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ROZPRAWY INŻYNIERSKIE

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Abstracts of papers for

Previous issue vol. 50, no. 3 (2002)

vol. 50, no. 4 (2002)

Next issue vol. 51, no. 1 (2003)

Contents of issue 4, vol. 50

1. K. Marynowski, Z. Kołakowski : Nonlinear flexural and torsional vibrations of axially moving orthotropic web
2. A. Foryś, A.S. Foryś : Analysis and optimization of a nonlinear, continuous, autoparametric system
3. J. Hoła : Experimentally determined effects of technological and service factors on stress-induced destruction of concrete under compression
4. J. Łukowski, M. Kaczmarek : Laboratory methods of determination of pore structure parameters: formation factor and tortuosity of permeable media by electric methods
5. C.J. Liu, A.H.J. Nijhof, L.J. Ernst, R. Marissen : Progressive failure modelling of transverse cracking in cross-ply laminates with double-edge-semicircular notches
6. J. Ocioszyński : Theoretical and experimental investigations of braking energy recovery in automobiles and heavy machinery
7. K. Wojciechowska : Modelling and simulation of filtration in the development of water treatment technologies

K. Marynowski, Z. Kołakowski : Nonlinear flexural and torsional vibrations of axially moving orthotropic web

A new approach to the analysis of the dynamic behaviour of an axially moving orthotropic web is presented. Mathematical model of the moving web system constitutes two nonlinear, coupled equations governing the transverse displacement and stress function. The results of numerical investigations show the solutions to the linearized and nonlinear problems. Free vibrations of the web with different initial stresses are analyzed. The effect of orthotropy factor and axial transport velocity on transverse and torsional vibrations are presented.

Contents

A. Foryś, A.S. Foryś : Analysis and optimization of a nonlinear, continuous, autoparametric system

In the present paper a transversely vibrating autoparametric system consisting of three non-prismatic rods is presented. The considerations refer especially to stability of the semi-trivial solution. Proper selection of the values of parameters may lead to considerable reduction of the autoparametric resonance effects or may shift the autoparametric resonance to another frequency region.

Contents

J. Hoła : Experimentally determined effects of technological and service factors on stress-induced destruction of concrete under compression

In the paper, the effects of different technological and service factors on the levels of fracture-initiating stress σ_i and critical stress σ_cr in concrete under compression have been compiled. Experimentally determined ranges of the stresses are given. Technological and service factors contributing to a high or low level of the stresses have been grouped together. It is shown how some technological and service factors affect the fatigue strength of concrete. This is done for a few selected concretes on the basis of known levels of the fracture-initiating stress σ_i and critical stress σ_cr.

Contents

J. Łukowski, M. Kaczmarek : Laboratory methods of determination of pore structure parameters: formation factor and tortuosity of permeable media by electric methods

The paper presents the methods of determination of structural parameters of porous materials: formation factor and tortuosity, based on conductometric techniques. The basic experimental procedures are reviewed and factors, which influence the relative conductivity of electrolyte saturated samples such as type of experimental technique, electrolyte and electrodes, length of sample, are presented. The role of surface conductance, polarization effects and frequency are analyzed.

Contents

C.J. Liu, A.H.J. Nijhof, L.J. Ernst, R. Marissen : Progressive failure modelling of transverse cracking in cross-ply laminates with double-edge-semicircular notches

A local-global progressive failure finite element (FEM) model was created in combination with the maximum strain criterion on an individual layer scale to study the formation of transverse cracks in cross-ply laminates with double-edge-semicircular notches. It is assumed that the laminate is made of homogeneous orthotropic layers before the occurrence of the matrix failure. Then, the average reduced layer stiffness as a function of the applied load is separated from the reduced laminate stiffness. Additionally, a maximum strain strength criterion is applied on a very local scale of a single layer to induce the local matrix failure. The initiation, propagation and multiplication of the transverse cracks starting from the notch are predicted in this way. The influences of the laminar thickness and the notch-width aspect ratios were also studied. Furthermore, the stress distribution and redistribution caused by the initiation and propagation of the transverse cracks were calculated. In addition to the stress concentration caused by the circular notch, an extra stress concentration in the 0° layers is induced by the transverse cracks in the 90° layers. This stress redistribution will in turn initiate more local failures in the 0° layers or at the interface between the longitudinal and transverse layers. The simulated results show a good agreement with experimental observations.

Contents

J. Ocioszyński : Theoretical and experimental investigations of braking energy recovery in automobiles and heavy machinery

The paper deals with theoretical computations and experiments concerning the possibility of energy recuperation in certain phases of automobile and heavy machinery driving cycles as well as in working cycles of heavy machinery working mechanisms.

Contents

K. Wojciechowska : Modelling and simulation of filtration in the development of water treatment technologies

The paper presents modelling and simulation of water filtration in a multilayer rapid filter. As far as modelling is concerned, a combination of phenomenological and theoretical models was described. Special attention is paid to modelling of the filter coefficient. The model developed is a basis for filtration simulation in the filter bed. Simulation results for the concentration of particles in the filtered water, concentration of particles deposited in the bed and the headloss in the bed are presented as 3D diagrams. They are consistent in quality with the values obtained in the physical process which is discussed in the analysis herein. Thus, it can be concluded that the model for the process was selected correctly, its parameters were set appropriately and the numerical solution of partial differential equations involved in the model was also correct. The developed numerical model may serve as a new tool for development of water treatment technologies. Numerical simulations were carried out, applying the "Mathematica" program.

Contents

Abstracts for 50, 3, 2002 (previous issue)

Abstracts for 51, 1, 2003 (next issue)

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