Wyniki wyszukiwania - Biblioteka Nauki

1

Fractional calculus for continuum mechanics – anisotropic non-locality

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Sumelka W.

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2016

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tom Vol. 64, nr 2

361--372

EN

In this paper, a generalisation of previous author’s formulation of fractional continuum mechanics for the case of anisotropic non-locality is presented. The discussion includes a review of competitive formulations available in literature. The overall concept is based on the fractional deformation gradient which is non-local due to fractional derivative definition. The main advantage of the proposed formulation is its structure, analogous to the general framework of classical continuum mechanics. In this sense, it allows to define similar physical and geometrical meaning of introduced objects. The theoretical discussion is illustrated by numerical examples assuming anisotropy limited to single direction.

2

A note on non-associated Drucker-Prager plastic flow in terms of fractional calculus

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Sumelka W.

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2014

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tom Vol. 52 nr 2

571--574

EN

In this paper, we consider a special case of the general fractional plastic flow rule, namely the one which is equivalent to the classical non-associated Drucker-Prager (D-P) plasticity model. Fractional plastic flow is obtained from the classical flow rule by generalisation of the classical gradient of a plastic potential with a fractional gradient operator. It is important that, contrary to the classical models, non-associativity of fractional flow appears without introduction of the additional potential. The classical associative D-P plasticity is obtained as a special case. The discussion on objectivity of the fractional gradient is also presented also.

3

Large scale architectural glass slumping process - challenges and limitations

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Malewski A. , Kozłowski M. , Sumelka W. , Połedniok M.

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2020

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tom Vol. 66, nr 4

485--505

EN

The paper focuses on the development of knowledge about the hot bending of curved architectural glass produced by the slumping process and the challenges as well as the limitations thereof. Due to the complexity of the process, many factors influence the final quality of the glass and the main objective was to better understand the procedure itself in order to improve the control and quality of the slumping process. As a result of the growing interest in this type of glass for architectural applications, the glass processing market is increasingly investing in the required technology. For the moment, this growing niche does not have a large number of direct explanations of the glass behaviour in the furnace in the available literature, which in turn encourages cooperation between the scientific community and manufacturers. This paper presents the conducted experiments that have led to a better understanding of the furnace's work and the impact of specific factors on its operation. Based on the 3D numerical model, a large sample of glass was produced, which was then scanned with a 3D laser using a method developed for the experiment. The results suggested that a more accurate test with usage of a full-size furnace is required. Based on this, the experiment was carried out using a large number of glass samples of different thicknesses. The results of the experiment helped to better understand and demonstrate the need for further research of this technology in order to optimize the quality of the process.

PL

W artykule skupiono się na rozwoju wiedzy na temat wielopłaszyznowego gięcia na gorąco szkła architektonicznego produkowanego w procesie opadania oraz na wyzwaniach i ograniczeniach samego procesu. Ze względu na złożoność procesu, wiele czynników wpływa na końcową jakość szkła, a głównym celem było lepsze zrozumienie samej procedury w celu poprawy kontroli i jakości procesu produkcji tego typu szkła. W związku z rosnącym zainteresowaniem tego rodzaju szkłem do zastosowań architektonicznych, rynek przetwórstwa szkła coraz częściej inwestuje w wymagane technologie. W chwili obecnej ta rosnąca nisza nie ma w dostępnej literaturze wielu bezpośrednich wyjaśnień na temat zachowania się szkła w piecu, co z kolei zachęca do współpracy pomiędzy środowiskiem naukowym a producentami. W niniejszym artykule przedstawiono przeprowadzone doświadczenia, które doprowadziły do lepszego zrozumienia pracy pieca oraz wpływu poszczególnych czynników na jego funkcjonowanie. W oparciu o trójwymiarowy model numeryczny wyprodukowano dużą próbkę szkła, która następnie została zeskanowana laserem 3D metodą opracowaną na potrzeby eksperymentu. Wyniki sugerowały, że konieczny jest dokładniejszy test z wykorzystaniem pełnowymiarowego pieca. Na tej podstawie eksperyment został przeprowadzony z wykorzystaniem dużej liczby próbek szkła o różnej grubości. Wyniki eksperymentu pozwoliły lepiej zrozumieć i wykazać potrzebę dalszych badań tej technologii w celu optymalizacji jakości procesu.

4

The analysis of non-linear free vibration of FGM nano-beams based on the conformable fractional non-local model

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Rahimi Z. , Sumelka W. , Shafiei S.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2018

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tom Vol. 66, nr 5

737--745

EN

Continuum models generalized by fractional calculus are used in different mechanical problems. In this paper, by using the conformable fractional derivative (CFD) definition, a general form of Eringen non-local theory as a fractional non-local model (FNM) is formulated. It is then used to study the non-linear free vibration of a functional graded material (FGM) nano-beam in the presence of von-Kármán non-linearity. A numerical solution is obtained via Galerkin and multiple scale methods and effects of the integer and non-integer (fractional) order of stress gradient (in the non-local stress-strain relation) on the ratio of the non-local non-linear natural frequency to classical non-linear natural frequency of simply-supported (S-S) and clamped-free (C-F) FGM nano-beams are presented.

5

Towards the Modelling of Anisotropic Solids

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Glema A. , Łodygowski T. , Sumelka W.

