三维Al基点阵材料设计、制备及力学性能研究

发布时间：2018-06-20 06:16

本文选题：点阵材料 + 3D打印技术　；参考：《中国科学技术大学》2017年博士论文

【摘要】：点阵材料是一种新型的胞状有序多孔材料,其单胞为杆单元组成的空间网架类结构。金属基点阵材料具有良好的力学性能和功能特性,在航空航天、交通运输、武器装备、电子器件等领域有着广泛的应用前景。本文针对目前金属基点阵材料在结构设计、制备方法、性能研究等方面存在的不足及其在航天领域的应用需求,通过计算机辅助设计、3D打印及熔模渗流工艺对Al基点阵材料的制备工艺进行了研究;通过准静态压缩试验及细观组织观察,对Al基点阵材料本构特征、变形行为及其机制进行了分析,得到了以下主要结果:1、利用 CATIA(Computer Aided Tri-Dimensional Interface Application)软件编制了点阵结构设计方法,设计出不同结构参数的金字塔型和四面体型点阵单胞及拓扑结构;根据3D打印技术原理,对聚丙烯、尼龙和光敏树脂等低熔点非金属打印材料及点阵模样"打印"工艺(选择性激光烧结和紫外激光固化)进行了试验与优化。结果表明,基于液态光敏树脂的光固化3D打印工艺,不仅成形速度快,而且打印出的模样细观结构完整,表面光洁度高,力学性能好,为后续金属点阵材料制备及其性能研究奠定了重要基础。2、针对点阵结构杆径和杆长较小、杆连接节点较多从而使石膏熔模制备及金属液在熔模内流动困难的特点,对熔模压力渗流法制备Al基点阵材料的工艺过程进行了系统研究,包括石膏浆料组成与配比、石膏熔模加热过程中结构及物性的变化、石膏熔模的高温强度及渗流后的溃散性以及渗流压力控制等,获得了具有良好流动性、热物性、力学性能和易溶性的石膏熔模组成和热处理工艺。通过对石膏熔模预热温度、Al液渗流温度和压力对多孔骨架中的金属液流动规律影响的研究,得到了最佳的渗流工艺,制备出不同构型、不同结构参数的多层Al基点阵材料,其几何精度与3D打印的模样基本一致。3、针对点阵材料的一般承载方式和应用场合,对Al基点阵材料准静态压缩行为及其与点阵构型、主要结构参数(杆截面形状、杆长、杆径、夹角、相对密度等)的依赖关系进行了考察。结果显示,Al基点阵材料与一般多孔材料相似,在应力应变曲线上也有明显的弹性区、平台区和致密化区。但与一般多孔材料不同的是,上述三个区域的长短、高低与点阵材料的相对密度呈非线性关系,并且与杆单元与单胞底面的夹角密切相关。点阵材料相对密度增加约1倍,平台流动应力增加近7倍;杆单元与单胞底面夹角为45°时,平台流动应力约7MPa,而当夹角增加至70°时,平台流动应力则增加到15MPa。在夹角、相对密度接近时,四面体型点阵材料的长径比要小于金字塔型,因此前者力学性能和吸能性能都要好于后者。随着长径比的减小,虽然四面体型点阵材料的流动应力、平均压溃力以及单位质量吸能都逐渐变大,但是能量吸收效率却有所降低。4、为了探索进一步改善材料性能的途径,对不同基体材料及不同杆截面形状的Al基点阵材料进行了力学性能研究。试验发现,与工业纯Al相比,采用高强度的6063和6066 Al合金为基体,点阵材料的流动应力明显提高,其中6066 Al合金的强化效果最明显,抗压强度高达50MPa左右。对圆形、半空心圆形及U形截面杆点阵材料的考察发现,U形截面更有利于提高材料的弹性模量和抗压强度,当其它参数相同时,U形截面杆点阵材料的抗压强度是圆形截面杆的2倍以上,其原因是三种杆中,U形截面杆具有最大的惯性矩,而点阵材料的抗压强度与杆单元的惯性矩成正比。5、为了揭示Al基点阵材料力学行为的物理机制,对材料宏、细观压缩变形模式、变形组织演变规律等进行了观察,发现纯Al基金字塔型点阵材料的压缩变形以杆单元的弯曲、折叠为主,无明显断裂,整体变形方式取决于杆单元与单胞底面的夹角。夹角较小时,如45°,点阵结构中所有杆单元同时弯曲和折叠,变形组织在点阵结构中均匀分布;反之,当夹角较大时,如70°,杆单元弯曲首先在一个局部区域内发生,然后局域化变形组织逐渐向其它区域扩展直至整体致密化。该变形方式与相应的应力应变曲线的形状是吻合的,即前者弹性区与平台区圆滑过渡,后者则在弹性区与平台区之间出现明显的屈服平台。6、鉴于Al基点阵材料的变形模式以杆单元的弯曲为主,试验中将Al基点阵材料压入6063 Al合金方管及用不同硅橡胶填入Al基点阵材料的孔隙,分别形成了内、外约束条件。对其进行的压缩试验表明,当位移较小时,填充方管的组合材料基本上沿袭了方管的变形模式,而当位移较大时,载荷-位移曲线明显升高,其值大于方管和点阵材料单独压缩时载荷的代数和,表明方管对点阵材料横向变形的约束产生了明显的强化效果。对于填充硅橡胶的场合,点阵材料不仅流动应力显著上升,而且在应力应变曲线上只出现弹性区和平台区,无致密化区,因此材料强度、吸能性和吸能效率均显著提高。
[Abstract]:Lattice material is a new type of cellular ordered porous material, its single cell is a space truss type structure composed of rod element. Metal base point array has good mechanical and functional properties. It has extensive application prospects in the fields of aerospace, transportation, weapon equipment, electronic devices and so on. This paper is aimed at metal base point array. The shortage of material in structure design, preparation method and performance research and its application demand in space field are studied. The preparation technology of Al based lattice materials is studied by computer aided design, 3D printing and melt mold seepage process. The constitutive characteristics of Al matrix lattice materials are changed by quasi static compression test and microstructure observation. The form behavior and its mechanism are analyzed, and the following main results are obtained: 1, the design method of lattice structure is compiled with CATIA (Computer Aided Tri-Dimensional Interface Application) software, and the single cell and topology structure of Pyramid type and tetrahedron with different structural parameters are designed. According to the principle of 3D printing technology, polypropylene, The low melting point non metal printing materials such as nylon and photosensitive resin and the dot matrix pattern "printing" process (selective laser sintering and UV laser curing) have been tested and optimized. The results show that the light curing 3D printing process based on liquid photosensitive resin is not only fast in forming, but also in fine microstructure and high surface finish. The mechanical properties are good. It lays an important foundation for the preparation and Performance Research of the subsequent metal lattice materials, which is based on the small diameter and length of the lattice structure and the length of the rod, so that the connecting joints of the rod are more so that the plaster mold is prepared and the metal liquid is difficult to flow in the molten mould. The process of the preparation of the Al based lattice material by the pressure seepage flow method is carried out. The systematic study, including the composition and proportion of gypsum slurry, the change of structure transitivity in the heating process of plaster mold, the high temperature strength of the plaster mold, the collapsibility after the seepage and the control of the percolation pressure, obtained the composition and heat treatment process of plaster mold with good fluidity, thermal properties, mechanical properties and solubility. The influence of molten mold preheating temperature, Al liquid percolation temperature and pressure on the flow law of metal liquid in the porous framework has been studied. The optimum percolation process is obtained. The multi-layer Al matrix matrix materials with different configurations and different structural parameters are prepared. The geometric precision and the pattern of 3D printing are basically.3, and