| Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 2000: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1999: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
(1)This study examines the effect of hybrid surface modification by vacuum carburizing and fine particle peening on fatigue strength behaviors of SCM415 material. We used quenched, vacuum carburized and hybrid, vacuum carburized and fine particle peened, specimen made of SCM415 and measured their hardness distribution, mechanical properties, fatigue strength and crack propagation. In terms of the fatigue behaviors, we investigated the relationship between the crack propagation rate da/dN and stress intensity factor range ΔK, da/dN and effective stress intensity factor range ΔKeff, as well as the fatigue crack initiation life N_i and crack failure life N_f of specimens. The results show specimens with hybrid surface modification are effective in the prevention of fatigue crack initiation and fatigue crack propagation.
(2)This study examines numerical analysis of particle velocity and temperature distribution of struck material surface in fine particle peening. When the particle is accelerated using a direct-pressure type, the velocity of a 50μm particle, just before striking the metal surface, was calculated to be 222m/s. In applying air pressure, the acceleration of fine particles show significant increase compared to larger sizes. Moreover, the experimental values agree well with the calculated ones. On the other hand, the temperature distributions show the maximum surface temperature to be 1000K and cools instantly.
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