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Tytuł:
Effect of SiO2 particle size and length of polypropylene glycol) chain on rheological properties of shear thickening fluids
Autorzy:
Antosik, A.
Głuszek, M.
Żurowski, R.
Szafran, M.
Powiązania:
https://bibliotekanauki.pl/articles/353056.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
shear thickening fluids
dilatant effect
onset of shear thickening
silica
polypropylene glycol
Opis:
Effect of SiO2 particle size and length of polypropylene glycol) chain on rheological properties of shear thickening fluids The rheological properties of shear thickening fluids based on silica powder of particles size in range 0.10 - 2.80 μm and poly(propylene glycol) of 425, 1000, 2000 g/mol molar mass were investigated. The effect of particle size and the length of the polymeric chain was considered. The objective of this study was to understand basic trends of physicochemical properties of used materials on the onset and the maximum of shear thickening and dilatant effect. Outcome of the research suggested that an increase in the particle size caused a decrease in dilatant effect and shift towards higher shear rate values. Application of carrier fluid of higher molar mass allowed to increase dilatant effect but it resulted in the increase of the initial viscosity of the fluid.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 3; 1511-1514
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Joining of Low-Carbon Steel Sheets with Al-Based Weld
Autorzy:
Boczkal, G.
Perek-Nowak, M.
Majewska, Z.
Powiązania:
https://bibliotekanauki.pl/articles/353774.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
resistance welding
Al/Fe interface
shear test
Opis:
The analysis of the connection steel/Al/steel made by resistance welding was performed. The used low-carbon steel had low content of carbon and other elements, aluminum was of 99.997 wt.% Al purity. Formation of various FeAl intermetallic phases found in the phase diagram depending on the duration of the process was analyzed. Two distinctively different types of structure depending on time of welding were observed: 1) hypoeutectic structure for samples processed for 5 s, and 2) eutectic structure for samples processed for 10 s and more. The shear test showed increase of mechanical properties of the connection for the samples welded 10 s.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 1; 37-42
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Rock Properties on Wear of M and SR Grade Rubber with Varying Normal Load and Sliding Speed
Autorzy:
Pal, S. K.
Rao, K. U. M.
Kumar, P. S.
Rajasekar, R.
Powiązania:
https://bibliotekanauki.pl/articles/356996.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
rock
rubber
wear
shear strength
surface roughness
Opis:
Rubbers are interesting materials and are extensively used in many mining industries for material transportation. Wear of rubber is a very complex phenomenon to understand. The present study aims to explain the influence of rock properties on wear of M and SR grade rubber used in top cover of conveyor belts. Extensive laboratory experiments were conducted under four combinations of normal load and sliding speed. The wear of both the rubber types were analyzed based on the rock properties like shear strength, abrasivity index and fractal dimension. A fully instrumented testing set up was used to study the wear of rubber samples under different operating conditions. In general, wear was higher for M grade rubber compared to SR grade rubber. Increase in shear strength of rocks depicts decreasing trend for the wear of M and SR grade rubber at lower load conditions. Moreover, a higher load combination displays no definite trend in both the rubbers. The strong correlation between the wear of rubber and frictional power for all rubber-rock combinations has given rise to the parameter A, which reflects the relative compatibility between the rubber and rock. Increase of Cerchar’s Abrasivity Index of rocks shows gradual enhancement in wear for M grade rubber in all the load and speed combinations whereas, it fails in SR grade rubber due to its higher strength. The wear of rubber tends to decrease marginally with the surface roughness of rocks at highest normal load and sliding speed in M grade rubber. However, the wear of M and SR grade rubber is influenced by the surface roughness of rocks.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 3; 1787-1793
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Crystal Lattice Rotations Induced by Shear Banding in fcc Metals Deformed at High Strain Rates
Autorzy:
Mania, Izabela
Paul, Henryk
Chulist, Robert
Petrzak, Paweł
Miszczyk, Magdalena
Prażmowski, Mariusz
Powiązania:
https://bibliotekanauki.pl/articles/2203719.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
