Wyniki wyszukiwania - Biblioteka Nauki

1

Analysis by numerical calculations of the depth and dynamics of the penetration of ordered cellular structure made by casting from AlSi10Mg eutectic alloy

100%

Piekło J. , Pysz S. , Małysza M. , Karwiński A.

Archives of Foundry Engineering

|

2011

|

tom Vol. 11, iss. 3 spec.

171--176

EN

Owing to high plastic deformability while maintaining stress values constant and relatively low, ordered cellular structures are characterised by excellent properties and the ability to dissipate the impact energy. Due to the low weight, structures of this type can be used, among others, for different parts of motor vehicles. For tests, a trapezoidal ordered cellular structure of 50.8 x 50.8 x 25.4 (mm) overall dimensions was selected. It was made as an investment casting from AlSi9Mg eutectic alloy by the method of Rapid Prototyping (RP). During FEM computations using an Abaqus programme, it was assumed that the material is isotropic and exhibits the features of an elastic – plastic body, introducing to calculations the, listed in a table, values of the stress-strain curve obtained in tensile tests performed on a MTS testing machine (10T). The computations used Johnson - Cook model, which is usually sufficiently accurate when modelling the phenomena of penetration of an element by an object of high initial velocity. The performed numerical calculations allowed identification of changes in speed and energy of the penetrator during structure perforation.

2

Design and rapid manufacture of selected cellular type structures

100%

Dotcheva M. , Thomas D. , Millward H.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

|

2008

|

tom z. 73 [253]

81-88

EN

The work presented in this paper aims to explore the enhancements that the Selective Laser Melting technology can bring to the design, manufacture, and performance of cellular type structures. Cellular type structures possess valuable characteristics such as low density, high strength, good energy absorption, good thermal and acoustic properties. These advantageous characteristics make them industry desirable but the difficulties of producing them limit their applications. The capabilities of some metal cellular structures as fundamental elements for creating new internal material configurations for injection moulding tools hat been evaluated. The preliminary investigation highlights ihe requirements and the feasibility of such structures for the purpose of injection moulding tooling. Lattice cellular structures appear to be mechanically competitive alternatives to prismatic honeycombs structures. It has been illustrated that lattice core of injection moulding can be capable of supporting significant structural and process loads while also could facilitating cross flow heat exchange.

3

Cellular structure of detonation wave in hydrogen-methane-air mixtures

84%

Porowski R. , Teodorczyk A.

|

tom Vol. 91, nr 3

130-135

EN

The paper reports on an experimental study of the cellular structure of detonation waves in hydrogen-methane-air mixtures. Experiments were performed in a 6-m circular cross section tube with inner diameter of 140 mm (full diameter of 170 mm) and a 0.8-m driver section tube with inner diameter of 90 mm. The initial conditions of stoichiometric hydrogen-methane-air mixtures were 1 atm and 293 K with varoius hydrogen content. The average detonation cell size for stoichiometric hydrogen-methane-air mixtures obtained by the smoked foil technique during the experiments was calculated with the 2D Fourier transform. Using the Cantera program, the detonation cell width was computed as a function of initial pressure and molar methane fraction in fuel for a stoichiometric methane-hydrogen-air mixture at initial temperature 295 K. The results of the computations were compared against the experimental results.

4

Glassy carbon foams as skeleton reinforcement in polymer composite

84%

Myalski J. , Hekner B.

Composites Theory and Practice

|

2017

|

tom R. 17, nr 1

41--46

EN

Glassy carbon foams were produced by the pyrolysis process using polyurethane foam with a layer of phenol-formaldehyde resin as the precursor. The pyrolysis process was conducted in vacuum conditions at 1000°C. The pyrolysis conditions were determined on the basis of carried out thermogravimetric analysis. The basic mechanical properties like the compressive strength of the carbon foams was measured and compared with the theoretical value. Furthermore, the glassy carbon foams were applied as skeleton reinforcement in epoxy resin matrix composites. Analysis of the mechanical properties revealed that the values of hardness and compressive strength of materials with spatial carbon foam are almost two times higher than for a pure matrix applied as the reference material. The major factors that influenced the final mechanical properties are the quality of the obtained foams and the amount of carbon in the material volume. Moreover, it was proved that the application of carbon foam with low mechanical properties led to significant increases in the compressive strength of the composite materials.

PL

Prezentowane w niniejszej pracy pianki z węgla szklistego zostały otrzymane w procesach pirolizy preform poliuretanowych z warstwą żywicy fenolowo-formaldehydowej. Proces pirolizy został przeprowadzony w warunkach odmiennych w stosunku do stosowanych powszechnie technologiach. W tym przypadku zastosowano próżnię oraz temperaturę 1000°C. Warunki pirolizy określono na podstawie przeprowadzonej analizy termograwimetrycznej. Właściwości mechaniczne otrzymanych pianek węglowych wyznaczono na podstawie wytrzymałości na ściskanie. Otrzymane dane porównano z wartościami teoretycznymi wyznaczonymi według równania Ashby’ego i Gibsona. Ponadto, w ramach badań wytworzono kompozyty z osnową polimerową, wzmocnione prezentowanymi pianami węglowymi. Analiza właściwości mechanicznych wykazała, że wartość twardości oraz wytrzymałości na ściskanie kompozytów wzmocnionych strukturami węglowymi jest niemal dwukrotnie wyższa od wartości czystej żywicy epoksydowej - materiału referencyjnego. Określono, że najważniejszymi czynnikami mającymi wpływ na właściwości mechaniczne są jakość wytworzonej pianki oraz ilość węgla w objętości materiału kompozytowego. Ponadto zostało udowodnione, że zastosowanie pianek węglowych o niskich właściwościach mechanicznych prowadzi do znacznego wzrostu wytrzymałości na ściskanie materiałów kompozytowych na osnowie polimerowej.

