|Budget Amount *help
¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1997 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1996 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fatigue tests in room air and in 3%NaC1 solution were conducted on a beta-titanium alloy, Ti-15Mo-5Zr-3Al, in order to clarify the effects of specimen thickness on fatigue crack growth behavior. The specimens with three kinds of thickness, that is, 0.5mm, 2mm and 10mm, were used. The results obtained were compared with those of (alpha+beta) -titanium alloy, Ti-6Al-4V.
Paying attention to the relationships between fatigue crack growth rate, da/dN,and stress intensity factor range, DELTAK,of Ti-15Mo-5Zr-3Al alloy in room air, da/dN in the region of DELTAK*10MPa・m^<1/2> was enhanced with decreasing specimen thickness, while da/dN in DELTAK>10MPa・m^<1/2> was almost similar for all the specimens. On the other hand, da/dN in 3%NaCl solution for the specimen with a thickness of 10mm was enhanced by comparison with those in room air at DELTAK*5MPa・m^<1/2>, though they were identical in both environments at DELTAK>5MPa・m^<1/2> for all the specimens.
For Ti-6Al-4V alloy, the da/dN-DELTAK relationships in room air were almost similar for all the specimens, while in 3%NaCl solution da/dN was accelerated markedly in DELTAK>13MPa・m^<1/2> for the specimen with a thickness of 0.5mm, DELTAK>12MPa・m^<1/2> for 2mm and DELTAK>25MPa・m^<1/2> for 10mm. However, da/dNs in both environments were similar in lower DELTAK levels.
Consequently, in room air the higher da/dN was found in Ti/15Mo-5Zr-3Al alloy compared to Ti-6Al-4V alloy. On the contrary, in 3%NaCl solution the acceleration in da/dN was not observed for Ti-15Mo-5Zr-3Al alloy, indicating little effect of corrosive environment on da/dN in higher DELTAK region.