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1

Experimental study on seismic upgrading of RC frames using innovative brace system with two‑stage characteristic

Zhao Jianchen, Sun Jian, Qiu Hongxing

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e128

EN

A novel gapped eccentric steel brace (GESB) was proposed to achieve a two-stage retroft strategy for seismic upgrading of reinforced concrete (RC) frames. The steel brace was isolated from the RC frame at low story drifts using thin layers of polymer cellular materials, while the brace was activated at high drifts. Mild steel coupling beam was introduced into the brace system as a damper to improve the energy dissipation capacity of the system. Four frames were subjected to pseudostatic reversed cyclic loading procedure, including one bare frame and three retroftted frames with the novel system. The experimental results indicated that the GESB system presented an obvious two-stage behavior which was generally superior in terms of providing second-stage enhancement of stifness while avoiding drastic intervention in the initial vibration characteristics of the primary structure. Besides, the yield of mild steel beam greatly increased the energy dissipation capacity of the system. Compared with the reference frame, cracks were more difuse in the retroftted frames rather than concentrated at the column end, which means all of the original structure elements were fully used.

2

Materiały komórkowe typu "hollow sphere" - metody wytwarzania, badanie właściwości mechanicznych oraz zastosowanie

Cieplak K., Majewski T.

Przegląd Mechaniczny

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2018

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nr 9

40--42

PL

W artykule opisano materiały komórkowe typu „hollow sphere”. W pierwszej części zawarty jest przegląd metod wytwarzania, przybliżono sposób ich realizacji oraz krótko scharakteryzowano. Szczegółowo opisano obecnie stosowane sposoby wytwarzania takich materiałów. W dalszej części omówiono badania dotyczące zarówno analiz numerycznych, jak i badań eksperymentalnych. W kolejnej części przedstawiono model przygotowany do wydruku 3D metodą DLP. Wymieniono przykłady zastosowania w branży przemysłowej i motoryzacyjnej.

EN

The article describes cellular materials of the “hollow sphere” type. The first part contains an overview of manufacturing methods. The way of their implementation is presented and briefly characterized. The presently manufacturing methods are described in detail. In the following, the research concerning both numerical and experimental analyzes is discussed. The next part presents a model prepared for 3D printing using the DLP method. Examples of application are listed in the industrial and automotive.

3

Detekcja osoby w wannie

Osiński K., Bujnowski A.

Elektronika : konstrukcje, technologie, zastosowania

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2016

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Vol. 57, nr 9

81-84

PL

Starzenie się społeczeństwa powoduje narastanie problemów chorób wieku starczego. Częstym problemem są zasłabnięcia w wannie podczas kąpieli. Celem publikacji jest przedstawienie metody identyfikacji tkanki ożywionej w wodzie z wykorzystaniem technik elektromagnetycznych. Obserwując zmiany amplitudy i częstotliwości pracy generatorów, pracujących w pętli sprzężenia zwrotnego z cewką, istnieje możliwość scharakteryzowania i określenia różnic w odpowiedzi generatorów na obecność metalu, wody oraz materiału komórkowego. Jest to metoda nieinwazyjna i niewymagająca ingerencji w poszycie naczynia oraz nieinwazyjna dla kąpiącego się.

EN

The aging population will increase the problems of diseases of old age. A common problem is faint in the bath during bathing. The aim of this paper is to present methods of identifying the living tissue in the water with the use of electromagnetic techniques. Observing the changes in amplitude and frequency generators operating in a feedback loop with the coil, it is possible to characterize and determining the differences in response generators to the presence of a metal, water, living tissue and not living tissue. It is non-invasive and requires no interference in the skin vessels and non-invasive for the patient.

4

Design of micro porous Al foams by high energy milling

Robert M. H., Silva R. R.

