Wyniki wyszukiwania - Biblioteka Nauki

1

Wstępne badania degradacji mechanicznej materiałów wkładek absorbujących energię uderzenia wykorzystywanych w hełmach strażackich

100%

Pieniak D. , Walczak A.

Zeszyty Naukowe SGSP / Szkoła Główna Służby Pożarniczej

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2017

|

tom Nr 61 (tom 1) (1)

121--135

PL

Do podstawowych funkcji hełmu strażackiego należy przechwycenie energii obciążenia zewnętrznego i jej rozproszenie w sposób bezpieczny dla strażaka ratownika. Wkładka absorpcyjna to drugi element, po skorupie, absorbujący energię uderzenia. Wykonana jest zwykle ze sztywnych materiałów porowatych, np. pianki poliuretanowej lub styropianowej. Wkładka często oddzielona jest od głowy wyłącznie cienką siatką, przez co podczas cyklicznego wkładania hełmu na głowę, w wyniku kontaktu, powstają cykliczne obciążenia eksploatacyjne. Ponadto w trakcie działań ratowniczo -gaśniczych, często dochodzi do niskoenergetycznych uderzeń hełmem, np. w przeszkodę w zadymionym pomieszczeniu. Cykliczne naprężenia ściskające, powstające w materiale wkładki, mogą powodować lokalne zmiany w strukturze materiału, np. lokalne zagęszczenie pianki w wyniku deformacji. W wyniku deformacji może zmienić się zdolność materiału wkładki do przenoszenia obciążeń krytycznych. W odniesieniu do materiału absorbera stawiane jest wymaganie, aby naprężenie przy uderzeniu nie przekraczało wartości granicznej, przy jednoczesnym uzyskaniu jak największej wartości pochłoniętej energii (jak największego pola pod wykresem naprężenie – odkształcenie). W obecnie wytwarzanych hełmach właściwość ta może być odmienna od charakteryzującej struktury hełmów użytkowanych przez kilka lat. Degradacja mechaniczna struktury materiału wkładki amortyzującej może prowadzić do pogorszenia właściwości absorpcyjnych. Dotychczas prowadzi się niewiele badań w tym kierunku. Jednakże jest to istotny problem, choćby z tego powodu, że uszkodzenia wkładki amortyzującej są trudne do wykrycia i zazwyczaj nie są podstawą do wycofania hełmu z eksploatacji.

EN

A basic function of firefighter’s helmet is to absorb the energy of external load and disperse it in a safe manner for a firefighter. The absorptive insert is a second component after helmet’s shell absorbing impact energy. It is usually made of a rigid porous material such as for example polyurethane or polystyrene foam. The insert is often separated from the firefighter’s head only with a thin mesh, thus due to a repeated insertion of the helmet, the cyclic operational loads occur. Additionally, during the rescue and firefighting operations, the low energy impacts with helmet occurs e.g. hitting an obstacle in a smoky room. The cyclic compressive stresses taking place in the insert material can cause local changes in the material structure e.g. local foam compaction due to deformation. As a result of the deformation, an ability of the insert material to transfer critical loads can be changed. With regards to the absorber’s material, it is required that tension on impact does not exceed critical value reaching at the same time the highest value of absorbed energy (the largest area under stress – strain graph). In nowadays produced helmets this property can differ from the structure of the older helmets in use. Mechanical degradation of insert material structure can lead to the deterioration of absorptive properties. So far, there are not many studies concerning that problem. However, it is a crucial problem even if by the reason of the fact that the damages of the insert are difficult to detect and usually are not the basis for the withdrawal of the helmets from the operational use.

2

Identification of Yield Point of Polymer-Based Composite Material in the Conditions of Increased Temperatures

100%

Arustamian A. , Sołek K. , Kalisz D.

