Artificial Joint Material Tribology Performance Appraisement Technical Research

In 21st century, mankind has entered the senile society. The number of people with arthropathy grows increasingly. Correspondingly, the demand of artificial joint becomes high day by day. Therefore artificial joints have been used extensively. A lot of patients have alleviated their pain, and raised their life quality. In actual application, however, corrosion wear problem and the friction of artificial joint always influence the service life of embeded joint. The study of these problems must be performed through simulated tests, therefore developing the imitating test machine becomes crucial. The purpose of simulated test machine is not only to reveal the motion in form and the kinetic performance of true natural joint, but also to enable the study of the biological mechanics of artificial joint as well as the tribological characteristics of related materials.In this paper, two kinds of machines of imitating test have been developed: the ball/disc friction testing machines and the artificial joint machines of imitating test. The corrosion wear property and the friction of joint material have been studied on these testing machines. The friction performance of material is studied on the ball friction testing machine, and the testing machine performance is stable. It can gather and show the change of friction coefficient at the same time. On this testing machine, the friction performance of joint materials has been studied under various conditions of operating conditions, and the candidate joint material pairs with lowest friction can be sorted out. Through simulation analysis, the artificial joint imitating tester was developed, on which the relative motion behavior between the ball and socket as well as the the degree of the corrosion-wear can be studied by the electrode potential of the rubbing pairs relative to a Pt reference electrode.The experiment in the medium of physiological saline was done on the ball/disc friction testing machine. The result shows that the friction coefficient of cermic/metal pair is smaller than that of metal/metal pair, i.e., cermic/metal pair shows good anti-friction performance. By comparison, silicon nitride/nickel-titanium alloy pair with minimum friction coefficient was selected as candidate artificial joint/socket pair. The results of experiment and simulation analysis of the artificial joint imitating machine show that the locus of ball - socket contact is a close spherical curve, imitating the relative motion between joint and socket. The result on the biological function measuring instrument shows that the potential of the socket of stainless steel in salt solution has bigger fluctuation than the potential of the ball of stainless steel in salt solution for metal/cetamic pair. So we may select the ball of stainless steel to couple with non-metal material socket in order to reduce corrosion-wear.