熔渗型自润滑复合材料基体的微孔结构设计与仿真分析

发布时间：2018-04-25 00:04

本文选题：自润滑 + 微孔结构　；参考：《济南大学》2015年硕士论文

【摘要】：熔渗型自润滑复合材料是运用仿生摩擦学知识研究出的一种自润滑材料。该复合材料的制备过程可以分为两个部分:(1)烧结制备具有微孔结构的网络基体;(2)真空压力熔渗固体润滑剂。在工作过程中,要求微孔基体具有足够的强度,以承受载荷;而润滑剂的主要作用是降低摩擦界面的摩擦系数,以保证润滑性。微孔基体的微观结构是保证复合材料润滑性的前提,因为微孔结构(如微孔大小、分布及形状)是决定浸渗固体润滑剂的数量、润滑剂分布的均匀性及在摩擦界面是否能够形成润滑膜的关键。本文以熔渗型自润滑复合材料基体的微孔结构为研究对象,基于均匀化理论和有限元分析方法,建立微孔单胞模型,对孔隙度、微孔结构进行仿真分析。基于熔渗型自润滑复合材料的性能要求,研究了孔隙度、微孔形状、孔径分布等结构特征参数对复合材料宏观性能的影响;根据复合材料基体的设计原则,进行基体材料的组分组成及组分比设计,采用粉末冶金烧结法制备出微孔基体,对其进行了微观结构和性能表征。根据对熔渗型自润滑复合材料微孔基体的理论分析结果可知,孔隙度是复合材料的一个重要结构特征参数,其与强度、硬度和自润滑性能有着紧密的联系。孔隙度与组成基体材料的粉末颗粒直径无关,只与粉末颗粒的形貌及排列方式有关,且当颗粒形貌为非球形时,烧结体的孔隙度较小;随着特征值的不断增大,孔隙度逐渐增加,而相对密度逐渐减小;随着孔隙度的不断增大,复合材料的相对弹性模量逐渐减小,泊松比逐渐增大,而抗压强度呈指数下降。为保证复合材料力学性能和自润滑性能的要求,微孔基体的孔隙度应控制在15%-30%范围内。单胞模型的有限元仿真分析表明:微孔形状分别为圆形、三角形、四边形及六边形时,随着载荷的不断增大,各种微孔形状的单胞模型产生的Mises等效应力值和应变值不断增大,但增大的速率均不同,即圆孔增大速率较慢,六边形较快;当位移载荷相同时,随着孔隙度的增大,单胞模型产生的等效应力增大,而等效应变减小。综合分析可知,微孔形状为圆形和方形时综合性能最好。以FeCrWMoV合金粉末为金属相,TiC粉末为陶瓷相,同时添加一定体积分数的复合造孔剂,采用粉末冶金烧结法制备出微孔基体。结果表明:烧结体微孔形状规则(主要呈圆形或方形),孔隙分布均匀,且互相贯穿成网络状;随着复合造孔剂体积分数的增加,烧结体的孔隙度不断增大;随着孔隙度的不断增大,烧结试样的压溃强度逐渐降低;保温时间影响烧结试样的微孔形状,当保温时间为60min时得到试样的微孔形状主要呈圆形和方形,且压溃强度较高。
[Abstract]:Infiltration self-lubricating composite is a self-lubricating material developed by using bionic tribology. The preparation process of the composite can be divided into two parts: 1) sintered to prepare the network matrix with microporous structure and 2) vacuum pressure infiltration solid lubricant. In the working process, the microporous matrix is required to have sufficient strength to withstand the load, and the main function of the lubricant is to reduce the friction coefficient of the friction interface to ensure the lubricity. The microstructure of the microporous matrix is a prerequisite for ensuring the lubricity of the composite, because the micropore structure (such as the size, distribution and shape of the micropore) determines the amount of solid lubricant impregnated. The uniformity of lubricant distribution and the key to the formation of lubricating film at the friction interface. Based on the homogenization theory and finite element analysis method, the microporous cell model is established, and the porosity and micropore structure are simulated and analyzed. Based on the performance requirements of infiltrated self-lubricating composites, the effects of structural characteristic parameters such as porosity, micropore shape and pore size distribution on the macroscopical properties of composites are studied. The composition and component ratio of the matrix were designed. The microporous matrix was prepared by powder metallurgy sintering method. The microstructure and properties of the matrix were characterized. Based on the theoretical analysis of the microporous matrix of the infiltrated self-lubricating composite, the porosity is an important structural characteristic parameter of the composite, which is closely related to the strength, hardness and self-lubricating properties. Porosity has nothing to do with the diameter of powder particles, but only depends on the morphology and arrangement of powder particles. When the particle morphology is non-spherical, the porosity of sintered body is smaller, and with the increasing of characteristic value, the porosity of the sintered body increases with the increase of the characteristic value. With the increase of porosity, the relative modulus of elasticity decreases, the Poisson's ratio increases, and the compressive strength decreases exponentially. In order to meet the requirements of mechanical properties and self-lubricating properties of composites, the porosity of microporous matrix should be controlled in the range of 15-30%. The finite element simulation analysis of the cell model shows that when the shape of the micropore is circular, triangular, quadrilateral and hexagonal, with the increasing of the load, the force and strain value of the Mises effect produced by the unit cell model of various micropore shapes increase continuously. But the rate of increase is different, that is, the increase rate of circular pore is slower, the hexagonal is faster, and when the displacement load is the same, with the increase of porosity, the equivalent stress produced by the unit cell model increases and the equivalent strain decreases. The comprehensive analysis shows that the comprehensive performance is the best when the shape of the micropore is circular and square. The microporous matrix was prepared by powder metallurgy sintering with FeCrWMoV alloy powder as metal phase tic powder as ceramic phase and adding a certain volume fraction of composite pore-forming agent. The results show that the micropore shape of the sintered body is regular (mainly circular or square, the pore distribution is uniform, and the porosity of the sintered body increases with the increase of the volume fraction of the compound pore-making agent, and the porosity of the sintered body increases with the increase of the volume fraction of the compound pore-making agent. With the increase of porosity, the crushing strength of the sintered sample decreases gradually, and the holding time affects the micropore shape of the sintered sample. When the holding time is 60min, the micropore shape of the sintered sample is mainly round and square, and the crushing strength is higher.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33

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