Contact Mechanics Analysis And Friction Performance Evaluation Of Artificial Hip Joint Materials

With the aging of our country’s population,the incidence of joint diseases is increasing year by year,and the number of young patients due to major diseases or accidental injuries is increasing,making people’s demand for high-quality artificial hip joints more urgent.The composition of artificial hip joint materials,the mechanical properties of the contact interface and friction and wear are important factors that affect its performance.Therefore,analyzing the contact pressure and friction and wear characteristics of the artificial hip joint has important theoretical reference values for improving its performance.In this thesis,two methods of finite element analysis and friction test are used to study the contact mechanical properties and friction and wear of artificial hip joints.Select 7 groups of materials such as"hard-hard"and"hard-soft",and use the finite element software ANSYS Workbench to analyze the corresponding contact mechanical properties.The results show that the contact pressure of the"hard-hard"material pair is far greater Due to“hard-soft”and stress concentration,the contact pressure of ceramic-to-ceramic under the same structural parameters is 10 times that of metal-to-ultra-high molecular weight polyethylene（UHMWPE）.The small gap and large femoral head diameter in different structural parameters make The contact pressure drop rate exceeds 70%and 42%.A larger abduction angle can reduce the contact pressure.When the abduction angle increases from 30°to 60°,the maximum reduction rate of the ceramic-to-ceramic contact pressure of the 7 sets of material pairs is 12.32%,but too large abduction angle will cause the contact pressure to increase sharply and lead to edge contact.By rounding the inner edge of the acetabulum,the edge contact can be reduced,and the larger the round angle,the better the effect.The"hard-soft"material is matched.The peak and change rate of contact pressure are relatively small under all structural parameters.The maximum contact pressure of metal to UHMWPE is only9.726MPa.When UHMWPE is used as an acetabular cup,the contact pressure is the smallest,but edge contact is prone to occur.Considering the contact mechanical properties,Choosing the"hard-soft"ceramic/polyetheretherketone（PEEK）and metal/PEEK material pairs is more conducive to improving the mechanical properties of the artificial hip joint.In a complete gait,the contact pressure of the 7 groups of materials is the largest The values both appear at 15%and 55%of a cycle,and wear is most likely to occur at 0.55s,when the human body is at the moment of one foot on the ground.A friction testing machine was used to test the friction and wear of different material pairs under different speed,load,and lubrication conditions.The results showed that the friction coefficient of each group of material pairs decreased with the increase of speed,and with the increase of load.Larger and larger,bovine serum albumin（BSA）solution can significantly reduce the friction coefficient.The friction coefficient of stainless steel/cobalt-chromium-molybdenum（CoCrMo）is between 0.265 and 0.322,and the friction coefficient of ceramic/PEEK and ceramic/CoCrMo pairs are respectively Between 0.066～0.083 and0.067～0.088,the friction traces of ceramic and PEEK materials are observed through an electron microscope,and the wear traces of ceramic and PEEK materials are found to be small.Calculate the wear volume of the sphere.The maximum wear volume of the sphere under the stainless steel/CoCrMo pair is 1.3×10^-3mm³,and the ceramic/PEEK The minimum wear volume of the ball under the pair is 3.0911×10^-5mm³.Comprehensive mechanical analysis and test results have found that the ceramic/PEEK material pair has excellent contact mechanics and friction and wear properties under small gaps,large femoral head diameters,and appropriate abduction angles.Based on this,it can be used for the design and installation of artificial hip joints.Choose to provide a certain reference value.