【作者】 雷鸿源；

【导师】 李静蓉；

【作者基本信息】 华南理工大学 ， 机械工程， 2021， 博士

【摘要】 兼具功能和结构双重属性的多孔结构,因拥有优异的综合性能而在机械、能源、化工、医学、建筑、电子、航空航天等诸多领域具有广泛的应用。多孔结构的孔隙是影响其功能的主要因素,所以,对于孔隙形状及分布的控制成为多孔结构设计的主要内容。本课题以多孔结构的“功能―属性―结构―工艺”设计模式为主线,以多孔结构参数之间的映射关系为理论基础,以点阵型和曲面型两种结构类型为研究对象,分别以立方体和六面体网格为单元体进行多孔结构参数化建模研究,提出按照功能指标确定结构参数的主动设计方法,并强化多孔结构设计的精确性和可控性。本文的主要研究工作包括:(1)结合点阵结构和开孔泡沫结构的设计特点,提出一种基于Voronoi划分的均匀点阵单元体的参数化建模方法。分析规则点阵单元体并确定其结构设计参数,从而建立孔隙表征参数与结构设计参数之间的映射关系模型;通过Voronoi划分生成种子点均匀分布的点阵单元体,并建立均匀点阵单元体的参数映射关系模型。均匀点阵单元体的参数化建模方法,具有孔隙分布全局可控且局部均匀的性质,为面向具体应用的定制孔隙多孔结构的设计提供理论和技术基础。(2)针对在复杂几何外形内生成与几何外形关联的点阵多孔结构的问题,提出基于六面体网格的点阵多孔结构参数化建模方法。将均匀点阵单元体与六面体网格相结合的方法,不仅能生成孔隙均匀分布和孔隙梯度分布的点阵多孔结构,还能在复杂几何外形内设计出孔隙参数可控的点阵多孔结构,这为给定设计空间的定制多孔结构设计提供了新的途径。(3)针对点阵单元体间孔隙表面的光滑过渡问题,将TPMS(Triply periodic minimal surface)曲面作为单元胞,提出基于TPMS的曲面多孔结构参数化建模方法。建立四种常用TPMS曲面单元胞的参数映射关系模型,并将TPMS曲面单元胞与六面体网格相结合,在复杂几何外形内生成孔隙特征可控的曲面多孔结构。鉴于嵌套式结构能极大提高孔隙率和比表面积的优点,提出以厚度为参数的嵌套式TPMS曲面多孔结构的设计方法。本文还采用Micro-CT技术分析曲面多孔结构的3D打印实物与设计模型之间的差异。(4)为了验证多孔结构的“功能→工艺”设计模式,本文结合具体应用进行多孔结构主动设计的参数化建模案例研究。提出了单参数控制法和多参数控制法两种多孔结构参数化设计方法;以骨植入体点阵多孔结构的等效弹性模量为功能参数,建立该参数与孔隙属性参数和结构设计参数之间的映射关系,从而实现“功能→结构”的主动设计过程;结合催化剂载体对于高孔隙率和大比表面积的要求,以多参数控制法设计TPMS曲面多孔结构,采用SLM增材制造技术制备样件,并通过甲醇蒸汽重整制氢实验验证这种“新结构+新工艺”的多孔催化剂载体具有较好的性能。更多还原

【Abstract】 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.更多还原