A Study Of Parametric Modeling For Active Design Of Porous Functional Structure

The porous structure with dual properties of function and structure has a wide range of applications in many fields such as machinery,energy,medicine,architecture,electronics,and aerospace due to its excellent comprehensive performance.The pore of the porous structure is the main factor affecting its function,and thus the control of the pore shape and distribution becomes the main content of the porous structure design.This study respectively takes the“performance-properties-structure-processing” design model of porous structure as the main line,the mapping relationship between porous structure parameters as the theoretical basis,and the lattice type and surface type as the research object.In this dissertation,cube and hexahedral grids are used to study the parametric modeling of porous structure for the unit cell,an active design method for determining structural parameters according to functional indicators is proposed,and the accuracy and controllability of porous structure design are strengthened.The main research work of this dissertation is as follows:(1)Combining the design characteristics of lattice structure and open-cell foam,a parametric modeling method of uniform lattice unit based on Voronoi division is proposed.This study analyzes the regular lattice unit cell and determines its structural design parameters,thereby establishing the mapping relationship model between the pore characterization parameters and the structural design parameters;Through Voronoi division,a lattice unit cell with uniformly distributed seed points is generated,and a parameter mapping relationship model of the uniform lattice unit cell is established.The parameterized modeling method of uniform lattice unit cell has the properties of globally controllable pore distribution and local uniformity,which provides a theoretical and technical basis for the design of customized pore porous structures for specific applications.(2)Aiming at the problem of generating lattice porous structures associated with geometric shapes in complex geometric shapes,a parametric modeling method for lattice porous structures based on hexahedral grids is proposed.The method of combining uniform lattice unit cell and hexahedral grid can not only generate lattice porous structure with uniform pore distribution and gradient pore distribution,but also design lattice porous structure with controllable pore parameters in a complex geometric shape,which provides a new way for customized porous structure design in a given design space.(3)Aiming at the smooth transition of the pore surface between the lattice units,the TPMS(Triply periodic minimal surface)is used as the unit cell,and a parametric modeling method for the surface porous structure based on TPMS is proposed.The parameter mapping relationship model of four commonly used TPMS surface cell is established,and the TPMS surface cell is combined with a hexahedral mesh to generate a curved porous structure with controllable pore characteristics in a complex geometric shape.In view of the advantages of the nested structure that can greatly improve the porosity and specific surface area,a design method of the nested TPMS curved porous structure with thickness as a parameter is proposed.This paper also uses Micro-CT technology to analyze the differences between the 3D printed object and the design model of the surface porous structure.(4)In order to verify the "performance?processing" design mode of porous structure,this dissertation conducts a case study of parametric modeling of active design of porous structure in combination with specific applications.Two porous structure parameterized design methods,single parameter control method and multi-parameter control method,are proposed;the equivalent elastic modulus of the lattice porous structure of the bone implant is used as the functional parameter to establish the mapping relationship between this parameter and the pore attribute parameter and the structural design parameter,which helps to realize the active design process of "performance?structure";According to the requirements of high porosity and large specific surface area of catalyst carrier,the porous structure of TPMS curved surface is designed by multi-parameter control method,and the sample is prepared by SLM augmentation technology.The good performance of the porous catalyst carrier with "new structure + new processing" is verified by the experiment of hydrogen production by methanol steam reforming.