Study On The Wear Performance Of The UHMWPE Used In Artificial Joint Replacement

Cobalt chromium molybdenum alloy(CoCrMo)and ultra-high molecular weight polyethylene(UHMWPE)are currently the most widely used materials in artificial joint implants due to their excellent mechanical properties,wear,and corrosion resistance.The lifetime of the artificial joints is dependent on the wear performances of the prosthetic material and the failure occurs primarily at the contact surfaces.In this paper,the wear performances,damage mechanism,and surface morphology changes of UHMWPE and CoCrMo contact surfaces between usage were investigated by experiments performed under different contact stresses and sliding distances.The reason is that the friction coefficient of UHMWPE of the UHMWPE/CoCrMo contact pair was reduced with the increasing contact stresses.First,the wear and surface morphology changes of UHMWPE were studied in the pin-disk test of 90°cross shear motion under different contact stress and sliding distance.The wear rate of UHMWPE is very high after 90° rotation,and it tends to be zero as the linear sliding continues.Along with the increasing contact stresses,the wear of UHMWPE increases,and the wear rate decreases.And in this stage,the damage of CoCrMo is mainly caused by UHMWPE abrasive grains.CoCrMo/UHMWPE contact surface wear test results.When the surface roughness of UHMWPE is relatively large,CoCrMo acts on the rough surface to make the surface smooth and clean.However,the CoCrMo has become rougher as can been seen from the wear morphology.The motion edge area of CoCrMo is severely damaged,and the middle area is less damaged;the greater the contact stress,the more severe the CoCrMo damage;the larger the sliding distance,the more severe the edge area damage.The contact stress is small,the middle area of UHMWPE is large,and the edge area is small;the contact stress is large,the middle and area of UHMWPE are large;the sliding distance is large,the surface change of UHMWPE is large,and the UHMWPE is seriously abraded.The wear cycle becomes longer,the surface change of UHMWPE decreases,and the number of wear increases.The damage mechanism of UHMWPE is mainly represented by adhesive wear and a small amount of abrasive wear and fatigue wear.