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  • Articles  (4,883,138)
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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 294 (1992), S. 466-478 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 2
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    Amsterdam : Elsevier
    Physics Letters B 317 (1993), S. 474-484 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 3
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    Solid state phenomena Vol. 137 (Mar. 2008), p. 91-98 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Mechanical spectroscopy and neutron diffraction studies were performed on severalsamples with compositions Fe - 25 at. % (Al + Si) and Fe - 15 at. % (Al + Si). It was found that thesolute grain boundary relaxation is strongly dependent on the degree of order in the sample. Adecrease in the orderdegree allows the development of a relaxation peak at around 1000 K duringcooling from 1200 K. In contrast, if the order degree is not decreased, the grain boundaries remainlocked and consequently the relaxation peak does not appear. The magnetic response both in the asquenchedand after thermal treatment states was also explored and correlated to the microstructuralstate
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  • 4
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    Solid state phenomena Vol. 137 (Mar. 2008), p. 99-108 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Fe3Al intermetallic compounds and several (Fe,Cr)3Al alloys with Cr content from 3 to25 % have been studied using isothermal mechanical spectroscopy. The Zener relaxation caused byreorientation of pairs of substitute atoms in Fe is observed in all studied alloys and used to evaluatethe activation parameters of Al (Cr) atom jumps in Fe. The second internal friction peak at highertemperatures was observed only in Cr containing alloys. Isothermal mechanical spectroscopy(employed frequency from 10-4 to 102 Hz) gives some advantages as compared with ordinarytechniques, i.e. study of anelasticity as a function of temperature. It allows to avoid transient effectsand to measure materials in a state close to equilibrium. This allows to distinguish clearly betweenAl atom diffusion in Fe3Al in B2 and D03 states (activation energies for Fe – 26 Al in the B2 rangethe HB2 ≈ 235 kJ/mol, and in the D03 ordered range the HD03 ≈ 286 kJ/mol). Effect of chromium onthe Zener relaxation is analysed
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  • 5
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    Solid state phenomena Vol. 137 (Mar. 2008), p. 109-118 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: High damping Fe - Cr and Fe - Al alloys have been studied in two different states: in thehigh damping state and in the suppressed damping capacity state. It has been shown that magneticdomain structures of Fe - Cr and Fe - Al alloys are fundamentally different in the high damping stateand in the state with the suppressed damping. Magnetic domain structure corresponding to the highdamping state can be characterized by an enhanced volume fraction of the easy movable 90o-domainwalls, but the state with the suppressed damping capacity can be characterized by the enhancedvolume fraction of the 180o-domain boundaries
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  • 6
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    Solid state phenomena Vol. 137 (Mar. 2008), p. 119-128 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Industrial high damping steels based on the Fe - Al metallic system have been studied.The optimization of the crystalline structure of the industrial damping steels has been shown to bevery important for the achievement of high mechanical properties including high fatigue resistance.In the same time the achievement of high damping properties strongly depends on the magneticdomain structure of the material and, consequently, on the heat treatment procedure
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  • 7
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    Solid state phenomena Vol. 137 (Mar. 2008), p. 137-144 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The influence of thermal cycling between - 196 °C and 200 °C and equivalent heattreatment at 200 °C on the amplitude dependence of internal friction at room temperature has beenstudied in as cast Cu – Al - Mn shape memory alloys with different chemical compositions. UsingX-ray diffraction one composition was found to be austenitic and two others martensitic with twomartensite types (2H and 18R) at room temperature. All specimens were thermally cycled for 100times. During one thermal cycle the specimen underwent altogether two phase transformations onein each direction. Thermal cycling causes microstructural changes in the specimens due to atomicreordering, thermal stresses, which are generated in the martensitic state due to the anisotropy ofthermal expansion, or due to the nucleation and propagation of interphase cracks in parent phase.During repeated thermal cycling the transition peaks obtained in mechanical spectroscopy becamenarrower due to an enduring change of the microstructure and annealing effect at 200 °C. Tocompare between the effects of thermal cycling and heat treatment one martensitic specimen wasannealed at 200 °C. For selected cycle numbers and heat treatment times the amplitude dependenceof damping was measured at room temperature. The influence of thermal cycling of martensiticspecimens on the damping level was found to be similar to the influence of heat treatment at200 °C. It is most likely that the highest heat treatment temperature is more important for theamplitude dependence of damping than the temperature change during thermal cycling. Cracks dueto thermal cycling were found in all cycled specimens. They have no significant effect on theamplitude dependence of damping of the martensitic samples, whereas some small influence couldbe observed in austenitic samples at room temperature
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  • 8
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    Solid state phenomena Vol. 137 (Mar. 2008), p. 181-188 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Study of anelasticity in AZ31 magnesium-based alloy in initial (hot-rolled at 370 оС)condition and after one and four passes of equal channel angular pressing is carried out. An internalfriction peak was found at 170 °C at a frequency f of about 1 Hz. Two possible mechanisms of thispeak are discussed: it is suggested that the peak origin is the grain boundary relaxation
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  • 9
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The simultaneous influence of both thermal and mechanical treatment was applied toproduce a geometrically complex shaft from 51CrV4 steel. This special treatment led to theformation of adjacent microstructures which were significantly different from each other. It wasfound that these microstructural changes were accompanied by a change of mechanical properties interms of hardness, electrical resistivity and especially internal friction. Specimens for structuralstudies and study of mechanical and physical properties were taken out from different places of theproduced shaft and tested in order to verify and understand the obtained gradation. The significantvariations in properties could be explained in terms of structure and dislocation behaviour underapplied cyclic stress using mechanical spectroscopy technique. The cold-work (Snoek-Köster) peakwas recognised and analysed in the structure of this steel
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  • 10
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    Solid state phenomena Vol. 137 (Mar. 2008), p. 199-208 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The work is devoted to the problem of role of ambient factors (external electromagneticfield, in particular) in the process of ageing of mechanically burden nonmetallic solids (rocks). Aspecific research point is the effect of temporary activation of Acoustic Emission (AE) of rocksspecimens during action of EM field pulses applied externally. Extended experimental studies ofresponses of AE have been conducted to evince the changes in defects accumulation process inloaded specimens due to external power impacts (EPI). The experiments have been held onnoiseless rheological machines available at Bishkek Geodynamic Research Center - RS RAS. Wehave tested a number of specimens made of different materials and analyzed the temporaldependence of AE activity during exposure in electric field and crossed electric and magnetic fields;the compressive load being constant. The effect of AE stimulation by power pulses (triggering) hasbeen verified. The obtained results allow to distinguish two kinds of AE activation. The first kindinvolves simultaneous well correlated growth of numbers of minor and major AEs (so-called selfconsistencyof temporal plots of activity of different range acoustic events). The second kindrepresents dissimilar variations: the increment of activity of minor energy AEs, but the decrementof those of major energy. The first kind of solids material responses to EPI is prevailing when thecompressive loads is under 0,85 of fracturing value. The episodes of dissimilar AE responses maysignify that electromagnetic control of defects accumulation process inside rocks is possible, inprinciple
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  • 11
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    Solid state phenomena Vol. 139 (Apr. 2008), p. 119-122 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: A modeling method is suggested on the basis of measurable structural and deformationparameters to estimate the interrelation between the interconnecting chains over amorphoussegments conformation structure distribution and the elastic modulus in tension experimentalvalue for a loaded oriented linear amorphous- crystalline polymer. Macromolecule chain pullingout value of polymer crystallite was defined using the Frenkel-Kontorowa’s dislocation model
