Wyniki wyszukiwania - Biblioteka Nauki

1

Practical Approach to Determining Dynamic Recrystallization Parameters Using Finite Element Optimization of Backward Extrusion Process

100%

Irani M. , Joun M.

Archives of Metallurgy and Materials

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2019

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tom Vol. 64, iss. 3

1175--1182

EN

In this study, we present a new method for obtaining the parameters of the Johnson-Mehl-Avrami-Kolmogorov equation for dynamic recrystallization grain size. The method consists of finite-element analysis and optimization techniques. An optimization tool iteratively minimizes the error between experimental values and corresponding finite-element solutions. Isothermal backward extrusion of the AA6060 aluminum alloy was used to acquire the main parameters of the equation for predicting DRX grain size. We compared grain sizes predicted using optimized and reference parameters with experimental values from the literature and found better agreement when the optimized parameters were applied.

2

Vistulian litho- and pedosedimentary cycles recorded in the Kolodiiv loess-palaeosol sequence (East Carpathian Foreland, Ukraine) determined by laser grain-size analysis

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Frankowski Z. , Łanczont M. , Boguckyj A.

Geological Quarterly

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2007

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tom Vol. 51, No 2

147-160

EN

In the Kolodiiv site, occur ring in the valley of the Sivka River (tributary of the Dniester River, Ukraine), Vistulian loess forms a subaerial cover over the Pleistocene terrace II. This terrace consists also of Eemian deposits (palaeosol or organic sediments) under lain by an alluvial succession of Wartanian age. The Kolodiiv 2 profile was studied in detail in order to reconstruct the conditions of loess accumulation, and consequently the climatic-environmental changes, that took place in this region. Eight lithogenetic units were distinguished in the profile: five trans formed by pedogenesis, and three loess beds. The main purpose of this study was to conduct a thorough examination of the units lithology, in particular the grain-size distribution, in order to investigate those loess-forming factors that are influenced by environmental changes (i.e. nature of source material, distance and dynamics of transport, type of deposition and redeposition, and hypergenetic processes). To achieve this, 174 samples were taken at 10 cm spacings along the profile, and the grain-size distributions of the deposits were determined using a laser method with 21 grain-size intervals examined in each sample and statistically analyses. Statistical analysis included: calculation of the main grain-size parameters (according to Folk and Ward's method), grain-size index (Ding etal., 1994) and also two statistical tests (Kolmogorov-Smirnov and Spearman rank correlation) applied in order to find differences or similarities between the grain-size distributions of the lithogenetic units distinguished. Stratigraphic variations in grain-size distribution reflect the division of the deposits into stratigraphic units previously arrived at. Mean values of grain-size index (Igs1) indicate that loess units 2, 4 and 6, differ from the palaeosol units 3, 5 and 7. The grain-size distribution of loess deposits in the Kolodiiv 2 profile varies, with marked dominance of the silt fraction, which indicates that these deposits were trans ported by winds of similar velocities carrying material a short distance from source. As the Aeolian conditions that formed loess deposits in the Kolodiiv 2 profile were generally stable, differences in the grain-size distribution of unit 2 representing the Upper Pleniglacial, suggest three cycles of loess deposition during that interval (with the middle cycle characterized by the most distinct, short-term oscillations in environmental dynamics). The variability in grain-size distribution in units 3-5, which to get her represent the Interplenivistulian (Middle Pleniglacial), reflects the climatic heterogeneity of this period. The palaeosol layers are diamictic. Higher values of grain-size indices show that all Upper Pleistocene palaeosol units of high (interglacial) and low (interstadial) rank are characterized by higher content of fine relative to coarse fraction the lowest mean values of grain-size index occur the soil unit 1, of Holocene age, suggests that this unit is probably a product of very recent, Neoholocene pedogenesis and does not represent the en tire Holocene epoch. The statistical tests results show, great similarity between loess units 2 and 4 (from the middle and upper part of the Pleniglacial), and also between palaeosol units 7 and 8 forming the Horohiv slpalaeosol unit (an Eemian palaeosol and interstadial palaeosols from the Early Vistulian). Further more, the individual nature of loess unit 6, deposited during the Lower Pleniglacial, seems to be associated with the climatic characteristics of this interval.

3

Badanie uziarnienia materiałów mineralnych 0,5 jim-100 mm

100%

Kamiński S. , Kamińska D.

