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1
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Processing Induced Change οf Thermal Transport Properties οf NiTi-Shape Memory Alloy

100%
Gibkes J., Bein B., Pelzl J., Wieck A., Frenzel J., Eggeler G., Delgadillo-Holtfort I., Chirtoc M.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6A
A-97-A-101
EN
Photothermal radiometry was applied to investigate the influence of a rolling process on the thermal properties of NiTi foils. The thermal diffusivity and thermal effusivity of the foils were determined at room temperature from the frequency variation of the photothermal signals in thermal transmission. Measurements were conducted on unrolled, rolled and thermally annealed samples. The thermal diffusivity and thermal effusivity are found to decrease considerably on rolling which is attributed to the influence of the rolling induced lattice defects.
2
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Crystal Plasticity Treated as a Quasi-Static Material Flow through Adjustable Crystal Lattice

100%
Kratochvíl J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
482-484
EN
Considering high pressure torsion experiments as a motivation, plastic behavior of crystalline solids is treated as a highly viscous material flow through an adjustable crystal lattice. Instead of the traditional decomposition rule considering the deformation gradient as a product of the elastic and plastic parts, the proposed model is based on its rate form: the velocity gradient consists of the lattice velocity gradient and the sum of the velocity gradients corresponding to the slip rates of individual slip systems; the slip strains themselves are not defined in the model. The geometrical changes caused by material flow and the slip strains can be specified a posteriori. Crystal lattice distortions are measured with respect to a lattice reference configuration. In an adopted rigid plastic approximation the lattice distortions are reduced to rotations. Constitutive equations incorporate non-local hardening caused by close range interactions among dislocations.
3
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Creep Deformation of Intermetallic TiAl-Based Alloy

100%
Lapin J., Staneková H.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
453-456
EN
In the present work, the creep deformation behaviour of a new cast intermetallic Ti-46Al-8Ta [at.%] alloy is analysed. Constant load tensile creep tests were performed at initial applied stresses ranging from 200 to 400 MPa in the temperature range from 973 to 1073 K. The measured creep deformation curves are analysed and the observed deviations from calculated curves are discussed based on microstructural changes observed in the studied alloy during creep. The kinetics of creep deformation are evaluated in terms of the true activation energy for creep and the stress exponent. Creep damage initiation and propagation leading to the fracture of the creep specimens are characterized as functions of the applied stress and temperature.
4
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A Research on Structured Analysis of Biomaterial of Dental Implant in Computer Aided Biomechanical Engineering Modelling

100%
Karaçalı Ö.
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vol. 125
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issue 2
186-188
EN
The research explained in this paper is about the mechanical principle applications on regulated form and function, forces, motion of teeth and dental implant - influencing the implant length and bone quality - in biomechanics engineering modeling in dentistry. The non-linear finite element method was employed as an advanced computer technique of structural stress analysis tool for biomechanics modeling using mechanical, mathematical, and biological definitions and concepts. A finite element model of dental implant with accurate geometry and material properties was developed to make realistic investigations on the implant biomaterial properties and mechanical behavior of new dental implant. The finite element models with non-linear contact elements were used to simulate an interface fixation within the implant system and the sliding function of the non-rigid connector. This research showed that implant design influences force transmission characteristics in peri-implant bone and mechanical signals affect bone tissue differentiation. Hence, it is important to control biomechanical loads on dental implants to maintain osseointegration and to promote early bone-implant interface healing. The results of this analysis are helpful for implant biomaterial selection and design for clinical interest.
5
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Modification of Microstructure and Properties of Extruded Mg-Li-Al Alloys of α and α+ β Phase Composition using ECAP Processing

100%
Dutkiewicz J., Rusz S., Maziarz W., Skuza W., Kuc D., Hilser O.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1303-1306
EN
Two magnesium based alloys containing 4.5 wt% Li and 1.5 wt% Al (alloy 1) and 9 wt% Li and 1.5 wt% Al (alloy 2) were cast under argon atmosphere and hot extruded at 350°C. Microstructure of alloy 1 consisted of hexagonal α phase of average grain size 20 μm and small aluminum rich precipitates being the most probably AlLi₂Mg phase. Alloy 2 in the extruded form consisted of lamellas of α+ β phases of thickness 5-20 μm and length above 100 μm. Significant grain refinement down to about 2 μ m was observed in one-phase hexagonal (hcp) alloy 1 after one pass of ECAP processing with helical component. Two-phase (hcp + bcc) alloy 2 showed higher non-homogeneity after the first equal channel angular pressing pass due to easier deformation of softer bcc phase, while both, α and β phases exhibited low angle grain boundaries. The hardness and the yield strength of the alloys were higher for alloy 1 (68 HV and 205 MPa, respectively) than those of alloy 2 (61 HV and 175 MPa). Subsequent equal channel angular pressing passes were performed at lower extrusion stress. The hardness of both alloys did not change significantly after subsequent equal channel angular pressing passes and revealed tendency to decrease. Two-phase alloy showed superplastic properties already after one equal channel angular pressing pass at 160°C with grain growth after superplastic tensile testing. Single phase hcp alloy did not show such properties after 1 pass, but after a few equal channel angular pressing passes it could be superplastically formed.
6
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Shape Change of Micelles Dragged with Constant Velocity as Addressed in Terms of Biolubrication Application

