Biblioteka Nauki

1

Some Toughness Results in Independent Domination Critical Graphs

100%

Ananchuen N. , Ananchuen W.

Discussiones Mathematicae Graph Theory

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2015

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tom 35

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nr 4

703-713

EN

A subset S of V (G) is an independent dominating set of G if S is independent and each vertex of G is either in S or adjacent to some vertex of S. Let i(G) denote the minimum cardinality of an independent dominating set of G. A graph G is k-i-critical if i(G) = k, but i(G+uv) < k for any pair of non-adjacent vertices u and v of G. In this paper, we establish that if G is a connected 3-i-critical graph and S is a vertex cutset of G with |S| ≥ 3, then [...] improving a result proved by Ao [3], where ω(G−S) denotes the number of components of G−S. We also provide a characteriza- tion of the connected 3-i-critical graphs G attaining the maximum number of ω(G − S) when S is a minimum cutset of size 2 or 3.

2

Influence of material thickness on the ductile fracture of steel plates for shipbuilding

80%

Jakub K. , Janusz K.

Polish Maritime Research

|

2022

|

tom nr 3

160--166

EN

In the shipbuilding industry, the risk of brittle fractures is relatively high because some units operate in arctic or subarctic zones and use high thickness (up to 100 mm) steel plates in their structures. This risk is limited by employing certified materials with a specific impact strength, determined using the Charpy method (for a given design temperature) and by exercising control over the welding processes (technology qualification, production supervision, and non-destructive tests). However, for offshore constructions, such requirements may prove insufficient. For this reason, regulations employed in constructing offshore structures require conducting crack tip opening displacement (CTOD) tests for steel and welded joints with thicknesses exceeding 40 mm for high tensile strength steel and 50 mm for other steel types. Since classification codes do not accept the results of CTOD tests conducted on specimens of sub-sized dimensions, the problem of theoretically modelling the steel construction destruction process is of key importance, as laboratory tests for notched elements of considerable thickness (100 mm and higher) are costly and problems stemming from high loads and a wide range of recorded parameters are not uncommon. The aim of this research is to find a relationship between material thickness and CTOD value, by establishing and verifying a numerical model that allows recalculating a result obtained on a sub-size specimen to a full- size specimen for a ductile fracture mode. This work presents results and conclusions from numerical modelling and compares them with laboratory test results of the elastic-plastic properties of high thickness steel, typically used in offshore applications.

3

Enhancement of tensile performance of concrete by using synthetic polypropylene fibers

80%

Jienmaneechotchai T. , Foytong P. , Khunkitti P. , Sata V. , Chindaprasirt P.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2023

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tom Vol. 32, No. 4

320--337

EN

The research attempted to investigate the effect of polypropylene fibers (PP fibers) on the mechanical characteristics of concrete. According to ASTM C39/C39M and ASTM C 1609/C1609M, standard testing methods were used to examine the concrete compressive and flexural strength, post-cracking behavior, and toughness. The mechanical properties were evaluated at different ages of concrete curing, namely 1 day, 7 days, and 28 days, and for different quantities of fiber volume portions, specifically 0.0%, 0.5%, and 1.0%. The results demonstrate that a fiber volume of 0.5% is the most effective in obtaining the highest compressive strength. The recorded values at the related testing ages were 31.07 MPa, 41.51 MPa, and 46.68 MPa. Additionally, the utilization of 0.5% and 1.0% volume of PP fiber in concrete resulted in improved flexural strength and post-cracking performance. The toughness values for these mixes were 2.0 and 2.6 times higher than those for the plain concrete. Upon analyzing the fracture surface, there was a homogeneous distribution of fibers, which played a significant role in enhancing the overall functionality of the concrete. The research validated that the inclusion of polypropylene fibers substantially enhanced the mechanical characteristics of concrete, emphasizing the potential of fiber reinforcement in concrete-based implementations.

4

Long cycles and neighborhood union in 1-tough graphs with large degree sums

80%

Hoa V.

