氮化硅陶瓷空心浮力球的制备及性能研究

发布时间：2018-05-08 10:11

本文选题：Si_3N_4陶瓷 + 空心浮力球　；参考：《上海材料研究所》2017年硕士论文

【摘要】：深海蕴含着大量的矿物、能源资源,生物物种多样性高度丰富甚至还可能包含解开地球生命起源之谜的钥匙。进入21世纪以来,各国对深海探测和开发逐渐变得更为重视,而深海探测与开发离不开深潜装备的发展,深海浮力材料是深潜装备所需的一类关键材料。氮化硅(Si_3N_4)是一类综合性能十分优异的结构陶瓷材料,已在工业、国防及航空航天等多个领域得到广泛的使用。Si_3N_4陶瓷空心浮力球的静水抗压强度高,球体密度低(可提供的浮力大),且在海水环境下十分稳定,是一种性能优异的深海浮力材料。本文讨论了陶瓷空心浮力球的设计,尤其是对半球壳成型工艺进行了较深入的研究,初步提出了陶瓷空心浮力球质量控制方法,并进行了地面压力试验验证,为Si_3N_4陶瓷空心浮力球的实际应用提供了部分试验依据。Si_3N_4陶瓷理论抗压强度和弹性模量较高的同时,密度则相对较低,是陶瓷空心浮力球的最佳选材。理论计算表明内径100mm、壁厚2mm的Si_3N_4陶瓷空心浮力球的极限抗压强度和极限屈曲强度分别为286.8和532.2 MPa,安全系数满足SF"g2的条件(设计压力115MPa)。通过ABAQUS有限元分析软件对Si_3N_4陶瓷空心浮力球进行屈曲强度和最大主应力分布计算,发现屈曲强度计算值与理论公式计算值相接近,最大主应力分布较为均匀,是一种理想的耐压结构体。对比了Si_3N_4陶瓷耐压罐的ABAQUS分析结果发现,陶瓷罐的结构对称性不如空心球体,从而存在较多的应力集中区域,这些对于结构的强度有着较大的影响。“海神”号无人潜水器的失事原因并不一定源于陶瓷空心球的内爆,其使用的陶瓷耐压罐的可能性更大。研究了用于Si_3N_4陶瓷半球壳成型的凝胶注模成型和3D打印快速成型的工艺参数。研究发现,凝胶注模成型的Si_3N_4陶瓷烧结件的致密度未能满足要求,断口显微观察发现生坯和烧结体中均存在较多针孔;3D打印成型的半球壳通过烧结可以制得理论密度达99.7%的半球壳样件,材料的抗弯强度达到1000MPa以上,韦伯模数为12,充分表明了3D打印成型的Si_3N_4陶瓷烧结材料的力学性能优异、可靠性高,通过3D打印成型技术可以进行Si_3N_4陶瓷空心浮力球的制备;但是3D打印成型的陶瓷半球壳生坯在后处理工艺中收缩不均,形成了壁厚梯度,空心球的外径同样存在不均匀现象。对陶瓷空心球的主要规格参数进行了测量,形成了相应的质量控制方法。Si_3N_4陶瓷半球壳的烧结密度应达到3.23g/cm~3以上方为合格品;已形成了公称直径100毫米、不同壁厚、球体密度分别为0.33、0.39、0.45 g/cm~3的陶瓷空心球系列实验室产品,这3个系列的产品浮力性能均优于目前采用的万米级深海浮力材料。对密度为0.33 g/cm~3的Si_3N_4陶瓷空心浮力球进行了内爆压力试验,29个样本的平均抗压强度达到203.8MPa,但测得的数据离散程度较大,表明制备工艺还尚需进一步优化。密度为0.39 g/cm~3的Si_3N_4陶瓷空心浮力球内爆压力能达到300MPa左右,具有更高的安全系数。Si_3N_4陶瓷空心浮力球成功地完成了145MPa下保压10小时的静压疲劳试验和115MPa下的1000次循环疲劳试验。陶瓷空心球的内爆过程研究表明,在受压阶段陶瓷空心球积累了大量弹性应变能,内爆发生的瞬间,一部分能量转换为材料断裂能,另一部分则转变为动能,表现为以球心为中心的虹吸效应;能量和物质开始由向中心处集聚瞬间变为向周围扩散,最终体系达到平衡。
[Abstract]:Deep sea contains a large number of minerals, energy resources, biological species diversity and even the key to the mystery of the origin of life of the earth. Since twenty-first Century, the exploration and development of the deep sea has gradually become more and more important, and deep sea exploration and development can not be separated from the development of deep submersible equipment. Deep sea buoyancy materials are deep submergence. Silicon nitride (Si_3N_4) is a kind of ceramic material with excellent comprehensive properties. It has been widely used in many fields such as industry, national defense and Aeronautics and Astronautics to get high static water compression strength of.Si_3N_4 ceramic hollow buoyancy ball, low density of sphere (which can provide large buoyancy), and it is very stable in sea water environment. It is a kind of deep sea buoyancy material with excellent performance. The design of ceramic hollow buoyancy ball is discussed in this paper, especially the forming process of the hemispherical shell is deeply studied. The quality control method of the ceramic hollow buoyancy ball is preliminarily put forward, and the ground pressure test is carried out to provide the practical application of the Si_3N_4 ceramic hollow buoyancy ball. The theoretical calculation shows that the ultimate compressive strength and the ultimate flexion strength of the inner diameter 100mm and the wall thickness 2mm hollow buoyancy ball are 286.8 and 532.2 MPa, respectively, according to the theory that the compressive strength and modulus of the ceramic hollow buoyancy ball are the best. The condition of SF "G2" (design pressure 115MPa). The flexion strength and maximum principal stress distribution of Si_3N_4 ceramic hollow buoyancy ball are calculated by ABAQUS finite element analysis software. It is found that the calculated value of the flexion intensity is close to the calculated value of