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Although Ti-6Al-4V has superior mechanical “properties” and corrosion resistance when compared to many other materials in implant applications, it is more susceptible to fretting initiated problems. This is because Ti-6Al-4V exhibits a greater tendency for material transfer when it slides over other materials or over itself. The insidious nature of fretting is more evident when it often leads to other degradation mechanisms such as pitting corrosion and crevice corrosion. To characterize the fretting fatigue behavior of Ti-6Al-4V fretting fatigue tests were conducted in a laboratory environment. The test parameters were selected to simulate the hip prostheses loading conditions. When the cyclic fatigue load of 3.30/0.33 kN (742/74 1bf) was applied to the fatigue specimen [producing the maximum fatigue stress of approximately 524 MPa (76 ksi) through the center section of the fatigue specimen] at a frequency of 6 HZ, the fatigue life of Ti-6Al-4V was reduced to a mere 69,660 cycles at a normal stress of 41.4 MPa (6 ksi). The test results showed that fretting reduced the fatigue life of Ti-6Al-4V when tested in laboratory environment simulating the hip prosthesis loading conditions. The reduction in fretting fatigue life was clearly evident from the fractographic analysis that can be interpreted as resulting from the production of mechanical surface damage that leads to numerous crack nucleation sites. Therefore, to enhance an understanding of fretting related problems in modular joints among the orthopaedic surgeons and researchers the parameters that influence fretting including the sensitivity of titanium to microstructure and the present state of knowledge on the mechanisms of fretting are discussed.
fretting-fatigue, fretting-corrosion, fretting-wear, mechanisms, parameters, microstructure, crack nucleation, fractography
Professor and Director, University of Utah, Salt Lake City, UT
Graduate Student, University of Utah, Salt Lake City, UT