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  • 12
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    Solid state phenomena Vol. 139 (Apr. 2008), p. 123-128 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: In their paper, R. Merkle et al [R. Merkle, J. Maier, K.D. Becker and M. Kreye, Phys.Chem. Chem. Phys. 6, 3633 (2004)] conducted an experimental study on the chemical diffusion ofoxygen in Fe-doped SrTiO3 single crystals driven by large changes in the oxygen ambient partialpressure. The stoichiometry dependence of the chemical diffusion coefficient was derived on thebasis of the concept of conservative ensembles for two independent trapping reactions, which thenserved for calculating the evolution of vacancy profiles. The theoretical predictions were comparedto the experimental results. In the framework of the same model, in the present communication, thechemical diffusion of oxygen was analyzed by the concept of a dynamic reaction front [M. Sinder,J. Pelleg, Phys. Rev. E 61, 4935 (2000); Z. Koza, Phys. Rev. E 66, 011103 (2002)]. We show, thatby using a quasi-chemical reaction rate profile, it is possible to obtain information relating to theposition and width of the zone where the reaction takes place. It is indicated, that the reaction ratedistribution can be directly calculated from measured concentration profiles of the immobilereactant
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  • 13
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    Solid state phenomena Vol. 140 (Oct. 2008), p. 9-16 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Due to its high quantum efficiency (QE) for luminescence, conventional coarse-grainedYAG:Ce (Y3Al5O12:Ce) finds widespread use in light conversion and scintillator applications.Nanocrystalline YAG:Ce may possess modified optical properties which are advantageous fortechnological applications, but this will depend on highly efficient energy conversion. In this work,the effect of the particle size and Ce concentration on the quantum efficiency and the opticallifetime of the YAG:Ce emission will be characterized and discussed. Nanocrystalline YAG:Cewith an average particle size of 20 to 50 nm was synthesized by the chemical vapour reaction(CVR) method and subsequently analyzed using various techniques. When comparing thenanocrystalline samples to a coarse-grained reference sample, the particle size and dopingconcentration was found to have a significant influence on quantum efficiency. It was establishedthat the nanocrystalline samples investigated exhibit a lower QE at ambient temperature than thecoarse-grained reference. The results of the optical lifetime measurements are discussed in relationto this reduction in QE
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  • 14
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    Solid state phenomena Vol. 140 (Oct. 2008), p. 17-26 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Recent progress in the growth of nitride based semiconductor structures made by plasmaassisted MBE (PAMBE) is reported. The technology is ammonia free and the nitrogen for growth isactivated by an RF plasma source from nitrogen molecules. A new approach for the growth ofnitrides by PAMBE at temperature range 500 - 600°C is described. The key for this technique is touse a thin, dynamically stable metal (In or Ga) layer on the (0001) GaN surface, which enables ahigh quality 2D step-flow growth mode to be achieved at temperatures much lower than thosedetermined by thermodynamic considerations. A new perspective for PAMBE in optoelectronicshas been opened recently by a demonstration of continuous wave operation of InGaN blue–violetlaser diodes. These laser diodes were fabricated on bulk GaN substrates with a low threadingdislocation density
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  • 15
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 283-302 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Using the self-consistent field approximation, the static concentration waves approachand the Onsager-type kinetics equations, the descriptions of both the statistical thermodynamics andthe kinetics of an atomic ordering of D019 phase are developed and applied for h.c.p.-Ti–Al alloy.The model of order–disorder phase transformation describes the phase transformation of h.c.p. solidsolution into the D019 phase. Interatomic-interaction parameters are estimated for bothapproximations: one supposes temperature-independent interatomic-interaction parameters, whilethe other one includes the temperature dependence of interchange energies for Ti–Al alloy. Thepartial Ti–Al phase diagrams (equilibrium compositions of the coexistent ordered α2-phase anddisordered α-phase) are evaluated for both cases. The equation for the time dependence of D019-type long-range order (LRO) parameter is analyzed. The curves (showing the LRO parameterevolution) are obtained numerically for both temperature-independent interaction energies andtemperature-dependent ones. Temperature dependence of the interatomic-interaction energiesaccelerates the LRO relaxation and diminishes a spread of the values of instantaneous andequilibrium LRO parameters versus the temperature. Both statistical-thermodynamics and kineticsresults show that equilibrium LRO parameter for a non-stoichiometry (where an atomic fraction ofalloying component is more than 0.25) can be higher than for a stoichiometry at high temperatures.The experimental phase diagram confirms the predicted (ordered or disordered) states for h.c.p.-Ti–Al
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  • 16
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 339-346 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The compensation effect, i.e. the linear dependence between characteristic enthalpy andentropy, has been frequently described in many fields of science and its close relationship to a phasetransition is often assumed. In this paper it is shown for example of grain boundary segregation thatthe compensation effect principally differs from the phase transition although they can occasionallyoccur at the same temperature
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  • 17
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The vaporization of samples in the SrO-CeO2 system was investigated by the use ofKnudsen effusion mass spectrometry in the temperature range of 1494 K – 1988 K. Partial pressuresof the gaseous species O2, CeO2, Sr, and SrO were determined over the samples investigated. Thepartial pressures of the species were used for the evaluation of thermodynamic activities of CeO2and SrO in the samples at 1800 K. The enthalpy of formation of SrCeO3(s) was obtained as[removed info]fH°(298 K) = -1644 ± 21 kJ mol-1. The Gibbs energy of formation of SrCeO3(s) from SrO(s) andCeO2(s) resulted as [removed info]fG°(1800 K) = -12.5 ± 2.8 kJ mol-1 for the phase field {SrCeO3 + ss of SrO inCeO2} and [removed info]fG°(1800 K) = -13.7 ± 2.1 kJ mol-1 for the phase field {SrCeO3 + SrO}. The influenceof the Yb concentration in the perovskite phase SrCe0.95Yb0.05O3 on the CeO2(s) activity was studiedas well. The thermodynamic properties obtained in the present study are discussed on the basis ofthe data available in literature
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  • 18
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 331-338 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: A computational method has been proposed for calculating the correct interaction parametersfrom experimental phase diagrams, despite reports that this problem was believed to be a"thermodynamically incorrect” one. It has been shown that the presumed difficulties are not offundamental importance. An original computer program has been applied to two well-knownsystems Bi – Sb (1) and Bi2Te3 – Sb2Te3 (2), and a good agreement between calculated andobserved values has been achieved. The values of interaction parameters [removed info]s= 7.1 ± 0.4, [removed info]l= 1.56 ±0.09 kJ mol-1 for (1) and [removed info]s = 5.9 ± 2.5, [removed info]l = 3.9 ± 2.5 kJ mol-1 for (2) have been found. The resultshave been analyzed and their statistical reliability has been established. In addition, the possibilitiesof calculating the liquidus curve from only the solidus experimental data the solidus from theliquidus experimental data have been demonstrated. It has been found that the prediction of liquidusfrom solidus is much more successful than predicting the solidus from the liquidus.The results allow one to determine with reliance that the backward problem of modeling regularsolutions for finding thermodynamic interaction parameters can be solved correctly. The calculatedparameters can be used for both the computational restoration of missing pieces of the experimentalphase equilibrium diagrams of binary and multinary systems and for the recognition of the physicalnature of regular solutions
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  • 19
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 347-354 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Helmholtz free energy functional for generalized lattice model is reduced to Ginzburg-Landau-like form. Connections between interatomic potentials characteristics and parameters ofGinzburg-Landau-like functional are established. Equations for equilibrium distributions of speciesin multicomponent systems are derived. Equations of rearrangement kinetics of multicomponentsystems are obtained. Description of the rearrangement processes via non-classical partialdifferential equations is proposed
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  • 20
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 355-366 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: At first, some comments are made concerning the capacity of prediction of themicrostructure for shape memory alloys by the Crystallographical Theory of Martensite. Secondly,the basic foundations of the phenomenological modeling of shape memory alloys behavior at themacroscopic scale are given. A special attention is devoted to the yield surface of phasetransformation initiation in the stress space and its convex dual: the set of effective transformationstrains in the strain space
