FRETTING FATIGUE OF BIOMATERIALS

摘要

The use of metals and materials for replacement and repair of human body parts are attracting more attention in recent times. Like any other components in service, biomaterials also undergo degradation due to fretting, wear and corrosion. Fretting wear, fretting fatigue and fretting corrosion are the three main areas of concern for the orthopedic surgeons. This paper reviews fretting fatigue along with various methodologies and mechanisms. Fretting of materials is controlled by several sets of variables working synergistically, making the process difficult to quantify. A fretting test rig for biomaterials has been developed simulating the conditions of the actual implants as close as possible. Fretting fatigue life is also controlled by contact geometries, which delay or accelerate the crack initiation. Several contact geometries have been mentioned which can influence the fretting life of the materials. Fretting conditions are also governed by normal pressure and slip amplitude regime in fretting maps. Physiological medium may aggravate or reduce the fretting failures depending on the nature of surface and the medium. Titanium alloys have been established as the most suitable materials for bio implants due to their attractive properties within the body environment. Some important aspects of the fretting damage of these alloys are mentioned in this paper. Fretting fatigue life of these alloys can be significantly improved by surface modification with specialized techniques such as plasma nitriding, ion implantation and Physical Vapour Deposited TiN coatings. The paper describes details of these methods as well.