Study Of Statistics And Vibration Damping Of Gearbox/transmission Casing

The gearbox casings play a vital role as they house the transmission components. The different components in housed are gears, shafts and bearings. The strength of the whole gearbox casing is important due to it has to withstand both static and dynamic loading and the strength of the gearbox casing's hooks as well has importance during the lifting off and fixing the gearbox.In the Transmission unit the vibration is generated by the excitation in gear mesh and rolling bearings. Generated vibration energy is transferred from gear to shaft and from shaft to bearing and from bearing it comes to gearbox/transmission housing via bearing holder. Some part of energy is absorbed by elastic part of gearbox/transmission and another part of energy excites the transmission.Vibration energy can be controlled by the modification of transmission's structure, while modification can be conducted by increasing the thickness of wall of structure or adding the damping material on structure.In this paper, suitable damping material has been used on marine gearbox to reduce the vibration energy. Computer simulations have been done on ANSYS. Static analysis is performed on gearbox house's hooks. For static analysis, first working load and constrain condition of gearbox housing is determined. Sub-model ANSYS advance tool has also been used, to obtain precise stress in a local/specific region; sub-modeling separates local analysis from the global model. Modal analysis without damping (Block Lanczos) has been performed to extract the 10 mode shapes. The natural frequencies and displacement on respective frequency are calculated.Modal analysis with damping (QR-DAMP method) has been performed to determine the suitable thickness of suitable damping material and constrained material, and also to determine the suitable position for the addition of damping materials (SA-3, DFM and QZD) on the face of gearbox housing. Damping materials (SA-3, DFM and QZD) has been analyzed at different temperatures i.e. 25o C, 30oC, 40o C and 50oC.