Variation of Axial Tension-Compression Fatigue Characteristics by UNSM on Ti-6Al-4V

doi:2011.25.6.42

J. Ocean Eng. Technol. > Volume 25(6); 2011 > Article

J. Ocean Eng. Technol. 2011;25(6):42-48.
DOI: https://doi.org/10.5574/KSOE.2011.25.6.042

Suh Chang-Min,Cho Sung-Am,Pyoun Young-Sik,Suh Min-Soo

School of Mechanical Engineering Kyungpook National University,Department of Prosthodontic College of Dentistry Kyungpook National University,School of Mechanical Engineering Sun Moon University,School of Advanced Materials Engineering Kookmin Univer

Ti-6Al-4V재의 UNSM처리에 의한 축인장압축피로특성변화

서창민,조성암,편영식,서민수

경북대학교 공과대학 기계공학부,경북대학교 치의학전문대학원,선문대학교 공과대학 기계공학부,국민대학교 신소재공학부

Keywords: Axial loading tension-compression fatigue test, S-N curve, UNSM (Ultrasonic nanocrystal surface modification) technology, Fish eye crack, Facet, Compressive residual stress

핵심용어: 축하중 인장압축피로시험, S-N 곡선, 초음파나노표면처리기술, 어안균열, 파셋터, 압축잔류응력

Abstract

The present study makes three original contributions to nanoskinned Ti-6Al-4V materials. The nanoskins were fabricated on Ti-6Al-4V material using various surface treatments: deep rolling (DR), laser shot peening (LSP), and ultrasonic nanocrystal surface modification (UNSM). These surface treatments are newly developed techniques and are becoming more popular in industrial fields. A fatigue strength comparison at up to 106 cycles was conducted on these nanoskinned Ti-6Al-4V materials. Fatigue tests were carried out using MTS under axial loading tension-compression fatigue (R = -1, RT, 5 Hz, sinusoidal wave). The analysis of the crack initiation patterns in the nanoskinned Ti-6Al-4V materials found an interior originating crack pattern and surface originating crack type. Microscopic observation was mainly used to investigate the fatigue fractured sites. These surface modification techniques have been widely adopted, primarily because of the robust grade of their mechanical properties. These are mainly the result of the formation of a large-scale, deep, and useful compressive residual stress, the formation of nanocrystals by the severe plastic deformation (SPD) at the subsurface layer, and the increase in surface hardness.