Resilient mounting of machinery on platelike and modified platelike substructures

Abstract

The problem of isolating machinery vibration from platelike substructures is analyzed. Simply supported, internally damped, square, rectangular, and circular plates are considered, as are rectangular plates with rigid cross members that divide the plates into separate quadrants. The machinery is supported either by eight or by four antivibration mounts located symmetrically about the plate centers. The attachment of dynamic vibration absorbers or lumped masses to the plates at each mount location is shown to be effective in reducing the force transmitted to the plate boundaries. The dynamic absorbers are tuned to suppress transmissibility at the fundamental resonance of the plate of concern, whereas the lumped masses become effective at frequencies above this resonance where their impedance predominates that of the plate. Utilization of the circular and quadrant plates greatly reduces the number of plate resonances that contribute to the force transmitted to the plate boundaries. Further, when machinery is supported by four antivibration mounts on square and rectangular plates, the number of resonances that are excited can also be reduced significantly if the mount locations are chosen judiciously. However, the use of other mount locations can yield a large number of pronounced resonances in excess of those excited when the machinery is supported by various arrangements of eight antivibration mounts—for which transmissibility does not appear to change greatly with the choice of mount location.