the general loading mode and application of the lattice materials are used. On the occasion, the quasi-static compression behavior of Al based lattice materials and the dependence of the main structural parameters (rod cross section shape, rod length, rod diameter, angle, relative density, etc.) are investigated. The results show that the Al based lattice materials are similar to those of the general porous materials, and there are also obvious elastic zones, platform area and density on the stress-strain curves. But unlike the general porous material, the length of the above three regions has a nonlinear relationship with the relative density of the lattice material, and is closely related to the angle between the rod element and the single cell bottom. The relative density of the lattice material increases about 1 times, the flow stress of the platform increases nearly 7 times, the angle of the rod unit and the single cell bottom is 45 degrees. The flow stress is about 7MPa, and when the angle of the sandwich increases to 70 degrees, the flow stress of the platform increases to the angle of 15MPa.. When the relative density is close, the ratio of the length to diameter of the tetrahedral lattice material is smaller than that of the Pyramid type, so the former is better than the latter. With the decrease of the length to diameter ratio, the flow of the tetrahedral lattice material The stress, the average crushing force and the unit mass absorption energy gradually become larger, but the energy absorption efficiency is reduced by.4. In order to explore the way to further improve the material performance, the mechanical properties of the Al based lattice materials with different matrix materials and different bar cross sections are studied. The experiment shows that the high strength 6 is compared with the industrial pure Al. The flow stress of the lattice material is obviously increased with the 063 and 6066 Al alloy as the matrix, and the strengthening effect of the 6066 Al alloy is the most obvious, the compressive strength is up to 50MPa. The investigation of the circular, semi hollow circular and U cross section material found that the U section is more beneficial to improve the elastic modulus and compressive strength of the material, when the other parameters are the same. The compressive strength of the U shaped cross section material is more than 2 times that of the circular section bar. The reason is that the U shaped cross section has the maximum moment of inertia in the three rod, and the compressive strength of the lattice material is proportional to the moment of inertia of the rod element. In order to reveal the physical mechanism of the Al based lattice material, the material macro and the meso compression deformation mode are observed. The deformation pattern of the deformation tissue is observed. It is found that the compression deformation of the pure Al foundation type lattice material is based on the bending and folding of the rod element, and there is no obvious fracture. The whole deformation mode depends on the angle between the rod element and the single cell bottom. The angle of the lattice is small, such as 45 degrees, all the rod units in the lattice structure are bending and folding at the same time. On the other hand, when the angle is large, when the angle is larger, such as 70 degrees, the bending of the rod unit occurs first in a local area, and then the localized deformation organization gradually extends to the other region until the whole densification. The deformation mode is in accordance with the shape of the corresponding stress-strain curve, that is, the former elastic zone and the platform area are smooth. In the latter, the apparent yield platform.6 appears between the elastic zone and the platform area. In view of the deformation mode of the Al based lattice material, which is dominated by the bending of the rod element, the Al based lattice materials are pressed into the 6063 Al alloy square tubes and the pores filled with the Al matrix matrix materials with different silicone rubber. The internal and external constraints are formed respectively. The compression test shows that when the displacement is small, the composite material of the filled square tube basically follows the deformation mode of the square tube, and when the displacement is large, the load displacement curve is obviously increased, and its value is larger than the algebra of the load when the square tube and the lattice material are compressed alone. It shows that the square tube has a obvious strengthening of the constraint on the transverse deformation of the lattice material. As for the situation of silicone rubber filling, the flow stress of the lattice material is not only increased significantly, but also on the stress-strain curve, only the elastic zone and the platform area, no densification zone, so the material strength, energy absorption and energy absorption efficiency are significantly improved.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.4

【相似文献】