【作者】 何剑雄；

【导师】 郭源君；

【作者基本信息】 湖南科技大学 ， 材料学， 2011， 硕士

【摘要】 水力机械过流部件的空蚀破坏历来为人们所广泛关注,我国西南河流流经喀什特地貌地区,流速高且水流中携带大量的气泡,当水流通过水轮机过流部件时造成严重的空蚀磨损,研究和开发新型抗空蚀材料一直是人们寻求解决水力机械空蚀的主要途径。本论文设计了纳米SiO₂/玻璃微珠/超高分子量聚乙烯（UHMWPE）复合材料体系,并通过压制烧结工艺制备出复合材料,考察了复合材料的硬度、冲击韧性、弹性模量和摩擦学性能,研究了复合材料的空蚀性能和空蚀机理,以此为基础进一步分析了材料空蚀率与材料主要机械性能的相关性。主要结论如下:1、改性后的纳米SiO₂和玻璃微珠在UHMWPE基体具有良好的分散性,纳米SiO₂和玻璃微珠的加入不仅可以提高UHMWPE材料表面硬度,同时还保持着较高的冲击韧性和弹性性能。与纯UHMWPE相比,复合材料耐磨损性能更好,磨损机制主要表现为不同程度的粘着磨损和疲劳磨损。2、相比纯UHMWPE,复合材料具有更好的抗空蚀性能,其中含4%纳米SiO₂和6%玻璃微珠组分的复合材料抗空蚀性能显著提高,这可解释为纳米SiO₂和玻璃微珠的加入使得空蚀裂纹的扩展受阻和钝化,提高了热传导性能,使空蚀时的冲击能量能快速传递开来,产生的热量被迅速带走。3、纳米SiO₂和玻璃微珠填充的UHMWPE复合材料空蚀损伤机理主要是由于气泡溃灭产生高速冲击波或微射流使材料表面产生塑性变形和孔洞,进而裂纹萌生、扩展导致材料剥落。4、复合材料抗空蚀性能与其机械性能密切相关,通过拟合,制备的复合材料硬度相关指数值在1.2².3之间,冲击韧性指数值0.3,弹性模量指数值在-1^-2之间,即复合材料空蚀率与表面硬度、冲击韧性和弹性模量倒数成正比。更多还原

【Abstract】 Cavitation is an ancient and complex problem existed in hydraulic machinery. In southwest of China, The rivers flowing through karst topography with high velocity flow, generate many air bubbles. Cavitation erosion wear is serious when hydraulic machineries running on the region of the river. To resolve the problem, the principal way of doing that is through research and development of new cavitation resistance materials.In this paper, a kind of ultra-high molecular weight polyethylene （UHMWPE） composites filled with nano-SiO₂ and glass microballoon is designed. The composites synthesized by sintering and compaction. Some properties such as hardness, impact toughness, elastic and tribology are measured. The cavitation erosion and cavitation mechanism of composites are studied. Finally, the correlations of the cavitation erosion rate with composite properties are analyzed.The main conclusions are as follows.1. Modified nano-SiO₂ and glass microballoon have favorable dispersibility in the matrix of UHMWPE. It is found that the hardness increased and the high impact toughness and elastic properties remained with the composites filled with nano-SiO₂ and glass microballoon. The results also showed that this kind of composites has excellent wear resistance, the main wear mechanisms were adhesion and fatigue.2. Compared with pure UHMWPE, the composites have good cavitation resistance properties. The erosion rate of the composites filled with 4% nanometer SiO₂ and 6% glass microballoon is twice the pure UHMWPE. This may be attributed to the fact that the propagation of cavitation crack is stoped and dulled when it meet the fillers. And, the fillers can improve the thermal conductive capability of composites. Therefore, when some of the impact energy is converted into heat, maybe a great part of the heat is carried off by means of fillers.3. The cavitation mechanism of composites filled with nano-SiO₂ and glass microballoon is confirmed that the plastic deformation and cavitation pinholes are formed with the shock waves or micro-liquid jet produced by bubble collapse. The cavitation damage is the results of initiation and growth of fatigue cracks. 4. The cavitation erosion resistance of composites is closely related to their mechanical properties and concern into the index. By fitting, the index of hardness is between 1.2 and 2.3, the index of impact toughness is between 0.2 and 0.3, and the index of reciprocal of elastic modulus is between 1 and 2. In other words, the cavitation rate of compositesis is proportional to hardness, impact toughness, and the reciprocal of elastic modulus.更多还原