Discussiones Mathematicae Graph Theory

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1998

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tom 18

|

nr 1

5-13

EN

For a 1-tough graph G we define σ₃(G) = min{d(u) + d(v) + d(w):{u,v,w} is an independent set of vertices} and $NC_{σ₃-n+5}(G)$ = $max{⋃_{i = 1}^{σ₃-n+5}$ $N(v_i) : {v₁, ..., v_{σ₃-n+5}}$ is an independent set of vertices}. We show that every 1-tough graph with σ₃(G) ≥ n contains a cycle of length at least $min{n,2NC_{σ₃-n+5}(G)+2}$. This result implies some well-known results of Faßbender [2] and of Flandrin, Jung & Li [6]. The main result of this paper also implies that c(G) ≥ min{n,2NC₂(G)+2} where NC₂(G) = min{|N(u) ∪ N(v)|:d(u,v) = 2}. This strengthens a result that c(G) ≥ min{n, 2NC₂(G)} of Bauer, Fan and Veldman [3].

5

The Existence Of P≥3-Factor Covered Graphs

70%

Zhou S. , Wu J. , Zhang T.

Discussiones Mathematicae Graph Theory

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2017

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tom 37

|

nr 4

1055-1065

EN

A spanning subgraph F of a graph G is called a P≥3-factor of G if every component of F is a path of order at least 3. A graph G is called a P≥3-factor covered graph if G has a P≥3-factor including e for any e ∈ E(G). In this paper, we obtain three sufficient conditions for graphs to be P≥3-factor covered graphs. Furthermore, it is shown that the results are sharp.

6

Influence of the content of a glass-polyester recycled additive on the properties of layered composites in dynamic tests

60%

Panasiuk K. , Hajdukiewicz G.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

|

2018

|

tom nr 56 (128)

36--40

EN

Polyester-glass composites are widely used in many industries, in various types of constructions, including dynamically loaded ones. This article examines the influence of the content of a glass-polyester recycled additive on the strength properties of layered composites. The recyclate was polyester-glass waste, which was pre-crushed and then milled into the appropriate fractions. Manual laminating technology was used to make the materials. The composite materials were made with a waste content of 0%, 10%, 20% and granulations of ≥ 1.2 mm and ≥ 3 mm. Samples for testing were prepared in accordance with the PN-EN ISO 179-1: 2010E standard (Plastics – Charpy Impact Assessment – Part 1: Non-instrumental impact test). Impact tests of the samples were performed using the Charpy method with the Zwick Roell RKP450 swinging hammer. The test results showed that the addition of polyester-glass recyclate, its content %, and its granulation size, have an impact on the composite resistance to loads in dynamic tests.

7

Wpływ utwardzania wydzieleniowego na udarność brązu berylowego AMPCOLOY 83

60%

Poprzeczka A. , Lisica A.

Logistyka

|

2009

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tom nr 6

PL

Właściwości brązów berylowych wynikają głównie z zastosowanej obróbki cieplnej, składającej się z zabiegów przesycania i starzenia (utwardzania wydzieleniowego). W nielicznych dostępnych publikacjach na ten temat występują różne rozbieżności. W niniejszej pracy zbadano wpływ parametrów utwardzania wydzieleniowego na udarność brązu berylowego AMPCOLOY 83 zawierającego 2% berylu. Brązy tego typu stosuje się m. in. na różnego rodzaju sprężyny, membrany, kontakty sprężynowe, amortyzatory, szczotki silników elektrycznych, narzędzia i elementy nieiskrzące oraz odporne na korozję.

EN

Beryllium bronze properties largely result from the application of heat treatment which consists in solution heat treatment and ageing (precipitation hardening). Few available publications on that provide us with various discrepancies. This paper includes a study of the influence that precipitation hardening parameters have on the impact strength of AMPCOLOY 83 beryllium bronze containing 2% beryllium. This type of bronzes are used for example on various types of springs, membranes, spring contacts, shock absorbers, electric motor brushes, non-sparking as well as corrosion-resistant tools and elements.

8

Wpływ wielokrotnych cykli cieplnych na ciągliwość symulowanej SWC stali o dużej wytrzymałości

60%

Mroczka K. , Tasak E.

Biuletyn Instytutu Spawalnictwa w Gliwicach

|

2003

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tom R. 47, nr 5

65--69

PL

Przedstawiono wybrane wyniki badań właściwości stali o wysokiej wytrzymałości poddanych różnym symulowanym, pojedynczym i złożonym, cyklom cieplnym. Stwierdzono, że wzrost czasu chłodzenia w zakresie t8/5 powoduje równoczesny spadek udarności i twardości. Te niekorzystne zmiany związane są z tworzeniem się wysp M-A oraz procesami utwardzania wydzieleniowego ferrytycznej osnowy.