Archives of Materials Science and Engineering

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2015

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Vol. 71, nr 1

5--15

EN

To explore a new route to produce metallic foams which results in a structure of closed micro porous. High energy milling is employed to incorporate particles of foaming agents in metallic powders to promote homogeneous distribution of micro gas bubbles during foaming. Design/methodology/approach: AA2014 powders were mixed with TiH2 particles as gas releasing agent, through high energy milling, producing composite powders. Powders were compacted and obtained compacted precursors were heated to promote foaming of the metal. Effect of processing conditions in the expansion of the metal, structural characteristics, density and mechanical properties under compression, of obtained foams was analyzed. Findings: Foaming composite powders of AA2014/TiH2 produced by high energy milling is a promising route to produce micro porous aluminium foams. The best foaming condition among the conditions investigated, occurs for the highest milling time (17 h) and highest heating rate (3°C/s) imposed during foaming, resulting in 140% of maximum expansion and foams with relative density of 0.44. Research limitations/implications: Main limitation of the proposed process is the long time required to produce composite powders by high energy milling, which can justify the process for specific purposes where micro porous are required. However, as all new development, further works can lead to the optimization of processing parameters, mainly concerning reduction of processing time, to make the process compatible to wider industrial applications. Practical implications: New products can be developed for specific applications requiring porous with micro scale. Originality/value: The use of the foaming agent structurally incorporated in the metal powder to produce precursors for foaming is original.

5

Thixoinfiltration: a new approach to produce cellular and other low density metallic materials

Robert M. H., Jorge A. F., Gatamorta F., Silva R. R.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 40, nr 2

180-187

EN

Purpose: the work presents an innovative approach for the production of cellular metallic materials as well as low density metal matrix composites, by using thixoforming techniques; thixotropic semisolid metal is infiltrated into removable and non-removable space holder preforms. Different kinds of preforms are tested to obtain open cell material (sponges), syntactic foams and low density composites. Products are evaluated concerning relative density and mechanical behavior under compressive stresses. Design/methodology/approach: Al alloy AA2011 was infiltrated in the semisolid state into preforms of sintered NaCl particles, sintered glass spheres, vermicular ceramic particles and porous ceramic granulates. After solidification, preforms were either removed by leaching (NaCl) resulting in open cell cellular product, or not (all others), resulting in composites of low density. Tomography tests were used to observe internal quality, and semi-static and dynamic compression tests were performed to evaluate the deformation ability of the material. Findings: results show that thixoinfiltration is a simple and low cost technique to produce different types of low density, porous material. Open cell material as well as syntactic foams and low density composites can be produced with reliable internal quality and dispersion of cells and reinforcement. Composites containing porous reinforcements can present some mechanical characteristics of the conventional cellular metals. Research limitations/implications: as all new developments, the complete understanding of the influence of processing variables upon the final quality of the product, as well as its consistency, must be provided before the technology can be widely used commercially. Practical implications: the technique can represent an alternative, low cost processing route for the fabrication of sponges, foams and low density composites, which can avoid restrictions and operational difficulties of presently available manufacturing processes based in liquid manipulation or powder sintering methods. Originality/value: infiltration of appropriate preforms by thixotropic metallic alloys to produce low density composites and cellular material is a new technique under development by the proposing group at FEM/UNICAMP.

6

Closed aluminium skeleton casting

Cholewa M., Dziuba-Kałuża M.

Archives of Foundry Engineering

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2008

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Vol. 8, iss. 1 spec.

53--56

EN

In this article authors showed method for manufacturing of skeleton castings with continuous external surface. Wall thickness of the external surface was 6 mm. The experimental casting was manufactured in order to verify the results of filling mould cavity which were obtained by numerical simulation. The aluminosilicate core was used to produce experimental aluminum skeleton castings with dimensions of (115x65x136) mm. Experimental casting was manufactured with elevated temperature of mould (370 K). Lower and stotted ingate with high geting system (300mm) was used. Analysis of ability of metal to fill the mould cavity in establish technological conditions was perfomed. Degree of refinement of structure in typicall region of skeleton casting was compared. Qualitative different degree of fineness of eutectic was confirmed. Selection of modification conditions AlSi alloy of skeleton casting is necessary. The manufacturing of skeleton casting in establish technological conditions enables obtained very good filling of mould cavity and suitable external geometrical form of casting.