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  • 21
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 367-376 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: To investigate the influence of stress on reactive diffusion, a remarkably clear experimenthas been designed. Thin film Al/Cu/Al and Cu/Al/Cu triple layers are deposited on curvedsubstrates of 25 nm radius and investigated by atom probe tomography. Due to the specificgeometry, the excess volume of the reaction product induces compressive and dilatational stress onopposite sides of the product layer, even in the case of semi-coherent or incoherent interphaseboundaries. The resulting stress gradient leads to additional driving force, which accelerates ordecelerates the reaction rate in dependence on the stacking sequence of the layer material. Byquantitative analysis, the induced level of stress can be quantified from the modified growth rate ofthe product
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  • 22
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 377-384 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: NiAl shape memory alloy thin films have been fabricated by a solid-state reaction inAl/Ni bilayer films. Two kinds of synthesis have been used. The first one consists in heating anAl/Ni bilayer film system to temperatures above 480 K. The second one implies the successivedeposition of nickel and aluminum films onto a substrate with a temperature above 480 K.Regardless of a kind of the solid-state synthesis, the films obtained reveal a two-way shape memoryeffect. It is supposed that the solid-state reaction in Al/Ni bilayers starts at a temperature AS of thereverse of the martensitic transition in NiAl alloy. This indicates that the NiAl shape memory alloythin films can be formed directly during the synthesis without need for lengthy heat treatment
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  • 23
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    Solid state phenomena Vol. 137 (Mar. 2008), p. 231-236 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: A brief historical review of scientific research in the field of anelasticity in solids carriedout during the last 50-70 years in the USSR, Russia and states of CIS is given
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  • 24
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 29-42 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Numerous solid-state transformations occur in metal iodides. These transformations canbe classified into three categories: polymorphic transformations, polytypic transitions and molecularsolids. Many of the modifications of metal iodides involve metastable phases transforming intostable phases. Revisions to the In-I and Th-I phase diagrams are made based on data found in theliterature
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  • 25
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 3-28 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The present paper deals with the application of the transient techniques forthermophysical analysis of the structural changes in materials. The technique has been applied forstudy of equilibrium transitions as well as for kinetic transitions. A special methodology has beendeveloped to study kinetic transitions like crystallization, melting, etc. in a “pseudo-equilibriumstates” by the help of porous structures. The paper includes three different issues: the transientmethods for measuring thermodynamic and transport parameters, data analysis and application ofthe pulse transient method for measurements of materials in thermodynamic equilibrium, pseudoequilibriumand in non-equilibrium (quasi-equilibrium) states. Equilibrium transitions in CsPbCl3and CsPbBr3 single crystals, kinetic transitions of freezing and thawing water in porous stones andnon-equilibriums states in E-glass and Al2O3 ceramics during sintering have been studied
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  • 26
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    Solid state phenomena Vol. 139 (Apr. 2008), p. 1-10 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: In the present study molecular dynamics simulations were carried out to investigate thedeformation of pure FCC aluminum and diamond cubic silicon interfaces under shear stress. Asecond nearest-neighbor modified embedded atom method was used to describe the interactionsbetween Al-Al, Si-Si and Al-Si atoms. The critical shear stress (CSS) was determined for variousAl/Si and Al/Al interfaces with different alignments and orientations. Structural analyses show thatthe deformation is localized at approximately 10 Å thickness of the interface in Al. The criticalshear stress of Al/Si interface was found to be significantly lower than the critical tensile stress dueto the partial stick-slip in sliding. In addition, it has been proven that there is no explicit relationshipbetween shear and tensile critical stresses, which is fundamentally different from isotropicmaterials, where the shear stress is about half of the tensile stress. The misorientation has a dramaticeffect in reducing shear stress at Al/Al interfaces, but has no effect on CSS in Al/Si. As a result, itwas shown that introducing Si improves the strength of the interface (and the composite material ingeneral) for different grain orientations
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  • 27
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    Solid state phenomena Vol. 138 (Mar. 2008), p. 451-475 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Properties of macromolecules confined in a narrow slit, pore or capillary are importantdue to of their practical importance. Theoretical treatment of such systems is also interestingbecause the introduction of confinement has an impact on most properties of polymer chains and itgained a longstanding attention. In order to determine the properties of such systems coarse-grainedmodels of confined polymers were designed where macromolecules were represented by unitedatoms. Lattice approximation was also often introduced. Different macromolecular architectureswere studied: linear, cyclic and star-branched chains. Computer simulation techniques (the variantsof the Monet Carlo method like the Metropolis algorithm and the Replica Exchange method as wellas Molecular Dynamics and Brownian Dynamics methods) applied for studies of such models werereviewed and evaluated. The structure of the polymer film and the dynamic properties were mainlypresented and discussed. The influence of the width of the slit, the temperature and the force fieldon the dimension and the structure of chains were studied. It was shown that a moderateconfinement stabilizes folded chains while a strong confinement does not
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    Solid state phenomena Vol. 139 (Apr. 2008), p. 11-22 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Nanostructured composites inspired by structural biomaterials such as bone and nacreform intriguing design templates for biomimetic materials. Here we use large scale moleculardynamics to study the shock response of nanocomposites with similar nanoscopic structural featuresas bone, to determine whether bioinspired nanostructures provide an improved shock mitigatingperformance. The utilization of these nanostructures is motivated by the toughness of bone undertensile load, which is far greater than its constituent phases and greater than most syntheticmaterials. To facilitate the computational experiments, we develop a modified version of anEmbedded Atom Method (EAM) alloy multi-body interatomic potential to model the mechanicaland physical properties of dissimilar phases of the biomimetic bone nanostructure. We find that thegeometric arrangement and the specific length scales of design elements at nanoscale does not havea significant effect on shock dissipation, in contrast to the case of tensile loading where thenanostructural length scales strongly influence the mechanical properties. We find that interfacialsliding between the composite’s constituents is a major source of plasticity under shock loading.Based on this finding, we conclude that controlling the interfacial strength can be used to design amaterial with larger shock absorption. These observations provide valuable insight towardsimproving the design of nanostructures in shock-absorbing applications, and suggest that by tuningthe interfacial properties in the nanocomposite may provide a path to design materials withenhanced shock absorbing capability
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    Solid state phenomena Vol. 139 (Apr. 2008), p. 23-28 
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    Topics: Physics
    Notes: We studied the atomic-level structure of a model Mg-MgH2 interface by means of theCar-Parrinello molecular dynamics method (CPMD). The interface was characterized in terms oftotal energy calculations, and an estimate of the work of adhesion was given, in good agreementwith experimental results on similar systems. Furthermore, the interface was studied in a range oftemperatures of interest for the desorption of hydrogen. We determined the diffusivity of atomichydrogen as a function of the temperature, and give an estimate of the desorption temperature
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    Solid state phenomena Vol. 141-143 (July 2008), p. 421-426 
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    Topics: Physics
    Notes: A new slurry making method for rheocasting termed “Melt Spreading and MixingTechnique” (MSMT), based on forced uniform solidification theory, has been proposed, by whichthe bulk metal is dispersed into thin liquid film that is cooled rapidly and uniformly to allowcopious nucleation. With a model alloy Al-wt%6.5Si to conduct a series of experiments, feasibilityof this method and influence of process parameters upon slurry microstructure were studied. Theresults show that semisolid slurry for mass production with uniformly fine nondendriticmicrostructures can be obtained consistently and continuously by optimizing process parameters
