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Wyświetlanie 1-15 z 20
Tytuł:
Acoustic Emission Study of Plastic Instabilities in AlSi1MgMn
Autorzy:
Molnárová, O.
Dobroň, P.
Chmelík, F.
Powiązania:
https://bibliotekanauki.pl/articles/1402161.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.40.Le
81.40.Lm
62.20.F-
46.32.+x
Opis:
The influence of the strain rate and heat treatment on the occurrence of plastic instabilities in a cast AlSi1MgMn alloy was studied. The samples were uniaxially loaded in compression at various strain rates and at room temperature. The tests were done with concurrent acoustic emission monitoring and the acoustic emission parameters are correlated to the microstructure and to the stress-strain curves in order to better understand the patterns of plastic deformation. All samples exhibited the Portevin-Le Chatelier effect of different types, dependently on the heat treatment and the applied strain rate. The occurrence of the Portevin-Le Chatelier effect is manifested by acoustic emission signals with high amplitudes. Statistical analysis of the acoustic emission signals shows the power-law probability distribution.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 801-804
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Activation Energy for Grain Growth of the Isochronally Annealed Ultrafine Grained Magnesium Alloy after Hot Extrusion and Equal-Channel Angular Pressing (EX-ECAP)
Autorzy:
Stráská, J.
Stráský, J.
Janeček, M.
Powiązania:
https://bibliotekanauki.pl/articles/1402085.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.fq
81.05.Bx
81.20.Hy
81.40.Lm
81.70.Bt
Opis:
Magnesium alloy AZ31 prepared by hot extrusion and 4 passes of equal-channel angular pressing (EX-ECAP) has ultra-fine grained microstructure with an average grain size of 900 nm. Grain growth is analysed using a general equation for the grain growth and an Arrhenius equation. The calculated value of the activation energy for grain growth differs with the annealing temperature. The fitted value of activation energy for grain growth in the intermediate temperature range (210-400°C) is in accordance with the results of other authors, but it is shown in this study that such value is abnormally low and physically meaningless. More real values of apparent activation energy in this temperature range were calculated from the model assuming a linear increase of activation energy with increasing annealing temperature. Result of this linear model of evolution of activation energy in the temperature range between 210-400°C is expressed by the interval estimation of apparent activation energy values. It is concluded that the evolution of apparent activation energy can be explained by a change in the mechanism underlying the grain boundary migration. In the low temperature range, the grain boundary diffusion is dominant since the material is ultra-fine grained, whereas at higher temperatures, the lattice self-diffusion is more important.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 578-581
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characterization of Hot Deformation of CW602N Brass
Autorzy:
Spigarelli, S.
El Mehtedi, M.
Cabibbo, M.
Powiązania:
https://bibliotekanauki.pl/articles/1402139.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.-t
81.05.Bx
81.20.-n
81.40.Lm
Opis:
Alpha brasses (in principle single-phase solid solution alloys containing less than 35% Zn) are usually processed by extrusion, forging or rolling. Although these materials are of widespread use, few detailed studies of the flow behavior of brass at high temperature are available. The hot workability of a CW602N brass (Cu-36.5%Zn-2%Pb) was thus investigated by torsion testing in the temperature range between 550 and 800°C, under equivalent strain rates ranging from 0.01 to 10 $s^{-1}$. The peak flow stress dependence on temperature and strain rate was described by the well-known Garofalo equation, with a stress exponent close to 4 and Q=220 kJ $mol^{-1}$. A considerably larger scatter of the experimental data was observed in the high temperature range. The detailed microstructural analysis of the deformed samples by scanning electron microscopy revealed substantial differences among the samples deformed in the low temperature regime and those torsioned at 750 and 800°C. These differences were analyzed and discussed to rationalize the different mechanical responses observed in the two hot-deformation regimes.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 726-729
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Creep Behavior of a Zirconium Alloy Processed by Equal-Channel Angular Pressing
Autorzy:
Sklenicka, V.
Dvorak, J.
Kral, P.
Svoboda, M.
Kvapilova, M.
Kopylov, V.
Nikulin, S.
Dobatkin, S.
