| Solid metal implants are prone to aseptic loosening,leading to a decrease in the service life of the implants.Part or all of the implant surface can be designed as a porous structure,and traditional manufacturing techniques cannot achieve the manufacture of complex pore structures.Selective Laser Melting(SLM)technology can almost realize the forming of arbitrarily complex structural parts,and the formed parts have good mechanical properties and high forming accuracy.In terms of implant molding,the molding performance of SLM technology has met the requirements,but the performance of SLM molding parts needs further research.In this thesis,the porous femoral implant is the research object,the femoral unit is optimized based on SLM technology,and the SLM molding process parameters are optimized to analyze the impact of different process parameters on the quality of the specimen.Based on the optimized process parameters,the performance of the SLM molded sample was evaluated and studied,and finally the porous femoral implant was molded by SLM technology.The main research contents of this thesis are as follows:(1)Analyze the requirements and constraints of porous implants,propose an optimization design method for porous structure based on SLM,and optimize the design of femoral unit structure.According to the selection of the porous element structure,three different load loading methods are designed,and the finite element analysis of the three porous element structures is carried out to determine the porous element structure of the femoral implant,which is the analysis of the subsequent compression performance and the molded porous femoral implants provide data files.(2)The orthogonal experiment was used to optimize the SLM forming process parameters.By analyzing the influence weights and laws of different process parameters on the microstructure,density and roughness of the formed samples,the optimal process parameter combination was determined.(3)On the basis of optimizing the process parameters,the performance evaluation of the SLM molded samples is carried out.Through microstructure analysis,it is found that there is a difference between the microstructure of the cross section and the longitudinal section of the SLM molded sample.Through microhardness test,it is found that the microhardness of the side and front of SLM molding sample is higher than that of the casting sample.Through the tensile test,it is found that the yield strength and tensile strength of the SLM molded sample are higher than ASTMF 136 and the casting standard,but its elongation is slightly lower than the ASTMF136 standard;Through the compression test,it is found that the elastic modulus and compressive strength of the SLM molded sample meet the requirements of human bones.Through friction and wear experiments,it is found that under different lubrication conditions,the friction coefficient of the SLM molded sample is lower than that of the cast sample.Through comparison,the friction coefficient of the side and front of the SLM molded sample is analyzed.The curve shows that there is basically no difference in the trend and size of the friction coefficient between the side and the front of the molded sample,and the friction coefficient of the side is slightly lower than the front.(4)Based on the analysis of the influence of the suspension structure and support structure on the quality of SLM molded parts,the optimized process parameter combination and reasonable support structure are used to form porous femoral implants.And analyze its overall molding effect and local molding effect separately.Although the molded porous femoral implant has local molding defects,it can still meet the molding requirements,verifying the feasibility of SLM molding porous femoral implants. |
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