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    Solid state phenomena Vol. 141-143 (July 2008), p. 427-432 
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    Topics: Physics
    Notes: Globulization of the grain refined AZ91 magnesium alloy with Ca on a cooling slope wasinvestigated. Dendritic morphology of the grains was transferred into round and well distributedsmall particles as a result of grain-refinement effect of Ca in the alloy. Semi-solid holding of thealloy was carried out at different temperatures to improve the spherecity of the globules. Resultsshow that, remelting at 540 °C for 30 min provides the best shape factor for the alloy. The study ofcoarsening kinetic in this alloy showed lower growth rate alternative other research which usedsame condition for produce semi-solid billet just in using Ca
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    Solid state phenomena Vol. 139 (Apr. 2008), p. 41-46 
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    Topics: Physics
    Notes: Pt nano-particles are supported on carbon materials at the electrode catalysts of protonexchangemenbrane fuel cells. Pt nano-particles are desirable to be strongly adsorbed on carbonmaterials for high dispersion, although strong Pt-C interactions may affect the catalytic activity ofsmall clusters. Thus we have examined H-atom absorption on Pt clusters supported or unsupportedon graphene sheets, using first-principles calculations. For Pt-atom/graphene systems, a H atom ismore weakly adsorbed than for a free Pt atom, and the H-Pt interaction becomes weaker if theinteraction between a Pt atom and graphene becomes stronger. For the Ptn-cluster/graphene systems(n=2-4), the H-Pt interactions are also substantially changed from those for free Pt clusters. In the Ptclusters on graphene, the Pt-Pt distances are substantially changed associated with the electronicstructurechanges by the Pt-C interactions. These structural and electronic changes in the Pt clustersas well as the presence of graphene itself seem to cause the changes in the absorption energies andpreferential sites of H-atom absorption
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    Solid state phenomena Vol. 139 (Apr. 2008), p. 47-52 
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    Topics: Physics
    Notes: Atomic and electronic structures of H-adsorbed Pd overlayers on Au(100) substrateshave been studied by first-principles calculations. The geometric strain effects change the electronicstructure and local reactivity of the surface. The lattice strained Pd overlayers on Au surfaces havelarger adsorption energies for atomic hydrogen than the unstrained Pd slabs. Adsorption energiesfor several adsorption sites on the models with different numbers of Pd overlayers have beenanalyzed from the viewpoints of strains and H-Pd and H-substrate interactions
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    Notes: Bismuth cuprate superconductor has a unique structure called a structural modulation(supercell, SC) consisting of modulated several unit cells. Strain induced by multilayered structureincreases the intensity of SC modulation, while an oxygen deficient sample shows expansion of SCsize. In this study, as opposed to the multilayer strain, by preparing samples with thick filmthicknesses the effect of strain on crystal structure was investigated including SC structure. Epitaxialgrowth was verified by x-ray diffraction, and the thicker film showed other epitaxial phase rotated 32°around the surface normal with respect to the initial epitaxial phase. The SC size estimated by x-rayreciprocal space mapping was double the size of the initial epitaxial phase. Interestingly, the initialepitaxial phase became a dominant structure after further deposition. In order to evaluate the differentSC size and SC modulation, a new index related with an incline of the modulation vector wasproposed
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    Solid state phenomena Vol. 139 (Apr. 2008), p. 59-64 
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    Topics: Physics
    Notes: Constant strain rate molecular dynamics simulations under the modified boundaryconditions were performed to elucidate the interaction processes between the kink motion of screwdislocation and the glissile self-interstitial atom cluster loops in bcc Fe by using an EAM potentialfor Fe fitted to ab initio forces. The junction formation and the helical dislocation mechanismswere identified as two possible interaction processes. In the junction mechanism, the initial Burgersvector 1/2〈111〉 of the cluster loop was transformed into 〈100〉. In the helical dislocationmechanism first the absorption, followed by the formation of the helical dislocation and theemission of the cluster loop through Hirsch mechanism was observed. Substantial hardening wasseen as result of the interactions. The stress-strain plots obtained for different loop sizes,temperature and strain rates were used to estimate the strengthening factors
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    Solid state phenomena Vol. 141-143 (July 2008), p. 665-670 
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    Topics: Physics
    Notes: An analytical model of apparent viscosity was built up based on analysis of energydissipation during rheocasting. By study the evaluation law of microstructure analyzed with aquantitative metallographic analysis system for semi-solid alloys, the variation law of apparentviscosity with time has been obtained. The model was verified in the experiment of A356 alloys witha coaxial double-bucket rheometer, and the results of simulated experiment and theoreticalcalculation are in a good agreement
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    Solid state phenomena Vol. 141-143 (July 2008), p. 695-700 
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    Topics: Physics
    Notes: The process of thixoforming incorporates a series of forming processes in the semi-solidstate, which can be categorized between the conventional processes of forging and casting andcombines the advantages of these processes. Thixoforming of steels in the semi-solid state, requiresround, solid particles (globulites) in a liquid matrix which is deformed with low forming forces. Inorder to achieve laminar material flow and to produce segregation-free components, the materialmust fulfil diverse criteria. First, the melting interval should be as large as possible for an easytemperature regulation. Next, low solidus and liquidus temperatures are advantageous regardingtool loading. Additionally, thixoformable steels should show a melting behaviour that is finegrainedand globular. Furthermore, these steels should possess low contents of intraglobular liquidphase fractions.This paper gives a survey of the current state of steel Thixoforming and deals with the developmentof adaptive heat treatment strategies. Regarding the structure formation and the development ofsuitable heat treatment strategies, the once semi-solid state yields new structures that can be appliedin ways not previously possible with conventional hardening processes. New microstructures andup to date unknown better mechanical properties can be adjusted with an optimised heat treatmentstrategy. By this, new fields of application for thixo-materials can be entered and also advancedprocedures for special applications can be established. For example the steel X210CrW12 leads to avery hard material with high wear-resistance, which can be used at higher temperatures than theconventional hardened material. In general, new generic microstructures after thixoforming resultsin unexpected favourable mechanical properties. Problems arise with respect to segregation andpores which resulting in inhomogeneous property distributions
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    Solid state phenomena Vol. 141-143 (July 2008), p. 725-730 
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    Topics: Physics
    Notes: Aluminum alloys are increasingly used in automotive and aeronautic applications toproduce high performance, lightweight parts. Among the reasons for this, is the emergence of highintegrity processes (HIP), which widens the field of application for cast aluminum alloys. In fact,metallurgical quality and consistency that characterize components produced by HIP are necessaryfor critical safety components. In addition to attaining maximum strength, critical safetycomponents need to be ductile and resistant to cyclic loading. According to the North American DieCasting Association, rheocasting is a high integrity process capable of producing parts with fewerdefects than conventional casting process. Rheocast components are known to have bettermechanical properties than permanent mold castings. Moreover, they can be heat-treated which isimpractical in the case of classical die cast components. However, the fatigue behavior of rheocastaluminum alloys has been investigated since about 2000 and few results have been published onthis subject. This paper reviews the studies of fatigue behavior of aluminum semi-solid castcomponents. Published experimental results on high cycle fatigue resistance (S-N diagrams), longcrack propagation, crack closure effects and short crack particularities are presented
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    Solid state phenomena Vol. 141-143 (July 2008), p. 219-224 
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    Topics: Physics
    Notes: This work is a contribution to improve the knowledge of components behavior producedby semi-solid processes particularly the Sub-Liquidus-Casting process. Die design was supported byusing the Procast simulation program. The effect of the different variables of the process instructural integrity of the product has been described and analyzed. The components were producedusing A356 alloy formed on a pilot plant with a 400 Ton THT press. The components study wasmade by RX, metallographic analysis and mechanical tests. The effects of T5 and T6 heattreatments were also studied
