High cycle fatigue behavior of implant Ti-6Al-4V in air and simulated body fluid

Issue title: Frontiers in Biomedical Engineering and Biotechnology – Proceedings of the 2nd International Conference on Biomedical Engineering and Biotechnology, 11–13 October 2013, Wuhan, China

Article type: Research Article

Authors: Liu, Yong-jie | Cui, Shi-ming | He, Chao | Li, Jiu-kai | Wang, Qing-yuan^;

Affiliations: Department of Mechanics and Engineering Science, Sichuan University, Chengdu 610065, China

Note: [] Corresponding author. E-mail: [email protected].

Abstract: Ti-6Al-4V implants that function as artificial joints are usually subjected to long-term cyclic loading. To study long-term fatigue behaviors of implant Ti-6Al-4V in vitro and in vivo conditions exceeding 107 cycles, constant stress amplitude fatigue experiments were carried out at ultrasonic frequency (20 kHz) with two different surface conditions (ground and polished) in ambient air and in a simulated body fluid. The initiation mechanisms of fatigue cracks were investigated with scanning electron microscopy. Improvement of fatigue strength is pronounced for polished specimens below 106 cycles in ambient air since fatigue cracks are initiated from surfaces of specimens. While the cycles exceed 106, surface conditions have no effect on fatigue behaviors because the defects located within the specimens become favorable sites for crack initiation. The endurance limit at 108 cycles of polished Ti-6Al-4V specimens decreases by 7% if it is cycled in simulated body fluid instead of ambient air. Fracture surfaces show that fatigue failure is initiated from surfaces in simulated body fluid. Surface improvement has a beneficial effect on fatigue behaviors of Ti-6Al-4V at high stress amplitudes. The fatigue properties of Ti-6Al-4V deteriorate and the mean endurance limits decrease significantly in simulated body fluid.

Keywords: Ti-6Al-4V, high cycle fatigue, surface condition, simulated body fluid, S-N curve

DOI: 10.3233/BME-130807

Journal: Bio-Medical Materials and Engineering, vol. 24, no. 1, pp. 263-269, 2014