大型运载火箭发射平台法兰结合面摩擦系数正交试验研究

大型运载火箭发射平台主承载结构通过法兰连接,法兰面摩擦系数影响法兰切向承载强度。法兰面摩擦系数受到表面粗糙度、表面处理方式及涂层状态的影响。采用混合水平正交试验法开展摩擦系数试验研究,通过直观分析与方差分析研究三种因素对摩擦系数的影响。分析表明,表面涂层对静摩擦系数的影响最大,法兰面涂覆无机富锌漆或环氧富锌漆能有效提高摩擦系数,表面粗糙度和表面处理方式对摩擦系数影响不显著。并对通过正交试验法优选的方案进行试验验证,试验分析表明最优方案能够达到较大静摩擦系数。     

水下振源体膜板空蚀的研究

水下大功率振源体工作一段时间后膜板中心附近位置出现空蚀现象,分析了膜板产生空蚀的原因及空蚀相关理论,通过提高材料抗空蚀性能和阴极保护两种方法来减轻空蚀破坏.提高材料抗空蚀性能包括改变材料、增加壁厚和提高表面粗糙度;阴极保护采用喷涂无机富锌涂料.     

采用电化学交流阻抗等测试方法研究无机富锌与有机富锌涂层在海水腐蚀环境中的失效机理

本文采用M398交流阻抗系统对无机富锌和有机富锌涂层进行电化学交流阻抗谱测定,采用截面电镜照片分析不同浸泡时间涂层微观形貌变化,采用EDAX分析涂层浸泡前后腐蚀产物。通过以上3种手段比较分析特定的无机富锌和有机富锌涂层在3.5%NaCl水溶液中的失效机理。     

换热器的液压胀接研究（二）——残余接触压力与摩擦系数

本文采用换热器管板单管模型研究了换热管与其液压胀接后的残余接触压力和静摩擦系数。用弹性卸载法测量了换热管从单管胀接模型中拉出后,模型外表面的周向应变,并由此计算出接触面处的残余接触压力的实验值。同时与作者前期工作中所得出的理论公式进行比较。在上述工作的基础上,根据残余接触压力和拉脱力求出了接触面的静摩擦系数。结果表明,该理论公式可以较为准确地计算换热管与管板液压胀接后的残余接触压力。本文提出了液压胀按时,换热管与管板接触面摩擦系数的测量方法。并对设计时摩擦系数的选取提出了建议。     

粗糙度各向异性对润滑接触面摩擦的影响

齿轮、轴承、凸轮等重载接触副的性能受表面粗糙度的显著影响。高负载情况下的摩擦因数与润滑接触面粗糙度的各向异性相关。测量的表面粗糙度可以分解为一系列具有不同波长、幅值的正弦表面粗糙度,因此,考虑各向异性正弦表面粗糙度,构建粗糙表面点接触瞬态弹性流体动力润滑(TEHL)模型,提出基于多重网格算法的粗网格构造新方法,提高粗糙表面润滑问题求解的稳健性。研究表面粗糙度各向异性对高负载情况下摩擦因数的影响规律。结果表明,粗糙度的各向异性影响接触面压力、油膜厚度分布、粗糙度形变量,从而影响摩擦因数。提出一个组合函数来量化粗糙度各向异性对摩擦因数的影响,表明全膜润滑到混合润滑的过渡不仅与载荷、速度等工况参数相关,还与粗糙度各向异性相关。     

用真实接触面积计算静摩擦系数

本文根据摩擦力与真实接触面积有关的摩擦理论,利用接触力学的赫芝公式计算真实接触面积,导出了在理想光洁条件下几种接触面相对滑动的摩擦力与摩擦系数计算公式,分析了摩擦系数的变化规律及在实践中的意义,并用公式计算了不锈钢与掺聚四氟乙烯胶木之间的摩擦系数,将其与实测资料对比获得满意的结果。文中还简单评述了包登的简单摩擦公式及摩擦系数与正压力无关的传统观念,指出了它们的局限性。     

喷漆机器人空气喷枪的新模型

针对实际生产中喷漆机器人空气喷枪喷雾的形状及其附着在平面工件表面形成椭圆形喷漆区域的情况,进行喷枪静止的喷涂试验,得到漆膜厚度测量数据。采用BP神经网络方法进行漆膜表面函数拟合,通过比较拟合后的x、y方向的不同断面上的漆膜分布曲线,提出一种新的椭圆形区域的漆膜厚度分布函数——椭圆双b 分布模型,采用遗传算法及最小二乘法对椭圆双b 分布模型进行数学拟合,求得其参数。以此模型对一个喷枪行程进行仿真,并与实际的单行程喷漆试验结果进行比较,验证了所建模型的正确性。给出该模型用于一般曲面喷涂时工件表面上任意点的漆膜厚度计算公式,以及喷漆机器人为了保持喷枪姿态需要的喷涂运动方程,为喷漆机器人采用离线编程技术提供一个更为实用的空气喷枪模型。     

