Theoretical and experimental modal analysis of the cylinder unit filled with PUR foam

Vibration can be considered as an undesired phenomenon in mechanical mechanisms as far as it decreases lifetime of the machine, limits its performance, influences other machines in the neighborhood or induces high level of noise. There are some application areas where the latter reason is referred to as the crucial one. All the measures which must be undertaken in those circumstances focus on either identifying and removing the excitation sources or minimizing harmful results of vibration. When it is not possible to change construction of vibrating mechanism and sources of vibration are beyond control the efficient way to improve machine dynamic behavior parameters is to enhance damping properties of the mechanical system. This approach can be realized as active or passive damping. Active damping methods include application of specially designed and adaptively controlled actuators which counteract the vibration motion and use springs of variable rigidity coefficient, viscous dampers with actively controlled internal flow, dampers with non-newton fluids etc. Those solutions are very efficient when well-tuned but expensive and difficult to be inserted into the existing design. That is why passive ways of vibration damping are the most often applied applications. To solve the noise and vibration problems and identify the dynamic properties of the mechanical systems new research methods both theoretical and experimental must be applied. In the past three decades, modal analysis has become a major technology in the quest for determining, improving and optimizing dynamic characteristics of engineering structures [6, 8, 12]. It has been successfully applied to solve structural dynamic problems in mechanical [5, 7, 9, 15, 16] and aeronautical [14] engineering. Recently modal analysis has also found its broad applications for civil and building [11] structures, biomechanical and harvest [3] problems, space structures, electrics and electronics [2] acoustical instruments [1], transportation [10] and nuclear plants. The origin of presented research is the technical problem of the curtain lifting mechanism making too much noise to be applied in a theatre. The mechanisms of scenography changing must work smoothly and quietly during a play otherwise they attract the spectators’ attention spoiling the art effect. PAwlowski w, kAczmArek l, loudA P. Theoretical and experimental modal analysis of the cylinder unit filled with Pur foam. eksploatacja i Niezawodnosc – maintenance and reliability 2016; 18 (3):428–435, http://dx.doi.org/10.17531/ein.2016.3.15.