Archives of Metallurgy and Materials

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2016

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tom Vol. 61, iss. 3

1561--1566

EN

Theoretical and practical research on the influence of temperature on mechanical characteristics of the composite material MM “Steel 1018” has been conducted. Both laboratory equipment used to measure of mechanical properties, the technique of material preparation and the experimental procedure were described. The analysis of the the obtained results revealed that with temperature increase the material yield point goes down.

3

Numerical approach in recognition of selected features of rock structure from hybrid hydrocarbon reservoir samples based on microtomography

100%

Kaczmarek Ł. D. , Zhao Y. , Konietzky H. , Wejrzanowski T. , Maksimczuk M.

Studia Geotechnica et Mechanica

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2017

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tom Vol. 39, nr 1

13--26

EN

The study employs numerical calculations in the characterization of reservoir sandstone samples based on high-resolution X-ray computed microtomography. The major goals were to determine porosity through pore size distribution, permeability characterization through pressure field, and structure impact on rock strength by simulation of a uniaxial compression test. Two Miocene samples were taken from well S-3, located in the eastern part of the Carpathian Foredeep. Due to the relation between sample size and image resolution, two X-ray irradiation series with two different sample sizes were performed. In the first approach, the voxel side was 27 µm and in the second it was up to 2 µm. Two samples from different depths have been studied here. Sample 1 has petrophysical features of conventional reservoir deposits, in contrast to sample 2. The approximate grain size of sample 1 is in the range 0.1–1.0 mm, whereas for sample 2 it is 0.01–0.1 mm with clear sedimentation lamination and heterogenic structure. The porosity, as determined by µCT, of sample 1 is twice (10.3%) that of sample 2 (5.3%). The equivalent diameter of a majority of pores is less than 0.027 mm and their pore size distribution is unimodal right-hand asymmetrical in the case of both samples. In relations to numerical permeability tests, the flow paths are in the few privileged directions where the pressure is uniformly decreasing. Nevertheless, there are visible connections in sample 1, as is confirmed by the homogenous distribution of particles in the pore space of the sample and demonstrated in the particle flow simulations. The estimated permeability of the first sample is approximately four times higher than that of the second one. The uniaxial compression test demonstrated the huge impact of even minimal heterogeneity of samples in terms of micropores: 4–5 times loss of strength compared to the undisturbed sample. The procedure presented shows the promising combination of microstructural analysis and numerical simulations. More specific calculations of lab tests with analysis of variable boundary conditions should be performed in the future.

4

High Temperature Random Stack Creep Property of Ni-Cr-Al based Powder Porous Metal Manufactured with Powder Sintering Process

100%

Kang T.-H. , Kim K.-S. , Park M.-H. , Lee K.-A.

Archives of Metallurgy and Materials

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2019

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tom Vol. 64, iss. 2

513--518

EN

Recently, attempts have been made to use porous metal as catalysts in a reactor for the hydrogen manufacturing process using steam methane reforming (SMR). This study manufactured Ni-Cr-Al based powder porous metal, stacked cubic form porous blocks, and investigated high temperature random stack creep property. To establish an environment similar to the actual situation, a random stack jig with a 1-inch diameter and height of 75 mm was used. The porous metal used for this study had an average pore size of ~1161 μm by rolling direction. The relative density of the powder porous metal was measured as 6.72%. A compression test performed at 1073K identified that the powder porous metal had high temperature (800°C) compressive strength of 0.76 MPa. A 800°C random stack creep test at 0.38 MPa measured a steady-state creep rate of 8.58×10-10 s-1, confirming outstanding high temperature creep properties. Compared to a single cubic powder porous metal with an identical stress ratio, this is a 1,000-times lower (better) steady-state creep rate. Based on the findings above, the reason of difference in creep properties between a single creep test and random stack creep test was discussed.

5

Compression of open-cell aluminium

100%

Kasza P. , Pęcherski R. B. , Lipowska B. , Stręk A. M. , Wańczyk K.

