Research On The Fretting Behavior Of The Taper Interface Of PEEK Artificial Hip Joint

With the aging of the population in our country becoming more serious,the number of patients with hip arthritis has increased year by year,so the market demand of artificial hip joint prosthesis has gradually increased.At present,the commonly used metal hip joint prosthesis has the disadvantages of heavy weight,poor corrosion resistance and easy release of heavy metal ions to human body,which limit the replacement effect and service life of the artificial hip joint.In recent years,PEEK material has been gradually recommended by experts as a substitute of metal such as CoCrMo due to its good biocompatibility,wear resistance and corrosion resistance.However,the influence of PEEK as the head material of hip joint on the taper stability of hip prosthesis has not been reported in literature.Therefore,in this paper,in view of the taper stability of PEEK hip prosthesis,tangential fretting,torsional fretting and fretting corrosion experiments between the taper materials were carried out.The fretting law of the taper interface was studied by using the finite element method,and the method to restrain the fretting of the taper interface was proposed.Based on the simplified experiment,the tangential fretting operation law and damage mechanism between PEEK and Ti6Al4 V contact pairs were studied.The results show that when the tangential fretting between PEEK / Ti6Al4 V contact pairs is in the partial slip region,the corresponding working condition is larger normal load and smaller fretting amplitude,while in the complete slip region,the corresponding working condition is smaller normal load and larger fretting amplitude.The stability value of friction coefficient decreases with the increase of normal load,and increases first and then decreases with the increase of fretting amplitude.Under the condition of small amplitude and large load,the damage of Ti6Al4 V is slight,while the wear area of PEEK shows obvious plastic deformation,the main damage is plastic deformation.Under the condition of large amplitude and small load,the wear areas of Ti6Al4 V and PEEK show intensive scratches,and the damage mechanism is mainly abrasive wear.The fretting wear of PEEK / Ti6Al4 V pair mainly occurs in peek sample,while the wear of CoCrMo / Ti6Al4 V pair mainly occurs in Ti6Al4 V sample.The volume wear caused by the pairing of the two materials is in the same order of magnitude,but the CoCrMo / Ti6Al4 V pairing shows obvious signs of corrosion in calf serum.The fretting corrosion experiment shows that the fretting corrosion current of PEEK / Ti6Al4 V pair is far less than that of CoCrMo / Ti6Al4 V pair,while the corrosion potential of PEEK / Ti6Al4 V pair is significantly higher than that of CoCrMo / Ti6Al4 V pair,and the CoCrMo / Ti6Al4 V pair will release more kinds and quantities of metal ions in the lubricating medium,and the total metal ion release amount is 4.19 times of PEEK / Ti6Al4 V pair,indicating that PEEK artificial hip joint has better corrosion resistance at the taper interface.The torsional fretting between PEEK / Ti6Al4 V contact pairs runs in the partial slip region under the condition of small torsional amplitude and in the complete slip region under the condition of large torsional amplitude.The stability value of friction torque increases first and then decreases with the increase of torsional amplitude,and increases gradually with the increase of normal load,while the equivalent friction coefficient decreases gradually with the increase of normal load.The center of the wear area is mainly adhesive wear,while the edge of the wear area has obvious wear marks and furrows due to the relatively large sliding distance between the materials,and the wear mechanism is mainly abrasive wear.The results of micromotion simulation of the taper interface show that the micromotion maximum of the taper fixed interface of PEEK hip joint prosthesis is 3.3 times of that of CoCrMo hip joint prosthesis,but it decreases sharply with the increase of assembly force of head.When the assembly force reaches 4kN,the changes of micromotion maximum and fretting work tend to be gentle.With the increase of the patient's weight,the micromotion of the taper fixed interface of PEEK hip joint prosthesis increased significantly.When the patient's weight increased from the standard weight to 3/2 times of the standard weight,the corresponding micromotion maximum increased by 80.65%.With the increase of patient's walking stride,the micromotion of the taper fixed interface of PEEK hip joint prosthesis increased correspondingly.When the stride increased to 3 / 2 times of standard stride,the micromotion maximum increased by 8.06%.when the stride decreased to 2/3 times of standard stride,the micromotion maximum decreased by 17.74%.The micromotion of the taper fixed interface of PEEK hip joint prosthesis decreased with the increase of the head size,taper surface roughness,taper angle,and increased with the increase of taper size.Among them,increasing the head size has the greatest effect on restraining the micromotion of the taper fixed interface.When the head size is increased from 28 mm to 30 mm,the corresponding micromotion maximum decreases by 16.13%.Compared with the optimization of the structural parameters of the hip taper,the effect of embedding CoCrMo sleeve in the PEEK head is more significant to restrain the micromotion of the taper fixed interface of the PEEK artificial hip joint.The sleeve design divides the taper fixed interface into two parts: the head / sleeve fixed interface and the sleeve / neck fixed interface,and the micromotion maximum decreases by 61.29% and 67.74% compared with the taper fixed interface of PEEK hip joint prosthesis without CoCrMo sleeve.