Prace Naukowe Instytutu Górnictwa Politechniki Wrocławskiej. Studia i Materiały

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2009

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tom Vol. 125, nr 35

113-120

PL

Opracowano unikatowy system składający się z kilku analizatorów optyczno-elektronicznych z zastosowaną metodą Elsieve do pomiaru krzywej uziarnienia. W zależności od potrzeb każdy z analizatorów może mierzyć oddzielnie lub przy wykorzystaniu odpowiedniego oprogramowania uzupełniać zespół sit pomiarowych. Zespoły analizatorów przeznaczonych do pomiaru różnych frakcji uziarnienia materiałów mineralnych można łączyć w dowolny układ, a ich wyniki sumować. Przedstawione badania są zgodne z normą PN-EN ISO 14688-2:2006 - Badania geotechniczne. Oznaczanie i klasyfikowanie gruntów [5].

EN

Nowadays there are available technical possibilities to avoid manually difficult and work-consuming measurements of soil grain composition (e.g. sieve or sedimentation analysis). Such measurements can be replaced by optical-electronic instruments called EIsieve that are more common in Poland. The instruments are used for determination of grain-size distribution of gains and particles with diameter form 0.5 to 100 mm. Additionally there is possibility to determine shape of grains by 3D measurements and other graining parameters. The measuring system can consist of any number of instruments, connected with recording computer. Every computer of any measuring instruments is connected with the server. The created network allows to save measuring results at computer that works with particular instrument and at other computers. Such a system is used for measurements of soil and other geomaterials grain composition in laboratory at Institute of Hydrogeology and Engineering Geology, Faculty of Geology, University of Warsaw.

4

A new model for the effect of grain size on the elastic modulus of nanocrystalline materials

100%

Ali Shafiei M.

Materials Science Poland

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2009

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tom Vol. 27, No. 1

279--285

EN

A new model is developed for the structure of nanocrystalline materials. Based on the developed model, a new approach for investigating the effect of grain size on the elastic moduli of nanocrystalline materials is introduced. The predictions of the model are strongly correlated with the experimental results reported in the existing literature.

5

Depositional environment of sediments along the southern coast of Tamil Nadu, India

100%

Angusamy N. , Rajamanickam G. V.

Oceanologia

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2006

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tom No. 48 (1)

87-102

EN

Grain size studies of sediments from beaches in the region from Mandapam to Kanyakumari, divided into 5 sectors, indicate that sediments are unimodal to polymodal in nature, coarse to fine grained, moderately to poorly sorted, and positively-negatively skewed in character. The inference to be drawn from these studies is that the variation in sedimentological parameters is governed by fluvial input, wave dynamics, and littoral transport of the sediments. Bivariant plots show that the Mandapam and Kanyakumari sectors can be classified as beach environments, whereas the Tuticorin and Valinokkam sectors come under the influence of riverine environments and the dune environment in the Manappad sector. The CM pattern of all five sectors shows a clustered distribution of sediments in the PQ and QR segments, indicating a graded mode of deposition. Visher diagrams depict a wave shadow environment for the Mandapam sector, whereas the Valinokkam, Tuticorin and Manappad sectors show double saltation populations characteristic of beaches, and the Kanyakumari sector is characterized by a more truncated population characteristic of a plunge zone, which is a high-energy environment.

6

Microstructure and mechanical properties of selective laser melted 18Ni300 steel

100%

Liang Y. , Qing L. , Yu H. , Huili Z. , Yuxin W.

Materials Science Poland

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2022

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tom Vol. 40, No. 3

64--71

EN

The energy transfer process of selective laser melting (SLM) is highly complex. In this work, experiments were carried out to study the effects of SLM on the microstructure and mechanical properties of 18Ni300 martensitic steel. With the increase in laser power, the grain size of the cladding layer decreases and the microstructure becomes dense. The side hardness is higher than upper surface hardness, and the tensile strength and elongation both increase first and then decrease. When the laser power is 300 W and the scanning speed is 1,000 mm/s, the comprehensive mechanical properties are the best, as the tensile strength, microhardness, elongation at break, and elongation after fracture are 1,217 MPa, 37.5%, 37.6%, and 8.93%, respectively. EBSD (Electron Backscatter Diffraction) shows that columnar crystals grow along the growth direction (z direction) in XOZ and YOZ planes, and the grains show weak texture. There are many small-angle grain boundaries, and the grain sizes are <10 μm.

