This paper describes a magnetic dynamic damper (MDD), which is a passive vibration absorber employing a permanent magnet and a conductor for both the restoring and damping force. The basic characteristics of this magnetic spring and damper system are examined through static loading tests and vibration tests using a pair of double cylindrical magnets. It is confirmed that the magnetic force analysis accurately simulates these tests results. Moreover, application of this system to a rotating machinery model shows that the MDD can effectively reduce two-dimentional vibration. The top heavy valve equipped on piping vibrates biaxially at different frequencies. In this case, the presented MDD consists of two groups of multiple small rectangular magnets facing each other across a gap and a conductor installed in the gap, and can be tuned to different frequencies in two different directions simultaneously. Comparison of calculation and vibration test indicates that the magnetic force analysis is good enough to estimate the restoring and damping characteristics of this MDD. Vibration tests using a valve-piping model are also carried out to examine the two-dimensional vibration reduction capability by the proposed MDD. These vibration reduction effects can be simulatde by the simplified analytical model.
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