The Simulation Experimental Research Of Artificial Shoulder Joint

The shoulder joint has an extremely important role in people’s daily life, which is the most significant friction pair joint in the upper limb of human body. However, shoulder joint disease is a common disease with a greater incidence of shoulder pain and dysfunction in the crowd. Only by shoulder joint replacement can people restore joint function when serious condition happens. The artificial shoulder arthroplasty surgery has been carried out early with a slow pace of development, while it will become the most potential for development and the demand in the 21 st century. Therefore, the friction and wear simulation experiments will be carried out to evaluate the friction and wear properties of the shoulder material pairs, which will be of great practical significance to manufacture more excellent performance of artificial shoulder material and facilitate the development of shoulder joint replacement.In this paper, the friction and wear test scheme of shoulder joint prosthesis was designed, based on the combination of the forged CoCrMo alloy or Ti6Al4 V titanium alloy and biomedical ultra high molecular weight polyethylene(UHMWPE) materials for the study. The artificial shoulder joint wear contrast tests were performed, which can investigate and compare the stage and cumulative weight loss, volume wear, linear wear rate and variation of different artificial shoulder joint pairs. The simplified shoulder joint socket-humeral head model was established and analyzed to obtain the stress distribution of the contact area by using abaqus software. Meanwhile, the biological tribology performance tests between Ti6Al4 V or CoCrMo and UHMWPE plate were implemented to analyze and contrast application of two kinds of metal materials used in artificial shoulder joint.The maximum stage volume losses of UHMWPE socket against CoCrMo and Ti6Al4 V were displayed in 2 million and 3 million respectively, whose values were 69.75 mm~3 and 87.51 mm~3 respectively. This paper could predict that the most serious wear and tear periods of CoCrMo and Ti6Al4 V material after implanted in shoulder were the first two years and the first three years respectively. The wear volumes of UHMWPE against CoCrMo and Ti6Al4 V were approximately 53 mm~3 and 76 mm~3 respectively when reached to the stable phase.The cumulative wear volume of UHMWPE socket against Ti6Al4 V is about 1.38 times of CoCrMo/UHMWPE pair after 5 million cycles. The equation slope of cumulative wear volume for UHMWPE socket against CoCrMo and Ti6Al4 V along with test cycles was 56.150 and 77.456 respectively after the linear fit, which can provide an available method for predicting service life of UHMWPE socket. The average linear wear rate of UHMWPE socket against CoCrMo and Ti6Al4 V was 0.1118 mm/MC and 0.1310 mm/MC, respectively.The contact area of simplified model centralized in the upper region of UHMWPE socket, and the stress distribution concentrated in the upper part of the contact area. The maximum stress of UHMWPE socket against CoCrMo was larger than Ti6Al4V/UHMWPE, also the maximum stress of CoCrMo humeral head against UHMWPE socket was larger than Ti6Al4V/UHMWPE pair under equal load.The friction coefficient of Ti6Al4V/UHMWPE was higher than that of CoCrMo/UHMWPE pair at the same period in the process of dry friction test. However, the result in the process of bovine serum lubrication was just the opposite, whose result was that the friction coefficient of Ti6Al4V/UHMWPE was higher than the same period of CoCrMo/UHMWPE pair. The wear rate of Ti6Al4V/UHMWPE was all higher than CoCrMo/UHMWPE pair in two different lubrication conditions.