Engineering Transactions

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2016

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tom Vol. 64, iss. 4

629--634

EN

The paper presents compression test results of self-made open-cell aluminium which was produced by the investment casting method. Two groups of samples were studied: prototype samples containing some structural imperfections (apparent density 0.485 g/cm3 ) and regular samples without visible mistakes (apparent density 0.312 g/cm3 ). Performed experimental research covered quasi-static compression tests with one hysteresis loop. Based on experimental results, new measures to help material characterisation were proposed: instant and average loop secant gradients (E**inst.sec and E**av.inst.sec) and average linear loop gradient (E**av.lin).

6

Stress–dilatancy of gravel for triaxial compression tests

88%

Szypcio Z.

Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation

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2018

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tom 50

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nr 2

7

Grain refinement, microhardness distribution, strain hardening behaviour and mechanical proprieties of RD-ECAPed AA 1050

88%

Halimi A. , Hemmouche L. , Chettah I. E. , Louchene Z. A.

Archives of Mechanics

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2023

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tom Vol. 75, nr 6

647--672

EN

This study aims to investigate the evolution of mechanical and microstructural characteristics of the 1050 aluminium alloy processed by Rotary Die Equal Channel Angular Pressing (RD-ECAP). The RD-ECAPed specimens were analysed after each pass using optical microscopy, quasi-static compression test and microhardness measurements. The results revealed a reduction in grain size from 29 _m before the RD-ECAP process to a minimum value of 2 _m at the second pass, corresponding to the maximum value of compressive yield strength, reaching 184MPa. Furthermore, there was an increase in hardness from 30 Hv to 63 Hv with a homogeneous distribution along the longitudinal surface, especially in the initial four RD-ECAP passes. Additionally, the appearance of a 45_ shear plane was observed at the last fifth pass, coinciding with the region of maximum microhardness.

8

Numerical and experimental study of the mechanical response of aluminum foams under compressive loading using CT data

88%

Mohammadi Nasrabadi A. A. , Hedayati R. , Sadighi M.

Journal of Theoretical and Applied Mechanics

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2016

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tom Vol. 54 nr 4

1357--1368

EN

Metal foams are relatively novel materials that due to excellent mechanical, thermal, and insulation properties have found wide usage in different engineering applications such as energy absorbers, bone substitute implants, sandwich structure cores, etc. In common numerical studies, the mechanical properties of foams are usually introduced to FE models by considering homogenized uniform properties in different parts of a foamy structure. However, in highly irregular foams, due to complex micro-geometry, considering a uniform mechanical property for all portions of the foam leads to inaccurate results. Modeling the micro-architecture of foams enables better following of the mechanisms acting in micro-scale which would lead to more accurate numerical predictions. In this study, static mechanical behavior of several closed-cell foam samples has been simulated and validated against experimental results. The samples were first imaged using a multi-slice CT-Scan device. Subsequently, experimental compression tests were carried out on the samples using a uniaxial compression testing machine. The CT data were then used for creating micro-scale 3D models of the samples. According to the darkness or brightness of the CT images, different densities were assigned to different parts of the micro-scale FE models of the foam samples. Depending on density of the material at a point, the elastic modulus was considered for it. Three different formulas were considered in different simulations for relating the local elastic modulus of the foam material to density of the foam material at that point. ANSYS implicit solver was used for the simulations. Finally, the results of the FE models based on the three formulas were compared to each other and to the experimental results to show the best formula for modeling the closed-cell foams.

9

High Temperature Random Stack Creep Property of NI-CR-AL based Powder Porous Metal Manufactured with Powder Sintering Process

88%

Kang T.-H. , Kim K.-S. , Park M.-H. , Lee K.-A.

|

10

Bending and Compression Properties of ABS and PET Structural Materials Printed Using FDM Technology

88%

Szczepanik S. , Bednarczyk P.

