Exam Question
(a) State FOUR sources of excitation that may induce vibration into the main hull girder. (8)
(b) Suggest methods for reducing the vibration levels induced by EACH of the exciting forces in (a). (8)
Class 2 (2nd Engineer)
SC&S
📅 Jan 2024
Reference Answer
### (a) Sources of Hull Girder Vibration Excitation
Four primary sources of excitation that may induce vibration into the main hull girder are:
1. **Main Propulsion Engine:** Large slow-speed diesel engines are a major source of vibration due to inherent imbalances and periodic forces.
* **Unbalanced Forces and Moments:** Reciprocating masses (pistons, crossheads) and rotating masses (crank throws, connecting rods) generate primary and secondary inertia forces and moments. While engines are designed to be balanced, residual imbalances can excite the hull, particularly at specific resonant frequencies.
Four primary sources of excitation that may induce vibration into the main hull girder are:
1. **Main Propulsion Engine:** Large slow-speed diesel engines are a major source of vibration due to inherent imbalances and periodic forces.
* **Unbalanced Forces and Moments:** Reciprocating masses (pistons, crossheads) and rotating masses (crank throws, connecting rods) generate primary and secondary inertia forces and moments. While engines are designed to be balanced, residual imbalances can excite the hull, particularly at specific resonant frequencies.
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