Wyniki wyszukiwania - Biblioteka Nauki

1

Stability of hybrid rotating shaft with simply supported and/or clamped ends in a weak formulation

100%

Tylikowski A.

Journal of Theoretical and Applied Mechanics

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2008

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tom Vol. 46 nr 4

993-1007

EN

In this paper, a technique of dynamic stability analysis proposed for the conventional laminated structures is extended to activated shape memory alloy hybrid rotating structures axially loaded by a time-dependent force. In the stability study, the hybrid shaft is treated as a thin-walled symmetrically laminated beam containing both the conventional fibers, and the activated shape memory alloy fibers parallel to the shaft axis. The stability analysis method is developed for distributed dynamic problems with relaxed assumptions imposed on solutions. The weak form of dynamical equations of the rotating shaft is obtained using Hamilton's principle. We consider the influence of activation through the change of temperature on the stability domains of the shaft in the case when the angular velocity is constant. The force stochastic component is assumed in the form of ergodic stationary processes with continuous realisations. The study of stability analysis is based on examining properties of Liapunov's functional along a weak solution. Solution to the problem is presented for an arbitrary combination of simply supported and/or clamped boundary conditions. Formulas defining dynamic stability regions are written explicitly.

PL

W pracy rozszerzono możliwości analizy stabilności układów ciągłych na obracający się wał hybrydowy poddany czasowo zmiennej sile osiowej przy osłabionych założeniach spełnianych przez rozwiązania. Kompozytowy wał hybrydowy obracający się ze stałą prędkością kątową traktowany jest jako cienkościenna belka zawierającą obok klasycznych włókien również włókna wykonane z materiału z pamięcią kształtu. Słabą postać równań ruchu wału wyprowadzono z zasady Hamiltona. Rozpatrzony jest wpływ aktywacji termicznej na obszar stabilości wału przy założeniu nie tylko swobodnego podparcia obu końców wału, lecz również przy podparciu utwierdzonym i mieszanym. Podczas wyprowadzania warunków stabilności korzysta się z badania właściwości funkcjonału Lapunowa wzdłuż rozwiązania słabych równań ruchu wału. Wyprowadzono jawną postać warunków stabilności.

2

Dynamics of thermally activated shape memory alloy reinforced laminated beams

100%

Pietrzakowski M.

Journal of Theoretical and Applied Mechanics

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1998

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tom nr 4

879-893

EN

A way of use of shape memory alloy (SMA) fibers for dynamics response modification of laminated beams is presented in the paper. The considered concept of adaptive control is based on the ability to change the Young modulus during a temperature activated, reversible, martenstic transition that is specific to SMAs. It is assumed that the laminate is midplane symmetric and the corresponding layers of the same fiber orientation are activated simultaneously, and the SMA fibers can freely elongate in the matrix. A cantilever laminated beam with mass distributed on its free edge is subject to numerical analysis. Due to the quasi-steady one-dimensional model of heat conduction, martensite fraction and natural frequency time relations for the phase transition of SMA have been obtained. The influence of temperature on natural frequencies of the system has been analysed for some different locations of activated plies and directions of SMA fibers. The frequency response functions varying with the material phase transformation for a harmonic load acting on the free end of the beam have also been presented.

PL

W pracy przedstawiono zastosowanie włókien ze stopu z pamięcią kształtu (SMA) do modyfikacji właściwości dynamicznych belek laminowanych. Koncepcję adaptacyjnego sterowania oparto na unikalnej zdolności stopów SMA do wyraźnej zmiany wartości modułu Younga w procesie odwracalnej przemiany martenzytycznej wywołanej temperaturą. Założono, że warstwy laminatu są ułożone i uaktywniane symetrycznie względem powierzchni środkowej, a włókna SMA mogą swobodnie odkształcać się w osnowie. Symulacja numeryczna dotyczy belki laminowanej utwierdzonej wzdłuż jednego brzegu, z masą równomiernie rozłożoną na swobodnym, przeciwległym brzegu. Zgodnie z przyjętym stacjonarnym, jednowymiarowym modelem przewodnictwa cieplnego, wyznaczono przebiegi czasowe temperatury i zawartości martenzytu we włóknach SMA, oraz przebiegi podstawowej częstości własnej w zakresie przemiany fazowej. Zbadano wpływ temperatury na częstości własne zmieniając położenie warstw uaktwnianych a także kierunek ułożenia włókien SMA. Zakładając wymuszenie harmoniczne działające na swobodny brzeg belki, wyznaczono charakterystyki amplitudowo-częstotliwościowe odpowiadające pełnemu zakresowi transformacji fazy materiałowej.

