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1

Numerical Analysis of the Folding of Fabric Sheets Under Given Boundary Conditions

Szablewski Piotr

Przegląd Włókienniczy - Włókno, Odzież, Skóra

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2023

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nr 6

36--42

EN

This paper deals with the numerical analysis of a stacking or folding of the flat textiles. This may be used for the solution of large deflection problems of flexible strips such as fabric sheets. It was assumed that during the run of bending phenomenon the flat strip of the fabric will be represented as its longitudinal section. The mathematical model of the fabric was presented as a flat deflection curve, i.e. heavy elastica. Elastica was described using the system of six first-order differential equations accompanied by a set of boundary conditions. The problem was solved by the numerical shooting method. The investigations can be used for simulation of fabric folding, stacking and for another applications from the field of textile mechanics.

PL

W artykule opisano analizę numeryczną procesu układania (składania) płaskich wyrobów tekstylnych. Przedstawiona metoda może być wykorzystana do rozwiązywania problemów dużych ugięć takich obiektów, jak np. płaski pas tkaniny. Założono, że w trakcie przebiegu zjawiska zginania płaski pas tkaniny będzie reprezentowany jako przekrój podłużny. Model matematyczny tkaniny przedstawiono w postaci płaskiej krzywej ugięcia, czyli ciężkiej elastyki. Elastyka została opisana za pomocą układu sześciu równań różniczkowych pierwszego rzędu wraz z zestawem odpowiednich warunków brzegowych. Problem rozwiązano numeryczną metodą strzału. Przeprowadzone badania i uzyskane wyniki można wykorzystać do symulacji układania tkanin oraz do innych zastosowań z zakresu mechaniki tekstyliów.

2

Parametryzacja krzywej ugięć nawierzchni podatnych

Pożarycki Andrzej, Górnaś Przemysław, Bilski Marcin, Turkot Adam

Drogownictwo

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2019

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nr 3

67--73

PL

W artykule opisano koncepcję wyrażenia dyskretnej postaci krzywej ugięć nawierzchni funkcją ciągłą, której jądro ma postać rozkładu t-Studenta. Przedstawiona postać funkcji (funkcji aproksymacyjnej) zależy od czterech parametrów, które poddano analizie pod kątem możliwości wykorzystania ich do formułowania prostych kryteriów oceny stanu technicznego nawierzchni metodami semi-inwazyjnymi. Przyjmując na podstawie literatury formułę oceny stanu technicznego podłoża nawierzchni przy wykorzystaniu parametru czaszy ugięć znanego jako BCI ustalono, że jeden z parametrów funkcji aproksymacyjnej wskazuje na identyczne zmiany stanu technicznego podłoża nawierzchni odcinka testowego. Tym samym potwierdza się przesłanie, że zarówno na podstawie parametrów sformułowanych w sposób klasyczny, jak i proponowanych przez autorów artykułu, można budować empiryczne kryteria oceny stanu technicznego nawierzchni, wspierając jednocześnie metodykę tworzenia strategii utrzymania w systemach zarządzania nawierzchnią.

EN

The paper describes the concept of expressing the discrete form of the pavement deflection curve with a continuous function, the kernel of which is in the form of a Student’s t-distribution. The presented form of the function (approximation function) depends on four parameters, which were analyzed in terms of the possibility of using them to formulate simple criteria for assessing the technical condition of the pavement using semi-invasive methods (like FWD type methods). Assuming, based on the technical description of the known formula of BCI parameter for assessing the technical condition of the pavement subbase, it was determined that one of the parameters of the approximation function lead to the same conclusions as ones based on BCI values. This confirms the message that both based on parameters formulated in a classical way and those proposed by the authors of this article, one can build empirical criteria for assessing the technical condition of the pavement, while supporting the methodology of creating a maintenance strategies in pavement management systems.

3

Load-deflection characteristics of steel, polypropylene and hybrid fiber reinforced concrete beams

Tamil Selvi M., Thandavamoorthy T. S.

Archives of Civil Engineering

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2015

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Vol. 61, nr 1

59--72

EN

Concrete is the most widely used construction material because of its specialty of being cast into any desired shape. The main requirements of earthquake resistant structures are good ductility and energy absorption capacity. Fiber reinforced concrete possesses high flexural and tensile strength, improved ductility, and high energy absorption over the conventional concrete in sustaining dynamic loads. The aim of this paper is to compare the properties of concrete beams in which three types of fibers are added individually. Steel fibers, polypropylene fibers and hybrid fibers were added to concrete in the weight ratio of four percentages in the preparation of four beam specimens. The fourth specimen did not contain fibers and acted as a control specimen. The dimensions of the beam specimens were 150 mm × 150 mm × 700 mm. The reinforced concrete beams of M30 grade concrete were prepared for casting and testing. Various parameters such as load carrying capacity, stiffness degradation, ductility characteristics and energy absorption capacity of FRC beams were compared with that of RC beams. The companion specimens were cast and tested to study strength properties and then the results were compared. All the beams were tested under three point bending under Universal Testing Machine (UTM). The results were evaluated with respect to modulus of elasticity, first crack load, ultimate load, and ultimate deflection. The test result shows that use of hybrid fiber improves the flexural performance of the reinforced concrete beams. The flexural behavior and stiffness of the tested beams were calculated, and compared with respect to their load carrying capacities. Comparison was also made with theoretical calculations in order to determine the load-deflection curves of the tested beams. Results of the experimental programme were compared with theoretical predictions. Based on the results of the experimental programme, it can be concluded that the addition of steel, polypropylene and hybrid fibers by 4% by weight of cement (but 2.14 % by volume of cement) had the best effect on the stiffness and energy absorption capacity of the beams.

4

Analysis of the stability of a flat textile structure

Szablewski P.

Autex Research Journal

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2006

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Vol. 6, no. 4

204--215

EN

This paper deals with a specific method of examining the state of equilibrium of a flat textile structure. This kind of structure is modelled as an inextensible elastica loaded with its dead weight and axial force. The elastica represents, as an example, a longitudinal section of a fabric. It is assumed that the elastica rests on a flat, immovable base. We considered only those forms of deformed elastica where it's the two ends were supported by pivot bearings, and the tangent at those points lay on the immovable supporting plane. In the analysis, the shape of the deflection curve was determined for a given axial force, and it was examined whether a given position is stable or unstable. The analysis was carried out on the basis of the energetic method, by examining the potential energy of the system. The investigations can be used for simulations of fabric buckling, folding and other applications of textile mechanics.