Journal of Casting & Materials Engineering

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2017

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tom Vol. 1, no. 2

39--42

EN

The bend and compression mechanical properties of 3D-printed polyethylene terephthalate (PET) and acrylonitrile butadiene styrene (ABS) rectangular and cylindrical specimens (fully-dense and with circular, hexagonal, and rectangular perforations) are presented. In three-point bending, fully-dense PET flexural strength was 69 MPa, yield stress was 48.9 MPa, and yield stress from compression was 31.4 MPa. For ABS, these values were 59, 41.7, and 51.2 MPa, respectively – not significantly different from those of polymers manufactured by common techniques. Whereas perforation reduced density, the strength values were significantly lower, decreased for the circular perforation to a value of 20% strength for the fully-dense specimen. Specific strengths dropped quite significantly for the specimens tested in bending, whereas they did not differ significantly when tested by compression.

11

Conversion of compression test data into flow curve, accounting for barrelling

88%

Khoddam S. , Hodgson P. D.

Computer Methods in Materials Science

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2021

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tom Vol. 21, No. 3

157--162

EN

Current solutions to convert the axis-symmetric compression test (ACT) data to flow data ignore the barrelling deformation in the sample. This work presents a solution for the test which accounts for the sample’s barrelling by discretising it into a finite number of layers of different radii. The solution assumes a constant and sliding friction at the anvil-sample interface. The sample’s flow behaviour is identified by combining a recent kinematic solution of the test, Prandtl–Reuss–Mises’s equations and a slab-analysis of the layers. It also involves an averaging of the effective plastic stresses developed in the individual layers. The solution is verified for a special case of no-barrelling which matches the currently used solution.

12

Investigation on the preparation and mechanical properties of porous Cu35Ni15Cr alloy for a molten carbonate fuel cell

88%

Li C. , Chen J. , Li W. , Ren Y. , He J.

Materials Science Poland

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2015

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tom Vol. 33, No. 4

887--893

EN

The preparation process of porous Cu35Ni15Cr alloy was studied in this paper. The effect of ball milling time and sintering temperature on the porosity of Cu35Ni15Cr alloy was identified. It was found that 18 h ball milling and 950 degrees C sintering are the most promising parameters for the preparation of porous Cu35Ni15Cr alloy. The products have a similar to ~62 % porosity. The alloy consists of an alpha phase and beta phase. The influence of deformation temperature and loading rate on the mechanical properties of Cu35Ni15Cr alloys was investigated. The results show that with decreasing deformation temperature, the yield strength and elastic modulus of the porous alloy increase. With the increase of loading rate, the yield strength of these alloys shows an increasing trend, but the elastic modulus is on a steady level.

13

Compressive Deformation Behavior of Thick Micro-Alloyed HSLA Steel Plates at Elevated Temperatures

88%

Lee J.-H. , Kim D.-O. , Lee K.

Archives of Metallurgy and Materials

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2017

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tom Vol. 62, iss. 2B

1191--1196

EN

The hot deformation behavior of a heavy micro-alloyed high-strength low-alloy (HSLA) steel plate was studied by performing compression tests at elevated temperatures. The hot compression tests were carried out at temperatures from 923 K to 1,223 K with strain rates of 0.002 s-1 and 1.0 s-1. A long plateau region appeared for the 0.002 s-1 strain rate, and this was found to be an effect of the balancing between softening and hardening during deformation. For the 1.0 s-1 strain rate, the flow stress gradually increased after the yield point. The temperature and the strain rate-dependent parameters, such as the strain hardening coefficient (n), strength constant (K), and activation energy (Q), obtained from the flow stress curves were applied to the power law of plastic deformation. The constitutive model for flow stress can be expressed as σ = (39.8 ln (Z) – 716.6) · ε(−0.00955ln(Z) + 0.4930) for the 1.0 s-1 strain rate and σ = (19.9ln (Z) – 592.3) · ε(−0.00212ln(Z) + 0.1540) for the 0.002 s-1 strain rate.

14

Wpływ obciążenia na przebieg odkształcenia warzyw o kształcie kulistym

75%

Bohdziewicz J. , Czachor G.

