Ti-6Al-4V 재의 UNSM처리에 의한 회전굽힘피로특성변화

• Published in: Han-guk haeyang gonghak hoeji (Online) Vol. 25; no. 6; pp. 49 - 55
• Main Authors: 서창민(Chang-Min Suh), 편영식(Young-Sik Pyoun), 서민수(Min-Soo Suh)
• Format: Journal Article
• Language: Korean
• Published: 한국해양공학회 2011
• Subjects: 해양공학; Rotating bending fatigue test 회전굽힘피로시험; Ultrasonic nanocrystal surface modification technology 초음파나노표면처리기술; S-N curve S-N 곡선; Compressive residual stress 압축잔류응력; S-N
• ISSN: 1225-0767; 2287-6715

In order to analyze feasibility of replacing a conventional 6-mm Ti bar with a 5-mm bar, a series of rotating bending fatigue tests were carried out on Ti-6Al-4V bars by strengthening the fatigue performance using a special technique called UNSM (Ultrasonic Nanocrystal Surface Modification). The results of S-N curves clearly showed that the performance of the 5-mm titanium specimen was similar to that of the 6-mm specimen when the UNSM treatment was applied. The 5-mm treated specimen converged with small scattering band into the linear line of the non-treated 6-mm one. Below the fatigue life of $10^5$ cycles, the UNSM treatment did not show any significant superiority in the bending stress and fatigue life. However, over the fatigue life of $10^5$ cycles, the effect of UNSM was superior for each fatigue life, and the bending stress became longer and higher than that of the untreated one. In the case of 6-mm Ti-bar with UNSM, the fatigue limit was about 592 MPa, and there was fatigue strength increase of about 30.7% at the fatigue life of $10^4$ cycles compared to the untreated 6-mm bar. Therefore, the compressive residual stress made by the UNSM in Ti-6Al-4V increased the fatigue strength by more than 30%.