3

Properties changes of Co-based amorphous alloy in thermal activation process

63%

Spilka M. , Griner S. , Kania A.

Archives of Materials Science and Engineering

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2013

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tom Vol. 64, nr 2

118--124

EN

Purpose: The paper presents a stress relaxation process of Co69Mo2Fe4Si14B11 metallic glass and properties changes in a temperature range up to 300 ºC after annealing from 1 to 16 hours (in case of plasticity and stress relaxation researches) and 2 hours (for the magnetic properties investigations). Design/methodology/approach: The plastic properties of the studied material were determined using the bend test, applied for metallic glasses. The investigations of magnetic properties were carried out using the Ferrometer measurement system. For the higher frequencies the Remacomp C-100 system was used, allowing determination of the magnetic properties of the ferromagnetic cores. Stress relaxation investigations in metallic glasses by a bending test were carried out. Findings: The influence of thermal activation on the properties changes of Co-based metallic glass was determined after annealing from temperature of 150 to 300°C. After the heat treatment carried out the best magnetic properties were obtained for the sample annealed for 2 hours at 150°C. The increase of the magnetic field frequencies causes a significant deterioration of the material magnetic properties. High plasticity the metallic glass ribbons have to 200°C during annealing to 16 hours. Increasing the annealing temperature causes brittleness of the material. Distinct relaxation processes are observed at higher temperatures and annealing times. Research limitations/implications: Metallic glasses after heat treatment become brittle, which reduces the possibility of using these materials, and often impossible to change their geometric form. Therefore, the heat treatment of metallic glasses must be carried out after the final forming of the geometry of shaped, cores, etc., or in conditions not leading to embrittlement of the material. Practical implications: Usage of metallic glasses is possible only in a narrow range of temperatures which does not lead to significant changes of properties or after proper heat treatment carried out in the aim of specified physical properties obtaining. The important is prediction of alloy properties changes during temperature changes and material using. Originality/value: In the article influence of low-temperature thermal activation processes, which was conducted up to 16 hours, on the stress relaxation and significant changes of magnetic properties of cobalt-based metallic glass were presented.

4

Heterogeneity of mechanical properties and fractures of Co-based metallic glass in a low-temperature thermal activation process

63%

Griner S. , Spilka M. , Kania A.

Journal of Achievements in Materials and Manufacturing Engineering

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2014

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tom Vol. 66, nr 2

53--60

EN

Purpose: The paper presents the changes of mechanical properties and the fractures of Co70.5Fe2.5Mn2Mo1Si9B15 metallic glass ribbons after a low-temperature activation process. Design/methodology/approach: The studied alloy was fabricated by continuous casting of the alloy stream on a turning wheel. The plastic properties were determined using the bend test. The investigations of unit cracking energy using the “tearing” test on the testing machine were carried out. The structure testing in transmission electron microscope and the static tensile test on the Instron testing machine were also carried out. Findings: The studies for 5 samples and for 2 ribbon sides were carried out. The highest plasticity occurred after annealing at 200°C for 1 h. The differences of mechanical properties in a function of a cross section of the ribbon were also presented. Practical implications: Despite the occurrence of heterogeneity of properties on the thickness of metallic glass ribbon the essential meaning have the averaging properties of a product which decided about possibility of practical application. Originality/value: In the article there was found that studied samples obtain different plasticity and different value of the yield point in the different bending methods.

5

Mechanical properties of a squeeze cast Mg-Al-Sr alloy

63%

Trojanová Z. , Drozd Z. , Lukáč P. , Chatey A.

Archives of Materials Science and Engineering

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2008

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tom Vol. 29, nr 2

97-104

EN

Purpose: The aim of the present work is to study the influence of temperature on tensile properties of the magnesium alloy AJ50, and to discuss possible hardening and softening mechanisms and thermally activated processes. Design/methodology/approach: Deformation behaviour of a Mg-Al-Sr magnesium alloy has been studied in tension as well as compression in the temperature interval from room temperature up to 300°C. Stress relaxation tests were performed with the aim to find applied stress components (internal stress and effective stress) and parameters of the thermally activated process/-es. Findings: The yield stress as well as the maximum stress of the alloy are very sensitive to the testing temperature. The work hardening coefficient O=dδ/dε decreases with increasing stress and temperature. Performed analysis of the O-α plots determined the hardening and softening mechanisms operating during the deformation. The internal stress decreses with increasin temperature, while the effective stress component increases. Practical implications: Estimated values of the activation volume as well as the activation energy indicate that the main thermally activated process is connected with the rapid decrease of the internal stress. Originality/value: An analysis showed that the main hardening process is the storage of dislocations at impenetrable obstacles. The activation

6

Kompozyty cementowe modyfikowane aktywowanym termicznie dodatkiem recyklingowym

63%

Kalinowska-Wichrowska K.