Inżynieria Rolnicza

|

2010

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tom R. 14, nr 1

85-91

PL

Przedstawiono wyniki pomiaru cech fizycznych wybranych warzyw o kształcie zbliżonym do kulistego. Przeprowadzono selekcję wagową, następnie realizowano test ściskania dla 10 egzemplarzy z każdej grupy warzyw. Na podstawie analizy zależności siła - przemieszczenie określono wartość dopuszczalnej siły Fdop oraz względnego przemieszczenia jako reakcji na zadane obciążenie. Stwierdzono zróżnicowanie wykluczające stosowanie uniwersalnych rozwiązań w konstrukcji maszyn lub linii technologicznych.

EN

The work presents measurement results for physical features of selected ball-shaped vegetables. Weight selection was carried out first, followed by a compression test for 10 pieces from each group of vegetables. Analysis of force-displacement relation showed the value of acceptable force Fdop and relative displacement as a reaction to preset load. The researchers observed diversification precluding the use of universal solutions for the construction of machines or processing lines.

15

Compression behaviour of magnesium-eutectic mixture layered composite

75%

Dziadoń A. , Mola R.

Kompozyty

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2008

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tom R. 8, nr 4

364-368

EN

Magnesium-eutectic mixture (Mg17Al12 and solid solution of aluminium in magnesium) layered composite has been prepared by sintering magnesium and aluminium sheets. Samples of the composite with different thickness ratio of the magnesium layers to the layers containing eutectic mixture were examined in the compression test. Experiment was performed to compare the strain behaviour and strength properties of composites loaded parallel or perpendicular to the layers. According to microscopic observations in both cases crack initiation occurred in the layers of eutectic mixture. Cracks were spreading along or across the layers depending on the load direction. The composites loaded parallel to layers exhibit extremely low plasticity because with cracking of layers containing eutectic mixture, catastrophic fracture of specimen was observed. Composites compressing perpendicular to layers show some plastic flow to failure despite splitting of the eutectic mixture layers. In this case cracks of layers containing eutectic mixture were arrested at the magnesium. With increase of thickness ratio layers containing eutectic mixture to layers of magnesium increases the yield strength of composites. During compression test delamination of the layers of composite was not observed.

PL

Kompozyt magnez-eutektyka (mieszanina faz Mg17Al12 i roztworu stałego aluminium w magnezie) został wykonany poprzez spiekanie arkuszy magnezu i aluminium. Próbki kompozytu o różnym stosunku grubości warstw magnezu do grubości warstw o strukturze eutektyki poddane zostały próbie ściskania. Badania przeprowadzono w celu porównania mechanizmu odkształcenia i własności wytrzymałościowych kompozytów obciążanych równolegle i prostopadle do warstw. W obydwu przypadkach inicjacja pęknięć następowała w warstwach faz o strukturze eutektyki. Pęknięcia przebiegały wzdłuż lub w poprzek tych warstw w zależności od kierunku obciążenia. Kompozyty obciążane równolegle do warstw charakteryzowały się wyjątkowo niską plastycznością. Pęknięcia pojawiające się w warstwach o strukturze eutektyki powodowały natychmiastowe zniszczenie próbki. Kompozyty ściskane prostopadle do warstw o strukturze eutektyki wykazywały niewielkie odkształcenie plastyczne pomimo pęknięć pojawiających się w warstwach o strukturze eutektyki. W tym przypadku pęknięcia warstw eutektyki blokowane były na granicy z magnezem. Stwierdzono wzrost granicy plastyczności kompozytów wraz ze zwiększaniem się grubości warstw o strukturze eutektyki w stosunku do grubości warstw magnezu. Podczas próby ściskania nie zaobserwowano delaminacji kompozytu.

16

Zachowanie się kompozytów MgZn6-SiCp w próbie ściskania

75%

Braszczyńska-Malik K. N. , Chmielowiec P.