Powiązania:
https://bibliotekanauki.pl/articles/1418491.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.40.Lm
62.20.Hg
81.05.-t
81.07.Bc
81.70.Bt
Opis:
A Zr-2.5 wt%Nb alloy was processed by equal-channel angular pressing and then tested under creep conditions at 623 K using a tensile stress within the range from 120 to 300 MPa. The results show conventional power-law creep with a stress exponent of n > 3 which is consistent with an intragranular dislocation process involving the glide and climb of dislocations. It is demonstrated that diffusion creep is not important in these tests. For comparison purposes, the experiments were conducted using both the unprocessed alloy and after processing by equal-channel angular pressing. It was found that under same testing conditions the measured minimum creep rates in the pressed alloy with ultrafine grain sizes were faster than in the same alloy in a coarse-grained unprocessed condition.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 485-489
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Creep Behaviour of a Zr-1 wt% Nb Alloy at Elevated Temperatures
Autorzy:
Kvapilová, M.
Kuchařová, K.
Kloc, L.
Sklenička, V.
Powiązania:
https://bibliotekanauki.pl/articles/1402075.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.40.Lm
62.20.Hg
81.05.-t
81.70.Bt
Opis:
This paper presents experimental data regarding creep behaviour of a Zr-1 wt% Nb alloy at elevated (623 K) and at high temperatures (873-1123 K) corresponding to loss-of-cooling situation of fuel cladding tubes for nuclear reactors. For an elaboration of methodological procedure and comparison purposes, the tensile creep tests were conducted using both constant stress and constant load over a wide range of applied stress. The substantial differences in the acquired creep data between constant stress and constant load creep testing were found especially at high stresses and large creep strain levels.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 548-551
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Critical View on the Creep Modelling Procedures
Autorzy:
Kloc, L.
Powiązania:
https://bibliotekanauki.pl/articles/1402073.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Hg
87.10.Kn
81.40.Lm
Opis:
Process of creep deformation is rather complex, consisting of many interconnected subprocesses, mainly: (i) the creep strain itself, based on dislocation mobility as well as grain boundary activity, (ii) development of dislocation substructure (work strengthening and dynamic recovery), (iii) development of phase structure (phase transformations, precipitation, particle coarsening, etc.), and (iv) nucleation and development of voids and microcracks, i.e. creep damage. The creep experiments are time consuming and expensive, moreover, it is not possible to make experiments under the service conditions of particular materials due to very slow creep strain, the process seems to be ideal field for computer modelling. The experimental data are obviously available for the steady conditions only, so the effects of varying conditions during startup or shutdown of the components can be described by modelling. The model of creep deformation is obviously based on the so-called "creep constitutive equation", which should describe the strain rate dependence on stress, temperature and some other variables. Nevertheless, the comprehensive physical description of all the above mentioned processes is still missing. This paper should illustrate the shortcomings of most "creep constitutive equations", confronting them to some experimental results on common structural materials under non-steady loading conditions.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 540-542
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Crystal Plasticity Treated as a Quasi-Static Material Flow through Adjustable Crystal Lattice
Autorzy:
Kratochvíl, J.
Powiązania:
https://bibliotekanauki.pl/articles/1418490.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.F-
81.40.Lm
83.50.-v
Opis:
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.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 482-484
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dependence of Order and Dynamics in Polymers and Elastomers under Deformation Revealed by NMR Techniques
Autorzy:
Stapf, S.
Kariyo, S.
Powiązania:
https://bibliotekanauki.pl/articles/2043553.pdf
Data publikacji:
2005-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Lg
82.35.Lr
76.60.-k
61.25.Hq
36.20.Ey
81.40.Lm
Opis:
Uniaxial stretching and swelling are considered as two limiting cases of deformations of elastomers. Under both conditions, the molecular dynamics is changed with respect to the behavior that describes the undisturbed, equilibrium elastomer. Particularly the spectrum of segmental motions, which reveals itself in the frequency-dependence of the longitudinal NMR relaxation time, is discussed in this study, but also order effects expressed via the dipolar coupling strength are investigated. For stretched elastomers, a significant change of the relaxation dispersion is found for three different types of rubber; it is a consequence of a change of the mode spectrum of segmental motions that becomes obvious at low frequencies (below 1 MHz at room temperature). In swollen elastomers, on the other hand, a cross-over towards a behavior expected for semi-dilute solutions is found, and a comparison to solutions of uncross-linked polymers reveals a significant effect of the cross-links only in the kHz range. A much more pronounced difference between elastomers and polymer solutions, however, is found from double-quantum encoded NMR measurements where the residual order introduced by the presence of permanent cross-links is maintained even in the presence of solvent.
