Analysis And Optimization Of Porous Bone Scaffolds Based On SLM Technology

The population aging in China in the 21 st century,is gradually increased,and with the development of the industry,the patients with bone disease increased year by year,the artificial bone implants become the important way to solve this problem,and the traditional processing way to precise forming of bone structure,hard and metal mechanical properties is not match with the human body skeleton.After implantation,bone cells are difficult to form effective stimulation,easy to produce "stress concentration","stress shielding" and other phenomena.The selection of appropriate processing methods to reduce the elastic modulus of bone tissue scaffolds has become a major focus of research.Selective laser melting technology by laser melting metal powder in the form of a layered overlay processing,can according to the accurate preparation of internal hole of the structure of the bone tissue scaffolds,and effectively reduce the elastic modulus of metal porous structure,porous structure,hole size can control the mechanical performance of control of design elements such as match the human body skeleton;In this study,porous bone scaffolds were prepared based on SLM technology,and the following studies were carried out:According to the literature,four kinds of porous bone scaffolds with different structures A,B,C and D with porosity of 65% ? 90% were designed,and the porosity gradient was set every 5%.Using the finite element simulation software for design of porous bone scaffold to simulate mechanical properties and fluid simulation,explores the Ti6Al4 V alloy,316 L stainless steel porous support bones deformation mechanism,the compression stress distribution,and through the fluid simulation for the rule of the flow of the body fluid inside the porous scaffolds,stress field and velocity field distribution.The porous structure and porosity range that can withstand the impact of body fluid without causing harm to human body were obtained.In order to study the mechanical properties of porous bone scaffolded by SLM technology,compression tests and hardness tests were carried out on 316 L stainless steel porous bone scaffolded and Ti6Al4 V porous bone scaffolded.The experiments proved that 316 L stainless steel porous bone scaffolded had good ductility and the deformation was mainly offset after being subjected to pressure.The element rod expands outwards and gradually compresses the internal space;Ti6Al4V porous bone scaffold has better compressive strength,and the deformation is mainly the fracture of the element rod,and the space is gradually compressed by multiple fractures in the compression process.In terms of hardness,Ti6Al4 V porous bone scaffold is obviously larger than 316 L stainless steel porous bone scaffold before and after heat treatment.Ti6Al4 V porous bone scaffold is due to 316 L stainless steel porous bone scaffold in terms of mechanical properties.According to the simulation results and compression test results,the porous bone scaffold with 90% porosity of C structure in Ti6Al4 V scaffold is suitable for human cancellous bone implantation.Porous bone scaffolds with75% porosity of structure B,80% ? 85% porosity of structure C and 70% ? 75%porosity of structure D are suitable for human cortical bone implantation.In 316 L stainless steel,porous bone scaffolds with 90% porosity of B structure and 90% porosity of C structure are suitable for human cancellous bone implantation,while porous bone scaffolds with 80% porosity of B structure,80% ? 85% porosity of C structure and 80%porosity of D structure are suitable for human cortical bone implantation.In order to understand forming porous bone scaffolds microstructure SLM technology and the evolution process,this article through metallographic test,SEM,XRD,EDS and other methods of two kinds of materials forming porous bone scaffold for the microstructure observation and phase analysis of 316 L stainless steel microstructure for austenitic organization,grain will continue to grow up and through the molten pool after heat treatment,Improve mechanical properties,reduce the existence of grain dislocation;The microstructure of Ti6Al4 V porous bone scaffold is?' martensite after forming,?' decomposition produces ? phase after heat treatment,and the grain continues to grow and coarser,enhancing the toughness of porous bone scaffold.The material composition and proportion of the porous bone scaffolds formed by the two materials did not change before and after SLM technology and heat treatment,and the porous bone scaffolds had good stability after molding.In this thesis,the advantages and disadvantages of the two materials are revealed through the comparison of simulation and experimental results between the SLM-shaped 316 L stainless steel porous bone scaffold and Ti6Al4 V porous bone scaffold.The 316 L stainless steel porous bone scaffold has good ductility and the scaffold structure is not easy to be destroyed.Ti6Al4 V porous bone scaffold has better mechanical properties under the same conditions and is more suitable for human bone implantation.Heat treatment can improve the mechanical properties of the porous scaffolds of both materials.