發(fā)布時間：2018-06-20 06:16

  本文選題：點陣材料 + 3D打印技術(shù)��； 參考：《中國科學技術(shù)大學》2017年博士論文

【摘要】：點陣材料是一種新型的胞狀有序多孔材料,其單胞為桿單元組成的空間網(wǎng)架類結(jié)構(gòu)。金屬基點陣材料具有良好的力學性能和功能特性,在航空航天、交通運輸、武器裝備、電子器件等領(lǐng)域有著廣泛的應(yīng)用前景。本文針對目前金屬基點陣材料在結(jié)構(gòu)設(shè)計、制備方法、性能研究等方面存在的不足及其在航天領(lǐng)域的應(yīng)用需求,通過計算機輔助設(shè)計、3D打印及熔模滲流工藝對Al基點陣材料的制備工藝進行了研究;通過準靜態(tài)壓縮試驗及細觀組織觀察,對Al基點陣材料本構(gòu)特征、變形行為及其機制進行了分析,得到了以下主要結(jié)果:1、利用 CATIA(Computer Aided Tri-Dimensional Interface Application)軟件編制了點陣結(jié)構(gòu)設(shè)計方法,設(shè)計出不同結(jié)構(gòu)參數(shù)的金字塔型和四面體型點陣單胞及拓撲結(jié)構(gòu);根據(jù)3D打印技術(shù)原理,對聚丙烯、尼龍和光敏樹脂等低熔點非金屬打印材料及點陣模樣"打印"工藝(選擇性激光燒結(jié)和紫外激光固化)進行了試驗與優(yōu)化。結(jié)果表明,基于液態(tài)光敏樹脂的光固化3D打印工藝,不僅成形速度快,而且打印出的模樣細觀結(jié)構(gòu)完整,表面光潔度高,力學性能好,為后續(xù)金屬點陣材料制備及其性能研究奠定了重要基礎(chǔ)。2、針對點陣結(jié)構(gòu)桿徑和桿長較小、桿連接節(jié)點較多從而使石膏熔模制備及金屬液在熔模內(nèi)流動困難的特點,對熔模壓力滲流法制備Al基點陣材料的工藝過程進行了系統(tǒng)研究,包括石膏漿料組成與配比、石膏熔模加熱過程中結(jié)構(gòu)及物性的變化、石膏熔模的高溫強度及滲流后的潰散性以及滲流壓力控制等,獲得了具有良好流動性、熱物性、力學性能和易溶性的石膏熔模組成和熱處理工藝。通過對石膏熔模預(yù)熱溫度、Al液滲流溫度和壓力對多孔骨架中的金屬液流動規(guī)律影響的研究,得到了最佳的滲流工藝,制備出不同構(gòu)型、不同結(jié)構(gòu)參數(shù)的多層Al基點陣材料,其幾何精度與3D打印的模樣基本一致。3、針對點陣材料的一般承載方式和應(yīng)用場合,對Al基點陣材料準靜態(tài)壓縮行為及其與點陣構(gòu)型、主要結(jié)構(gòu)參數(shù)(桿截面形狀、桿長、桿徑、夾角、相對密度等)的依賴關(guān)系進行了考察。結(jié)果顯示,Al基點陣材料與一般多孔材料相似,在應(yīng)力應(yīng)變曲線上也有明顯的彈性區(qū)、平臺區(qū)和致密化區(qū)。但與一般多孔材料不同的是,上述三個區(qū)域的長短、高低與點陣材料的相對密度呈非線性關(guān)系,并且與桿單元與單胞底面的夾角密切相關(guān)。點陣材料相對密度增加約1倍,平臺流動應(yīng)力增加近7倍;桿單元與單胞底面夾角為45°時,平臺流動應(yīng)力約7MPa,而當夾角增加至70°時,平臺流動應(yīng)力則增加到15MPa。在夾角、相對密度接近時,四面體型點陣材料的長徑比要小于金字塔型,因此前者力學性能和吸能性能都要好于后者。隨著長徑比的減小,雖然四面體型點陣材料的流動應(yīng)力、平均壓潰力以及單位質(zhì)量吸能都逐漸變大,但是能量吸收效率卻有所降低。4、為了探索進一步改善材料性能的途徑,對不同基體材料及不同桿截面形狀的Al基點陣材料進行了力學性能研究。試驗發(fā)現(xiàn),與工業(yè)純Al相比,采用高強度的6063和6066 Al合金為基體,點陣材料的流動應(yīng)力明顯提高,其中6066 Al合金的強化效果最明顯,抗壓強度高達50MPa左右。對圓形、半空心圓形及U形截面桿點陣材料的考察發(fā)現(xiàn),U形截面更有利于提高材料的彈性模量和抗壓強度,當其它參數(shù)相同時,U形截面桿點陣材料的抗壓強度是圓形截面桿的2倍以上,其原因是三種桿中,U形截面桿具有最大的慣性矩,而點陣材料的抗壓強度與桿單元的慣性矩成正比。5、為了揭示Al基點陣材料力學行為的物理機制,對材料宏、細觀壓縮變形模式、變形組織演變規(guī)律等進行了觀察,發(fā)現(xiàn)純Al基金字塔型點陣材料的壓縮變形以桿單元的彎曲、折疊為主,無明顯斷裂,整體變形方式取決于桿單元與單胞底面的夾角。夾角較小時,如45°,點陣結(jié)構(gòu)中所有桿單元同時彎曲和折疊,變形組織在點陣結(jié)構(gòu)中均勻分布;反之,當夾角較大時,如70°,桿單元彎曲首先在一個局部區(qū)域內(nèi)發(fā)生,然后局域化變形組織逐漸向其它區(qū)域擴展直至整體致密化。該變形方式與相應(yīng)的應(yīng)力應(yīng)變曲線的形狀是吻合的,即前者彈性區(qū)與平臺區(qū)圓滑過渡,后者則在彈性區(qū)與平臺區(qū)之間出現(xiàn)明顯的屈服平臺。6、鑒于Al基點陣材料的變形模式以桿單元的彎曲為主,試驗中將Al基點陣材料壓入6063 Al合金方管及用不同硅橡膠填入Al基點陣材料的孔隙,分別形成了內(nèi)、外約束條件。對其進行的壓縮試驗表明,當位移較小時,填充方管的組合材料基本上沿襲了方管的變形模式,而當位移較大時,載荷-位移曲線明顯升高,其值大于方管和點陣材料單獨壓縮時載荷的代數(shù)和,表明方管對點陣材料橫向變形的約束產(chǎn)生了明顯的強化效果。對于填充硅橡膠的場合,點陣材料不僅流動應(yīng)力顯著上升,而且在應(yīng)力應(yīng)變曲線上只出現(xiàn)彈性區(qū)和平臺區(qū),無致密化區(qū),因此材料強度、吸能性和吸能效率均顯著提高。
[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.
【學位授予單位】：中國科學技術(shù)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB383.4

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