shear bands
high strain rates
texture
SEM/EBSD
Opis:
In this paper, the microstructural and texture changes in polycrystalline CuZn30 alloy, copper, and AA1050 aluminium alloy have been studied to describe the crystal lattice rotation during shear bands formation. The hat-shaped specimens were deformed using a drop-hammer at the strain rate of 560 s-1. Microstructure evolution was investigated using optical microscopy, whereas texture changes were examined with the use of a scanning electron microscope equipped with the EBSD facility. The microstructural observations were correlated with nanohardness measurements to evaluate the mechanical properties of the sheared regions. The analyses demonstrate the gradual nature of the shear banding process, which can be described as a mechanism of the bands nucleation and then successive growth rather than as an abrupt instability. It was found that regardless of the initial orientation of the grains inside the sheared region, a well-defined tendency of the crystal lattice rotation is observed. This rotation mechanism leads to the formation of specific texture components of the sheared region, different from the one observed in a weakly or non-deformed matrix. During the process of rotation, one of the {111} planes in each grain of the sheared region ‘tends’ to overlap with the plane of maximum shear stresses and one of the <110> or <112> directions align with the shear direction. This allows slip propagation through the boundaries between adjacent grains without apparent change in the shear direction. Finally, in order to trace the rotation path, transforming the matrix texture components into shear band, rotation axis and angles were identified.
Źródło:
Archives of Metallurgy and Materials; 2023, 68, 1; 319--329
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructure and Mechanical Properties of an AZ91 Magnesium Alloy Processed through Backward Extrusion
Autorzy:
Chalay-Amoly, A.
Zarei-Hanzaki, A.
Fatemi, S. M.
Powiązania:
https://bibliotekanauki.pl/articles/353050.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
magnesium alloy
extrusion
mechanical properties
shear punch test
Opis:
A cast AZ91 magnesium alloy was processed via backward extrusion (BE) method at different temperatures of 250, 350 and 450°C. Metallography investigations were conducted at three different regions of BE-processed cup (wall, bottom and flow channel). The main feature observed at the wall of the BE cup was mechanical twins, the frequency of which was decreased by increasing the process temperature. Flow localization in the form of shear banding occurred within the flow channel at all deformation temperatures. The bottom of the BE-processed cup at 250°C exhibited coarse initial grains along with continuous network of eutectic phase at the grain boundaries. However, increasing the process temperature to 350 and 450°C led to the fragmentation of the γ-Mg17Al12 network down to the fine particles, where a considerable grain refinement was also traced particularly at 450°C. Furthermore, shear punch testing method was employed to evaluate the room temperature mechanical properties of the backward extruded specimens. The results show that BE-processed material would benefit from higher strength compared to the as-received material; however, the ductility follows different trends depending on the deformation temperature.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 1; 149-157
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Study on the Melting Temperature, Microstructural and Improved Mechanical Properties of Sn58Bi/Cu Solder Alloy Reinforced with 1%, 2% and 3% Zirconia (ZrO2) Nanoparticles
Autorzy:
Amares, S.
Durairaj, R.
Kuan, S. H.
Powiązania:
https://bibliotekanauki.pl/articles/2049682.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
SnBi solder
low melting temperature
microstructure
hardness
shear load
Opis:
This paper investigates the influence of 1%, 2% and 3% zirconia (ZrO2) nanoparticles to the melting, microstructural and mechanical properties of the Sn58Bi solder. Melting temperatures of 145.11°C, 140.89°C and 143.84°C were attained correspondingly for the 1%, 2% and 3% ZrO2 reinforced Sn58Bi solder. The microstructures especially the spacing between the lamellar structures of the Sn58Bi solder alloy was narrower for 1% ZrO2 added with Sn58Bi solder alloy. The highest and lowest hardness value of 32.28 HV and 27.62 HV was recorded for 1% and 2% ZrO2 additions respectively. Highest shear strength value was noted for the 3% ZrO2 added SnBi/Copper joint with 0.8712 kN, while the lowest value of 0.4380 kN noted for the 1% ZrO2 added SnBi/Copper joint. The presence of small-sized ZrO2 nanoparticles can be seen to be properly dispersed at the solder joint to increase the shear load at maximum joint stress.
