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Abstracts of papers for

Previous issue vol. 48, no. 1 (2000)

vol. 48, no. 2 (2000)

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Contents of issue 2, vol. 48

1. A. Foryś and J. Kowynia: Charitonov theorem and stability of parametrically excited systems
2. M. Nader: Experimental investigations of special vehicles vibration with regard to their influence on human organism
3. G. Socha and P. Kujala: Fracture toughness of laser stake welds in shipbuilding industry
4. T. Szolc: On discrete-continuous modelling of the railway bogie and the track for the medium frequency dynamic analysis

A. Foryś and J. Kowynia: Charitonov theorem and stability of parametrically excited systems

The present paper concerns the application of the Charitonov theorem to an analysis of stability of parametrically excited mechanical or physical systems with intervally changing parameters of systems. In such systems the problems of stable solutions of the equation of motion also arise. In some methods the stability analysis of the parametrically excited systems with intervally changing parameters transformes into the analysis of stability of some n-th degree interval polynomials. On the basis of ChT we can check that the solution is stable in the whole interval of changing parameters, without constructing of the boundary of instability regions. Examples of application of the ChT to the analysis of stability of some special systems in steady states of the periodic parametric resonance are considered.

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M. Nader: Experimental investigations of special vehicles vibration with regard to their influence on human organism

The paper presents investigations into the impact of vibration on drivers in selected vehicles Tatra 815 and Liaz. The investigations were carried out using the method of overall evaluation for constant rate of travel. It was found that the permissible limits of noxiousness, defined by the health protection regulations, were exceeded.

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G. Socha and P. Kujala: Fracture toughness of laser stake welds in shipbuilding industry

A new technology of stake welding with the use of high power lasers was developed in the framework of EU research program "Advanced Welding for Closed Structures". This technology enable welding from outside of closed profiles due to high penetration of laser beam into the material. More than 650 static, fracture toughness and fatigue tests were performed during the research program to investigate strength of such welds. In this paper, investigations of static strength and fracture toughness are presented, results of fatigue testing will be reported elsewhere. As the result of the tensile and bend tests, very good strength and ductility of fusion zone (FZ) and heat-affected zone (HAZ) were found. Also the fracture toughness in lowered temperature was found to be satisfactory. Both traditional impact (Charpy) test and modern methods of measuring the crack tip opening displacement (CTOD) were utilised, and their results in the form of tearing energy per unit surface were compared. Also fatigue crack growth rate (FCGR) tests were performed at the constant DK value, the crack was propagating in the direction transversal to the weld midline. This technique allowed the observation of FCGR variations in different zones of the welded joint.

Contents

T. Szolc: On discrete-continuous modelling of the railway bogie and the track for the medium frequency dynamic analysis

In the present paper, the dynamic interaction between a bogie of a modern railway passenger car and a track is considered with the aid of a discrete-continuous mechanical model. This model enables us to investigate the bending-torsional-axial vibrations of the wheelsets coupled with the vertical and lateral vibrations of the track through the wheel-rail contact forces. The numerical results are obtained in the form of natural frequencies, eigenfunctions and frequency response functions for the linearized bogie-track system as well as in the form of time histories and corresponding amplitude spectra of forced vibrations obtained by means of computer simulation performed for the non-linear system. In the computational examples for the bogie-track interaction, the influence of static and dynamic properties of several kinds of the track on the system dynamic response is studied.

Contents

Abstracts for 48, 1, 2000 (previous issue)

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