tester by rubbing a 10 mm diameter steel ball on the coatings at normal atmospheric conditions. Corrosion tests were performed using potentiodynamic polarization measurements in a 3,5 % NaCl solution. It was observed that the corrosion and wear resistance of the coatings increased along with the reduction of porosity and roughness by the heat treatment