Źródło:
Archives of Metallurgy and Materials; 2021, 66, 2; 407-418
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Deformation Mechanisms and Fracture of Ni-Based Metallic Glasses
Autorzy:
Lesz, S.
Griner, S.
Nowosielski, R.
Powiązania:
https://bibliotekanauki.pl/articles/353790.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
metals
transmission electron microscopy
scanning electron microscopy
fracture
shear bands
Opis:
The cracking of materials and fracture surface is of great practical and academic importance. Over the last few years the development of the fractography of crystalline alloys resulted in a useful tool for the prediction or failure analysis. Many attempts have been made to observe cracks using optical microscopy, X-ray topography and transmission electron microscopy (TEM). Of these techniques, the resolution of optical microscopy and X-ray topography is too poor. By contrast, the resolution of TEM is high enough for detailed information to be obtained. However, in order to apply TEM observations, a thin foil specimen must be prepared, and it is usually extremely difficult to prepare such a specimen from a pre-selected region containing a crack. In the present work, deformation mechanisms fracture surfaces of Ni-based metallic glass samples have been studied by specially designed experiments. In order to study the deformation mechanisms and fracture the Ni-based metallic glasses have been investigated in the tensile test. The structure and fracture surfaces after the decohesion process in tensile tests were observed using transmission electron microscope (TEM) and scanning electron microscope (SEM), respectively. The studies of structure were performed on thin foils. Moreover the investigated tape was subjected to a banding test. Then, the tape was straightened and the thin foil from the area of maximum strain was prepared. This thin foil sample was deformed before the TEM investigation to obtain local tears.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 2A; 791-796
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characteristics of Die-Attach Method by Sinter Bonding Using Ag-40Cu Mechanically Alloyed Particles
Autorzy:
Choi, Woo Lim
Lee, Jong-Hyun
Powiązania:
https://bibliotekanauki.pl/articles/355701.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
mechanical alloying
Ag-Cu
die-attach
sinter bonding
shear strength
Opis:
Ag and Cu powders were mechanically alloyed using high-energy planetary milling to evaluate the sinter-bonding characteristics of a die-attach paste containing particles of these two representative conductive metals mixed at atomic scale. This resulted in the formation of completely alloyed Ag-40Cu particles of 9.5 μm average size after 3 h. The alloyed particles exhibited antioxidation properties during heating to 225°C in air; the combination of high pressure and long bonding time at 225°C enhanced the shear strength of the chip bonded using the particles. Consequently, the chips sinter-bonded at 225°C and 10 MPa for 10 min exhibited a sufficient strength of 15.3 MPa. However, an increase in bonding temperature to 250°C was detrimental to the strength, due to excessive oxidation of the alloyed particles. The mechanically alloyed phase in the particle began to decompose into nanoscale Ag and Cu phases above a bonding temperature of 225°C during heating.
Źródło:
Archives of Metallurgy and Materials; 2019, 64, 2; 507-512
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of the strain path and the second phase particles on the microstructure and the texture evolution of the AA3104 alloy processed by ECAP
Wpływ schematu odkształcenia oraz cząstek drugiej fazy na rozwój mikrostruktury i tekstury stopu AA3104 przetwarzanego metodą wyciskania w kanale równokątowym
Autorzy:
Paul, H.
Baudin, T.
Brisset, F.
