Toshiro Miyajima

Effects of reinforcements on sliding wear behavior of aluminum matrix composites

Effects of reinforcements on the wear behavior of aluminum matrix composites were investigated by pin-on-disk tests. The matrix materials were 2024 and ADC12 aluminum alloys. The volume fractions of SiC whiskers (V fw ) were 5-29% (MMC w ), Al 2 O 3 fibers (V ff ) were 3-26% (MMCf), and SiC particles (V fp ) were 2-10% (MMCp). The MMCs were rubbed against a carbon steel pin under a load of ION at a sliding velocity of 0.1 ms -1 . The degree of improvement in dry sliding wear resistance brought about by reinforcement is strongly dependent on the kind of reinforcement as well as its volume fraction (V f ). Initial severe wear did not occur for MMCs with V fp = 5%, V ff = 10% and V fw = 22%. The V f at which the steady-state wear rate decreased to the minimum value was 2, 10 and 29% for MMCp, MMC f and MMC w , respectively. For MMC f , however, the wear rate increased above a certain value of V ff . Fiber and particle fragments were large in size and angular in shape, so that they promoted abrasion on the steel counterface. The aggressive action on the counterface increased in the order MMC w , MMCp and MMC f . By summarizing our results and those in the literature, we conclude that particle reinforcements are the most effective in improving the wear resistance of MMC.

PRECISION CUTTING OF MOLDING DIE USING SQUARE END MILL

The precision cutting of a molding die is realized using a square end mill on a 5-axis control machine. In this study, first the tool setting errors are analyzed and the compensation method of the errors is proposed. The effectiveness of compensation in precision cutting is confirmed. Next, the form accuracy of the spiral tool pass is compared with contour one in precision cutting of a spherical surface. Finally, the molding die with spherical surface is manufactured using a square end mill made out of single-crystal diamond based on the results of the compensation of the errors and the comparison of the two tool passes, and the form accuracy and surface roughness of the molding die are measured.