1 Effects of Temperature on Magnetorheological Fluid Elastomeric Lag Dampers for Helicopter Rotors

A snubber type magnetorheological fluid elastomeric (MRFE) lag damper was developed as a retrofit to a fluid-elastomeric (FE) lag damper to provide adaptive lead-lag damping augmentation for a hingeless helicopter rotor. This MRFE damper consists of a flexible cylindrical snubber body, a flexible elastomeric center wall fitted with two MR flow valves, through which MR fluid enclosed in the snubber body can pass through and be activated by a magnetic field in the MR valve. During normal operation, the MRFE damper is exposed to temperature variations due to ambient temperatures and in-service self-heating. To characterize performance at different operating temperatures, the MRFE damper was tested in the fixed frame under a helicopter rotor in-plane bending frequency (lag/rev) at temperatures varying from 20°C to 50°C. Complex modulus and equivalent viscous damping were used to compare the MRFE damper characteristics at varying temperatures with a baseline passive FE damper. The field-off MRFE damping was comparable to the baseline damping at all test temperatures. A significant controllable damping range was also observed as current was applied to magnetic valves in the MRFE damper at all temperature conditions. To account for the non-linear hysteresis behavior of the MRFE damper, a hydro