Powiązania:
https://bibliotekanauki.pl/articles/351090.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
ECAP
mikrostruktura
tekstura
stopy aluminium
microstructure
texture
shear band
aluminium alloy
Opis:
The effect of the strain path on the microstructure and the texture evolution of the severely deformed AA3104 aluminium alloy was investigated by a transmission electron microscopy (TEM) and a high resolution scanning electron microscopy (SEMFEG) equipped with the electron backscattered diffraction facility. A commercial purity material was deformed at room temperature via equal channel angular pressing up to 10 passes, following the routes A, BC, and C. A good quality billet after 10 passes was obtained only in the case of route C. In the case of route A and BC, macro-cracking appeared after 5 and 3 passes, respectively. Although the different routes led to differences in the microstructure of the billets, the global texture evolution turned out to follow nearly the same course. The TEM observations and the SEMFEG local orientation measurements allowed to identify the misoriented planar dislocation arrangements in all the samples. Their instability within some narrow areas led to the kink-type bands, which were precursors of the shear bands. The influence of the second phase particles on the deformation microstructure and the local texture depended on the particle size. Irrespective of the applied deformation routes, the large (>5 μm), not deformable second phase particles influenced the strengthening of the matrix by forming local distortions in their vicinity, whereas the fine dispersoids (∼50 nm) had a visibly unclear effect on the dislocation structures formed in the examined strain range.
W pracy analizowano wpływ zmiany drogi odkształcenia na ewolucję mikrostruktury i tekstury silnie odkształcanych próbek stopu aluminium - AA3104, wykorzystując techniki transmisyjnej (TEM) i skaningowej (SEMFEG) mikroskopii elektronowej. Materiał o czystości technicznej odkształcano w temperaturze otoczenia, w matrycy równo kątowej (ECAP) do 10-ciu przepustów, wg drogi A, BC oraz C. Wyniki prowadzonych analiz pokazują, że jedynie w przypadku drogi C uzyskano po 10-ciu przepustach dobry jakościowo wstępniak. W przypadku drogi A i BC po 5 i 3 przepustach, odpowiednio, pojawiały się obserwowane makroskopowo pęknięcia. Pomimo, że zróżnicowane drogi odkształcenia prowadzą do silnego zróżnicowania w obrazie mikrostruktury, ewolucja tekstury globalnej jest podobna. Obserwacje mikrostrukturalne prowadzone w skali TEM oraz pomiary orientacji lokalnych z wykorzystaniem techniki SEMFEG dokumentują formowanie się płaskich układów dyslokacyjnych, niezależnie od zastosowanego schematu odkształcenia. Dodatkowo obserwowana wewnątrz wąskich obszarów niestabilność tych struktur prowadzi do pojawienia się pasm ugięcia które są prekursorami pasm ścinania. Wpływ cząstek drugiej fazy na ewolucję struktury odkształcenia oraz zmiany w lokalnym obrazie tekstury w pobliżu cząstek, silnie uzależnione są od rozmiaru cząstek. Jednakże, niezależnie od zastosowanego schematu odkształcenia, duże (>5 μm) nieodkształcalne cząstki silnie determinują umocnienie osnowy w ich bezpośrednim sąsiedztwie, podczas gdy wpływ drobnych wydzieleń dyspersyjnych (∼50 nm) nie jest jasno zdefiniowany.
Źródło:
Archives of Metallurgy and Materials; 2011, 56, 2; 245-261
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Die Attachment Method on a Cu Finish by Pressure-Assisted Sinter Bonding in Air Using Cu Formate Paste
Autorzy:
Jo, Kyeong Hwan
Lee, Jong-Hyun
Powiązania:
https://bibliotekanauki.pl/articles/351336.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
die attach
Cu formate paste
sinter bonding
Cu finish
shear strength
Opis:
A paste containing Cu(II) formate rods was prepared, and characteristics of sinter bonding at 250°C under a pressure of 10 MPa were investigated to accomplish a high-speed die attachment for wide-bandgap power chips on Cu finish in air. Synthesisn of the plate-type Cu formate particles from CuO was accomplished through a wet reaction for 180 min. Cu, formed in situ in the bondline by pyrolysis of the formate during heating for the attachment, was sufficiently active to lead high-speed sintering within a carbon dioxide-hydrogen atmosphere derived from the pyrolysis, and the oxide layer on the Cu finish was reduced by the hydrogen. As a result, sinter bonding for 10 min formed a robust bonding with a shear strength approaching 27 MPa.