Kompozyty

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2005

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tom R. 5, nr 1

99-103

PL

Przedstawiono wyniki badań własności mechanicznych kompozytów poddanych próbie jednoosiowego ściskania. Osnowę kompozytów stanowił stop Mg - 6% wag. Zn. Badane kompozyty były umacniane zmiennym udziałem wagowym cząstek węglika krzemu, wynoszącym 10, 20 i 30% wag. Kompozyty wytworzono prostą i niedrogą metodą odlewniczą, polegającą na mechanicznym mieszaniu ciekłego metalu z wprowadzonymi cząstkami w atmosferze ochronnej. Otrzymane kompozyty charakteryzowały się jednorodnym rozmieszczeniem fazy umacniającej w objętości osnowy. Ponadto, komponenty nie wykazywały tworzenia warstw reakcyjnych na granicy cząstka/osnowa. Osnowa kompozytów składała się z roztworu stałego cynku w magnezie (faza [alfa]) oraz eutektyki [alfa]+[beta] utworzonej w przestrzeniach międzydendrytycznych. Wartość umownej granicy plastyczności kompozytu zawierającego 10% wag. cząstek SiC wyniosła 110 MPa. Wytrzymałość na ściskanie kompozytu była natomiast równa 344 MPa. Wzrastający dodatek cząstek fazy umacniającej kompozyt powodował obniżenie wartości odkształcenia plastycznego przenoszonego przez materiał (rys. 2) w próbie ściskania. Rosnący udział wagowy cząstek SiC spowodował również wzrost wskaźników mechanicznych kompozytu. Zarówno umowna granica plastyczności, jak i wytrzymałość na ściskanie kompozytów wzrastały (rys. 3) wraz z rosnącym udziałem fazy wzmacniającej. W pracy zamieszczono także wyniki analiz przebiegu ścieżek pękania, powstałych w wyniku działania maksymalnych naprężeń ścinających (rys. rys. 4 i 5). Pęknięcia powstające w badanym materiale kompozytowym rozprzestrzeniały się po fazach stopu osnowy bez udziału granic rozdziału cząstka/osnowa, co świadczy o silnym połączeniu osnowy i fazy wzmacniającej kompozyt. W czasie badań nie obserwowano pęknięć rozprzestrzeniających się od cząstek SiC do osnowy czy przebiegających po granicach rozdziału pomiędzy cząstkami a osnową kompozytu.

EN

The results of mechanical testing of magnesium matrix composites under compression have been presented. The Mg - 6 wt.% Zn alloy was used as a composite matrix. The investigated composites were reinforced with different amount of silicon carbide particles, namely 10, 20 and 30 wt.% of SiCp. A simply and non-expensive casting method involving mechanical mixing of liquid metal and the introduced particles under the protective atmosphere was used to obtain the investigated materials. The resulted composites were characterized by uniform distribution of silicon carbide particles within the matrix alloy. Moreover, the components did not reveal creation of a reaction layers at the matrix/particles interfaces (Fig. 1). The matrix alloy was composed of a solid solution of zinc in magnesium ([alpha] phase) and a eutectic of [alpha]+[beta] phases located in interdendritic spaces. The yield strength value of composite reinforced with 10 wt.% of SiC particles was 110 MPa. The ultimate compressive strength of the composite was equaled to 344 MPa, what was shown in Figure 2. Increase the weight fraction of the reinforced phase caused a decrease in the plastic strain carried by the composites. However, it increased the values of the mechanical parameters measured during compression tests. Both of the parameters (the proof stress and the ultimate compressive strength) increased with the weight fraction of SiC particles (Fig. 3). In this paper the results of examination of the cracking path of the composites have been also described. The main cracking path followed the direction of the maximum shearing stress (Figs 4 and 5). The cracks in the tested composites, that arose during compression, propagated in the magnesium alloy matrix avoiding the interfaces between the SiC particles and matrix. This proves the strong connection between the metal matrix and the reinforcing phase. The performed analyses of the composite microstructure after compression tests did not reveal any cracks propagation at the matrix/particles interfaces or from the SiC particles to matrix.