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    Solid state phenomena Vol. 141-143 (July 2008), p. 213-218 
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    Topics: Physics
    Notes: The deformation process of steel in the semi-solid state, or thixoforming is an alternativesolution to the classical industrial processes that are the casting or the hot forging.Thixoformed steel parts are of better quality and may substitute advantageously parts realized incast iron leading to an improvement of the rigidity, for example, but also parts in aluminium alloysobtained by the main deformation processes: for lower volume, thixoformed steel parts, keeping thesame functionality, present superior mechanical properties than the parts realized in aluminiumalloys. The industrial development of the steel thixoforming must be accompanied by theknowledge and the various parameters control of the process: steel grades definition andelaboration, the homogeneous high-temperature heating of the slug before deformation, conceptionor re-conception of the part to adapt it to the process and the practice properties, the equipmentdefinitions which are used for the deformation operation at the semi-solid state. The handlingsystem is also important in the thixoforming process; it is going to allow the slug transfer, at thesemi-solid state, between the heating zone and the tooling or to evacuate the thixoformed parttowards the mean assuring the quality heat treatment of the part. The means choice which areindustrially going to ensure the process have a big importance to obtain successful production lineand so, a cost reduction by “finished” part competitive with regard to processes used classicallytoday. After the description of the applicable key points to the main parameters and the solutionsused to obtain a successful product: high mechanical characteristics, near net shape or net shapegeometry, no flash and limited machining operation, ... are described , The investigations finishedwith an approach comparing the part cost realised by thixoforming process with regard to classicalprocesses
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    Solid state phenomena Vol. 141-143 (July 2008), p. 231-236 
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    Topics: Physics
    Notes: Magnesium alloys are increasingly used in automotive, aeronautic and electronicapplications to produce high performance, light weight parts. In the thixomolding process the semisolidslurry is injected into a mold at controlled temperature such that the melt has specific flowbehavior. This allows the fabrication of near net shape components with controlled microstructureand good mechanical properties. The numerical modeling of such applications presents unusualchallenges for both the physical modeling and the solution algorithm. This paper presents 3Dsolutions of the injection molding of semi-solid AZ91 magnesium alloys. The methodology dealswith the shear thinning, temperature dependent viscosity behavior and is able to accurately solve thehigh velocity flows encountered during semi-solid magnesium molding. The approach is applied tothe injection of a tensile bar and the results compared with experimental data. The numericalsolutions indicate that the material forms a jet at the exit of the gate and a swirling flow forms as thematerial advances along the first larger diameter section. The wall regions are filled first, leaving avoid inside. This agrees very well with the experimental observation
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    Solid state phenomena Vol. 141-143 (July 2008), p. 225-230 
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    Topics: Physics
    Notes: A technique to achieve the globular weld structure using stirring the localized semisolidzone during butt-joining of zinc AG40A (Zamak-3) die cast alloy is reported. Since the semisolidtemperature range of this alloy is very narrow, the accurate controlling of weld pool temperaturemust be considered. By presented process, globular microstructure of the weld zone can beachieved. Moreover the near weld zone would have the globular structure due to semisolid holding.A gas heating system was designed to heat up the nitrogen gas to desired temperature accurately. Aheating element was embedded in a castable ceramic block while a stream of gas could pass closelyaround the hot element length. Hot nitrogen gas flow through a precise ceramic nozzle was used tocreate a localized semisolid pool. At this stage a fine stirrer was introduced into the weld seam inorder to mix the two sides into a single uniform joint. Local mechanical properties of differentzones show a good strength in the weld metal zone and heat affected zone by results of the shearpunch tests and hardness tests. Air entrapment in the pool decreases by controlling the speed ofsubstrate movement and stirrer rotation under the nozzle. The strengths of each zone show relativecorrespondence to the variation of the hardness values
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    Solid state phenomena Vol. 141-143 (July 2008), p. 243-248 
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    Topics: Physics
    Notes: Isothermal semi-solid extrusion experiments using steel grade X210CrW12 as work materialwere performed on an industrial forging machine. An improved and up-scaled tool design wasapplied, based on the concept of self-heating ceramic dies tested in previous laboratory-scale studiesand allowing for die preheating temperatures of up to 1400°C.Steel rods of complex cross sectional geometry were formed at low extrusion forces. Shape accuracyof as-formed rods is accurate and metallurgical examination yields no evidence of liquid phaseseparation. With a view on the intended industrial implementation construction of ceramic tools hasto be improved in order to avoid rupture of ceramic parts due to thermo-mechanically induced stressesand to benefit from the advantages inherent to ceramics in metal forming
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    Solid state phenomena Vol. 141-143 (July 2008), p. 255-260 
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    Topics: Physics
    Notes: This paper presents an analysis of the effect of CO2 laser processing parameters on thesurface modification and heat treatment of steels. The CO2 laser and sample movement processparameters are presented. The controlled operation of these in conjunction with each other isrequired to obtain better surface hardness and structure. H13 tool steel samples were rotated at highspeeds to keep exposure times below 0.3s. Laser processed samples were analysed using EDXspectroscopy, optical microscopy, Vickers and Martens micro-hardness testing, and X-raydiffraction (XRD). Results show how the hardness profile through the surface is related to the lasertreatment and resultant microstructures. Increased surface hardness was noted due to a completemicrostructural transformation to an amorphous state in the glazed samples. The usefulness of suchcoatings on tool steels, in conjunction with other thermal barriers, for the forming of semi-solidsteel alloys is presented
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    Solid state phenomena Vol. 141-143 (July 2008), p. 237-242 
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    Topics: Physics
    Notes: The correlation between the evaluation of the mechanical and of the fatigue behaviour ofthe rheocast, T5 and T6 heat treated SSM A356 aluminium alloy with respect to the microstructuresof the component has been investigated. The study has been carried out on a suspension arminjected in a rheocasting 800 tons plant in Stampal S.p.A. The new rheocasting is a process thatallows obtaining the alloys in a semisolid state directly from the liquid state, by controlled coolingof the molten alloys. The resulting microstructures are very fine, free from defects andhomogeneous: these characteristics improve the mechanical properties of the alloys and speciallythe response to cyclic stress, an important issue for a suspension component. After a preliminarytensile test analysis, axial high frequency fatigue tests have been carried out at room temperature onspecimen cut out from the suspension arm to determine the Wöhler curve and the number of cyclesto failure. The results of this work allow a comparison of the effects of heat treatment process, T5 orT6, on Semi-Solid components for industrial applications in the automotive field.On the basis of these analysis the correlation between microstructure and mechanical performancescan be established
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    Solid state phenomena Vol. 141-143 (July 2008), p. 249-254 
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    Topics: Physics
    Notes: Oxide coatings offer great potential for their use in forming operations in the semi-solidstate. Advantages of these types of coatings are high resistance against abrasive wear, high hothardness and low thermal conductivity. Nevertheless deposition by pulsed Magnetron Sputter IonPlating-PVD for oxide coatings is quite challenging: deposition rates are low and insulating layerson the target surface can cause arcing. On laboratory scale it was possible to deposit γ-Aluminausing PVD in a temperature range, where hot working steel can be utilized. The next important stepin the development towards an industrial application for larger forming tools is the upscalingprocess to larger coating units. In this work the process development of oxide coatings on anindustrial coating unit for large tools was described. To increase adhesion of oxide top-layeradditional bond coats were applied. Different process parameters like oxygen content, total pressureand substrate bias were varied, to improve the performance. The relationship between coatingproperties and process parameters of the deposited films were characterized by X-Ray-diffraction,Nanoindentation and Scanning Electron Microscopy (SEM). By using reactive pulsed PVD-processit was possible to deposit γ-Al2O3 on large steel tools for semi-solid melt protection. The developedcoatings showed for thixoforging processes of X210CrW12 an extraordinary stability in field tests.The lifetime of the permanent moulds was increased by using PVD thin film coatings as a toolprotection
