The dynamics analysis of a magnetic fluid shock absorber with different inner surface materials

Abstract

Suffering low frequency and small amplitude shaking, energy dissipation of long overhanding structures on the spacecraft under weightless environment is a key research topic for the safety of such spacecraft. The paper presented a novel magnetic fluid shock absorber to reduce the vibration of low frequency and small amplitude. The proposed shock absorber had the composite magnet structure including three magnets in the working element and it was attached with different inner surface materials. To the best of our knowledge, this was the first time to consider the relationship between inner surface materials and damping performance of the shock absorber. First, the damping performance of the shock absorber with various magnetic fluid volume percentage and gap size was investigated by reducing the free oscillations of the brass plate. Meanwhile, the magnetic restoring force between the working element and the repulsion magnet was measured. The experimental results showed that the magnetic restoring force versus the distance was almost linear, under small amplitude. When the distance was greater than 20 mm, the approximate calculation formula of the equivalent stiffness could be obtained. We analyzed the influence of the different internal surface materials of the shock absorber on the damping performance by calculating the fluid resistance which was determined by both the viscous shear force and the capillary force. Experimental results verified that the capillary force had a significant influence on fluid resistance and couldn’t be ignored. In terms of the vibration decay time, the damping efficiency of chemigum was 61.39% and 57.87% better than that of fluororubber for the gap of 2 mm and 3 mm respectively. According to the logarithmic decay rate, the damping efficiency of chemigum was 2.965 times that of fluororubber under the gap of 2 mm and was 2.515 times under the gap of 3 mm. For the reason that the shock absorber was used in aerospace, weight was an important factor. Our experiments proved that we must take into account both the densities of materials and the damping performance when selecting inner surface materials.