National Institute of RandD for Technical Physics

RO, Romania

National Institute of RandD for Technical Physics

RO, Romania
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Andrusca L.,Technical University Gheorghe Asachi | Goanta V.,Technical University Gheorghe Asachi | Barsanescu P.D.,Technical University Gheorghe Asachi | Savin A.,National Institute of RandD for Technical Physics
IOP Conference Series: Materials Science and Engineering | Year: 2016

In real life experience, machine and structure elements are subjected to complex loading history. Combined loading testes facilitate the understanding of materials behavior subjected to multiaxial stress state. In this paper are presented experimental investigations used to evaluate the influence of an initial type of loading on material properties which will be subsequently tested through another load type. Initial tests are tension tests, by different elongations, and subsequent tests are torsion tests, until break. Circular cross section specimens will be used in these tests. Tension tests have been performed on a universal testing machine. Subsequently torsion tests have been conducted through an attachable device. It was found that the energy associated with plastic deformation obtained by subsequent torsional tests has the dominant influence on the material total plastic energy, although initial test was tension. © Published under licence by IOP Publishing Ltd.


Sturm R.,University of Ljubljana | Grimberg R.,National Institute of RandD for Technical Physics | Savin A.,National Institute of RandD for Technical Physics | Grum J.,University of Ljubljana
Composites Part B: Engineering | Year: 2015

In this study the effect of moisture absorption on the mechanical properties of glass-reinforced polyester composites is evaluated using both destructive and nondestructive tests. The composite resins were produced with two different production processes, while the mechanical properties of the composite materials were measured using DMA destruction tests. According to the DMA tests, the dependency in terms of temperature for the real component of the complex elastic modulus (E′), the imaginary component of the complex elastic modulus (E″), as well as tan(δ) can be traced. For a more efficient use of the composite materials, the compliance tensor was obtained with nondestructive tests based on ultrasound. A method for the generation and reception of Lamb waves in plates of composite materials is described, based on using air-coupling, low-frequency, ultrasound transducers in a pitch-catch configuration. The results of the nondestructive measurements made in this study are in good agreement with those obtained when using the DMA destructive tests. © 2014 Elsevier Ltd. All rights reserved.


Neamtu B.V.,Technical University of Cluj Napoca | Neamtu B.V.,CNRS Neel Institute | Chicinas I.,Technical University of Cluj Napoca | Isnard O.,CNRS Neel Institute | And 3 more authors.
Intermetallics | Year: 2013

Nanocrystalline Ni3Fe compacts were successfully prepared by spark plasma sintering starting from wet mechanically alloyed powders. The influences of the sintering conditions: sintering temperature, sintering time and particle size on the compact magnetic properties are investigated. It is found that high sintering temperature, increased sintering duration and larger particle size leads to compacts with improved soft magnetic properties. A contamination with carbon of the compacts during the sintering processes has been found to reduce their magnetic properties. It is found that a heat treatment at the temperature of 450 °C during 4 h, in hydrogen atmosphere, leads to an improvement of the compact coercivity and of the maximum relative permeability of the compact to up to 600% and 50% respectively. Spark plasma sintering can consequently be considered as promising compaction technique for processing Ni3Fe nanocrystalline powder in particular and nanocrystalline soft magnetic alloys in general. © 2012 Elsevier Ltd. All rights reserved.


Tabakovic I.,University of Minnesota | Qiu J.-M.,University of Minnesota | Dragos O.,National Institute of RandD for Technical Physics
Journal of the Electrochemical Society | Year: 2016

The CoPt films with 9.7-91 at% Co and thicknesses of 15-20 nm were obtained from a new designed stable hexachloroplatinate solution at a controlled potential deposition. The effects of the substrate (Ru and Cu) and an organic additive (saccharin) on composition, crystal structure and magnetic properties of the CoPt films were studied. It was demonstrated that a Ru electrode substrate provides well-defined surface for the epitaxial growth of hcp phase, resulting in high perpendicular anisotropy. The addition of saccharin (Sacc) as an organic additive into the plating solution caused a dramatic improvement of the epitaxial growth of CoPt film on the Ru substrate. At the film thickness of interest, for bit-patterned media BPM (15-20 nm), the out-of-plane coercivity showed the highest value of 6700 Oe and the squarness Mr/Ms ∼1. © 2016 The Electrochemical Society.


Corodeanu S.,National Institute of RandD for Technical Physics | Chiriac H.,National Institute of RandD for Technical Physics | Radulescu L.,Grigore T. Popa University of Medicine and Pharmacy | Lupu N.,National Institute of RandD for Technical Physics
Journal of Applied Physics | Year: 2014

Results on the development and testing of a novel magnetic sensor based on the detection of the magneto-impedance variation due to changes in the permeability of an amorphous wire are reported. The proposed application is the quasi-noncontact monitoring of the breathing frequency and heart rate for diagnosing sleep disorders. Patient discomfort is significantly decreased by transversally placing the sensitive element onto the surface of a flexible mattress in order to detect its deformation associated with cardiorespiratory activity and body movements. The developed sensor has a great application potential in monitoring the vital signs during sleep, with special advantages for children sleep monitoring. © 2014 AIP Publishing LLC.