7

The Influence of Grain Size on the Mechanical Damping Behavior of Aluminum

100%

Jang H. , Choi K. , Shin J. , Bae D. , Choi H.

Archives of Metallurgy and Materials

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2019

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tom Vol. 64, iss. 2

475--479

EN

An understanding of the fundamental correlation between grain size and material damping is crucial for the successful development of structural components offering high strength and good mechanical energy absorption. With this regard, we fabricated aluminum sheets with grain sizes ranging from tens of microns down to 60 nm and investigated their tensile properties and mechanical damping behavior. An obvious transition of the damping mechanism was observed at nanoscale grain sizes, and the underlying causes by grain boundaries were interpreted.

8

Structural and textural evolution of zirconia nanocrystals induced by thermal treatment

100%

Adamski A. , Jakubus P. , Sojka Z.

Materials Science Poland

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2008

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tom Vol. 26, No. 2

373--380

EN

Nanometric tetragonal and monoclinic zirconia was synthesized from zirconyl chloride by the modified forced hydrolysis method. Phase transitions and morphological changes accompanying zirconia calcination in the temperaure range 600-1000 °C were studied by XRD, HR-TEM techniques and N2-porosimetry. Ageing of the amorphous hydrous zirconia at 100 °C for 48 h in the mother solution and its subsequent calcination at 600 °C for 6 h strongly favoured formation of single-phase tetragonal ZrO2 of the thermal stability enhanced by 250 °C. Influence of the calcination temperature on phase composition, grain size, grain boundaries and pore structure of the resultant ZrO2 material was analyzed.

9

Grain size measurement using a semi-automatic calculation tool

100%

Mernache F. , Sehisseh A. , Amrane A. , Hadji S. , Melhani Y. , Grine M. , Messai L.

Computer Methods in Materials Science

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2023

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tom Vol. 23, No. 1

27--34

EN

This paper focuses on the development of a semi-automatic calculation tool to measure the Mean Linear Intercept (MLI) grain size of ceramics and other materials. The calculation tool was first verified and validated by using a certified micro-ruler and literature microstructures. It was then used to investigate the grain growth of UO2 pellets elaborated under different conditions. The tool offers the advantage of accuracy as well as the ability to quantify microstructures obtained with poor image quality. The estimated measurement errors were found to be less than 1 μm. The developed tool, mainly for the purpose of time-saving, allowed us to follow the microstructure (grain size) evolution of the elaborated UO2 fuel with different additives.

10

Studies on the properties of suspensive polyvinyl chloride grains separated blowing away from fluid bed

100%

Wąsicki A.

Ars Separatoria Acta

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2002

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tom No. 1

149-159

EN

The studies on properties of polyvinyl chloride grains separated by blowing them away from a fluid bed at three air flow rates have been carried out. Seven trade batches of PVC obtained by suspensive method have been tested. Fikentscher number, thermal stability, plasticizer absorptivity, swelling in plasticizer as well as mixing with plasticizer have been determined. The differences in grain structure in the individual fractions were found in all the batches under study. These differences affect polyvinyl chloride properties (mainly swelling), plasticizer absorptivity and thermal stability.

11

Size Effect in Centrifuge Cone Penetration Tests

100%

Bałachowski L.

Archives of Hydro-Engineering and Environmental Mechanics

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2007

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tom Vol. 54, nr 3

161-181

EN

In-flight penetration tests with 12 mm mini-cone, were performed in the centrifuge of L.C.P.C. in Nantes, in two uniform quartz sands of different grain size. Stress level effect and particle size effect on the cone resistance were analyzed. Geometry and particle size effects were found for cone penetration in coarse sand especially at a penetration less than the critical depth. The irregularities on the profile of mini-cone penetration in coarse sand can be attributed to particle size effect. The evidence of geometry size effect was not very marked for the relatively narrow range of acceleration applied.

12

Quantitative Evaluation of the Microstructure and Mechanical Properties of Hot Rolled 23MnB4 Steel Grade for Cold Upsetting

88%

Kuc D. , Szala J. , Bednarczyk I.