潮汐环境下防撞钢套箱防腐涂装体系设计研究

为了探究潮汐环境下防撞钢套箱的防腐维护技术,以嘉绍大桥防撞钢套箱作为新型涂装体系的研究对象,揭示了3种新型涂装体系的不同防腐效果。从外观、漆膜厚度、附着力及耐久性方面可以发现,超强耐磨环氧漆2道+聚硅氧烷面漆的涂装体系耐腐蚀效果最佳。     

用新型摩擦装置测定薄板成形的摩擦系数

采用一种新型的测量板成形中工具与工件之间摩擦系数的模拟装置,试验测定了不同厚度及成分的钢板在不同条件下的摩擦系数。被测钢板有08Al,IF钢,IF钢镀锌板,测试中改变润滑条件,辊距、辊径和板厚,板表面取向。结果表明摩擦系数与润滑和冲头的几何形状密切相关。     

一种内燃机油清净性的快速测评方法研究——基于模式识别的漆膜评分系统

研究了一种内燃机油高温清净性的快速测评方法 ,通过模拟内燃机油在活塞工作时的成漆过程 ,在330± 1 0℃的铝箔表面滴油形成漆膜 ,以漆膜的颜色变化考察内燃机油清净性与抗氧性。本方法的漆膜评分通过一个计算机辅助评分系统完成。在特定的光照环境中采集漆膜图象 ,利用一定的算法对漆膜图象进行有效特征提取 ,然后对特征区域内的黄、棕、褐、黑色区域分别进行加权统计 ,根据统计值判定漆膜评分     

Measurements of friction in strip drawing under thin film lubrication

Strip drawing is used to investigate the friction behaviour under thin film lubrication in metal forming with plastic deformation. Friction coefficients are measured under a wide range of tribological conditions. The surface roughness is measured on an interferometric profilometer. The results show that the friction coefficient decreases with increasing oil film thickness h_w, as estimated using a formula appropriate for smooth tool and workpiece. Measurements of the surface topography show that change in friction is associated with a change in contact ratio between the tool and strip. The effect of strip reduction, strip roughness and die roughness on the friction coefficient is also investigated.     

Thermoelastohydrodynamic Analysis of Spur Gears with Consideration of Surface Roughness

Thermoelastohydrodynamic lubrication (TEHL) analysis for spur gears with consideration of surface roughness is presented. The model is based on Johnson’s load sharing concept where a portion of load is carried by fluid film and the rest by asperities. The solution algorithm consists of two parts. In the first part, the scaling factors and film thickness with consideration of thermal effect are determined. Then, simplified energy equation is solved to predict the surfaces and film temperature. Once the film temperature is known, the viscosity of the lubricant and therefore friction coefficient are calculated. The predicted results for the friction coefficient based on this algorithm are in agreement with published experimental data as well as those of EHL simulations for rough line contact. First point of contact is the point where the asperities carry a large portion of load and the lubricant has the highest temperature and the lowest thickness. Also, according to experimental investigations, the largest amount of wear in spur gears happens in the first point of contact. Effect of speed on film temperature and friction coefficient has been studied. As speed increases, more heat is generated and therefore film temperature will rise. Film temperature rise will result in reduction of lubricant viscosity and consequently decrease in friction coefficient. Surface roughness effect on friction coefficient is also studied. An increase in surface roughness will increase the asperities interaction and therefore friction coefficient will rise.     

Enhanced friction model for high-speed right-angle gear dynamics

The modeling of elastohydrodynamic lubrication friction and the analysis of its dynamic effect on right-angle gears, such as hypoid and spiral bevel types are performed in the present study. Unlike the classically applied empirical constant coefficient of friction at the contacting tooth surfaces, the enhanced physics-based gear mesh friction model is both spatial and time-varying. The underlying formulation assumes mixed elastohydrodynamic lubrication (EHL) condition in which the division and load distribution between the full film and asperity contact zones are determined by the film thickness ratio and load sharing coefficient. In the proposed time-varying friction model, the calculation of friction coefficient is performed at each contact grid inside the instantaneous contact area that is being subjected to mineral oil lubrication. The effective friction coefficient and directional parameters synthesized from the net frictional and normal contact forces are then incorporated into a nonlinear time-varying right-angle gear dynamic model. Using this model, the effect of friction on the gear dynamic response due to the transmission error and mesh excitations is analyzed. Also, parametric studies are performed by varying torque, surface roughness and lubrication properties to understand the salient role of tooth sliding friction in gear dynamics. The simulation results are included. But experimental verification is needed.     

