Abstract:
Structural health monitoring is the key for the smooth operation of engineering machinery and the
basic of maintenance engineering. Maintenance of military helicopters put many challenges for
the maintenance team due to high amplitude and frequency of vibrations produced in the parts.
Certain techniques are used to for the vibration isolation and damping of the sub-assemblies and
parts from the vibration sources mainly moving machinery parts. This thesis is based on an
industrial problem faced in a military helicopter. A structural member of the parts breaks before
its normal operation hours. Due to failure of vibration isolation and damping subjected to changing
vibration level with the aging of machinery. With age, helicopter moving parts wear and tear and
the design tolerances loosens, the vibration level increases. Both amplitude and frequency changes
with the changing tolerances. Elastomer’s coating is used for this specific part. Material used and
the thickness of material for coating are the factors which needed to be researched for the changed
level of vibration and to enhance the fatigue life of the part. In this research work, numerical
simulation technique is used to calculate stresses due to subjected vibration amplitude and
frequency. Stress values are calculated for two complete vibration waves. Thickness of elastomer
coating is changed each time using a specific material. Then material is changed and stresses are
recalculated for the different thicknesses. Optimal material and thickness are identified for the
lowest level of stress on the part. Aluminum 6061 is the material of the part which do not exhibit
endurance limit so fatigue life changes for each stress condition. Mesh independence is achieved
and the results are validated. Best material and the specific thickness of the elastomer for this
specific level of vibration is suggested for the part.