EN

It has been presented some selected test results for high strenght steels subjected to different simulated thermal cycles, simple and complex ones. It was found that the increase in cooling time in the range of t8/5 resulted in the simultaneous decrease in toughnees and hardness. These negative changes are connected with formation of martensite-austenitic island and processes of precipitation hardening of ferritic matrix.

9

Modifikacija struktury i mekhanicheskikh svojjstv stali ponizhennojj pokalivaemosti pri impul'snom zakalochnom okhlazhdenii zhidkost'ju

60%

Betenja G. , Aniskovich G.

Motrol. Motoryzacja i Energetyka Rolnictwa

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2013

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tom 15

|

nr 7

10

The Suitability of Using C30E Steel Materials for Damping the Effects of Improvised Explosive Devices

60%

Adamec N. , Štiavnický M. , Pálušová M. , Bella V.

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

|

2012

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tom Vol. 3, Nr 1 (7)

11-20

EN

There are nowadays different kinds of homogenous steel armours (e.g. different kinds of steel sheets Armox, Russian armours including 2P, 43 PSM etc.) or aramide fibres which can be used alone or in composites. This paper follows the relationship between the strength parameters and microstructure in the steel armours used for personal protection and military vehicles. The results described in the paper, pick up the threads of previous work performed at the Mechanical Engineering Department in Armed Forces Academy of gen. M.R. Stefanik in Liptovsky Mikulas.

11

Residual strength and toughness after impact loading for RC slabs strengthened with different layers of geogrid

60%

Ahmed A. M. E. , Hamdy O. , Saad Y. L. Z. , Ahmad S. S. E.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2023

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tom Vol. 32, No. 2

117--134

EN

This study presents an experiment for investigating the residual strength and toughness of reinforced concrete, RC, and slab reinforced by a geogrid as shrinkage reinforcement along with lower tensile steel reinforcement. Three different parameters were considered, slab thickness, number of geogrid layers, and thickness of the upper concrete cover. Fifteen slab samples with sizes of 50 × 50 cm exposed to the impact load on its center before being re-load by the static load and six slab samples exposed to the static load only. The load and deflection relation were recorded through the static loading process for all specimens, where loading capacity, toughness, and toughness index were measured. The results show an enhancement in the slabs residual strength as the slab thickness and concrete cover increased. On the other hand, the residual strength of slabs has a remarkable decrease with the increase in geogrid layers. Moreover, the toughness has a positive relationship with the concrete cover and has an inverse relation with the slab thickness and the number of layers. A geogrid reduced the number and distribution of cracks and mitigated their severity, especially for double layers with the same concrete cover.

12

Badanie własności mechanicznych stali drobnoziarnistej Domex 700MC

60%

Mazur M.

Zeszyty Naukowe. Quality. Production. Improvement

|

2016

|

tom No. 1 (4)

107--119

PL

W rozdziale przedstawiono wyniki badań własności mechanicznych stali drobnoziarnistej Domex 700MC. Badania prowadzone w ramach badań własności zmęczeniowych stali klasyfikowanych do aplikacji nowych materiałów w konstrukcjach naczep samochodowych. Przedstawione badania obejmują wyniki statycznej próby rozciągania oraz udarności w zakresie temperaturowej – 70 do + 100°C. Analiza badań uzupełniona została o analizę struktury materiału oraz spektrometryczną analizę składu chemicznego materiału.

13

Analysis of the cracking process of layered composites with polyester-glass recyclate using dynamic tests

60%

Panasiuk K. , Kyzioł L. , Hajdukiewicz G.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

|

2019

|

tom nr 57 (129)

73--78

EN

Layered composites are materials that are widely used in industry due to their low manufacturing costs. They are used, among others, as a construction material for the construction of light aircraft, cars, wind turbine blades and the hulls of vessels. The universality of their use has contributed to the formation of a large amount of post-production and post-use waste from these composites. Layered composites, using recycled polyester and glass, or recycled composite waste, may be materials that could be used in the economy. The polyester-glass waste used in the composite was created by crushing and then grinding and sieving to obtain the appropriate granulation. Materials with a waste content of 0%, 10%, 20% and with granulation of this waste of ≤ 1.2 mm were made using the hand lamination method. Test specimens were prepared from the material plates that were obtained in accordance with the PN-EN ISO 179-1: 2010E standard (Plastics – Charpy Impact Assessment – Part 1: Non-instrumental impact test). Impact tests of samples were carried out according to the above-mentioned standards using a Zwick Roell RKP450 swinging hammer. Test bench instrumentation and software enabled the bending forces to be recorded, as well as the deflection of the samples for short time intervals and displacement, so a detailed force-deflection graph could be obtained. During the analysis, the results of the research were focused on describing the kinetics of the process where the samples were destroyed (fracture mechanics), this allowed for the initial determination of the material’s resistance to dynamic loads. The results obtained showed that the increase of the recycled content in the produced composite contributed to the lowering of the destructive force threshold in the impact tests, as well as the simultaneous increase of the plasticity of the material. The increase of the sample’s deflection with the occurrence of the maximum force resulted in the energy of the elastic state being increased (Ue).

