Papers by Author: Y. Ma

Abstract: Single-crystal diamond tools can be used for cutting high precise parts with high efficiency, but it is very difficult to abrade it, which is one of study purposes in this paper. This project can be done on the high precise machine tools by using a diamond abrasive wheel with super fine grain size. In this paper, the abrading mechanism is represented, an efficient abrasive method is invented, the major factors which have an important effect on abrasive efficiency and accuracy are discussed, such as abrasive wheel grain size, bonding agent, hardness, speed, pressure and feeding speed etc and some results raising abrasive efficiency and accuracy are obtained. By using the single-crystal diamond tool abraded by author, the degree of roughness of the parts can come up to Ra0.05.

Abstract: Plain low carbon steel produced by compact strip production (CSP) process was analyzed using TEM, EELS and XEDS. Nano-sized oxides and sulfides were observed in the steel. The nano-oxides are mainly ferrospinel of <20nm in size, and the nano-sulfides are MnS and FeS particles with size of 20-100 nm. They distributed both in grains and at grain boundaries. These nano precipitates could form in cast slab before heavy deformation by rolling process. It is proposed that besides the grain refinement, the nano-pricipitation plays an important role in yield strength enhancement. This mechanism may provide a new approach to strengthen plain low carbon steels.

Abstract: The piezoresistive effect in iodine-doped carbon nanotube films was investigated by a three-point bending test. Carbon nanotubes were synthesized by hot filament chemical vapor deposition. The experimental results showed that the gauge factor for I-doped and undoped carbon nanotube films under 500 microstrain was about 350 and 65 respectively at room temperature, exceeding that of polycrystalline silicon (30) at 35°C. The origin of the piezoresistivity in the films may be ascribed to a strain-induced change in the band gap for the doped tubes and the intertube contact resistance and defects for the undoped tubes.