Design And Analysis Of Porous Bone Tissue Scaffold Based On Grid Mapping

The bone tissue defects caused a great number of inconveniences to the patients’ life and works that result from trauma,disease or any other reasons.The bone tissue scaffold repair technology has been considered to be the most effective method for the treatment of bone tissue defects due to its wide range of material source,rapid recovery of postoperative limb function,less postoperative complications and some other advantages.Bone tissue porous scaffold is a form and functional substitute,which can be used to repair bone tissue defects.According to the bionic structure requirement,it should have an external contour that is highly consistent with the contour of the defect bone surface,which helps to match other bone tissue better.At the same time,it should also have an internal three-dimensional through porous structure that is similar to the internal pores of natural bone,which helps to satisfy the demand of mechanical and biological properties.According to the design requirements of bone tissue porous scaffolds,the modeling method of porous scaffold has been explored.Proposing an optimum design scheme based on the theory of finite element analysis,a route of design and optimization on bone tissue porous scaffold which has controllable structure has been constructed.In this method,bone tissue porous scaffold model which has the appearance of individual bones and adjustable internal pore structure parameters can be built.This thesis mainly covers the following four aspects:Firstly,based on the theories and techniques of finite element meshing and CSG solid modeling,an universe modeling method for bone tissue porous scaffold has proposed.The external contour of the porous scaffold structure obtained in this method can not only match the shape of the bone tissue,but also the internal structure can be regulated by the design parameters,which provides a new technical route and implementation method for the bionic modeling of the bone tissue porous scaffold.Then,considering the structural characteristics of the porous tissue scaffold designed in this thesis,a reasonable parametric modeling method for porous scaffolds has been proposed.The finite element model of porous scaffold which will be used for simulation analysis can be constructed.Based on the finite element stress analysis of porous scaffolds under real force situation,a method of scaffold structure encryption design for reducing the peak of equivalent stress by encrypting scaffold partly has been explored,and the effectiveness of the method has been verified by finite element theory calculation and experiment.Next,based on the structural optimization design theory and the characteristics of porous scaffold designed in this thesis,a structural optimization design method of bone tissue porous scaffold based on biomechanical simulation and uniform stress criterion has been proposed.The scaffold optimized by this method will have a more uniform equivalent stress distribution and a lower peak of equivalent stress.At the same time,the structure of the scaffold will be more reasonable due to the decrease of volume and the increase of porosity.Finally,considering the porous scaffold design method in this thesis,the overall framework of the porous scaffold design system based on grid mapping has been proposed.Under the Windows platform and the Visual Studio 2013 development environment,the development of the system has been implemented with the combination of Netgen and Open Cascade tool library in the idea of modular design.The system mainly includes tetrahedral meshing,scaffold parametric model building,scaffold materialized model modeling,optimized scaffold materialized model modeling function.