Dynamic characteristics of a new damping element based on surface extension principle in nanopore

Abstract

This paper presents a development of a new damping element which is used as a principle of surface extension in nanopore. The surface extension force of water in hydrophobic nanopore in pressurization process is different from that decompressurization process. This principle is applied to a damping element. The nanopore is constructed by silica gel. A silica gel ball of 100–200 μm ∅ has many nanopores of 7–20 nm ∅ in it. The coated spherical silica gel and water are inserted in a piston–cylinder unit in order to work as a damper. If compression force is added to the piston–cylinder unit (damper), water flows into the nanopore under balance of pressure and surface extension force. If this damper is decompressed, water moves out to the outlet of the pore. The surface extension forces for compression are larger than that of decompression. This difference in force of the surface extension produces a damping energy. Size of the pore, performance of surface extension force, fatigue life of coated material and static characteristics of the damper have already been presented by our group. Hence dynamic characteristics are presented in this paper. Two types of dampers, single cylinder type and double cylinder type, are presented, and energy dissipations of these two dampers are investigated for frequency response and piston stroke. Then the following conclusions are arrived at: (1) Energy dissipation of the single cylinder-type damper is larger than that of the double cylinder-type damper. (2) Amount of energy dissipation is almost constant, even if the input frequency is changed. This characteristic is different from the oil damper. (3) Damping efficiency for unit volume is very high, so large energy can be dissipated by small size damper. (4) Heat does not occur by the dissipation of energy. So characteristics of damping performance do not change by temperature.