A new composite vibration isolator for gearbox found in large vessels

Gearboxes are important sources of vibration and noise in large vessels. Severe vibration induced by the gearbox may cause damage and stealth failure, and wave load and explosion transmitted to the gearbox may destroy it and cut power of vessels. For this reason a new mount has been designed with special emphasis on these harmful vibrations. The mount is a hollow annular box consisted of small rib-supported boxes, which is made from composite laminates and visco-elastic materials. Every small box works like a cantilever. So, the vertical component of structural stiffness is tunable via modifying the length or section of cantilever. The directional stiffness of this mount can be changed simply by changing the fiber direction too. The ribs have relative movement because of vibrations of the mount. Then the constrained layer damping between one pair of ribs generates damping force. With the help of an additional damping device, the vibration energy can be absorbed. So, the natural frequencies and ratio of the first two modal frequencies can be changed easily. Finite element analysis has been applied to confirm its dynamic and static performance. The results prove that the proposed isolator is effective in vibration isolation for the gearbox with less additional weight or space requirement