7

Manufacturing of cellular A2011 alloy from semi-solid state

Robert M. H., Delbin D.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 1

115-122

EN

Purpose: The work presents a new method to produce cellular metallic material by pressing the alloy in the thixotropic semi-solid state into a layer of space holder particles, which are removed from the product after the forming operation. Design/methodology/approach: It is investigated the influence of the thixoforming temperature and the size of space holder particles, in the ability of penetration of the slurry in the porous preform as well as the structure of the obtained porous material (general aspect, quantitative and qualitative characterization of porosity microstructure of cells walls and density of the product). Findings: Cylindrical samples presenting three different ranges of porosity were produced. The cellular material obtained contains open porosity, being characterized as sponge. Products were analyzed by tomography and metallographic techniques. Results show that the proposed process is able to produce acceptable porous material, in a simple and low cost technique. The quality of the product depends rather on the processing temperature than on the size of space holder particles. Low liquid fraction in the thixotropic slurry can lead to incomplete infiltration and deformation of the preform. In the analyzed conditions influence of the size of space holder particles could be observed neither in the processing ability nor in the quality of the product. Density of produced porous material increases as processing temperature increases, due to the increase of cells walls thickness. Research limitations/implications: The investigated process is suitable only for alloys with a significant solidification range. Practical implications: The new method to produce cellular metals can represent energy savings and is highly operational when compared to conventional methods based on liquid infiltration, since lower temperatures are involved and no need of liquid handling is required. Originality/value: the process proposed is a new one; no techniques based on thixoforming of the alloy into porous preforms are known so far.

8

Production of cellular A2011 alloy from semi-solid state

Robert M. H., Delbin D.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

137--140

EN

Purpose: The work investigates a new method to produce cellular A2011 alloy and analyses the influence of processing parameters on the quality of the product. Design/methodology/approach: The proposed process involves pressing the alloy in the thixotropic semi solid state into a layer of space holder particles, which are removed after the forming operation. It is investigated the influence of the thixoforming temperature and the size of space holder particles, in the ability of penetration of the slurry in the porous pre-form as well as the structure of the obtained porous material. Products were analyzed by tomography and metallographic techniques. Findings: The proposed process showed to be able to produce acceptable porous material in a simple and low cost technique; the cellular material produced was characterized as sponge, as presented open and interconnected porosity. The quality of the product depends rather on the processing temperature than on the size of space holder particles. Low liquid fraction in the thixotropic slurry can lead to incomplete infiltration and deformation of the pre-form. In the analyzed conditions influence of the size of space holder particles could be observed neither in the processing ability nor in the quality of the product. Density of produced porous material increases as processing temperature increases, due to the increase of cells walls thickness. Research limitations/implications: The investigated process is suitable only for alloys with a significant solidification range. Practical implications: The new method to produce cellular metals can represent energy savings and is highly operational when compared to conventional methods based on liquid infiltration, since lower temperatures are involved and no need of liquid handling is required. Originality/value: The process proposed is a new one; no techniques based on thixoforming of the alloy into porous pre-forms are known so far.

9

Analiza wpływu wytrzymałości prętów sześciennej struktury komórkowej na rozkład granicznych energii

Kordzikowski P., Janus-Michalska M., Pęcherski R.B.

Rudy i Metale Nieżelazne

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2004

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R. 49, nr 3

114-120

PL

Celem pracy jest zbudowanie efektywnego modelu sprężystego zachowania się materiałów komórkowych oraz zastosowanie energetycznego kryterium J. Rychlewskiego do określenia stanu granicznego, który w tym wypadku odpowiada osiągnięciu granicy liniowej sprężystości. Przyjęto sześcienną strukturę komórkową o powtarzającym się regularnym układzie sześciu prętów połączonych w sztywnym węźle. Pręty mogą odkształcać się sprężyście pod wpływem sił osiowych lub momentów gnących sił poprzecznych. Wyznaczono w sposób analityczny moduły sprężyste oraz krytyczne energie dla trzech sprężystych stanów własnych. Zbadano możliwości modelowania rozkładu sztywności struktury z punktu widzenia energii krytycznych. Jako przykład do rozważań przyjęto na podstawie literatury strukturę kości gąbczastej, której budowa może być przynajmniej w przybliżeniu opisana omawianą sześcienną strukturą komórkową. Podobną analizę można przeprowadzić z większym lub mniejszym przybliżeniem także dla charakteryzujących się strukturą komórkową materiałów ceramicznych, polimerów oraz intermetalików.