100%
Bełdowski P., Winkler R., Hładyszowski J., Jung S., Gadomski A.
Acta Physica Polonica A
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2016
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vol. 129
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issue 2
188-189
EN
Molecular dynamics simulations have been performed for a model of coarse-grained lipids in water. We try to establish structural properties of micelles when they are dragged past each other. The lipid-lipid and lipid-water interactions are taken from a coarse-grained model first introduced by Marrink et al. This work focuses on shape changes upon mutual interaction of micelles when dragged with constant velocity. We find that micelles can change their shapes from spherical to cylindrical regardless of the number of constituting lipids. We address this result toward understanding facilitated vs. obstructed lubrication of articular cartilage by synovial fluid at nanoscale level.
7
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Effect of Rolling with Cyclic Movement of Rolls Method on Structure and Hardness of CuCr0.6 Alloy

88%
Rodak K., Urbańczyk-Gucwa A., Radwański K.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1151-1154
EN
A novel severe plastic deformation method entitled rolling with cyclic movement of rolls was proposed to fabricate ultrafine grained CuCr0.6 copper alloy. The alloy in the solution treated conditions was processed by rolling with cyclic movement of rolls method by using process parameters as amplitude of rolls movement (A = 0.9 mm), frequency of rolls movement (f = 1 Hz), rolling reduction (ε_{h} = 50%) and rolling rate (v = 1, v = 2, v = 3 rpm). Light microscopy, scanning electron microscopy and a electron backscattering diffraction detector, and scanning transmission electron microscopy were used for microstructural characterization, and hardness tests for a preliminary assessment of mechanical properties. Quantitative studies of the average diameter of the subgrains d (μm) and the average diameter of the grains D (μm) were performed using the scanning electron microscopy/electron backscattering diffraction method. Misorientation angles were analyzed by the Kikuchi-line technique using TSL-OIM software. The results show that the samples underwent very high strain at the lateral areas and smaller at the central areas. As a result, the microstructure became heterogeneous and remained unchanged with change in compression rate. The transverse movement of rolls causes in the material significant effect of refining structure in peripheral areas of sample.
8
Content available remote

Controlling Mechanisms of Creep Deformation of New Air-Hardenable TiAl-Based Alloy

88%
Staneková H., Lapin J., Pelachová T.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
512-515
EN
In the present work, controlling mechanisms of creep deformation of a new cast air-hardenable Ti-46Al-8Ta [at.%] alloy was studied. Long-term constant load tensile creep tests combined with an abrupt change of the applied stress were performed at 700°C. The response of the alloy to a stress reduction is analyzed. Transient behaviour with zero creep before recommencing creep at a reduced load is related to possible creep deformation mechanisms. The dislocation microstructures are analysed for creep strains corresponding to the minimum creep rate by transmission electron microscopy. The controlling mechanisms of creep deformation are identified from the transient creep behaviour of the alloy during stress reduction, the stress exponent and dislocation microstructures observed after creep testing.
9
Content available remote

Kinetics and Mechanical Studies of Melaminium bis(trichloroacetate) dihydrate

88%
Kanagathara N., Marchewka M., Gunasekaran S., Anbalagan G.
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vol. 126
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issue 3
827-832
EN
The thermal decomposition kinetics of melaminium bis(trichloroacetate) dihydrate (MTCA) has been studied by thermogravimetry and derivative thermogravimetry techniques using non-isothermal experiments at three different heating rates 10, 15, and 20°C min^{-1}. Non-isothermal studies of MTCA revealed that the decomposition occurs in three stages involving dehydration and decomposition. The apparent activation energy (E_{a}) and the pre-exponential factor (ln A) of each stage of thermal decomposition at various linear heating rates are calculated using Flynn-Wall, Friedman, Kissinger, and Kim-Park method. A significant variation of effective activation energy (E_{a}) with conversion (α) indicates that the process is kinetically complex. The linear relationship between the A and E_{a} values is well established (compensation effect). Isothermal kinetics of thermal decomposition of MTCA was found to obey Avrami-Erofeev's (A4) and power law (P3) equations. In addition to the above, mechanical properties have been estimated by Vicker's microhardness test for the grown crystal.
10
Content available remote

Deformation Microstructures in Metallic Materials after Severe Plastic Deformation by Rolling with Cyclic Movement of Rolls

88%
Urbańczyk-Gucwa A., Bednarczyk I., Jabłońska M., Rodak K.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
975-978
EN
The results of the microstructure investigations of the pure Al and AlMg5 alloy and pure Cu and CuFe2 alloy after the application of severe plastic deformation implemented by rolling with the cyclic movement of the rolls are presented in this paper. The rolling with the cyclic movement of the rolls was carried out at values: the rolling rate v=1 rpm, the frequency of rolls movement f=1 Hz, the amplitude of rolls movement A=1.6 mm. Maximal values of rolling reduction at 6 passes was ε_{h}=80%. The structure of the these materials was analyzed using scanning transmission electron microscope. The quantitative studies of the substructure was performed with MET-ILO software, on the basis of images acquired on scanning transmission electron microscope. Performed substructure investigations showed that using the rolling with the cyclic movement of the rolls method can refine the microstructure of these materials to the ultrafine scale.
11
Content available remote

Acoustic Emission Study of the Deformation Behavior of Mg-Mn Alloys Containing Rare Earth Elements

75%
Illkova K., Dobroň P., Chmelík F., Letzig D., Bohlen J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
634-638
EN
Magnesium-manganese (Mg-Mn) based alloys with various chemical composition were processed by indirect extrusion at two different speeds. Alloying with Mn and rare earth elements has significant influence on the microstructure and on the texture of the alloys under investigation. This paper deals with the acoustic emission analysis of the deformation behavior of the extruded Mg-Mn alloys. The acoustic emission measurements were performed during the uniaxial tension and compression tests, and the obtained results are discussed with respect to the influence of rare-earth elements on the deformation behavior, particularly in terms of the activation of dislocation glide and twinning.
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