| With the progress and development of society,the change of people's awareness of healthy life and the popularization of medical technology,the demand for artificial joints is increasing,and the artificial joint market in my country is developing more and more rapidly.Artificial joint is an implanted organ that can replace all the functions of joints in the human body.Therefore,the requirements for materials are relatively high.TC4 titanium alloy has become one of the main materials for artificial joint production due to its own characteristics and excellent performance.The surface quality of the artificial joint has a great influence on the performance of the product,but because the machinability of the TC4 titanium alloy material is relatively poor and the surface of the artificial joint is irregularly curved,the surface processing is more difficult.Therefore,after studying the current status of TC4 titanium alloy surface processing technology at home and abroad,this thesis uses photocatalytic colloidal jet polishing to perform ultra-precision polishing of TC4 titanium alloy workpieces.According to the principle and technical requirements of the photocatalytic colloidal jet polishing technology,this thesis firstly designed the trapezoidal opticalliquid coupling porous nozzle and the circular optical-liquid coupling porous nozzle to improve the processing efficiency of the technology under the premise of ensuring the processing accuracy.And based on the theory of computational fluid dynamics(CFD),two simulation models of porous nozzles are established,and the flow field distribution characteristics of the two nozzles are analyzed and compared using Fluent software,so as to verify the performance of the two nozzles.Secondly,two optical-liquid coupling porous nozzles were used to perform jet polishing on the TC4 titanium alloy workpiece under the same processing parameters.The SJ-410 surface roughness meter was used to measure the TC4 workpiece.The result showed that the surface roughness of the workpiece after jet polishing was greatly reduced,and the processing effect of the two nozzles was consistent with the simulation result.Finally,the TC4 workpiece that has been polished by the photocatalytic colloid jet is further analyzed on its surface characteristics,and compared with the workpiece that has not been polished by the jet.Micro XAM-800 optical profiler was used to measure the surface morphology of the workpiece before and after processing.The results showed that the surface roughness of the workpiece without jet polishing was76.7nm,and the surface roughness of the workpiece processed by the trapezoidal lightliquid coupling porous nozzle was 2.87 nm.The circular light-liquid coupling porous nozzle is 3.61 nm,and the photocatalytic colloidal jet polishing technology can significantly improve the surface quality of the TC4 titanium alloy workpiece;The metallographic structure of the surface of the TC4 workpiece proves that the metallographic structure of the workpiece surface will not change before and after the photocatalytic colloid jet polishing,and the material removal rate of the primary ?phase in the metallographic structure is higher than that of the ? phase;The ?-X360 n X-ray residual stress analyzer was used to analyze the residual stress on the surface of the TC4 workpiece before and after jet polishing.The results showed that the normal stress of the residual stress on the surface of the workpiece before and after jet polishing was reduced from 75 MPa to 67 MPa,and the shear stress was reduced from13 MPa to 3MPa,the photocatalytic colloidal jet polishing technology reduces the residual stress on the surface of the TC4 workpiece during the processing;The infrared spectra before and after processing showed that chemical bonds such as Ti-O-Ti were found on the surface of the TC4 workpiece after jet polishing,which verified the processing mechanism of the photocatalytic colloid jet polishing TC4 titanium alloy. |
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