the theoretical formula, and the maximum principal stress distribution is more uniform. It is a kind of ideal pressure resistant structure. Compared with Si_3N_4 The ABAQUS analysis results of the ceramic pressure tank show that the structural symmetry of the ceramic tank is not as good as that of the hollow sphere, and there are more stress concentration areas. These have great influence on the strength of the structure. The cause of the failure of the "Hai Shen" unmanned submersible is not necessarily due to the internal explosion of the ceramic hollow sphere. The technical parameters of gel injection molding and 3D printing for Si_3N_4 ceramic hemispherical shell molding were studied. It was found that the density of the Si_3N_4 ceramic sintered parts formed by gel casting could not meet the requirements. The microscopic observation of the fracture surface found that there were many pinholes in the blank and the sintered body, and the hemispherical shell of 3D was printed and formed. It is possible to produce a half spherical shell sample with theoretical density of 99.7%. The flexural strength of the material is above 1000MPa and the Webb modulus is 12. It shows that the mechanical properties of the Si_3N_4 ceramic sintered materials with 3D printing are excellent and the reliability is high. The Si_3N_4 ceramic hollow buoyancy ball can be prepared by the 3D printing molding technology; but 3D beating can be used. In the post treatment process, the shrinkage of the printed ceramic hemispherical shell is not uniform, the wall thickness gradient is formed, and the outer diameter of the hollow sphere is also inhomogeneous. The main specifications of the ceramic hollow sphere are measured, and the corresponding quality control method of the.Si_3N_4 ceramic hemisphere shell should be reached to more than 3.23g/cm~3. It has formed a series of laboratory products of ceramic hollow spheres with a nominal diameter of 100 mm, different wall thickness and 0.33,0.39,0.45 g/cm~3, respectively. The buoyancy performance of the 3 series of products is superior to the current 10000 meter deep sea buoyancy material. The internal explosion pressure of the Si_3N_4 ceramic hollow buoyancy ball with a density of 0.33 g/cm~3 is carried out. The experimental results show that the average compressive strength of the 29 samples is up to 203.8MPa, but the discretization of the measured data shows that the preparation process still needs to be further optimized. The internal explosion pressure of the Si_3N_4 ceramic hollow buoyancy ball with a density of 0.39 g/cm~3 can reach about 300MPa, and the higher safety factor.Si_3N_4 ceramic hollow buoyancy ball has successfully completed the 145MPa. The static pressure fatigue test of 10 hours under pressure and 1000 cyclic fatigue tests under 115MPa. The study of the internal explosion process of ceramic hollow spheres shows that a large amount of elastic strain energy has been accumulated in the ceramic hollow sphere at the compression stage, the moment of the initiation of the implosion, the conversion of part of the energy into the fracture energy of the material and the other part of the kinetic energy. The siphon effect of the center, the energy and substance begin to gather from the center and instantly change to the periphery, and the final system reaches equilibrium.

【学位授予单位】：上海材料研究所
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P754.5;TQ174.758.12

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