Acta Scientiarum Polonorum. Architectura

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2019

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tom 18

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nr 1

PL

W artykule zaprezentowano wyniki badań własnych nad kompozytami cementowymi, których skład zmodyfikowano dodatkiem recyklingowym powstałym (obok kruszyw recyklingowych) w wyniku specjalnie opracowanego procesu recyklingu betonu objętego polskim patentem PAT.229887 (2018). Wykorzystanie tak przygotowanej zaprawy recyklingowej w charakterze dodatku typu II lub jedynie wypełniacza w kompozytach cementowych to trafna droga do zagospodarowania tego materiału i silny akcent w kierunku zrównoważonego budownictwa. Jak dowodzą wyniki badań, odpowiednio dobrane parametry procesu obróbki cieplno-mechanicznej pozwalają na aktywację właściwości pucolanowych tego materiału. Proponowana metoda recyklingu jest przykładem kompleksowego rozwiązania problemu, jakim jest całkowite przetworzenie gruzu betonowego w wartościowe produkty wtórne i ponowne włączenie ich do procesu produkcji budowlanej.

EN

The article presents the results of the research on cementitious composites, the composition of which was modified by a recycled additive, created (next to recycling aggregates) as a result of a specially selected concrete recycling process according to Polish patent PAT.229887 (2018). The use of a specially prepared recycling mortar as a type II additive or only a filler in cement composites, is the right way to develop this material and a strong stress towards sustainable construction. Properly selected parameters of the thermo-mechanical treatment process enable activation of pozzolana properties of this material. The proposed recycling method is an example of a comprehensive solution to the problem of complete conversion of concrete debris into valuable secondary products and their re-integration into the construction production process.

7

Compressive behaviour of a squeeze cast AJ50 magnesium alloy

63%

Trojanová Z. , Drozd Z. , Lukáč P.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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tom Vol. 22, nr 2

47-50

EN

Purpose: There is very limited information about the mechanical properties of Mg-Al-Sr alloys and therefore it is important to investigate mechanical properties at different temperatures and to estimate the mechanisms responsible for the deformation behaviour of Mg-Al-Sr alloys at elevated temperatures. Design/methodology/approach: Deformation behaviour of a Mg-Al-Sr magnesium alloy has been studied in compression in the temperature interval from room temperature up to 300 degrees centigrade. Stress relaxation tests were performed with the aim to find parameters of the thermally activated process. Findings: The yield stress as well as the maximum stress of the alloy are very sensitive to the testing temperature. Analysis of the work hardening coefficient determined the hardening and softening mechanisms operating during the deformation. Practical implications: The estimated activation energy and values of the activation volume indicate that the main thermally activated process is very probably the glide of dislocations in the non-compact planes. Originality/value: An analysis showed that the main hardening process is the storage of dislocations at impenetrable obstacles. The activation volume values indicate that the main thermally acivated process is connected with recovery process.

8

Wpływ warunków termicznej aktywacji ekspandowanego grafitu na aktywność elektrochemiczną w procesie utleniania fenolu

63%

Krawczyk P. , Skowroński J. M.

Przemysł Chemiczny

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2009

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tom T. 88, nr 6

668-672

9

Improved rate controlled model for stress relaxation in vegetable tissue

63%

Blahovec J.

International Agrophysics

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2001

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tom 15

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nr 2

10

Application of Daftardar-Gejiji and Jafari method to kinetic analysis of thermal inactivation of Jack bean urease

51%

Sobamowo G. , Adeleye O.

