A Study on Optimal Design of Hybrid Mountings and Allocation of Damping Materials
|School||Shanghai Jiaotong University|
|Course||Design and manufacture of ships and marine structures|
|Keywords||Hybrid structure Vibration level difference Vibration isolation mass Structural dynamic optimization Damping loss factor|
Most of vibrations generated from marine engines and equipments in the operation and transmitted to the hull structure directly through the mounting. Excessive vibrations will prevent the effective operation of the ships. It is very important to carry on the vibration and noise reduction strategy during the design of the mounting for warships and submarines for the purpose of improvement of the vitality of ships. The effective way to isolate the vibration and is to absorb and reflecet the power on the vibration energy transfer path. The essence is to make the structure stiffness uncontinuous, the impedance of structure mutations, introduce non-structural materials to absorb and waste part of the energy, and then decrease the vibration. Hybrid mounting as a new type of vibration isolation component fully demonstrates the thought above. The design principles of the hybrid isolation mountings are: the utility of different materials (steel, aluminum and composite materials) to construct the panels and webs with different thickness, as well as, insert large mass components (for example, insert isolation mass block at the junction of the bottom panels and webs) or to use damping materials and so on which can realize the“jump”of the structural impedance. Then the use of optimization methods in components design can fulfill the demanded performances. Fewer studies have been reported on the roles of materials selection, component size, vibration isolation mass, damping materials and structural optimal design method in the dynamic design for hybrid mounting.Take metal-glass fiber material hybrid mounting design as an example, the corresponding structural dynamic optimization mathematical models are established to study the roles of materials, component size, and vibration isolation mass, damping materials and optimal design method during the design for hybrid mounting. Computational results showed the advantages of hybrid mounting than the conventional steel mounting in vibration reduction. The introduction of composite materials plays a key role on vibration; the effectiveness of vibration isolation mass is also demonstrated. While the adoption of optimal design method is the necessary mean during the design of hybrid mounting.Damping material has been widely used for its good energy absorption characteristics in engineering structural vibration and noise reduction design. The invention of new damping materials is difficult and expensive. This paper discusses the feasibility to increase the damping efficiency by adding a certain percentage of holes on the existing damping materials under the condition of the same weight of damping materials.The corresponding design method is given to optimize the distribution of the damping materials on the controlled object surface to satisfy the specified requirements under the strategy of minimum dosage. Finally, study the design thought about using different damping materials to composite gradient damping material. A cantilever plate is used as an example; Topology optimal design and modal damping design are carried out for the damping structure.