Variation of Rotating Bending Fatigue Characteristics by UNSM on Ti-6Al-4V |
Suh Chang-Min,Pyoun Young-Sik,Suh Min-Soo |
School of Mechanical Engineering Kyungpook National University,School of Mechanical Engineering Sun MoonUniversity,School of Advanced Materials Engineering Kookmin University |
Ti-6Al-4V재의 UNSM처리에 의한 회전굽힘피로특성변화 |
서창민,편영식,서민수 |
경북대학교 공과대학 기계공학부,선문대학교 공과대학 기계공학부,국민대학교 공과대학 신소재공학부 |
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© 2011 The Korean Society of Ocean Engineers
Open access / Under a Creative Commons License
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Keywords:
Rotating bending fatigue test, S-N curve, Ultrasonic nanocrystal surface modification technology, Compressive residual stress |
핵심용어:
회전굽힘피로시험, S-N 곡선, 초음파나노표면처리기술, 압축잔류응력 |
Abstract |
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%. |
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