Źródło:
Archives of Metallurgy and Materials; 2020, 65, 3; 1057-1061
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructural Changes of the Nanostructured Bainitic Steel Induced by Quasi-Static and Dynamic Deformation
Autorzy:
Marcisz, J.
Burian, W.
Rozmus, R.
Janiszewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/351132.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nanostructured bainitic steel
dynamic deformation
adiabatic shear bands
transmission electron microscopy
Opis:
Changes in the microstructure of nanostructured bainitic steel induced by quasi-static and dynamic deformation have been shown in the article. The method of deformation and strain rate have important impact on the microstructure changes especially due to strain localization. Microstructure of nanostructured steel Fe-0.6%C-1.9Mn-1.8Si-1.3Cr-0.7Mo consists of nanometer size carbide-free bainite laths and 20-30% volume fraction of retained austenite. Quasi-static and dynamic (strain rate up to 2×102 s-1) compression tests were realized using Gleeble simulator. Dynamic deformation at the strain rate up to 9×103 s-1 was realized by the Split Hopkinson Pressure Bar method (SHPB). Moreover high energy firing tests of plates made of the nanostructured bainitic steel were carried out to produce dynamically deformed material for investigation. Adiabatic shear bands were found as a result of localization of deformation in dynamic compression tests and in firing tests. Microstructure of the bands was examined and hardness changes in the vicinity of the bands were determined. The TEM examination of the ASBs showed the change from the internal shear band structure to the matrix structure to be gradual. This study clearly resolved that the interior (core) of the band has an extremely fine grained structure with grain diameter ranging from 100 nm to 200 nm. Martensitic twins were found within the grains. No austenite and carbide reflections were detected in the diffraction patterns taken from the core of the band. Hardness of the core of the ASBs for examined variants of isothermal heat treatment was higher about 300 HV referring to steel matrix hardness.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 4; 2317-2329
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characteristics and Tensile-Shear Properties of Refill FSSW Joint Under Different Plunge Depths in 2060 Aluminum Alloy
Autorzy:
Wang, Yue
Chai, Peng
Powiązania:
https://bibliotekanauki.pl/articles/2049695.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
refill friction stir spot welding
aluminum alloy
defect characteristics
tensile shear properties
Opis:
Refill friction stir spot welding (refill FSSW) was used to weld 3.2-mm-thick 2060 aluminum alloy. Joint formation, defect characteristics and tensile-shear property were analyzed. Results show that keyhole can be completely eliminated under different plunge depths. However, defects such as void, unconnected welding, hook can be observed under the plunge depths of 3.4-4 mm.The size of the overall void initially increased and then decreased with the increase of the plunge depth, while the void was the smallest under the plunge depth of 3.4 mm. The unconnected defect at the lap interface gradually shrank a welding line from obvious crack. Different hook morphologies were observed under different plunge depths. The tensile-shear load of joint increased with the increase of the plunge depth and was up to the largest under the plunge depth of 4 mm. All the tensile-shear specimens fractured along the lap interface. Compared with the void, the unconnected defect had a greater influence on the tensile-shear property.
Źródło:
Archives of Metallurgy and Materials; 2021, 66, 2; 451-460
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stress and Strain Analysis and Microstructure of Al/Cu Clad Composite Fabricated by Cold Extrusion
Autorzy:
Junting, L.
Yahong, X.
Yongkang, L.
Jianyong, L.
Shuangjing, Z.
