Motoyuki Murashima

Proposal of Lightweight and Low Starting Torque Slide Bearing with Looped Carbon Fibers Brush

This paper addresses a novel lightweight and low starting torque bearing with looped carbon fiber brush (LCFB). LCFB simulates bristle of living being. Moreover, the static friction coefficient is nearly equal to the kinetic friction coefficient. By applying LCFB to a slide bearings, where a shaft is supported by multiple LCFBs, it is realized low starting torque bearings as well as lightness compared to conventional ball bearings. In this paper, we manufacture prototype LCFB slide bearings. With the bearings, we compare friction torque between LCFB slide bearings, slide bearings and deep groove ball bearings. As results, the ratio of starting torque to regular torque of LCFB slide bearing is from 0.93 to 1.07 which is smaller than that of the slide bearing. When micro-spline shaft is used as a mating material of LCFB slide bearing, the torque reduces because of decrease of real contact area between LCFB and mating materials. In addition, since LCFB utilize elastic deformation of fibers, LCFB slide bearings are not endurable in heavy radial load as high as load rating of ball bearing. Therefore, we define the load capacity of LCFB slide bearing from buckling load of a carbon fiber bundle to avoid overload state. We propose the load capacity as a design guideline of LCFB slide bearings.

Mechanical Properties of Carbon Nanotubes with One-Dimensional Intramolecular Junction

Mechanical properties of single-walled carbon nanotubes with one-dimensional intramolecular junctions (CNT-IMJs) are investigated using first-principles density functional theory calculations. The influence of Stone-Wales (SW) defects (a pair of five- and seven-membered rings) at a junction on the Youngs modulus, tensile strength and breaking strain of the CNT-IMJs are discussed from the charge density and interatomic distance. Our calculations reveal that deformation concentration on a seven-membered ring causes the decrease in the strength and elongation of the CNT-IMJs. It is found that the tensile strength and breaking strain of the CNT-IMJs depend on the position of SW defects, while the number of SW defects hardly affects them. The applicability of AIREBO classical interatomic potential to simulate tensile deformation in the CNT-IMJs is also discussed.