14

Some recent results on domination in graphs

60%

Plummer M.

Discussiones Mathematicae Graph Theory

|

2006

|

tom 26

|

nr 3

457-474

EN

In this paper, we survey some new results in four areas of domination in graphs, namely: (1) the toughness and matching structure of graphs having domination number 3 and which are "critical" in the sense that if one adds any missing edge, the domination number falls to 2; (2) the matching structure of graphs having domination number 3 and which are "critical" in the sense that if one deletes any vertex, the domination number falls to 2; (3) upper bounds on the domination number of cubic graphs; and (4) upper bounds on the domination number of graphs embedded in surfaces.

15

Udarność staliwa L15G w temperaturze -40oC

51%

Ronatowski J. , Głownia J.

Krzepnięcie Metali i Stopów

|

1998

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tom nr 38

219--223

PL

Zbadano wpływ odtleniania i obróbki cieplnej staliwa L15G na jego udarność w temperaturze -40 i -60oC. Wykazano, że wymagane wartości udarności 40 J/cm2 można uzyskać tak po normalizowaniu jak i ulepszaniu cieplnym tego staliwa.

EN

This study demonstrates that deoxidation and heat treatment of cast steel L15G have effect on its impact toughness in -40 and -60oC. Is was found that value of 40 J/cm2can obtain after normalization or after quenching and tempering.

16

Comparitive Investigation of Mechanical Indices of Sheep's Wool and Dog Hair Fibre

51%

Ragaisiene A. , Rusinaviciute J.

Fibres & Textiles in Eastern Europe

|

2012

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tom Vol. 20, no. 6A (95)

43--47

EN

The aim of this research is to analyse and compare mechanical indices - breaking force, tenacity, elongation at break, work of break, and toughness of dog's hair and sheep's wool fibre and to investigate the relationship between the geometrical and mechanical indices of these fibres. In textiles it is very important to choose the right component for the blend. Fibre length, diameter, linear density, tenacity, elongation at break and other strength properties are very important for these fibres parameters of yarn. It was estimated that sheep's and dog's fibres are visually very different and the diameter of these fibres varied in a big interval; however their length is more similar. Also it was established that geometrical indices of the fibres influence their mechanical indices of them i. e. fibres of minimal length have maximal values of these indices.

PL

Celem tej pracy była analiza porównawcza parametrów mechanicznych takich jak, siła zrywająca, wytrzymałość właściwa na rozciąganie, wydłużenie przy zerwaniu, praca przy zerwaniu włókien sierści psów i wełny owiec oraz analiza związków pomiędzy parametrami mechanicznymi i geometrycznymi tych włókien. Bardzo ważne jest dobranie właściwych komponentów w przędzach mieszankowych, należy wziąć pod uwagę długość włókna, średnicę, masę liniową, wytrzymałość na rozciąganie, wydłużenie przy zerwaniu oraz inne parametry wytrzymałościowe. Włókna z wełny owiec i sierści psów bardzo różnią się wizualnie i pod względem średnicy, natomiast ich długość jest bardziej zbliżona. Wykazano, że geometryczne parametry tych włókien wpływają na ich parametry mechaniczne, np. najkrótsze włókna mają najwyższe wartości parametrów wytrzymałościowych.

17

The influence of heat treatment on toughness of extruded profiles from EN AW − 6060 aluminium alloy

51%

Romański P. , Stradomski G. , Ciepiela W. , Pilarczyk J. W.