17

Analysis of Ti6Al4V P/M Properties Under Thermomechanical Compression Tests

75%

Sleboda T. , Fourie J.

Archives of Foundry Engineering

|

2013

|

tom Vol. 13, iss. 3 spec.

149--152

EN

Since titanium powder metallurgy poses opportunities for the manufacture of a range of components, there now exists the need to establish its performance characteristics under industrial conditions that these components need to operate under. In line with this, there is a need to analysing amongst others the mechanical properties of Ti6Al4V P/M [1, 5] under various thermomechanical conditions and compression tests. The main objective of the research is to study and compare the properties after forging of high quality Ti6Al4V powder metallurgy alloy with that of titanium ingot. Both samples has been manufactured under the same thermo mechanical conditions. P/M alloy will be prepared from the mixture of elemental powders, and will have the chemical composition of that of ingot Ti6Al4V alloy as per ASTM 1580-1 standard. Powder mixtures will be fully densified by hot compaction under precisely controlled conditions using the Thermal Technology Inc. press at AGH University of Science and Technology in Poland. Various physical tests will be conducted including mechanical property tests and microstructural analysis. Additionally simulations will be performed using simulation software, GForm ™ , using parameters used on actual forgings. Results will be compared to physical tests performed earlier.

18

Wpływ temperatury i środowiska na plastyczność intermetali Fe-Al w próbie ściskania

75%

Jóźwiak S. , Bojar Z. , Chmielewski T. , Mróz W.

Krzepnięcie Metali i Stopów

|

1998

|

tom nr 36

87--96

PL

W pracy przedstawiono wyniki badań właściwości mechanicznych odlewniczego stopu Fe-40%at Al przeprowadzonych za pomocą próby ściskania w temperaturach do 700°C w środowisku argonu i powietrza. Wykazano wzrost właściwości plastycznych badanego stopu w temperaturach powyżej 600°C.

19

Influence of ultrasound assist during hot air drying on properties of dried apple crisps

75%

Banaszak J. , Pawłowski A.

|

nr 3

20

Dobór reprezentatywnego obszaru do analizy wpływu parametrów kształtowania plastycznego na rozwój mikrostruktury w próbie ściskania

75%

Grosman F. , Kuziak R.

Prace Naukowe Politechniki Warszawskiej. Mechanika

|

2003

|

tom z. 201

127--132

PL

W artykule podjęto próbę określenia obszaru ściskanej próbki cylindrycznej, który pozwoli na prawidłowe wyznaczenie zależności między rozwojem mikrostruktury a globalnymi parametrami kształtowania plastycznego. Doświadczenia przeprowadzono za pomocą symulatora Gleeble3800, w którym odkształcano cylindryczne próbki stali 0H18N9. Analizę lokalnych warunków odkształcenia plastycznego przeprowadzono metodą symulacji numerycznej procesu ściskania osiowosymetrycznego z wykorzystaniem programu FormFEM. Przeprowadzone badania symulacyjne potwierdziły możliwość wyznaczenia obszaru reprezentatywnego, w którym lokalne warunki odkształcenia plastycznego odpowiadają warunkom nominalnym (globalnym) przyjętym dla próby ściskania. Położenie tego obszaru wyznacza punkt leżący na środku wysokości próbki w odległości r=0.8R(b), gdzie R(b) jest promieniem beczki.

EN

The main aim of the paper was to determine the representative area in the cylindrical samples in which the local deformation parameters are equivalent to the global ones. Based upon the finite-element simulations and microstructure observations, a location of representative area was proposed. It was established that all necessary criteria are fulfilled by the area located in the middle of the sample lying at a distance of 0.8R(b) from the sample`s centre, where R(b) is the barrel radius.