Źródło:
Acta Physica Polonica A; 2005, 108, 2; 247-259
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Developing Superplasticity in Ultrafine-Grained Metals
Autorzy:
Kawasaki, M.
Langdon, T.
Powiązania:
https://bibliotekanauki.pl/articles/1402058.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Bx
81.20.Hy
81.40.Lm
Opis:
The processing of bulk metals through the application of severe plastic deformation provides an opportunity for achieving exceptional grain refinement with grain sizes typically lying in the submicrometer or even the nanometer range. Provided these small grains are reasonably stable at elevated temperatures, these ultrafine-grained metals will exhibit excellent superplastic properties when pulled in tension at elevated temperatures. Most ultrafine-grained materials have been produced using either equal-channel angular pressing or high-pressure torsion. This paper examines the results for superplasticity reported to date using metallic alloys processed by equal-channel angular pressing and high-pressure torsion, compares the experimental strain rates with those predicted using the theoretical model for conventional superplastic flow and then demonstrates the feasibility of preparing deformation mechanism maps that provide comprehensive information on the flow mechanisms.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 470-478
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dislocation Substructure Evolution during Hydrostatic Extrusion of Al-Mg-Si Alloy
Autorzy:
Chrominski, W.
Lewandowska, M.
Powiązania:
https://bibliotekanauki.pl/articles/1402087.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Bx
61.72.Ff
81.20.Hy
81.40.Ef
81.40.Lm
Opis:
Hydrostatic extrusion is a technique which allows to produce rods with ultrafine grains and unexpectedly enhanced mechanical properties caused by grain refinement. However, the mechanism of such a refinement is not fully understood at this stage. 6xxx aluminium alloys series are usually processed by extrusion. In this study, commercial 6082 aluminium alloy was extruded at ambient temperature in a cooled die in two stages to the true strain of ε =3.2. Such a processing results in a not fully refined microstructure which allows to study different stages of grain refinement. The texture, dislocation substructures and grain refinement were investigated using electron backscatter diffraction and transmission electron microscopy techniques. The results revealed that two main texture components are present in the extruded rods - ⟨111⟩ fiber texture and ⟨001⟩ recrystallized grains. Transmission electron microscopy inspection revealed dislocation structures that can be associated with different stages of plastic deformation according to the low energy dislocation structures hypothesis proposed by Kuhlmann-Wilsdorf.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 585-588
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Loading Mode on the Evolution of the Dislocation Structure in Magnesium
Autorzy:
Máthis, K.
Gubicza, J.
Csiszár, G.
Čapek, J.
Clausen, B.
Šíma, V.
Lukáš, P.
Powiązania:
https://bibliotekanauki.pl/articles/1402130.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Bx
83.85.Hf
83.60.La
81.40.Lm
Opis:
The evolution of the dislocation structure in randomly textured cast magnesium as a function of loading mode is studied using whole neutron diffraction pattern line profile analysis and elasto-plastic self-consistent modeling. Both the experimental results and the theoretical data indicate the onset of basal slip at low stresses and the key role of prismatic slip in the macroscopic yield. Dependence of the second-order pyramidal slip on the loading mode is revealed.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 700-703
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of Pre-Forming Process and PVC Foam Reinforcement on the Deformation Behavior of Aluminum Tube under Axial Loading
Autorzy:
Ekşi, S.
Kapti, A.
Genel, K.