Hutnik, Wiadomości Hutnicze

|

2015

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tom Vol. 82, nr 1

101--104

EN

The aim of this work was to analyze the influence of heat treatment on toughness of hot extruded aluminum profiles from EN AW - 6060 aluminum alloy over. The result of the conducted research has pointed out that the heat treatment had a significant effect on the toughness of aluminum profiles. In the study it was found that the highest values of toughness were achieved after supersaturation of hot extruded aluminum profiles.

PL

Celem pracy była analiza wpływu obróbki cieplnej na udarność wyciskanych na gorąco profili ze stopu aluminium EN AW – 6060. Wyniki przeprowadzanych badań ukazały, że obróbka cieplna ma istotny wpływ na udarność profili aluminiowych. W badaniach udowodniono, że najwyższą wartość udarności uzyskano po przeprowadzonym procesie przesycania wyciskanych na gorąco profili aluminiowych.

18

Nowe staliwo ledeburytyczne o osnowie umacnianej wydzieleniowo

51%

Pacyna J.

Prace Instytutu Odlewnictwa

|

2016

|

tom Vol. 56, no. 1

3--6

PL

Zaprojektowano nowe staliwo ledeburytyczne o osnowie umacnianej wydzieleniowo związkami międzymetalicznymi, którego skład chemiczny uzupełniono zbilansowanym węglem i dodatkiem około 4,25% V. Uzyskano skłonną do umacniania związkami międzymetalicznymi martenzytyczno-austenityczną osnowę z siatką ledeburytu na granicach krystalitów. Twardość (około 400 HV20) i praca złamania KV (około 3 J) nowego tworzywa są minimalnie większe od tych samych właściwości dotychczas stosowanego staliwa G200CrNiMo4-3-3, które głównie stosowane jest na walce bruzdowe w walcowniach średnich i dużych. O zastosowaniu w praktyce przemysłowej nowego staliwa zdecydują jego właściwości tribologiczne.

EN

A new ledeburite cast steel was designed based on a matrix precipitation hardened with intermetallic compounds of a chemical composition enriched by adding about 4.25% V totally balanced with carbon. A martensitic-austenitic matrix with a ledeburite network at the crystallite boundary prone to the strengthening effect with intermetallic compounds was obtained. Both hardness (about 400 HV20) and fracture energy KV (about 3 J) of the new material are only slightly superior to the same properties offered by the cast G200CrNiMo4-3-3 steel used so far for the section rolls operating in medium and large rolling mills. The applicability of the new cast steel in industrial practice will mainly depend on its tribological properties.

19

The influence of heat treatment on toughness of extruded profiles from EN AW-6063 aluminium alloy

51%

Romański P. , Stradomski G. , Pilarczyk J. W.

Hutnik, Wiadomości Hutnicze

|

2016

|

tom Vol. 83, nr 5

223--227

EN

The aim of this work was to analyze the influence of heat treatment on toughness of hot extruded aluminium profiles from EN AW-6063 aluminium alloy. The result of the conducted research has shown that the heat treatment had a significant effect on the toughness of aluminium profiles. In the study it was found that the highest values of toughness were achieved after supersaturation process of hot extruded aluminium profiles.

PL

Celem pracy była analiza wpływu obróbki cieplnej na udarność wyciskanych na gorąco profili ze stopu aluminium EN AW-6063. Wyniki przeprowadzanych badań ukazały, że obróbka cieplna ma istotny wpływ na udarność profili aluminiowych. W badaniach wykazano, że najwyższą wartość udarności uzyskano po przeprowadzonym procesie przesycania wyciskanych na gorąco profili aluminiowych.

20

Influence of hybrid fibers on toughness behavior of high strength flowing concrete

51%

Dawood E. T. , Ramli M.

Archives of Civil Engineering

|

2011

|

tom Vol. 57, nr 3

249-260

EN

This study investigates the use of steel fibers and hybrid composite with a total fibers content of 2% on the high strength flowing concrete and determines the density, compressive strength, static modulus of elasticity, flexural strength and toughness indices for the mixes. The results show that the inclusion of more than 0.5% of palm fibers in hybrid fibers mixes reduces the compressive strength. The hybrid fibers can be considered as a promising concept and the replacement of a portion of steel fibers with palm fibers can significantly reduce the density, enhance the flexural strength and toughness. The results also indicates that the use of hybrid fibers (1.5 steel fibers + 0.5% palm fibers) in specimens increases significantly the toughness indices and thus the use of hybrid fibers combinations in reinforced concrete would enhance their flexural toughness & rigidity and enhance their overall performances.