Fundamental Study On Friction Characteristics Of Artificial Finger Joint Textured Surface Based On 3D Printing

Artificial joint during the friction and wear in the body can cause aseptic loosening,localized tumors,such as postoperative complications,serious when even will shorten the service life of joint prosthesis,and the need for secondary revision surgery,cause unnecessary suffering to patients,and joint prosthesis in good biocompatibility at the same time should also have excellent tribological performance.For this reason,scholars at home and abroad devote themselves to the research and development and modification of prosthetic materials.Among the numerous modification means,surface texture technology,as a physical modification means without changing the properties of the matrix material,has been widely concerned by scholars at home and abroad because of its excellent frictional and biological properties regulation ability.Based on this,the design parameters of single texture and the optimization design of artificial knuckle gradient texture surface were studied in this work,and the effects of different printing directions on the surface friction properties of printing parts under melt deposition molding process were analyzed by combining experiment and numerical simulation.The main research contents are as follows:Based on the Navier-Stokes equations,a single texture model under hydrodynamic pressure lubrication was established.The influences of design parameters such as shape,depth ratio and area ratio on the dynamic pressure performance of single texture were calculated and analyzed.The results show that the dynamic compressive properties of the symmetric texture do not change when the motion direction is opposite,while the asymmetric texture with the opposite wedge structure shows the opposite dynamic compressive properties.The dynamic pressure performance of symmetric and asymmetric convergent textures increases first and then decreases with the depth increasing.In the simulated range,the dynamic pressure performance is better when the depth ratio is close to 1.The dynamic compressive properties of the texture increase with the increase of area ratio,but too large area ratio will lead to cavitation and further aggravate the degeneration or wear of the texture.Comparing the dynamic compressive properties of groove texture and pit texture,it is found that the dynamic compressive properties of pit texture are generally better than groove texture under the same design parameters.Therefore,pit texture should be given priority in the texture design of artificial joints.In addition,the influence of working conditions on the dynamic pressure performance of the texture is obvious.The smaller the thickness of the liquid film of the texture,the more significant the influence of the design parameters on the dynamic pressure performance is,while the change of the velocity in the simulation range has little effect on the dynamic pressure performance.By establishing the lubrication calculation model of the textured surface of the artificial knuckle under hydrodynamic pressure lubrication,the influence of different gradient texture on the dynamic pressure performance of the textured surface was studied.The calculation results show that the introduction of gradient texture has a significant effect on the dynamic pressure performance because the joint surface clearance changes with the change of position.For the textured surface with an area rate gradient distribution,the principle that the area rate at both ends is higher than the area rate in the middle region should be followed,and the gradient change should be increased as much as possible within the allowable range.In the simulation range,the dynamic pressure performance of the textured surface with an area rate gradient distribution of 30%-10%-30% is optimal.For the textured surface with depth gradient distribution,the introduction of gradient distribution does not have a positive effect on the textured surface.In the simulated range,the textured surface with uniform depth distribution of 5μm-5μm-5μm shows the best dynamic pressure performance.The influence of molding process parameters on the surface quality of printing parts was studied,and the influence of different printing directions on the surface friction properties of printing parts was analyzed by means of friction and wear test and numerical simulation.The increase of the layer height and printing speed will reduce the surface quality of the printed parts.The surface quality of the printed parts with the layer height of 0.1mm and the printing speed of 20mm/s is better.The change of the printing direction significantly affects the friction properties of the print surface under lubrication condition.When the printing direction is 90°,the print surface has the smallest friction coefficient and wear amount.After numerical simulation by Fluent,it is found that when the texture direction of the print surface increases from 0° to 90°,the influence of groove texture on the lubrication medium gradually changes from the guiding effect to the hindering effect,which weakens the ploughing effect of the wear debris on the material,and then reduces the wear on the print surface.