Powiązania:
https://bibliotekanauki.pl/articles/1031785.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.-t
81.05.Bx
81.05.Rm
81.40.Lm
81.70.-q
81.05.Pj
Opis:
In this study, the effects of pre-forming and foam reinforcement on the axial compression behavior of circular thin-walled aluminum tubes were experimentally investigated. Compression tests were performed in a computer controlled test machine at the cross-head speed of 1 mm/s. Pre-forming has changed the folding behavior of tube and increased the energy absorbing capacity 1.26 times that of empty tube. The PVC reinforcement has increased the energy absorbing capacity 1.22 times. PVC reinforcement increases the stability of tube wall deformation; hence it positively affects the energy absorption. The energy absorbing capacity of pre-formed and PVC foam reinforced tubes increase approximately 1.4 times that of empty tube. It was however shown that the reinforcement and pre-forming had no significant effect on the maximum load.
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 875-878
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fabrication and Properties of the Photosensitive Anisotype $n-Cd_{x}Zn_{1-x}O$/p-CdTe Heterojunctions
Autorzy:
Khomyak, V.
Brus, V.
Ilashchuk, M.
Orletsky, I.
Shtepliuk, I.
Lashkarev, G.
Powiązania:
https://bibliotekanauki.pl/articles/1376075.pdf
Data publikacji:
2014-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.40.+w
73.40.Lq
81.15.Lm
Opis:
We have fabricated photosensitive anisotype $n-Cd_{x}Zn_{1-x}O$/p-CdTe heterojunctions by a deposition of $Cd_{0.5}Zn_{0.5}O$ film onto freshly-cleaved CdTe monocrystalline wafers using a radiofrequency magnetron reactive sputtering of a zinc-cadmium alloy target. Fundamental electrical properties of the heterojunctions were studied. Dominant mechanisms of a current transport were found. $n-Cd_{x}Zn_{1-x}O$/p-CdTe heterojunctions were photosensitive and were able to operate both in photovoltaic and photodiode modes.
Źródło:
Acta Physica Polonica A; 2014, 126, 5; 1163-1166
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
FEA of Plastic Flow in AZ63 Alloy during ECAP Process
Autorzy:
Kocich, R.
Kursa, M.
Macháčková, A.
Powiązania:
https://bibliotekanauki.pl/articles/1419003.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Bx
81.20.Hy
81.40.Lm
81.40.Pq
83.50.Ha
Opis:
Magnesium alloys based on Mg-Al-Zn system are very attractive materials in many industries due to their specific properties. One of common forming manners suitable for this kind of material is the application of severe plastic deformation method. This paper is focused on the deformation behavior of AZ63 alloy at equal channel angular pressing process in the temperature range of 250-320°C. For this purpose finite element analysis was used. Main attention was devoted to the influence of processing parameters on the material flow. Among other, changes of the flow during equal channel angular pressing in chosen regions of the pressed samples were monitored. As variables, temperature, friction coefficient, strain rate, φ-angle or back pressure application were chosen. The comparison of the material flow lines at different conditions shows the affecting of material flow. There are obvious considerable differences between regions adjacent to the inner radius and those adjacent to the outer radius. For example in the case μ = 0 the dead zone is delimited by the angle Ψp = 36°, while in the case of friction given by the coefficient μ = 0.04, the value of the angle was Ψp = 26.5°.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 581-587
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Press Ram Pulsation on Deep Drawability of Dual Phase Steel Sheet
Autorzy:
Olguner, S.
Tolga Bozdana, A.
Powiązania:
https://bibliotekanauki.pl/articles/1031199.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Hy
81.40.Lm
02.70.Dh
Opis:
A study of the influences of press ram pulsation on deep drawability of dual phase steel sheet is presented. General characteristics of deep drawing process, press ram pulsation technique and dual phase steels are briefly discussed. A finite element model is used to evaluate the influence of pulse motion profile of press ram on the thickness reduction of steel sheet and forming load. Commercial finite element software package DEFORM-3D is used for modelling and simulation of cylindrical cup drawing. The effects of superimposed low frequency vibrations of the press ram are investigated. Pulsation amplitudes of 0.5, 0.25, and 0.125 mm are created on the die with the corresponding pulsation frequencies of 5, 10, and 20 Hz. Finite element simulations are carried out using material model of dual phase (DP600) steel, that is one of the most widely used materials in automobile industry, in order to improve crash safety and fuel economy. Results obtained with press ram pulsation are compared with results for the conventional press ram motion and significant effect of proposed method is demonstrated.
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 742-745
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 20

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