Archives of Metallurgy and Materials

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2017

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tom Vol. 62, iss. 2A

551--556

EN

The article presents the results of tests of influence of the thermo-mechanical treatment parameters on the mechanical properties and microstructure of steel 23MnB4 for cold-upsetting. Measurements of the ferrite grains and pearlite colonies were conducted with the use of Met-Ilo program supplemented by additional procedures dedicated to structure analysis of ferritic-pearlitic steel. The process of rolling was conducted in simulation in semi-continuous finishing train arrangement with different temperature and cooling rate. Elaborated procedure of quantitative analysis of microstructure and conducted mechanical properties tests will be used during preparations of modified technologies of wire rod rolling to prepare products made of steel, the microstructure of which is characterised higher utility properties.

13

Zeroing of the osl signal as a function of grain size: investigating bleaching and thermal transfer for a young fluvial sample

88%

Truelsen J. L. , Wallinga J.

Geochronometria

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2003

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tom Vol. 22

1-8

EN

Previous studies have indicated that the OSL signal from coarser grain-size fractions might be more completely reset during fluvial transport. In this study we investigate whether this feature is real, or rather an artefact of thermal transfer effects that might affect finer grains more due to smaller thermal lag during heat treatment. Our experimental results obtained on three grain-size fractions (90-125, 180-212 and 425-500 mm) clearly show that better bleaching of coarser grains is not caused by differences in thermal transfer. On the basis of our results we advise selecting a coarse grain size for analysis when dating young fluvial deposits.

14

The equal channel angular extrusion process of multiphase high strength aluminium bronze

88%

Gronostajski Z. , Hawryluk M. , Kuziak R. , Radwański K. , Skubiszewski T. , Zwierzchowski M.

Archives of Metallurgy and Materials

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2012

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tom Vol. 57, iss. 4

897-909

EN

The aim of the research was to determine the deformation condition of ECAP process of multiphase high strength aluminium bronze BA1032. The studies have indicated that it is possible to deform multiphase aluminium bronze BA1032 in the ECAP process at a temperature of 400°C and die angle Φ=110°. The deformation of the bronzes at lower temperatures encounters some difficulties - cracks appear which make repeated ECAP impossible. The cracks appear on the top surface of the samples where it contacts the surface of the outlet channel. FEM simulations show that the largest plastic strains occur in this area. The proposed ECAP method of large plastic deformations as applied to the investigated aluminium bronzes makes it possible to obtain very strong refinement especially of eutectoid α+ γ2.

PL

Celem pracy było określenie warunków odkształcania w procesie ECAP wysokowytrzymałych wielofazowych brązów aluminiowych. Przeprowadzone badania wskazują na możliwość odkształcania wielofazowych brazów aluminiowych w tym procesie w temperaturze 400 °C dla kąta matrycy Φ=110°. Pewne trudności sprawia odkształcanie brązu w niższych temperaturach, gdyż pojawiają się wówczas pęknięcia, które uniemożliwiają prowadzenie procesu wielokrotnego przeciskania próbek przez kanał katowy. Pęknięcia pojawiaja sie na górnej powierzchni próbek w miejscu kontaktu z powierzchnią kanału wyjsciowego. Jak wykazuje symulacje MES w miejscu tym występują największe odkształcenia plastyczne. Zastosowana metoda dużych odkształceń plastycznych ECAP w przypadku badanych brazów aluminiowych pozwala uzyskać bardzo silne rozdrobnienie głównie eutektoidu α+ γ 2.

15

Deformation of Aluminium Bronze by HPT and ECAP Methods

88%

Gronostajski Z. , Skubiszewski T. , Zwierzchowski M.

Journal of Machine Engineering

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2014

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tom Vol. 14, No. 1

18--28

EN

Aluminium bronzes BA1032 having a multiphase microstructure, is low-deformable materials with strength close to that of high-strength steels. The influence of high-pressure torsion (HPT) and equal channel angular pressing (ECAP) on aluminium bronze structure was presented. The HPT method was found to be unsuitable for the processing of the investigated aluminium bronzes. The studies have indicated that it is possible to deform multiphase aluminium bronzes BA1032 in the ECAP process at a temperature of 400-500°C. The deformation of the bronzes at lower temperatures encounters some difficulties cracks appear which make repeated ECAP impossible.

