摘要
钢-铜-塑自润滑材料是由低碳钢、铜粉、聚合物复合而成,具有抗氧化、耐腐蚀、磨合性能优异等优点,在无油及少油润滑条件下得到广泛应用。由于自润滑材料的表层为聚合物基复合材料,其传热特性对自润滑材料的摩擦磨损性能有重要影响,甚至导致其变形,不能正常工作。研究自润滑材料传热特性对于自润滑材料的开发、生产及应用有着重要的作用。
本学位论文以钢-铜-塑自润滑材料表层为二硫化钼填充聚甲醛基的复合材料为研究对象,运用数值单元体法建立了计算填充复合材料有效导热系数的模型,针对单元体模型提出了用有限元法和等效热阻法来确定该复合材料的等效导热系数两种计算方法,并运用上述方法研究了二硫化钼含量对聚甲醛基复合材料导热系数影响规律。计算结果表明有限元法与热阻法的计算结果比较接近。
复合材料的导热系数不仅与各相含量有关,还与填充相形状与排列方式有密切的关系:在研究填充相二硫化钼含量对复合材料导热系数影响的基础上,运用有限元法分别计算了填充相分别为球体、正方体、长方体、圆柱体的复合材料的导热系数,研究表明填充相在相同含量的情况下由于形状不同导热系数差距很大。比较了填充相在基体中横向和纵向排列方式下的导热系数,计算结果表明填充相排列方式不同也导致复合材料导热系数相差很大。
分别对钢-铜-塑自润滑材料表层为二硫化钼填充聚甲醛基和纯聚甲醛基的试样进行了摩擦磨损实验,得到了自润滑材料的摩擦系数和试样底面中心处温度变化情况。实验结果表明表层为纯聚甲醛基比表层为二硫化钼填充聚甲醛基的自润滑材料摩擦系数和温度都要高。通过对表层为二硫化钼填充聚甲醛基的自润滑材料各层结构分析,利用传热学、摩擦学的基本原理建立了该自润滑材料在摩擦磨损实验条件下的导热模型,用有限元软件计算模拟了试样的瞬态温度场,模拟结果与实验结果能够较好地吻合。
As a general sliding bearing material, the steel-copper-plastics self-lubricating layered multi-phase materials are composed of low carbon steel, copper powder and polymer. It has better anti-oxidation, anti-corrosion and excellent running-in friction. It is widely used as self-lubricating bearing materials in case of few or no lubricating oil. However, heat transfer has an important influence on the tribological performance of the self-lubricating materials because the rubbing surface material is from polymer-based composites with lower heat transfer ability and lower melting point.
In this thesis, it was selected polyoxymethylene (POM) composites filled by molybdenum disulfide (MoS_2) particles. A numerical method was used to establish a numerical model to predict the effective thermal conductivity. Based on this model two methods including finite element and effective heat resistance are proposed to calculate the effective thermal conductivity of the composites. It was found that their calculation results were similar.
The thermal conductivity was not only affected by the filler content but also by the filler's shape and array in the composites. On the basis of studying the effect of M0S2 content on the effective thermal conductivity of composite, using the finite element method it was calculated the composites' effective thermal conductivity in which the filler shapes were sphere, square, rectangle and cylinder respectively. The calculation results showed that the filler shape played an important role in the aspect of effective thermal conductivity. As the filler was placed in transverse and lengthways in the composites, it gained obvious different results.
The friction and wear experiments were carried out with the self-lubricating surface materials of pure POM or POM filled by M0S2 under end-face rubbing conditions. It was found that the friction coefficient and surface temperature of POM filled by M0S2 were lower than those of pure POM. According to the structure analyzing of each layer of self-lubricating composites filled by M0S2, the heat transfer model of the self-lubricating composites was established based on heat transfer theory, tribological principle, instant temperature distributions analyzed by using ANSYS software. The results showed that the simulation data were in good agreement with the experimental results.
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