Wyniki wyszukiwania - Biblioteka Nauki

1

Impact of the research conditions on the accuracy of the designation of high performance concrete strength parameters

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Wałach D. , Wałach D.

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2

Effect of curing temperature on flexural properties of silica-based geopolymer-carbon reinforced composite

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Tran D. H. , Kroisová D. , Louda P. , Bortnovsky O. , Bezucha P.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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tom Vol. 37, nr 2

492-497

EN

Purpose: The aim of this paper is to find out the curing temperature at which we can achieve the best mechanical properties and adhesion between silica-based geopolymer matrix (Q1) and carbon HTS 5631 1600tex 24K fibre. Design/methodology/approach: The carbon fibre was impregnated with silica-based geopolymer by means of home-made “impregnation machine”. This equipment was designed based on simulating the real pultrusion or filament winding technique. Composite samples were made manually in silicon mould and cured under hot vacuum bagging technique at different temperatures. Flexural properties were determined under three-point bending mode in accordance with British Standard BS EN ISO 14125:1998. The sections perpendicular to fibres and surfaces of the composites were analysed by means of scanning electron microscope (SEM) to estimate the adhesion between geopolymer matrices and fibre reinforcement. Findings: Relatively wide range of curing temperature from 70oC to 100oC at which we can obtain high flexural properties, maximal values of flexural strength 570 MPa, flexural modulus 65 GPa and relative deformation of composite was 0.98% when the composite was cured and dried at 75oC. Adhesion of the geopolymer matrix to carbon fibre was very good and hardly to determine the differences by SEM image observation within the range of optimal curing temperature. Research limitations/implications: The curing time was too long to provide the geopolymerization process before it had been completed, this factor caused that it should be carried out in the future and we may use liquid absorption to determine how many cavities are in the composites. Practical implications: The research presents original information on the influence of different curing temperatures on mechanical properties and micro-structure of silica-based geopolymer matrix – carbon composite. The results are useful for further investigations. Originality/value: Determining the optimal curing temperature and micro-structure of silica-based geopolymer system to make it easy to find the curing time and other conditions to get the best properties of this type of materials.

3

Tribological and surface morphological characteristics of titanium alloys: a review

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Gupta M. K. , Etri H. E. , Korkmaz M. E. , Ross N. S. , Krolczyk G. M. , Gawlik J. , Yaşar N. , Pimenov D. Y.

Archives of Civil and Mechanical Engineering

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2022

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tom Vol. 22, no. 2

art. no. e72, 1--23

EN

Being easily fabricated, welded, biocompatible, having a high strength-to-weight ratio, withstanding comparatively high temperatures up to 800°C and low modulus of elasticity make grade titanium and its alloys an important choice for automotive, biomedical and aerospace industries. In contempt of the different pleasant assets of Ti-6Al-4V alloy, the operation of this alloy is restricted especially when it comes to tribological and surface morphological characteristics. Enhancing these properties is important, for this purpose, a diversity of attempts and studies have been conducted. This paper mounts a review of morphological and tribological behaviors of titanium alloys including Ti-6Al-4V against different materials counting with carbide tools and other types of materials under dry and lubricated sliding conditions. The surface morphological, wear, and other properties have been discussed in this review article.

4

Ocena ryzyka kruchego pękania wspomaganego przez wodór złączy spawanych stali okrętowej o wysokiej wytrzymałości

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Ćwiek J.

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tom nr 1

155-162

PL

Oceniano podatność na niszczenie wodorowe stali 14HNMBCu (S690Q) o wysokiej wytrzymałości i jej połączeń spawanych przy obciążeniu monotonicznie rosnącym oraz stałym w wodzie morskiej. Badania przeprowadzono w powietrzu oraz w środowisku wody morskiej przy potencjale korozyjnym i przy polaryzacji katodowej. W próbie rozciągania z małą prędkością odkształcenia próbek gładkich jako mierniki podatności na kruchość wodorową przyjęto: wydłużenie, przewężenie i właściwą energię zniszczenia. Obecność lub brak opóźnionych pęknięć próbek z karbem przyjęto za miarę odporności na niszczenie wodorowe przy stałym obciążeniu.

EN

Hydrogen degradation of high-strength steel and its welded joints has been evaluated under monotonically increasing, and constant load modes in sea-water. Tests were carried out in air, and sea-water at open circuit potential and under cathodic polarization. Relative values of: elongation, reduction in area, and fracture energy were chosen as measures of hydrogen degradation in slow strain rate tests (SSRT) on cylindrical smooth specimens.

5

Analysis of the Properties of Air-textured Sewing Threads

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Jonaitiené V. , Stanys S.

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tom Vol. 12, no. 1 (45)

84--87

EN

The aim of this research was to assess how certain mechanical characteristics of sewing threads varied while different parameters were changed during the manufacturing process. Air-textured technical sewing threads are a relatively new product on the market. The applications of the end product could be selected depending on the mechanical characteristics of the product during usage. Some applications require very high tenacity, others require very low friction forces during the sewing process. Air texturing appears to be a technology which can accommodate the manufacturing possibilities of threads with different end characteristics and also allow the usage of different types of fibre filaments. Two types of yarns were manufactured during this research: high-tenacity PES yarns were used in both core and sheath elements in one case; in the other case, the same high-tenacity PES yarns were used in the core while Polytetrafluorethylene (PTFE) was used in the sheath elements. The threads were manufactured in the Department of Textile Technology at Kaunas University of Technology, using a Stahle Eltex air-texturing machine and a Heberlein HemaJet texturing nozzle. In addition, tensile and friction tests were performed during the research. Different manufacturing parameters were changed during air-texturing, including air pressure and overfeeds of effect & core yarn. The results clearly showed the good mechanical characteristics of the sewing threads manufactured.

PL

Celem badań było określenie jak wybrane właściwości mechaniczne nici szwalnych zmieniają się przv zmianie parametrów procesu wytwarzania. Nici szwalne teksturowane powietrzem są stosunkowo świeżym produktem rynkowym. Dobór nici powinien być dostosowany do ich właściwości mechanicznych i warunków pracy. Pewne zastosowania wymagają dużej wytrzymałości, inne występowania małych sil tarcia podczas szycia. Teksturowanie powietrzem okazało się technologią pozwalającą na otrzymywanie nici o różnych charakterystykach oraz na stosowanie różnych typów włókien składowych. Podczas prowadzonych przez nas badań wyprodukowano dwa typy włókien: jeden - w którym wysokowytrzymałe włókna poliestrowe zastosowano na rdzeń i otoczkę, i drugi - w którym te same włókna poliestrowe stanowiły rdzeń, a otoczka składała się z włókien politetrąfluoroetylenowych. Nici były wytwarzane w Katedrze Technologii Włókienniczej na Uniwersytecie Technologicznym w Kownie (Litwa) przy zastosowaniu teksturarki Stahle Eltex i dysz teksturujących Heberlein HemaJet. Podczas badań wykonano testy wytrzymałościowe i tarciowe. Podczas procesu produkcyjnego zmieniano szereg parametrów, w tym ciśnienie powietrza oraz naddatek przędzy na otoczkę w stosunku do rdzenia. Otrzymane wyniki jednoznacznie wskazują na dobre właściwości mechaniczne wyprodukowanych nici.