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    Solid state phenomena Vol. 144 (Sept. 2008), p. 65-70 
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    Solid state phenomena Vol. 144 (Sept. 2008), p. 71-76 
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    Topics: Physics
    Notes: This paper presents an assessment of dynamic properties of a die hammer. The object ofresearch is the steam-air die hammer MPM 10000 B that is considered taking into account thedeformations of the working material. Based upon the technical specifications, two calculationmodels of the hammer were developed assuring the proper selection of the parameters. Next, thenumerical simulations were performed, which results were presented in a graphical form as timehistories of displacements and accelerations of particular elements of the hammer. It wasdemonstrated that the analyzed design of a die hammer has sufficiently low level of vibrationamplitudes as well as their accelerations
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    Solid state phenomena Vol. 144 (Sept. 2008), p. 77-82 
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    Topics: Physics
    Notes: A mathematical model of the control system of a mobile crane is presented in the paper.The system controls the slewing motion of the chassis as well as it is applied in the model of theemergency subsystem which changes the jib reach. The latter one is initiated at the moment whenthe threat of loss of stability occurs. Some results of numerical analysis are presented in this paper.The results are related to different strategies of control of the slewing motion as well as to differenttypes of controllers applied in the main loop of control and emergency subsystem. The results ofexperimental studies are reported as well. The experiments were performed using custom-builttesting setup, which represents a kinematic model of a crane
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    Solid state phenomena Vol. 144 (Sept. 2008), p. 202-207 
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    Topics: Physics
    Notes: Modern computer technology and knowledge on building of mathematical models enablecreation of models of control systems. These systems can be created for different objects withoutany need to build real scientific test stands in the initial stage of investigations. It, in turn, enablesan essential limitation of the costs as well as performance of fast analysis of usability of the definedmethods. This approach constitutes a big improvement in a whole process of designing of such asystem
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    Solid state phenomena Vol. 144 (Sept. 2008), p. 196-201 
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    Topics: Physics
    Notes: The aim of this work was to design a control system for the shape memory alloy (SMA)actuator operated airfoil (a cross section of wind turbine blade). Design of SMA control is focusedon the reliable operation of the SMA actuators. The actuator should follow the targeted shapeaccurately and without too much delay. Another objective is to avoid overheating which is the mostcritical damage to the structure. SMA actuator shape control is in principle possible to do with anyposition control method, but the specific properties of the SMA actuators, like the hysteresis, thefirst cycle effect and the long term changes, need to be taken into account.In this work, a wing profile prototype was measured using optical fiber sensors and traditionalstrain gauges. Also, external laser sensors were used to measure displacements of upper/lowersurface and trailing edge. Shape change was obtained by embedding SMA wire actuators into fiberreinforced polymer (FRP) composite structure. SMA actuators were laminated in such way thatbending of trailing edge is always downwards. Actuators are activated with Joule heating and thetemperature is measured with integrated thermocouples and optical fiber temperature sensors.As a result, this work gave information about the usability of optical fibers sensors in active FRPcomposite structures. Measurements also give information about the efficiency of SMA actuators inshape control of relatively stiff FRP structures
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    Solid state phenomena Vol. 144 (Sept. 2008), p. 191-195 
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    Topics: Physics
    Notes: Magnetic resonance imaging (MRI) is currently a widely used technology for obtaining athree-dimensional image of a patient’s internal structures. This study examines the measurementproperties of an optical tracking system utilised in the MRI room. The results were used to assessthe suitability of the device to be used as a part of the control system of a surgical robot. Theposition and orientation of the instrument, MRI scanner and the patient are measured using anoptical tracking system in the MRI room. The measurement data can be used to display theinstrument used as a part of the image of the patient. The optical tracking system used in the MRIroom can also be considered as a part of the control system of a robot located in the room. Whenconsidering such use, the operations of the measuring device in different measurement conditionsmust be known. In terms of robot control, it is important to know the deviation attributed tomeasurement when defining the translation vector and orientation between two trackers. Fivemeasurement series were carried out using the measurement device to examine the deviation in thetranslation vector and orientation data between two trackers. The distance and position between thetrackers were changed between the measurement series. During the measurement series, themeasurement device was moved to different distances from the trackers and the translation vectorand orientation between the trackers were defined on the basis of the measurement results obtained.The measurements showed that the deviation of the translation vector did not significantly changeas the measurement distance increased, but the deviation of orientation data between differenttrackers increased significantly. Deviation in the translation vector increased as the distancebetween trackers increased, but deviation in orientation did not change significantly
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    Solid state phenomena Vol. 144 (Sept. 2008), p. 208-213 
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    Topics: Physics
    Notes: In modern engineering environment all information about product is stored in the PDM(Product Data Management) system. These systems allow enumerated configurations of product byusing mechanisms of BOM or versioning. However problems arise when product has a largenumber of configurations that are updated frequently. This is common situation in market ofconsumer goods.In the present paper this issue is addressed by extending an engineering configuration concept.An initial idea of engineering configurator is to have a product defined by generic BOM with allpossible components. The BOM also includes a set of constrains, that define valid combinations ofcomponents. However it is difficult to maintain such generic BOM. This paper proposes an idea ofBOM decomposition into simple and manageable units belonging to single product space.Decomposition is also performed in the domain of constrains. Configuration problem is split intoindependent sub-problems, which could be delegated to different engineers to work on, or to domaintenance. The resultant structure is easy to comprehend for engineer, because it follows anatural way of thinking during product design. Therefore, changes in configurations could be donemuch faster, less time is spend for verifications
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    Solid state phenomena Vol. 141-143 (July 2008), p. 451-456 
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    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The effect of processing parameters on the semi-solid microstructure has beeninvestigated in the course of semi-solid slurry preparation of A356 Al alloy by ultrasonic vibrationmethod. The A356 melt in temperature of 630660°C was poured into a special metal cup, andexposed to ultrasonic vibration at 20 kHz or isothermal holding for a certain time after vibration.The results show that the semi-solid slurry with primary α-Al crystals smaller than 90 μm and anaverage shape coefficient F S (SF was defined as SF4 A/L2P) above 0.5 could be prepared byultrasonic vibration for a time less than 144 s. In the isothermal holding period after a short time ofultrasonic vibration, the average particle diameter increased with the increase of holding time, butF S decreased at first, and then increased a little. It was discovered that ultrasonic vibration is a goodmethod to prepare semi-solid slurry with fine and relatively round primary crystals due to cavitationand acoustic streaming effects
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    Solid state phenomena Vol. 141-143 (July 2008), p. 457-461 
