### STATIONARY VIBRATIONS OF A SYSTEM WITH AN IMPACT ABSORBER SUBJECTED TO PERIODIC IMPULSES OF FINITE DURATION

Pages 44 - 50

Impulsive loadings, or repetitive brief impacts, produced by machines and mechanisms of the shock action, are widely spread in the engineering practice. In many cases, trustworthy results of their dynamic analyses can be obtained by taking account of the shape and duration of their impulses.

In the paper, the periodic mode of the system motion and the parameters of the impact absorber applicable to one-sided periodic impulses of rectangular form are examined. The structure to be protected and the absorber are simulated as a system of a single collision of masses. The impacts are accepted to be instantaneous and taken into account by means of the coefficient of restitution. The damping properties of the protected structure and the absorber are considered on the basis of the viscid friction hypothesis; therefore, the damping properties of the whole system are disproportionate.

The relations identified in the course of the research are used to find the impulse frequency characteristics (IFC) of the protected structure to identify the absorber parameters. The affect of duration of external impulses produced onto the IFC, characterized by the drastic increase in the amplitudes as compared to that in the case of a single impulse of the same magnitude, is the subject of research. It is proven that the maximal ordinates of IFC decrease slightly against the increase in the duration of external impulses; therefore, the efficiency of the impact absorber changes insignificantly, and it is equivalent to that of a dynamic absorber. It is noteworthy that if the duration of external impulses is under 10 % of the duration of the period, they may be replaced by instantaneous impulses.

DOI: 10.22227/1997-0935.2012.4.44 - 50

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