等温淬火球墨铸铁的滚动接触磨损性能研究

将2种等温淬火球墨铸铁(Austempered Ductile Iron, ADI)和合金钢车轮材料分别与合金钢钢轨材料匹配,研究各摩擦副的滚动接触磨损性能.结果表明:与合金钢车轮材料相比,2种ADI材料的磨损性能均有大幅度的改善.硬度低、石墨球直径小且密度大的ADI材料自润滑效果好,相对应的摩擦副抗磨损性能最好;硬度高、石墨球直径大且密度小的ADI材料自润滑效果较差,相对应的摩擦副抗磨损性能居中;合金钢车轮材料不具备自润滑能力,相对应的摩擦副抗磨损性能最差.     

磨损增强型超疏水材料的制备及性能研究

通过在有机硅烷中掺杂微纳米级尺度的SiO2颗粒,利用硅烷的水解和聚合成功地制备了1种具有优异耐磨性能和稳定性的超疏水材料.通过该方法所制备的超疏水材料不仅具有良好的耐磨性,而且其超疏水性能可在一定条件下通过表面的磨损得到增强或恢复.该超疏水材料在较苛刻的环境下仍能保持良好的化学稳定性.扫描电镜分析表明贯穿于整个材料且构成材料厚度的微纳米聚合物复合层是赋予该超疏水材料耐磨损性能的主要原因.     

围绕变壁温水平圆柱热源接触熔化的理论分析

研究围绕变壁温热源的接触熔化,建立表面温度随角度变化的水平圆柱热源接触熔化模型.对紧密接触熔化区的液体传热与运动状态进行分析,运用Nusselt液膜理论建立熔化控制方程,并采用理论求解,得到稳定熔化时的熔化速度解析解,所得结果包含了文献关于定壁温热源熔化的分析结果.通过分析不同温度分布下发生接触熔化的熔化速度、液膜厚度和压力分布情况,得到温度分布对熔化影响的规律.     

A mesh-dependent model for applying dynamic contact angles to VOF simulations

Typical VOF algorithms rely on an implicit slip that scales with mesh refinement, to allow contact lines to move along no-slip boundaries. As a result, solutions of contact line phenomena vary continuously with mesh spacing; this paper presents examples of that variation. A mesh-dependent dynamic contact angle model is then presented, that is based on fundamental hydrodynamics and serves as a more appropriate boundary condition at a moving contact line. This new boundary condition eliminates the stress singularity at the contact line; the resulting problem is thus well-posed and yields solutions that converge with mesh refinement. Numerical results are presented of a solid plate withdrawing from a fluid pool, and of spontaneous droplet spread at small capillary and Reynolds numbers.     

Fluorocarbon plasmas for nanotexturing of polymers: A route to water-repellent antireflective surfaces

In this work the roughening of polystyrene by means of radiofrequency plasmas fed with CF₄ has been studied. The effect of the Ar addition to the feed, the input power and the treatment duration has been investigated in terms of etching and fluorination degree. Wettability and reflectance performances of selected textured surfaces, coated with a fluorocarbon film from a C₄F₈ fed plasma, have been characterized. All the considered surfaces, even those poorly structured, once coated, show slippery superhydrophobicity, while antireflective transparency appears to be limited to precise texturing characteristics.     

A simple method for the preparation of superhydrophobic PVDF-HMFS hybrid composite coatings

A superhydrophobic surface was obtained by embedding hydrophobically modified fumed silica (HMFS) particles in polyvinylidene fluoride (PVDF) matrix. The water contact angle (WCA) on the PVDF-HMFS hybrid composite coating is influenced by the content and nature of silica particles in the coating. As the silica concentration in PVDF matrix was increased from 33.3% to 71.4%, WCA increased from 117° to 168° and the sliding angle decreased from 90° to <1°. Surface topography of the coating was examined using scanning electron microscopy. An irregular rough surface structure composed of microcavities and nanofilaments was found to be responsible for the superhydrophobicity. The method is simple and cost-effective and can be used for preparing self-cleaning superhydrophobic coating on large areas of different substrates.     

液滴撞击等温固体平壁的数值模拟

建立了液滴撞击等温固体平壁的物理和数学模型,数值模拟了撞击后液滴的变形和反弹过程,将模拟结果与文献中的实验结果做了比较,两者吻合较好,表明所采用的模型可以模拟液滴在水平壁面上的运动形态.通过比较不同条件下铺展因素随时间的变化规律,分析了液滴碰撞速度、初始接触角对变形过程的影响.     

含氟丙烯酸酯-苯乙烯共聚物的制备及其表面性能的研究

研究了聚合工艺、含氟丙烯酸酯类单体种类和用量、苯乙烯和自由基引发剂用量及硅烷偶联剂、催化剂等因素对含氟丙烯酸酯-乙烯共聚物表面性能的影响。结果表明：聚合工艺、含氟丙烯酸酯类单体种类和用量对共聚物表面的憎水性能有显著的影响;采用延时滴加含氟丙烯酸酯类单体可提高共聚物膜表面的憎水性;随含氟丙烯酸酯类单体侧链含氟烷基的链长和氟原子数及含氟单体用量的增加,共聚物水接触角增大,吸水率下降;共聚物薄膜的硬度则与含氟丙烯酸酯类单体中α-取代基、侧链含氟烷基的链长和用量、苯乙烯用量、引发剂浓度等相关;硅烷偶联剂和催化交联剂的加入可提高共聚物薄膜的强度。     

具周期裂纹的半平面周期接触问题的奇异积分方程数值解法

运用Hilbert核的奇异积分方程的数值解法研究具任意形状裂纹的各向同性弹性半平面在周期压头作用下的周期接触问题,将所考虑问题转化为第一型或第二型的奇异积分方程组．最后给出带垂直裂纹的半平面在光滑平底压头作用下的数值结果．令α→∞时,就得到非周期经典结果．     

考虑接触应力非线性分布的接触力元模式及其验证分析

在作者提出的非连续变形计算力学模型中,采用接触力元模型描述多体接触界面上的接触特性．由于这种模型中假定接触应力沿接触界面为线性分布,从而得到的接触界面应力分布往往出现跳跃等非光滑性特征,该文对此进行了改进,采用具有高阶光滑性的非线性函数建立了能够考虑界面上接触应力非线性分布的接触力元模式,以期合理地揭示多体系统中界面的接触特性．对某一典型算例进行了数值计算,通过与大型通用非线性有限元结构分析软件ABASQUS的计算结果对比,验证了所建议计算模型的合理性与有效性．两种方法计算得到的界面接触对上的接触力基本相同;而由于采用的应力分布模式的假定不同,接触应力有所差别,由于在该文计算模型中接触对上的接触应力是按照未知量直接求得的,因此按照所建议的非线性接触力元模式所得到的接触应力更为合理．