Development of a new magnetorheological impact damper with low velocity sensitivity

The velocity sensitive characteristic of the conventional linear magnetorheological (MR) damper is undesirable in the application of impact protection. It will induce large damping forces when the damper suffers high velocity impacts, whilst comprising the energy dissipation efficiency of the damper and posing a serious threat to occupants and mechanical structures. This work reports a new MR impact damper (NMRID) with low velocity sensitivity. Unlike the conventional MR impact damper (CMRID) in which MR fluids (MRFs) flow from one chamber to the other through a small annular gap between the piston and cylinder, the NMRID has a whole annular gap between the shaft and cylinder that is filled with MRFs, and the MRFs work in a pure shear mode without any liquid flow. In this work, a NMRID and a CMRID were prototyped. The velocity sensitivities of these two impact dampers were compared via numerical analysis and experimental impact tests. The analysis and test results indicate that NMRID possesses a much lower velocity sensitivity than the CMRID; the dynamic range of the NMRID decreases less than CMRID with the increase of nominal impact velocity. Then, to demonstrate the controllability of NMRID, impact tests with a bang-bang control were implemented, and the peak force of NMRID was successfully controlled around a target force under different levels of nominal impact velocity. This research proves that the designed NMRID is less sensitive to velocity than the CMRID and the NMRID has good controllability, demonstrating that the NMRID can serve as a better candidate than CMRID in applications with high impact velocity.