EN

This work was aimed to develop a model of an elastic behaviour of cellular materials and to apply Rychlewski's energy criterion in the determination of a state of transition corresponding in this case to the limit of linear elasticity. A hexahedronal cellular structure with a repeated regular arrangement of six bars connected in a rigid node has been assumed. The bars can deform elastically under the influence of axial forces, bending moments or shearing forces. Coefficients of elasticity and critical energies for three elastic eigenstates have been determined analytically. The possibility of modelling structure rigidity distribution from the point of view of critical energies was studied. A spongy bone structure known from the literature, which can be approximately described by the hexahedronal cell structure, was taken as an example in analysing the problem. It is possible to perform similar approximate analysis for the ceramic, polymer and intermetallic materials characterised by a cellular structure.

10

Materiały wysokoporowate - metody wytwarzania i zastosowanie

Darłak P., Dudek P.

Odlewnictwo - Nauka i Praktyka

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2004

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R. 6, nr 1

3-17

PL

Autorzy, stawiając sobie za cel przybliżenie tematyki z zakresu materiałów porowatych, zwrócili szczególną uwagę na analizę wszystkich dostępnych informacji, opisujących metody ich wytwarzania, również w aspekcie zachodzącej ewolucji na przełomie kilkudziesięciu ostatnich lat. Biorąc pod uwagę fakt, że w Polsce znajomość zagadnień wytwarzania pian metalowych nie jest szeroko spopularyzowana, znaczna część artykułu poświęcona jest próbie scharakteryzowania znanych technik wytwarzania, jak również technologii od niedawna stosowanych, znajdujących się w fazie badań, tj. gazarów i pian syntaktycznych. W artykule zamieszczono szereg fotografii przedstawiających charakterystyki, budowę oraz zastosowanie materiałów komórkowych w konkretnych przykładach. Materiały wysokoporowate, z powodu swoich unikalnych właściwości fizycznych, głównie bardzo malej gęstości, zdolności do tłumienia energii mechanicznej oraz pochłaniania fal dźwiękowych, znalazły szerokie spektrum zastosowań. Ich odmienna budowa strukturalna idealnie predysponuje te materiały do zastosowania w przemyśle samochodowym, lotniczym i kosmicznym, otwierając tym samym olbrzymie rynki zbytu, stąd może wynikać zauważalnie wzrastające zainteresowanie materiałami o obniżonej gęstości.

EN

The authors presented many aspects of scope of manufacturing high porous materials. Therefore, a lat of information regarding metallic foams in various aspects, describing the production in the last century, has been collected. Taking into consideration that in Poland the knowledge concerning the metal foams is not widely highlighted, the significant part of publication describes existing commercial methods as well as methods being under investigation, namely: gasars and syntactic foams. In each chapter examples of characteristic structure as well as application of high porosity materials have been given. The porous materials, due to their unique physical properties, such as ultra-low density, ability to annihilate mechanical energy as well as sound wave, have found a wide spectrum of application. This fact stimulates their using in automotive, aircraft and space industries.

11

Elastic bending of an isotropic porous beam

Magnucki K., Stasiewicz P.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no 2

351-360

EN

The subject of this paper is an isotropic porous beam with a rectangular cross section. Mechanical properties of the isotropic porous material vary across the depth of the beam. A nonlinear hypothesis of deformation of a plane cross section of this beam is described. The system of differential equations and boundary conditions of the problem is derived on the basis of the principle of minimum potential energy. A numerical analysis for simply supported beams under uniformly distributed load is made. A comparative analysis with the use of FEM and the COSMOS/M system is presented.