Journal of Applied Mathematics and Computational Mechanics

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2018

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tom Vol. 17, nr 2

65--76

EN

Jack bean urease has been used as a good catalyst for hydrolysis of urea in various applications such as biotechnology and biomedical engineering. The wide range of applications require proper understanding of the thermal inactivation of the enzyme. Consequently, the theoretical analysis of the enzyme kinetic of the thermal inactivation is required. In this paper, a new iterative method proposed by Daftardar-Gejiji and the Jafari method is applied to analyse the kinetic of thermal inactivation of jack bean urease (EC3.5.1.5). The kinetics of the urease consist of three-reaction steps and included the Arrhenius equation for temperature-dependent rate constants as well as the temperature change in the initial heating period. The approximate analytical solutions are verified with results of numerical method using Runge-Kutta with the shooting method, and good agreements are established between the results of the methods. From the analytical investigation, it is established that the molar concentration of the native enzyme decreases as the time increases while the molar concentration of the denatured enzyme increases as the time increases. The time taken to reach the maximum value of the molar concentration of the native enzyme is the same as the time taken to reach the minimum value of the molar concentration of the denature enzyme. It is hoped that the information given in this theoretical investigation will assist in the kinetic analysis of thermal inactivation of the experimental results over handling rate constants and molar concentrations.

11

The effectiveness of modified sodium bicarbonate in the purification of exhaust gases from HCl and HF

51%

Wysocki D. , Szymanek A.

Journal of Achievements in Materials and Manufacturing Engineering

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2022

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tom Vol. 114, nr 2

57--66

EN

Purpose: The effectiveness of gas purification depends on the sorption properties of sorbents. The aim of the research was to determine the ability of sodium sorbents to remove gaseous pollutants such as HCl and HF. Design/methodology/approach: The research used baking soda subjected to mechanical and thermal activation, which was introduced into the hot flue gas circuit, similar to the dry flue gas cleaning method used in all kinds of boilers. Findings: In almost all cases, mechanical and thermal treatment of baking soda allowed for a significant improvement in the reduction of hydrogen chloride and hydrogen fluoride concentrations in the exhaust gases produced during the combustion of polyethylene terephthalate (PET) bottles. Research limitations/implications: The preparation of sorbents must consider the optimum development of the material's specific surface area, especially during thermal activation, to prevent pores from sintering. Practical implications: In wet and dry flue gas cleaning processes, sodium compounds are used in the power industry. Appropriate preparation of the sorbent allows for improving the effectiveness of reducing the concentration of harmful substances and reducing investment and operating costs. Originality/value: From the point of view of process optimisation, the results obtained will contribute to the identification of optimal operating conditions in dry sorbent injection systems to prevent the pores on the surface of the sorbent from clogging when injected into hot flue gases.

12

Thermogravimetric studies of active carbons from lignocellulosic materials

51%

Pawlicka A. , Bartkowiak M. , Doczekalska B.

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2013

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tom 84

13

Non-Ferrous Metal Sorbents Based on Waste and Side Products of Mineral Benefication Plants

51%

Minenko V. , Denisova J. , Samusev A. , Makarov D.

Inżynieria Mineralna

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2019

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tom R. 21, nr 1

99--104

EN

The saponite-containing product from the stage of process water clearing at benefication plant of the PAO Severalmaz was thickened using the electrochemical separation for use as sorbent of nickel and copper ions. The product features a high sorption capacity relatively the nickel and copper ions. It has been established that the sorption capacity can be enhanced by roasting the product at 750°С to 194 and 212 mg/g for the nickel and copper ions respectively. An organomineral sorbent for nickel ions based on copper-nickel ore tailings of the JSC „The Kolskaya Mining and Metallurgical Company”, thermally activated at 700ºС, has been synthesized. The surface modification was performed by using the non-covalent immobilization of dimethylglyoxime.

PL

Produkt zawierający saponit z etapu oczyszczania wody technologicznej w zakładzie wzbogacania PAO Severalmaz został zagęszczony przy użyciu rozdzielania elektrochemicznego w celu zastosowania jako sorbent jonów niklu i miedzi. Produkt cechuje się dużą pojemnością sorpcyjną, w stosunku do jonów niklu i miedzi. Ustalono, że pojemność sorpcyjna może być zwiększona przez prażenie produktu w temperaturze 750°C do 194 i 212 mg/g odpowiednio dla jonów niklu i miedzi. Zsyntetyzowano organo-mineralny sorbent dla jonów niklu oparty na odpadach z wzbogacania rud miedzi i niklu JSC „The Kolskaya Mining and Metalurgical Company”, aktywowany termicznie w 700ºС. Modyfikację powierzchni przeprowadzono stosując niekowalencyjną immobilizację dimetyloglioksymem.