Powiązania:
https://bibliotekanauki.pl/articles/351206.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
aluminum/copper clad composite
cold extrusion
microstructure
critical shear strain
finite element method
Opis:
A five-zone describing model for extrusion of aluminum/copper clad composite was established. Stress and strain were also analyzed by finite element method. The distribution rules of grain size were researched by critical shear strain theory, and zoning phenomenon of grain size was discovered. The grain size of deformed aluminum material becomes gradually finer from center to the interface. The grain size is much fine and the critical shear strain reaches the maximum value in the interface. The grain size of copper material reduces gradually from center to both the interface and exterior surface, which is caused by the higher value of critical shear strain in the interface and exterior surface. The analysis results were verified by microstructure observation and mechanical properties test, indicating that the distribution of grain size for cold extrusion forming can be interpreted by critical shear strain theory.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 4; 1813-1818
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical Simulation of Turbulence Flows in Shear Layer
Symulacja numeryczna płynięcia turbulentnego w warstwie ścinanej
Autorzy:
Fortova, S. V.
Powiązania:
https://bibliotekanauki.pl/articles/352136.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
mathematical modeling
shear layers
energy cascade
turbulence
modelowanie matematyczne
warstwa ścinana
płynięcie turbulentne
Opis:
For various problems of continuum mechanics described by the equations of hyperbolic type, the comparative analysis of scenarios of development of turbulent flows in shear layers is carried out. It is shown that the development of the hydrodynamic instabilities leads to a vortex cascade that corresponds to the development stage of the vortices in the energy and the inertial range during the transition to the turbulent flow stage. It is proved that for onset of turbulence the spatial problem definition is basic. At the developed stage of turbulence the spectral analysis of kinetic energy is carried out and the Kolmogorov “-5/3” power law is confirmed.
W pracy dokonano analizy porównawczej rozwoju przepływu turbulentnego w warstwach ścinanych dla wielu problemów dotyczących mechaniki ośrodków ciągłych opisanych przez równania typu hiperbolicznego. Wykazano, że rozwój niestabilności hydrodynamicznych prowadzi do cyklicznych zawirowań podczas przejścia do stadium przepływu turbulentnego. Udokumentowano, że dla wyjaśnienia mechanizmu pojawienia się turbulencji kluczowe znaczenie ma przestrzenna analiza problemu. Przeprowadzono analizę widmową energii kinetycznej dla zaawansowanego stadium przepływu turbulentnego oraz potwierdzono wartość wykładnika “-5/3” w równaniu Kołmogorowa.
Źródło:
Archives of Metallurgy and Materials; 2014, 59, 3; 1155-1158
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Plastic Instabilities Induced by the Portevin - Le Châtelier Effect and Fracture Character of Deformed Mg-Li Alloys Investigated Using the Acoustic Emission Method
Autorzy:
Pawełek, A.
Piątkowski, A.
Wajda, W.
Skuza, W.
Tarasek, A.
Ranachowski, Z.
Ranachowski, P.
Ozgowicz, W.
Kúdela, Jr.
Kúdela, S.
Powiązania:
https://bibliotekanauki.pl/articles/353865.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
lightweight alloys
acoustic emission
fracture
Portevin-Le Châtelier phenomenon
twinning
dislocations
shear bands
Opis:
The results of the investigation of both mechanical and acoustic emission (AE) behaviors of Mg4Li5Al and Mg4Li4Zn alloys subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloys and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the relation between plastic flow instabilities and the fracture characteristics. There are discussed the possible influence of the factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries, interaction of solute atoms with mobile dislocations (Cottrell atmospheres) as well as dislocation pile-ups which may lead to the microcracks formation due to the creation of very high stress concentration at grain boundaries. The results show that the plastic flow discontinuities are related to the Portevin-Le Châtelier phenomenon (PL effect) and they are correlated with the generation of characteristic AE pulse trains. The fractography of broken samples was analyzed on the basis of light (optical), TEM and SEM images.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 2A; 897-904
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 24

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