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2010

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tom Vol. 16, No. 1

73-84

EN

In the paper the material model for metals and its numerical applications are presented. The material model is stated in terms of continuum mechanics, in the framework of the thermodynamical theory of viscoplasticity. The fundamental achievement is that the constitutive relation includes a description of anisotropy of metal microstructure. Such approach gives qualitatively and quantitatively new results compared with the existing models because it is possible to trace the directions of softening and predict a damage path in process time. Numerical examples comprise full spatial modelling for HSLA-65 steel in adiabatic conditions (the analysis of anisotropic bodies can be led only on 3D models) including: tension of sheet steel and twisting of thin walled tube. During analyses strain rates of order 104-107 s–1 are observed and the process time up to full damage (loss of continuity in the localisation zone) is around 100-300 mi s.

6

Piotr Perzyna : Scientific Conductor within Theory of Thermo-Viscoplasticity

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Glema A. , Łodygowski T. , Sumelka W.

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tom Vol. 62, iss. 3

193–-219

EN

In this paper, authors reminisce on years of scientific cooperation and achievements on the personality of Piotr Perzyna and his Theory of Thermo-Viscoplasticity, which are displayed from remembrance. All the essence of latin words Master, Doctor, Docent, Professor are in some kind the reflection of the scientific history that has happened during the last 40 years. For every author the shift of 10 to 20 years shows that Piotr Perzyna served with his personality and knowledge for two to three different generations, working with authors as 20/30/50 years younger man. Now, one year after Piotr Perzyna passed away in 2013 (50 years after publishing the basic paper on Theory of Thermo-Viscoplasticity in 1963), the role he has played for authors has become much clearer and conspicuous as well as in a wider context. Like P iotr = P eter = P etrus = Kηϕας ´ Professor Perzyna is the rock on which we build. Let it remain not only in memory.

7

Determination of hazardous metal ions in the water with resonant MEMS biosensor frequency shift – concept and preliminary theoretical analysis

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Rahimi Z. , Yazdani J. , Hatami H. , Sumelka W. , Baleanu D. , Najafi S.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2020

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tom Vol. 68, nr 3

529--537

EN

Heavy metal ions (e.g. cadmium, chromium, copper, nickel, arsenic, lead, zinc) have significantly serious side effects on the human health. They can bind with proteins and enzymes, altering their activity, increasing neurotoxicity, generating reactive oxygen species (ROS), promote cellular stress and resulting in their damage. Furthermore, the size, shape and type of metal are important for considering nano- or microtoxicity. It then becomes clear that the levels of these metals in drinking water are an important issue. Herein, a new micro-mechanical sensor is proposed to detect and measure these hazardous metals. The sensor consists of a micro-beam inside a micro-container. The surface of the beam is coated with a specific protein that may bind heavy metals. The mass adsorbed is measured using the resonant frequency shift of the micro-beam. This frequency shift due to the admissible mass (which is considered acceptable for drinking water based on the World Health Organization (WHO) standard) of manganese (Mn), lead (Pb), copper (Cu) and cadmium (Cd) is investigated for the first, second and third mode, respectively. Additionally, the effects of micro-beam off-center positions inside the micro-container and the mass location and investigated.

8

Wybrane aspekty bezpieczeństwa ludzi, budynków i mienia poprzez systemy ochrony pasywnej

38%

Łodygowski T. , Sielicki P. W. , Sumelka W. , Peksa P. , Olejnik M. , Puk K.

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tom nr 5

926--938

PL

Aktualny stan wiedzy w zakresie ochrony i bezpieczeństwa ludzi, budynków i mienia narażonych na działania terrorystyczne, a w szczególności eksplozje materiałów wybuchowych jest obecnie pomijany w polskich przepisach dotyczących infrastruktury publicznej w tym bezpieczeństwa ludzi na ulicach aglomeracji miejskiej. Wydarzenia z ostatnich lat (zamach podczas maratonu w Bostonie USA w kwietniu 2013 roku) wskazują na powiększającą się konieczność rozpatrzenia kwestii bezpieczeństwa aglomeracji miejskich, w tym w szczególności podczas imprez masowych. Niniejsza praca obejmie swym zakresem dyskusję wybranych aspektów projektowania systemów ochrony pasywnej. Wytyczne, bazują na doświadczeniach uzyskanych w trakcie wcześniejszych badań eksperymentalnych i teoretycznych oraz najnowszych osiągnięciach będących rezultatem badań w ramach grantu UOD-DEM-1-203/001, Temat: Modularny system ekranów szybkiego montażu dla ochrony ludzi, budynków i mienia przed skutkami wybuchu. Kierownik: Prof. T.Łodygowski, Politechnika Poznańska, czas trwania : 2013-2016.

EN

Extremely high pace of development force engineers to handle complicated and unusual problems. Commonly accepted design methodologies very often must undergo severe changes and improvements exceeding widely accepted standards to deliver the reliable results. The authors of this work handle complex problem of explosive loading also known as high velocity impulse loading which occurs during an impact. The class of such problems very often refers to the unusual impulse which, in particular, can be subjected to the masonry structures. These commonly used long structures can be characterized as composite material composed of two distinct sections: bricks and mortar. Moreover, the passive safety system is adopted to increase the threshold of the masonry. Additionally, the steel wired mesh and aramid fabrics are used to retrofit the brick wall.