Beam-like structures, constructed from many long strands that are constrained rather than bonded together, can provide appreciable levels of structural damping through friction between individual strands. This paper describes experimental and numerical studies, carried out on square-section metal beams, which are aimed at improving understanding of the relationship between construction and performance. A beam is formed from a pack of squaresection strands that is held together at various compression loads with pre-calibrated clamps. Flexural deformation of the assembled beam is simulated using standard finite element analysis employing simple Coulomb friction at the interfaces. The validity of the assumptions used in the models is confirmed by comparison with three point bend tests on a regular nine strand construction at several different clamp loads. Dynamic loss factors for this beam are obtained by conducting forced vibration tests, which show that the damping is insensitive to frequency. Subsequent numerical studies are used to investigate the effects of increasing the number of strands whilst maintaining the overall cross-section geometry of the beam. It is found that the system stiffness drops and loss factor increases when more strands are used for a maintained beam cross-section. Interestingly, the energy dissipated by each beam construction is almost the same. These results provide a vital and necessary insight into the physics for stranded structures and materials that are largely prevalent in mechanical (e.g. cables) and electrical (e.g. wires) elements.
This paper investigates the dynamic characteristics of pulley systems with different numbers of bolt holes. Models with four, six and eight bolt holes were chosen for the pulley. Three sets of cyclic pressure were applied to the pulley system to resemble the different running revolutions of an engine. The study investigates the effect of the number of holes on the system's stiffness and natural frequency. Finite element models were used to simulate the obtained deformations, stresses and frequency response function (FRF) for pulley models comprising four, six and eight bolt holes under different cyclic pressures. The results show that the stiffness and natural frequency increased with increasing the number of the bolt holes. This in turn, reduced the resulted deformations and stresses.
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