16

A comparative Study on the Mechanical and Corrosion Properties of the ZM20 and ZM21 Alloys after Casting and Rolling

88%

Gören H. A. , Ünal M. , Türen Y. , Ahlatçı H. , Sun Y.

Archives of Metallurgy and Materials

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2022

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tom Vol. 67, iss. 4

1387--1394

EN

In this study, the effects of grain refinement and production methods on the corrosion, corrosive wear and mechanical properties of the as-cast and as-rolled Mg-2 wt.% Zn (ZM20) and Mg-2 wt.% Zn-0,51 wt.% Mn (ZM21) alloys were examined by using OM, XRD, SEM, hardness and uniaxial tensile test. Additionally, the potentiodynamic polarization, immersion corrosion test and corrosive wear properties of the ZM20 and ZM21 alloys were compared. According to the XRD results, MgZn and MgZn2 phases were found in the alloys and also MnZn3 phase occurred in the ZM21 alloy with the addition of manganese. Both during solidification forming nucleation points with the added manganese and during rolling the broken secondary phase particles distributed into the matrix prevented grain growth and led to the formation of a more refined structure. The tensile test results showed that the strength of the as-cast ZM21 alloys were better than that of the as-cast ZM20 alloys and further improvement in mechanical properties occurred with the rolling of the both alloys. The most superior hardness was found in the as-rolled ZM21 alloy. In the total 400-m reciprocal corrosive wear test in the 3.5% NaCl solution, the lowest mass loss was in the as-rolled ZM21 alloys. In the potentiodynamic corrosion test, the highest corrosion resistance was occurred by the as-cast ZM20 alloy.

17

The Influence of Grain Size on the Mechanical Damping Behavior of Aluminum

88%

Jang H. , Choi K. , Shin J. , Bae D. , Choi H.

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18

Study of phase transition in Bi3TiNbO9-BaBi2Nb2O9 ceramics

88%

Adamczyk M. , Kusz J. , Hofmeister W. , Zubko M. , Kozielski L. , Pilch M. , Bochenek D. , Wodecka-Duś B.

Archives of Metallurgy and Materials

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2016

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tom Vol. 61, iss. 3

1503--1510

EN

The subject of the paper is lead free bismuth layer structure oxides (1-x)Bi3TiNbO9-xBaBi2N2O9(x=0; 1; 2; 3 mol). The influence of Bi3TiNbO9/BaBi2Nb2O9 ratio on dielectric and structural properties was studied in a wide range of temperatures. Change in the ratio causes a decrease in the maximum value of dielectric permittivity and shifts the temperature of ε`max to low values, leading to linear decreasing of average grain size and linear increasing of ceramics density. These results indicate an augment of the packing degree and the participation of pores are significantly decreased with the increase of BaBi2Nb2O9compound intake. Moreover, for 0.7Bi3TiNbO9-0.3BaBi2Nb2O9 ceramics the dielectric phase transition is broadened and the properties characteristic for the ferroelectric relaxor appear.

19

Practical Approach to Determining Dynamic Recrystallization Parameters Using Finite Element Optimization of Backward Extrusion Process

88%

Irani M. , Joun M.

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20

Coastal processes of Central Tamil Nadu, India: clues from grain size studies

88%

Angusamy N. , Rajamanickam G. V.

Oceanologia

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2007

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tom No. 49 (1)

41-57

EN

The sediments of the beaches along the central coast of Tamil Nadu from Pondicherry to Vedaranyam were studied for their textural variation. 108 sediment samples collected from the low-, mid-, and high-tidal zones, as well as the berms and dunes of different beach morpho-units were analysed. The study area was divided into three sectors (northern, central and southern) on the basis of prevailing energy conditions and oceanographic parameters. The poorly sorted, negatively skewed, coarser sediments of the northern sector are indicative of denudational processes taking place there. Medium-to-fine, moderately-to-well sorted, positive-symmetrically skewed sediments dominate the central sector, probably as a result of the influence of palaeo-sediments deposited by rivers from inland as well as by waves and currents from offshore. Fine, poorly sorted, positive-symmetrically skewed sediments dominate the southern sector, highlighting depositional processes. Linear Discriminant Function Analysis (LDF) of the samples indicates a shallow marine environment origin for all the three sectors. These results show that reworked sediments, submerged during the Holocene marine transgression, are being deposited on present-day beaches by waves, currents and rivers in the study area.