多层波纹钢板转子阻尼器能量耗散系数计算方法

多层波纹钢板转子阻尼器是利用干摩擦原理实现转子阻尼减振的支撑零件。这种阻尼器能在高低温等恶劣环境下工作,同时阻尼特性受转子偏心影响小,可以通过改变阻尼器钢板的厚度提高阻尼器的能量耗散性能。在有限元法和摩擦学原理的基础上进行理论分析,根据多层波纹钢板转子阻尼器的能量耗散分布,提出多层钢板阻尼器的能量耗散系数的计算方法。该方法首先通过有限元分析获得接触应力,然后采用Mindlin接触模型推导出两层干摩擦接触表面摩擦耗能的计算公式,最后得出转子阻尼器整体的能量耗散系数。试验证明了该计算方法是正确可行的,具有较高计算精度。     

Approximate Formula for the Contact between Truncated Surfaces and Frictional Characteristics of a Journal Bearing in Mixed Lubrication

This paper presents an approximate formula for the contact of a non‐Gaussian distribution of truncated surfaces, which is useful for mixed lubrication theory, and gives a method for the determination of the truncation parameters in this formula from a measured roughness profile. Using this approximate formula for a contact, the approximate formula for the friction coefficient of a journal bearing in mixed lubrication, which was previously proposed by the authors, is modified for truncated surfaces, and the frictional characteristics are demonstrated for various parameters of truncated roughness using the modified formula.     

A multi-scale model for friction in cold rolling of aluminium alloy

A simple and robust friction model is proposed for cold metal rolling in the mixed lubrication regime, based on physical phenomena across two length scales. At the primary roughness scale, the evolution of asperity contact area is associated with the asperity flattening process and hydrodynamic entrainment between the roll and strip surfaces. The friction coefficient on the asperity contacts is related to a theoretical oil film thickness and secondary-scale roll surface roughness. The boundary friction coefficient at the “true” asperity contacts is associated with tribo-chemical reactions between fresh metal, metal oxide, boundary additives, the tool and any transfer layer on the tool. The asperity friction model is verified by strip drawing simulations under thin film lubrication conditions with a polished tool, taking the fitting parameter of the boundary lubrication friction factor on the true contact areas equal to 0.1. Predicted values of average friction coefficient, using a boundary friction factor in the range 0.07–0.1, are in good agreement with measurements from laboratory and industrial rolling mill trials.     

Application of ellipsometry to the characterization of reaction films formed by ZnDTPs on sliding steel surfaces

Spectroscopic ellipsometry (SE) was used to determine the thickness of zinc dialkyldithiophosphate (ZnDTP) reaction films formed on steel surfaces. Simultaneous measurements of friction coefficient and electrical contact resistance (ECR) were carried out using a cylinder-on-disk tribometer to form ZnDTP reaction films under a sliding condition, with monitoring of both the change of friction and the formation of ZnDTP reaction films during sliding. The film thickness was obtained by regression fitting of the data generated by the dispersion model to the experimental data. The results indicated that the thickness of the reaction film influenced the friction behavior of ZnDTP.     

考虑表面粗糙度和热效应的线接触非牛顿混合润滑分析

为了研究表面粗糙度及热效应对非牛顿混合润滑的影响,基于平均流量模型,考虑表面粗糙度以及热效应,建立线接触非牛顿混合润滑模型。研究表面粗糙度对膜厚、膜厚比、平均摩擦因数、载荷比以及温度分布的影响,并与等温解进行比较。结果表明:随着表面粗糙度的增大,油膜温度逐渐升高,尤其是出口区与入口区的温升最为显著,且油膜温升越大,载荷比及平均摩擦因数越大,膜厚比越小;与等温解相比,热解的膜厚比及平均摩擦因数小,载荷比大;等温与热条件相比,中心膜厚与最小膜厚随表面粗糙度的变化趋势差异显著,说明热效应对混合润滑的影响不可忽略。     

Solution and analysis of VL combined seal lubrication model under the effect of wear

Through the finite element calculation of VL combined seal models under different wear conditions, contact pressure distributions of models are obtained. Considering the coupling effect between seal deformation and lubricating oil film, a mathematical model of elastohydrodynamic lubrication for VL combined seal is established. Based on the theory of small deformation, the elastic deformation of VL composite seal under high pressure is obtained by the deformation influence coefficient matrix method. Considering the influence of sealing surface wear and surface roughness, the oil film thickness distribution and oil film pressure distribution of VL combined seal are solved by the finite difference method. The analysis results show the wear of VL combined seal, the decrease of viscosity, the increase of roughness and rotational speed can raise the thickness and pressure of lubricating oil film. The correctness of numerical simulation is verified by experimentally measuring the friction torque and leakage rate of seal.