Papers by Tamara Aleksandrov Fabijanic
Mjerne Karakteristike Bakrenih Referentnih Pločica Tvrdoće Po Vickersu
Metals, Feb 23, 2017
In this paper, the electrochemical corrosion resistance of near-nano and nanostructured WC-Co cem... more In this paper, the electrochemical corrosion resistance of near-nano and nanostructured WC-Co cemented carbides was investigated. WC powders with an average grain size d BET in the range from 95 nm to 150 nm and with an addition of vanadium carbide (VC) and chromium carbide Cr 3 C 2 as grain growth inhibitors were used as starting powders. The mixtures with 6 wt. % and 9 wt. % Co were consolidated by two different processes; sintering in hydrogen atmosphere and the sinter-HIP process. WC-Co samples were researched by direct current and alternating current techniques in the solution of 3.5% NaCl at room temperature. Corrosion parameters such as corrosion potential (E corr), corrosion current density (j corr) and polarization resistance (R p) were determined by electrochemical techniques. From the conducted research, it was found that the consolidation processes and microstructural characteristics-grain growth inhibitors, grain size of the starting WC powders and η-phase-influenced the electrochemical corrosion resistance. η-phase enhanced the formation of a passive layer on the samples' surfaces, thereby reducing the tendency of the sample dissolution and increasing the stability of oxides forming therewith a passive layer on the sample surface.
Electrochemical corrosion resistance of nanostructured hardmetals in acid media
Određivanje Modula Elastičnosti Čelika
Influential factors on hardness uniformity of Vickers hardness blocks for high hardness range
Measurement, 2016
Abstract Reference Vickers hardness blocks for high hardness range were developed from WC 9–Co an... more Abstract Reference Vickers hardness blocks for high hardness range were developed from WC 9–Co and WC 6–Co mixtures by two different processes of powder metallurgy, conventional liquid phase sintering in hydrogen and vacuum-sintering with subsequent hot isostatic pressing in one cycle, sinter-HIP, in order to analyse the appropriateness of the manufacturing process and the influence of starting characteristics of the mixtures on hardness uniformity and overall metrological characteristics. WC powder of 150 nm grain size and 2.5 m 2 /g specific surface area with the addition of grain grow inhibitors was used as starting material. The emphasis of the research was placed on hardness uniformity of the test surface as it is the most important property placed on hardness blocks. For that purpose the surface of the blocks was divided into radial and circumferential divisions, forming different sections on the block surface. Hardness measurements were performed in each section with HV1 measuring method. A total of 40 indentations were performed, based on which the conclusions about hardness uniformity of Vickers hardness blocks were drawn. Hardness measurements and uniformity were tested by analysis of variance, ANOVA, for single factor in order to determine if significant hardness variations across the block surface were present. From the research conducted it was concluded that hardness distribution across test surfaces of Vickers hardness blocks had a trend according to a process of manufacturing and the amount of binder in the WC–Co mixture. The best material and metrological characteristics were obtained on the block manufactured by sinter-HIP with 9 wt.% Co.
Nanomaterials, Apr 19, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Application of thermography in determining the proportionality limit
The influence of Nb content on the mechanical properties of micro alloyed low carbon steels
Journal of Material Sciences & Engineering, Jun 27, 2018
Influence of C content on electrochemical corrosion resistance of nanostructured hardmetals
Investigation of deformation by digital image correlation
Conventional methods for investigation of metallic materials during elastic and plastic deformati... more Conventional methods for investigation of metallic materials during elastic and plastic deformation cannot provide the full insight into materials behaviour during deformation. Lately new methods for investigation of deformation are being intensively used. Digital Image Correlation (DIC) has proven to be very suitable method for exploring of deformation zone. It is a non-contact method that allows detailed analysis of the deformation zone. Along the qualitative values, this method provides also the quantitative values of deformation that can be applied for construction and/or validation of various mathematical models. By analysis of the actual deformation, it is possible to obtain so-called deformation maps, which clearly illustrate the amounts of deformation in different parts of the deformation zone. In order to test the method of digital image correlation, static tensile testing was conducted on samples from low carbon steel. During static tensile testing surface of samples were continuously recorded with a digital camera. Subsequent analysis of acquired deformation images was done using digital image correlation, in order to determine deformation maps in deformation zone. Results of digital image correlation were compared with the results of the static tensile tests.