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    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Semi-solid metal forming (SSM) has been recognized as a new forming technology, whichis different from the present metal forming methods. Basic research on SSM has been put intooperation and a number of SSM techniques have been widely applied in industry. In the application ofSSM technique, at present, it is mainly used to produce the low melting point alloys such as Al-base,Zn-base and Mg-base alloys, but the high melting point alloys, for example steels as the most widelyuseful metal are not extensively studied and applied. In the present work, the electromagnetic stirringmethod was used to prepare semi-solid slurry of spring steel–60Si2Mn and stainlesssteel–1Cr18Ni9Ti. At the same time, spring steel–60Si2Mn and stainless steel–1Cr18Ni9Ti weredirectly rolled into thick strips in the semi-solid state (Rheo-rolling). It is aimed at studying themicrostructure and properties of the strips to establish the feasibility of rheo-rolling for the productionof the steel strips. According to the present research work, it has been shown that rheo-rolling processcombines the casting and hot rolling into a single step for near net-shape production, compared withthe conventional hot-rolled metallurgical process. Besides being such a cost-effective process,rheo-rolling process possesses irregular crystal grains such as rosette-type primary crystals in themicrostructures because of sufficient agitation during solidification. The overall homogenization ofthe macrostructures in the whole part of steel ingot can be achieved
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    Solid state phenomena Vol. 144 (Sept. 2008), p. 140-144 
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    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The formation of borides in an Al–3 wt.% B alloy produced from reaction betweenaluminium and boron oxide (B2O3) has been investigated. Melting and cooling experiments werecarried out to explore the growth characteristics of aluminium boride crystals. During heating upto1300 oC boron dissolved into molten aluminium and subsequently cooled to form solid aluminiumborides in the aluminium matrix. At room temperature boride particles was identified as AlB2.Although, AlB12 phase is the first phase to form directly from the Al-B liquid above 1000 oC whichtransforms to stable AlB2 crystals by a peritectic reaction during cooling. Scanning electronmicroscope (SEM) and X-ray diffraction (XRD) techniques were employed. Results showed thatthe shape and distribution of the borides are dependent on the cooling conditions of the liquid Al-Balloy
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    Notes: Ever since copious nucleation was shown to be an efficient, cost effective method for producingsemi-solid slurry, many processes have been developed to take advantage of the cost savingsinherent in this method of slurry production. Despite great advances in various aspects of semi-solidprocessing, the cost competitive nature of the industry, most noticeably the auto industry, hasprevented a wider adoption of semi-solid casting technology. This research aims to realize a moreindustrial appealing process by combining the synergistic benefits of semi-solid casting technologywith metal matrix nanocomposite (MMNC) technology, thus creating higher value products withsuperior properties cost-effectively. To do this, a process that produces a semi-solid slurry thoughthe nucleation catalysis induced by nanoparticle additions as small as 1 wt. % to alloys is proposedand the results are presented in this paper. Examination of the potential for nano-scale inoculants tocatalyze nucleation of solidification showed that despite their small sizes, inoculants on the scale oftens of nanometers are capable of catalyzing nucleation in the zinc and aluminum alloys studied.Employing the differential scanning calorimetry (DSC), differential thermal analysis (DTA), anddroplet emulsion techniques with nanocomposite samples showed a significant reduction inundercooling owing to the homogeneous distribution of nanoparticles by ultrasonic mixing and thepotency of those nanoparticles to catalyze nucleation. Comparison of undercoolings betweendifferent types of nanoparticles, such as silicon carbide (SiC), gamma and alpha alumina (Al2O3),and titanium carbide (TiC), to relative potencies predicted by minimum lattice disregistry showed astrong correlation. Results were also examined in light of free growth and nucleation controlledgrain initiation. For nanoparticles predicted to be potent nucleation catalysts by lattice disregistry,the undercoolings observed fell into the free growth controlled grain initiation regime
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    Solid state phenomena Vol. 141-143 (July 2008), p. 499-504 
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    Topics: Physics
    Notes: The effect of reheating to the semisolid state (soaking treatment) on the microstructureevolution of the A356 aluminum alloy prepared by ultrasonic melt treatment was studied in thispaper. The results showed that in general the longer the soaking process the larger and the moreround the grains obtained. Higher roundness occurs at shorter soaking times in the fine-grained ascastsamples, and at longer times in the inhomogeneous or the coarser-grained as-cast structures.The optimum thixotropic condition (high roundness, 0.72, and small globule sizes 〈 90 μm) areachieved after 5 min. soaking in the samples treated by UST at 623 and 620oC, which is the typicalsoaking time dictated by the industrial practice in SSM. The amount of entrapped eutectic asobserved after soaking treatments is uniquely very small, suggesting that the UST-treated ingots willhave better formability in the semisolid state. The growth rate constants are substantially low: in theorder of 479-748 μm3/s. These growth rate constants are much lower than those reported for MHDcastA356 ingots. The growth rates of the samples produced by UST in the liquid state (i.e., 626,623 and 620oC. Note that liquidus temperature is 619oC) are lower than those of the samples treatedin the semi-solid temperatures, i.e., 617 and 614oC. The Ostwald ripening is most likely thedominant growth mechanism in the UST-treated samples during the soaking treatments. Theseresults reveal the feasibility and competence of UST as a potential route for thixotropic feedstockproduction
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    Solid state phenomena Vol. 141-143 (July 2008), p. 511-516 
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    Topics: Physics
    Notes: The semi-solid forming (SSF) of aluminum alloys offers many advantages overconventional casting processes. Nevertheless, the semi-solid forming is still far from its fullcommercial potential and mainly used in specific niche markets. The market positioning requiressimple, low cost, and versatile SSF processes that are capable of processing a wide range of alloycomposition including wrought alloy compositions. However, wrought alloys must be adapted toobtain the desired semi-solid processing ability and proper mechanical properties. The processing ofthese attractive alloys with the SEED process offers the possibility to better target specificapplications and customers’ needs. In the present paper, the alloy development of AA-6061 aimingto minimize the hot tearing propensity during forming process is reported. An overview of theindustrial SEED process used to produce the semi-solid AA-6061 feedstock is presented. Themechanical properties of the cast parts subjected to a specific heat treatment were evaluated. As partof the joint effort between Alcan International Limited and the National Research Council ofCanada (NRC), the fatigue results obtained from the semi-solid AA-6061 die cast parts will be alsoreported
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    Solid state phenomena Vol. 141-143 (July 2008), p. 523-527 
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    Topics: Physics
    Notes: This paper deals with the examination of the influence of alloying elements on thethixoformability of a Cr steel. It focuses on the liquid fraction curves of different Cr steels withmodifications of composition. The effect of composition modifications was observed. The solidfraction versus temperature has been obtained by a thermodynamics software (MTData) and byDifferential Scanning Calorimetry (DSC), limited to low heating rates. MTData permits to obtaininformation on the influence of alloying elements, with the advantage of the possibility to changethe chemical composition very easily. The DSC tests determine the influence of the heating rate onthese curves
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    Solid state phenomena Vol. 141-143 (July 2008), p. 529-534 
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    Topics: Physics
    Notes: The growing importance of Al-Sn based alloys for producing self lubricating bearingmaterials in automotive industries necessitates the development of new alloys for improvedperformance. The recent thermodynamic work by Schmid-Fetzer at Clausthal University ofTechnology predicted that the addition of Cu to the binary Al-Sn system makes the miscibility gapstable. With the guidance of the calculated phase diagram, experimental investigations wereconducted on the ternary Al-Sn-Cu system to understand the solidification behaviour of thisimmiscible system under intensive forced convection. The experimental focus was to investigate theeffects of shear rate, shearing temperature and cooling rate on the solidified microstructure
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    Solid state phenomena Vol. 141-143 (July 2008), p. 517-522 
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    Topics: Physics
    Notes: The semisolid processing technology is not widely used due to the high cost of raw materialand the equipment it requires. New low-cost raw materials and processes could be the key to expandthe use of this technology. This paper describes an initial effort to develop new Al-Si-Mg in terms ofraw material production and processing. The morphological evolution of all the alloys produced wascharacterized during their reheating to the semisolid state at 45 and 60% solid fraction, as well as thesemisolid behaviour in terms of viscosity versus shear rate. The adaptation of the semisolidtechnology to the thixoforming process via eccentric press was tested using an equipment up to 25tons. This type of equipment is not commonly employed in this kind of processing. Results indicatethat alloys with low silicon content, e.g., 2 or 4wt%Si, behave similarly to alloys with 7wt%Si, whichare normally used in the thixoforming process, with a viscosity of about 2 * 105 Pa.s. The semisolidbehaviour of low silicon alloys indicates the potential expansion of the range of raw materials for thisapplication. Thixoforming of semisolid materials in an eccentric press appears to be a very promisingtechnology, yielding parts that, despite their simplicity and restricted shape, display a very good finalmechanical behaviour
