Design And Experiment Of The Longitudinal Vibration Absorber For Ship Propuision Shafting Based On Magneto-Rheological Elastomer

Propellers are the main propulsion mechanism of surface naval and underwater ships, it produces a thrust pushing the ship forward. However, the rotary motion of the propellers could cause the spatially non-uniform wake field in the stern of the ship, which produces axial pulse forces and transferred to the hull through the propulsion shaft, thrust bearing and bases. This phenomenon has a bad effect on the ride comfort and the safety of the equipments on the surface naval. As for the underwater ships, the structure borne noise caused by the propeller pulse force is the main source of ship radiated noises which is harmful for its stealth performance. Therefore, studying on the transmission law of propeller pulse forces and the internal vibration mechanism in propulsion shaft is the key to controlling the vibrations and noises of ship.Magneto-rheological elastomers(MREs) are a smart material. Typically, MREs are composed of a host gel material and micro-size iron additives. One vital feature of MREs is called the Magneto-rheological effect, which is that their mechanical properties such as elastic moduli(including Young’s modulus E as well as shear modulus G) can be properly controlled by a magnetic field. Thus, MREs have been a promising material for constructing stiffness adjustable vibration absorbers.Researches of longitudinal vibration control on ship propelling shaft system are carried out. In this paper, ideas about the structure design of new-type of semi-active dynamic vibration absorber are put forward based on the characteristics of the smart material magneto-rheological elastomers(MRE-SDVA). A method of exploiting the stiffness adjustable characteristic of MRE to realize the effective control of the longitudinal vibration of the ship shafting system under variable operating conditions is developed and presented in detail.The specific contents include:(1) A MRE-based dynamic vibration absorber connected to ship shafting in parallel is introduced. The ship shafting-absorber mechanical system is set up.(2) The structure design and manufacture of MRE-SDVA.(3) The frequency-shift and temperature property experiment of a single SDVA.(4) The wide frequency vibration absorption capacity test of three SDVAs in combined type.Summarise up, experimental results proved the conception to design an stiffness adjustable vibration controllers is feasible. The designed SDVA has been verified it has better performance in terms of frequency-shift characteristics and vibration absorption effects, which are of directive significance for the engineering design and application of the DVA.