The Measurement Capability of the Reference Force Standard Installed in Lims
Laboratorij za ispitivanje mehanickih svojstva (LIMS) Fakulteta strojarstva i brodogradnje je nos... more Laboratorij za ispitivanje mehanickih svojstva (LIMS) Fakulteta strojarstva i brodogradnje je nositelj državnog etalona za silu u mjernom podrucju 50 N – 200 kN s mjernom sposobnoscu <0, 12%. Krajem 2005. u LIMS-u je instaliran referentni etalon sile nazivne vrijednosti 500 kN. U radu je opisana sljedivost mjerenja sile u RH prije i poslije instalacije referentnog etalona. Procjena mjerne sposobnosti dana je na temelju preliminarnih komparativnih mjerenja provedenih pomocu posrednickih etalona nazivnih sila 20 kN, 50 kN, 100 kN, 200 kN i 500 kN koji su sljedivi do nacionalnih etalona sile Republike Njemacke. Posrednicki etaloni koristeni su u mjernom podrucju 40 -100 % vrijednosti nazivne sile kako bi se dobila sto manja nesigurnost mjerenja. Na temelju izvrsenih mjerenja doneseni su određeni zakljucci koji su ujedno i daljnje smjernice za poboljsanje mjerne sposobnosti referentnog etalona sile. Poseban naglasak je na utjecaju referentnog etalona na mjernu sposobnost LIMS-a, te na njegov položaj u europskim i svjetskim mjeriteljskim krugovima za mjernu velicinu sile.
Nanomaterials
In this paper, a 3D phase-field model for brittle fracture is applied for analyzing the complex f... more In this paper, a 3D phase-field model for brittle fracture is applied for analyzing the complex fracture patterns appearing during the Vickers indentation of fused silica. Although recent phase-field models for the fracture caused by the indentation loading have been verified by some simpler academic axis-symmetric examples, a proper validation of such models is still missing. In addition, heavy computational costs, and a complicated compression stress field under the indenter, which demands different energy decompositions, have been identified as the most important impediments for the successful application of the phase-field method for such problems. An adaptive strategy is utilized for reducing the computational costs, and some modifications are introduced, which enable an accurate simulation of the Vickers indentation fracture. Here, the fracture initiation ring outside the contact zone is detected by using different energy decompositions, and the dominant cone-crack formation u...
MJERNA SPOSOBNOST REFERENTNOG ETALONA SILE INSTALIRANOG U LIMS-u
Analiza Površine Nanostrukturiranih Tvrdih Metala Nakon Provedenih Elektrokemijskih Ispitivanja
Nanostrukturirani Tvrdi Metali – Novi Izazovi Metalurgije Praha
Development of reference hardness blocks for the high hardness range by the powder metallurgy pro... more Development of reference hardness blocks for the high hardness range by the powder metallurgy process will be presented in this paper. Development would start with the selection of powder, matrix and grain growth inhibitors as well as parameters related to the technological process of obtaining which are related to milling, compacting and sintering. Mentioned would be realized in order to ensure the measurement traceability of the Vickers hardness for the Republic of Croatia for the high hardness range and to contribute to the spectrum of materials and processes of manufacturing reference blocks for the Vickers hardness on the global level.
Instrumentirana metoda utiskivanja na nanostruktiriranim tvrdim metalima
Coating adhesion determination by interface identation test
Međupovrsinski indentacijski test sastoji se od mjerenja duljine pukotine stvorene na međupovrsin... more Međupovrsinski indentacijski test sastoji se od mjerenja duljine pukotine stvorene na međupovrsini prevlake i osnovnog materijala kao posljedica utiskivanja Vickers metodom. Uporabom međupovrsinskog indentacijskog testa i definiranjem kriticnog naprezanja potrebnog kako bi doslo do stvaranja pukotine, lomnom žilavosti uspjesno se može opisati prionjivost prevlake na supstrat tj. osnovni materijal. U radu je opisana metodologija međupovrsinskog indentacijskog testa kao i primjena istog na "međupovrsinski materijal", te analiza dobivenih rezultata. Svrha istraživanja je ispitivanje mogucnosti određivanja lomne žilavosti "međupovrsinskog materijala" na temelju međupovrsinskog indentacijskog testa.
The paper describes comparison of Vickers hardness measurement in the high hardness range. The me... more The paper describes comparison of Vickers hardness measurement in the high hardness range. The measurements were performed on the block made of WC-Co hardmetal on the reference Vickers hardness machine. The software package for the indentation analysis was developed. In order to confirm reliability of the results the hardness measurements were performed on the primary Vickers microhardness machine. On the basis of comparison was concluded that measured Vickers hardness fit well.
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Papers by Tamara Aleksandrov Fabijanic