| 1.Background, Motivation and Objective : To fabricate efficient electromagnetic motors being based on the optimized design, a technique to produce three-dimensionally-shaped magnetic core is required. The metal powder compaction method is a promising candidate for making arbitrary shaped cores. However, it is difficult to increase the density and uniformity using conventional pressing machine. This means that the magnetic efficiency in low and the mechanical strength is not enough for the applications. To overcome this problem, we investigate the use of ultrasonic vibrations in the compacting process, expecting the effects of the vibration on the density and strength as well as the reduction in the friction between the die and the work. A design method for the vibrating die and punch is considered in the first past of the report, while the effects of the ultrasonic vibrations on the compaction rate are experimentally studied in the later part. 2.Statement of Contribution/Methods : An ultrasonic power combiner for eight Langevin transducers was designed through finite element modeling for the compaction die. A vibration system for the pressing punch was also developed using a vibration direction converter. The die was vibrated radially at 28 kHz, while the upper and lower compacting punches were excited by 40-kHz longitudinal vibrations. 3.Results : The die is made of SKH-9 steel, and operated in the fundamental radial mode at 28 kHz. It has a 10-mm-diameter compacting part in the center, and eight bolt-clamped Langevin PZT transducers. Using finite element analysis, the peripheral shape of the die was determined as shown in Fig. 1 to obtain a larger vibration amplitude at the inner surface of the center hole. A 40-kHz ultrasonic vibration punch consists of a longitudinal-longitudinal vibration direction converter and two BLT transducers. In the design, the punch head is separated from vibration system, and the condition for the efficient vibration transmission is considered. 4.Discussion and Conclusions. The performance of the vibration systems were evaluated through the electrical admittance measurements, the vibration distribution measurements and the high amplitude operation test. Using the developed vibration system and an oil pressing machine, the compaction ere carried out experiments for the metal powder called gSoft Magnetic Compositeh. It is iron powder covered with insulating and banding layer. |