Chiriac H.,National Institute of RandD for Technical Physics | Corodeanu S.,National Institute of RandD for Technical Physics | Lostun M.,National Institute of RandD for Technical Physics | Ababei G.,National Institute of RandD for Technical Physics | Ovari T.-A.,National Institute of RandD for Technical Physics
Journal of Applied Physics | Year: 2010

Results on the magnetic behavior of glass-coated amorphous wires with metallic nucleus diameters in the submicron range are reported for the first time. The magnetic behavior of nearly zero magnetostrictive submicron amorphous wires is different from that observed in amorphous microwires with typical dimensions and similar composition. Submicron wires are bistable, whereas typical microwires show an almost anhysteretic loop. Bistability of submicron wires is maintained even in a very thin surface layer, which was shown to display a helical magnetic anisotropy. The origin of this specific behavior is the shape anisotropy which becomes dominant at lower dimensions of the metallic nucleus. The study of submicron amorphous wires opens up the way for new applications of amorphous wires. © 2010 American Institute of Physics.


Ovari T.-A.,National Institute of RandD for Technical Physics | Chiriac H.,National Institute of RandD for Technical Physics
Journal of Applied Physics | Year: 2014

Magnetoelastic anisotropy calculations and experimental switching field data are used to investigate the origin of the domain wall pinning in rapidly solidified amorphous glass-coated nanowires and submicron wires. The correlation of experimental and calculated results have shown that the magneto-mechanical coupling between internal stresses induced during preparation and magnetostriction is responsible for the pinning of the domain walls in amorphous wires with diameters below 300 nm, whilst in thicker submicron wires demagnetization is also important. The results are important for fully understanding and controlling magnetic switching in rapidly solidified amorphous nanowires for future applications. © 2014 AIP Publishing LLC.


Ovari T.-A.,National Institute of RandD for Technical Physics | Grigoras M.,National Institute of RandD for Technical Physics | Chiriac H.,National Institute of RandD for Technical Physics
Journal of Applied Physics | Year: 2010

Results on the magnetoresistance (MR) effect in Co-based amorphous glass-coated microwires with nearly zero magnetostriction and no granular structure are reported. MR measurements have been performed in parallel and perpendicular configurations, in both low field and high field regimes. The results show that high field resistance variations are caused by the corresponding magnetization processes in both parallel and perpendicular configurations. In case of low parallel field, no resistance variation has been emphasized. A sharp MR response was observed in case of a perpendicularly applied low field and it was attributed to the interdomain wall between the inner core and the outer shell of such microwires. The sharpness of the low field MR peak can be controlled through the microwire dimensions. The results bring new information about the domain structure of amorphous microwires and open up new application opportunities for these materials. © 2010 American Institute of Physics.


Grimberg R.,National Institute of RandD for Technical Physics
12th International Conference of the Slovenian Society for Non-Destructive Testing: Application of Contemporary Non-Destructive Testing in Engineering, ICNDT 2013 - Conference Proceedings | Year: 2013

The metamaterials, electromagnetic structures with distinguished properties have started to be studied, and especially used, only in the last 10-15 years. One of the possible applications is represented by electromagnetic nondestructive evaluation in the range of UHF and microwave. This paper makes a review of the metamaterial concept; of main realization in the domain of electromagnetic nondestructive evaluation using a "perfect lens", emphasizing the fact that important for the increasing of spatial resolution of the evaluation methods is the use of evanescent waves, and their manipulation being able to do with "poor man's lens".


Borza F.,National Institute of RandD for Technical Physics | Lupu N.,National Institute of RandD for Technical Physics | Dobrea V.,National Institute of RandD for Technical Physics | Chiriac H.,National Institute of RandD for Technical Physics
Journal of Applied Physics | Year: 2015

Ferromagnetic Fe-Ni-Co-Al-(Ta,Nb)-B microwires with diameters from 170 μm to 50 μm, which possess both superelastic and good magnetic properties, have been prepared by rapid quenching from the melt using the in rotating water spinning technique followed by cold-drawing and ageing. The cold-drawing and annealing processes lead to the initialization of premartensitic phases as confirmed by the X-ray diffraction and scanning transmission electron microscopic investigations, more significantly in the 50 μm cold-drawn microwires. An increase in the coercive field and in the saturation magnetization has been obtained by annealing, more importantly in the case of Nb-containing alloy. Ageing by thermal or current annealing led to the initialization of the superelastic effect. High values of strain of up to 1.8%, very good repeatability under successive loading, and values of superelastic effect of up to 1.2% have been achieved. The structural analysis coupled with the stress-strain data suggests that these materials annealed at 800 °C have superelastic potential at reduced ageing times. The magnetic behavior was found to be easily tailored through both thermal and thermomagnetic treatments with changes in the magnetic parameters which can be contactless detected. The results are important for future applications where both mechanical and magnetic properties matter, i.e., sensing/actuating systems. © 2015 AIP Publishing LLC.

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