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 57-62 
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    Topics: Physics
    Notes: Skutterudite materials have received great attention because their promising propertiesfor thermoelectric (TE) applications. Among the family of skutterudites, CoSb3 has been intensivelyinvestigated due to its large electrical conductivity and Seebeck coefficient. However, its thermalconductivity is too high to make it an effective TE material. Nanostructuring of CoSb3 has thedesirable effects of reducing its lattice thermal conductivity as the point imperfections or grainboundaries can scatter phonons (heat carrier) more effectively than electrons (charge carrier). In thisstudy, nanostructured CoSb3 was synthesized by solvothermal routes using CoCl2·6H2O and SbCl3as precursors dissolved in anhydrous ethanol with the reaction temperature kept at 240°C. Inaddition to the CoSb3 phase, other Co-Sb compounds were also formed during the reaction process.In this paper, we investigated the effects of processing parameters, such as concentration ofCoCl2·6H2O, SbCl3 and NaBH4 in ethanol and thermal duration of solvothermal synthesis, on theyield of CoSb3 phase
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 67-74 
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    Topics: Physics
    Notes: PLZT9/65/35 thick films were prepared from the solution containing PVP360(polyvinylpyrrolidone, with average molecular weight of 360000). With the solutions, the criticalthickness of a single PLZT layer could increase to ~624nm compared with 77nm-thick filmsprepared without PVP360. Furthermore, by adding 20~35% excess of Pb to the precursor solutions,the nano-porous rosette-like structures and a small amount of pyrochlore remnant, which werefound very common in the PVP-modified films, could be eliminated. 35% Pb excess was also foundto initiate liquid-phase sintering, leading to dense and crack-free films. The effect of Pb excess onthe rosette removal and densification behavior of the films was discussed. Moreover, the optical andelectrical properties of the PLZT films with 35% Pb excess were also studied
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 75-82 
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    Topics: Physics
    Notes: Thermoelectric (TE) materials are attracting renewed attention for clean energyconversion. Reducing the dimension of materials to 2D/1D (e.g. thin film and nanowire) is onemajor approach to achieve high figure of merit (ZT) in the existing TE materials system.Electrodeposition has been widely used in fabricating various low dimensional TE materials.However, electrodeposition behavior of CoSb3 skutterudites is rarely reported. In this work, wereport the co-deposition behavior of cobalt and antimony in citric based solutions byelectrodeposition. The effects of deposition potential and concentration of cobalt and antimonycontaining precursors were studied. The focus of the study will be on the crystalline properties andchemical composition of the deposited films
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 93-98 
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    Topics: Physics
    Notes: Ceramic composite armour in general utilises a front layer of dense ceramic, typicallybacked by a second layer of metal. Thereby creating a sharp interface that is the weakestlink within the material system and would result in cracking of the ceramic prematurely andhence not able to provide the requisite protection. One promising possibility has been foundis the use of functionally gradient materials as armour materials. In such materials, the highhardness of ceramics is combined with the ductility of metals. Laboratory scaleexperiments were being performed to exhibit the potential of this material in terms ofphysical and mechanical properties. A comparison was made with the current ceramicarmour system and it was found that the new material system had better ballistic properties
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 109-114 
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    Topics: Physics
    Notes: In the present paper, effects of through-the-thickness stitching of delaminated glass/epoxycomposite laminates with two different types of aramid threads, Kevlar® and Twaron® threads, on thebuckling loads are studied. The buckling loads are predicted based on the Southwell, Vertical displacementand Membrane strain plot methods from the experimental data. Flexural modulus of the stitched andunstitched glass/epoxy composite laminates, knot tensile strength of Kevlar® and Twaron®stitching threads are obtained experimentally. From the Southwell, Vertical displacement andMembrane strain plot methods it is observed that stitching either by Kevlar® or Twaron® threadsis effective in improving the buckling strength of glass/epoxy composite laminates when thedelamination length is greater than 0.5L, L is the length of the laminate
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 99-108 
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    Topics: Physics
    Notes: Fiber reinforced polymer composites are generally known to possess highstrength and attractive wear resistance in dry sliding conditions. The behaviour of suchcomposites performing in abrasive wear situations needs a proper understanding. Hence,in the present work of the three-body abrasive wear behaviour of two dimensional stitchedcarbon fabric, E-glass woven fabric and three dimensional E-glass woven fabric reinforcedvinyl ester composites was investigated. Three-body abrasive wear tests were conductedusing rubber wheel abrasion tester (RWAT) under different abrading distances at twoloads, wherein the wear volume loss were found to increase and that of specific wear ratedecrease. The results indicate that the type of fabric in vinyl ester have a significantinfluence on wear under varied abrading distance/loads. Further, it was found that carbonfabric reinforced vinyl ester composite exhibited lower wear rate compared to E-glasswoven fabric reinforced vinyl ester composites. The worn surface features, as examinedthrough scanning electron microscope (SEM), show higher levels of broken glass fiber intwo dimensional glass woven fabric reinforced vinyl ester composite compared to carbonfabric and three dimensional glass fabric reinforced vinyl ester composites
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 115-124 
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    Topics: Physics
    Notes: Traditional sandwich structure consists of two face sheets and a core. With an internalsheet inserted into the core, a two-core sandwich structure is then formed. Two-core sandwichstructures with composite laminated face sheets and a thin internal sheet subjected to low velocityimpact are studied in this paper. Local displacement of the core under the point of impact isinvestigated. Simulated results show that the local displacement of the core along the direction ofthe impact has been decreased significantly by introducing the internal sheet into a traditional singlesandwich structure and by reducing the space between the internal sheet and the impacted face sheet.Shear deformation in the cores of a two-core sandwich structure is also investigated and attention isfocused on shear strains on interfaces between face/internal sheets and the cores. Results furthershow that strain levels in selected elements at the interested interfaces depend upon locations of theselected elements and arrangements of the internal sheet
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 125-132 
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    Topics: Physics
    Notes: In this paper, the local approach based on the Weibull stress criterion was used toinvestigate the interfacial fracture behavior between LX88A coating and Q345 steel. LX88A coatingwas deposited by high velocity electric arc spraying technology (HVAS). The finite element method(FEM) was used to analyze the stress-strain fields of the coating specimen which consisted of threedifferent specimen geometrics or modes of loading. It was found that the Weibull stress for allspecimen geometries was almost identical under the same fracture probability when the interfacialfracture initiation occurred for different specimen geometries. It showed that the geometrydependence on the interface brittle fracture toughness data can be reduced through application of thelocal approach, and the local approach can be used to describe the interfacial fracture behavior
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 133-138 
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    Topics: Physics
    Notes: The ternary nitride (Zr,Ti)N thin films were grown on silicon substrates by ion-assisteddual d.c. reactive magnetron sputtering technique. The substrates were exposed to ion bombardmentwith varying kinetic energy in the range of 3-103 eV under N/Ar ratio of 1:3. The (Zr0.6Ti0.4)N wasformed at all growth conditions. X-ray diffraction measurement indicates the presence of (Zr,Ti)Nsolid solution with (111) and (200) preferred orientations. The (200) orientation is only presentwhen the films are grown at ion bombardment energies higher than 33 eV. Optimum conditions forfilm growth produced hardness in the range of 27-29 GPa
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    Solid state phenomena Vol. 136 (Feb. 2008), p. 139-144 
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    Topics: Physics