5

Modelling of the material destruction of vertically arranged honeycomb cellular structure

84%

Piekło J. , Małysza M. , Dańko R.

Archives of Civil and Mechanical Engineering

|

2018

|

tom Vol. 18, no. 4

1300--1308

EN

The paper presents the results of the experimental and numerical analysis of material destruction of honeycomb cellular structure. Based on the experimental research, the results of numerical calculations regarding the compression process were verified along with the correctness of used constitutive numerical model. The destruction was analyzed for the casting with no structural defects and for the casting with detected porosities. The results were compared to the structural strength of the honeycomb structure manufactured on the CNC machine. The metallic honeycomb structure was manufactured as a casting of Al alloy in the investment casting technology. For manufacturing purposes the honeycomb model was obtained in additive manufacturing process. The castings and the CNC honeycomb were used in the compression test trials. The process was controlled by the displacement and the results were registered as the changes of the height and the force value. Based on the experimental results the numerical model of honeycombs was introduced for the numerical analysis of the energy absorption and compression process. The results showed good correlation between the experiment and FEM (Finite Element Method) analysis.

6

Biobased polyurethane foams modified with natural fillers

67%

Prociak A. , Kurańska M. , Malewska E. , Szczepkowski L. , Zieleniewska M. , Ryszkowska J. , Ficoń J. , Rząsa A.

Polimery

|

2015

|

tom T. 60, nr 9

592--599

EN

Two biopolyols have been synthesized from rapeseed oil and applied to obtain rigid and flexible polyurethane foams. Biopolyols were prepared using a two-step method of epoxidation and opening of the oxirane rings. It was found that, regardless of the type of prepared foams, the addition of biopolyols to the polyurethane composition reduces its reactivity, which was confirmed by changes of the dielectric polarization, as well as the reduction of the maximum temperature in the foam core during the foaming process. In the case of the rigid polyurethane polyol, biomodification caused a decrease of the apparent density of the foams, but the foam involving biopolyol had a higher compressive strength. An increase of added ground walnut shells in rigid polyurethane foams also improved their mechanical properties. The introduction of a biopolyol based on rapeseed oil and ultra-fine cellulose to the polyurethane formulation resulted in high resilience flexible foams with improved comfort factor.

PL

Z oleju rzepakowego zsyntetyzowano dwa rodzaje biopolioli, które zastosowano następnie do wytworzenia sztywnych i elastycznych pianek poliuretanowych. Biopoliole otrzymywano dwuetapową metodą epoksydacji i otwarcia pierścieni oksiranowych. Stwierdzono, że — niezależnie od rodzaju pianek — użyty biopoliol wpływa na zmniejszenie reaktywności systemu poliuretanowego, co potwierdzają zmiany polaryzacji dielektrycznej, a także obniżenie maksymalnej temperatury w rdzeniu pianek w trakcie procesu spieniania. W przypadku sztywnych pianek poliuretanowych modyfikacja biopoliolem spowodowała zmniejszenie gęstości pozornej pianek i poprawę ich wytrzymałości na ściskanie. Wprowadzenie napełniacza w postaci zmielonych skorup orzecha do kompozycji pianek sztywnych również poprawiło ich właściwości mechaniczne. Zastosowanie modyfikacji biopoliolem z oleju rzepakowego oraz dodatkiem ultradrobnych cząstek celulozy umożliwiło wytworzenie pianek elastycznych o zwiększonej wartości współczynnika komfortu z zachowaniem dużej odbojności.

7

Flax fibers as natural filler for rigid polyurethane-polyisocyanurate foams based on bio-polyol from rapeseed oil

67%

Kurańska M. , Prociak A.

|

2015

|

tom R. 112, z. 1-Ch

47--54

EN

The influence of flax fibers on the physical and mechanical properties and the flammability of rigid polyurethane-polyisocyanurate foams obtained from rapeseed oil-based polyol was analyzed. The rigid polyurethane-polyisocyanurate foams with apparent density of 40−48 kg/m3 were prepared. It has been found that the introduction of flax fiber has a beneficial effect on selected properties of obtained foams.

PL

Analizowano wpływ włókien lnianych na właściwości fizykomechaniczne oraz palność sztywnych pianek poliuretanowo-poliizocyjanurowych otrzymanych z udziałem bio-poliolu z oleju rzepakowego. Otrzymano porowate materiały poliuretanowo-poliizocyjanurowe o gęstościach pozornych w zakresie 40−48 kg/m3. Stwierdzono, że wprowadzenie włókien lnianych wpływa korzystnie na wybrane właściwości otrzymanych pianek.