Andrzej Czerwiński

The paper is concerned with the analysis of a model describing the transverse vibrations induced by periodically variable fluid flow. Motion of the system was described by using partial differential equations with periodically variable coefficients. The analysis was performed by Galerkin method and orthogonal polynomials as shape functions. The instability regions were determined by Floquet theory. The influence of several parameters and boundary conditions on the natural frequencies and the instability regions were investigated.

The paper summarises the noise measurements of a bobbin cutting machine, also referred to as a longitudinal paper cutter machine, taken as a part of the procedure involved in the declaration of compliance of the machinery. Noise measurements were taken with a view to improve the conditions in the work environment. Due to the machine operation, noise level conditions were determined by testing the impulse response inside the machine room. Calculations were carried out in an attempt to improve the working conditions for machine operators.

This paper summarises the results of the testing of the mechanical and acoustical behaviour of polyurethane materials with desirable properties. Testing was performed on several samples of materials which were modified during the manufacturing processes. Tests of mechanical parameters included, among other things, the Young modulus and the energy dissipation rate. Tests were conducted on the model 43 MTS Criterion hydraulic testing machine. In the framework of the acoustic research, sound absorption coefficient measurements were conducted. The sound absorption coefficient was measured with the type 4002 Bruel & Kjaer standing wave apparatus. Characteristics of the tested materials are provided.