Numerical methods for theoretical analysis of foil bearing dynamics

The bearing under consideration is a self-acting, gas bearing with a flexibly supported foil. In order to conduct the theoretical analysis, three systems were identified: a rotor, a gas film and a flexible structure. Each of these elements has been mathematically analysed and analytical equations have been formulated. It was found, that the gas flow in the bearing can be described by the Reynolds equation, whereas a spring-damper model was selected for the structural analysis. The Reynolds equation is a differential equation the exact solution to which is unknown. The work describes the finite difference method in detail, where the partial derivatives in the Reynolds equation are replaced by a system of algebraic equations. In order to solve the resulting system, the Alternating Direction Implicit method (ADI) was used. Based on that and on the analysis of interactions between the three systems the equations have been computed. The accuracy of methods has been verified by means of series of numerical tests. Chosen results are described in this paper.     

Effect of modified glass fiber on tribological performance of water-lubricated bearing

Glass fiber (GF) is becoming one of the most popular reinforcement materials used in many fields. However, it still has some disadvantages such as brittleness and poor wear resistance. In order to improve its tribological property, the GF was modified and use high-density polyethylene (HDPE) as the matrix material to verify it. In this work, friction tests of HDPE samples with seven different compositions of modified GF were carried out. Different working conditions were applied to determine the tribological properties and service life as used in water-lubricated bearings. Their friction coefficient, surface morphology, wear scar, wear quality and wear mechanism were investigated. The results showed that the modified GF could significantly improve the HDPE tribological properties. Moreover, the wear mechanism of pure HDPE was mainly adhesive wear and slight fatigue wear, and the composite material was mainly abrasive wear. The 30% GF composite material had the best wear resistance, its friction coefficient was reduced by 51.56% under 0.4 MPa and 500 r/min. The findings from this experiment will provide a new method for reducing friction and wear of water-lubricated bearings.     

输电铁塔四地脚螺栓塔脚板抗拉承载力试验与计算方法研究

针对架空输电线路铁塔中常用的四地脚螺栓塔脚板进行了抗拉承载力试验和理论计算方法研究。首先,选取8个试件进行塔脚板抗拉承载力试验研究,分析塔脚底板板厚及有无加劲板对塔脚板抗拉承载力的影响;其次,通过有限元模拟塔脚板的应力分布情况,并结合“塑性分析,弹性设计”的思想,提出了一种基于屈服线理论的四地脚螺栓塔脚板抗拉承载力计算公式;最后,与试验结果、有限元仿真结果、已有技术规定中的计算结果进行了对比。结果表明:建议公式与试验结果和仿真结果较为吻合,相关技术规定中的计算结果偏于保守,验证了本文建议公式的精确性;底板厚度和加劲板的作用对塔脚板承载力影响较大。研究结果可为输电铁塔四地脚螺栓塔脚板结构设计提供参考。     

POLYMERIZATION OF A NEW SUBSTITUTED ACETYLENE BEARING A FURAN RING WITH PALLADIUM ACETYLIDE CATALYSTS

A substituted polyacetylene bearing a furan ring, poly(2-propynyl 2-furoate) (PPF), was synthesized for the first time with palladium acetylide complex catalysts in CHCl3 at 60℃ to give a soluble and stable polymer with a yield of ca.75%. Some features for polymerization of 2-propynyl 2-furoate are described and discussed. The resulting polymer was characterized by IR, GPC and ^1H-NMR analysis.     

支化滚环扩增均相光散射检测单核苷酸多态性

结合简便、高效的支化滚环扩增反应与光散射技术,建立了一种均相、无标记检测单核苷酸多态性的方法.通过设计与突变型DNA完全匹配的锁式探针,突变型DNA可作为模板,使锁式探针在连接酶作用下于45℃连接成环,由Phi29 DNA聚合酶在33℃引发支化滚环扩增反应,生成大量的长链DNA产物.反应产物在0.2 mol/L HCl...     

T形型钢混凝土柱正截面承载力的计算方法探讨

在总结了型钢混凝土(SRC)柱承载力计算一般方法的基础上,针对T形型钢混凝土柱, 结合中国现行规范,分析了此种柱的受力特点和破坏模式,提出T形型钢混凝土柱正截面极 限承载力的计算方法,并采用该方法对一T形型钢混凝土柱的承载力进行验算. 结果表明与 试验数据吻合较好,说明本文方法具有较好的精确度和适用性.     

轧辊用高钒高速钢的滚-滑动磨损性能及失效行为研究

在高应力滚-滑动(滑动率约10%)条件下,利用自制的磨损试验机研究了高钒高速钢的磨损性能,并利用电子显微镜分析了失效行为.结果表明:高钒高速钢的相对耐磨性是高铬铸铁(Cr20)的2倍以上.磨损失效形式为显微切削与疲劳剥落的复合,兼有碳化物碎裂.碳化物对磨损失效有重要作用,高铬铸铁中的杆状M7C3型碳化物易于弯曲、碎裂而在其内部形成大量裂纹,促进磨损表面产生大块的疲劳剥落;高钒高速钢中团块状VC硬度高、形态好、具有精细亚结构、不易碎裂,可有效地抵御显微切削和疲劳剥落,是高钒高速钢耐磨性优良的原因.     

等离子喷涂铁基涂层的疲劳磨损裂纹行为

采用等离子喷涂制备了铁基涂层,使用球盘式疲劳磨损试验机进行涂层的疲劳磨损试验,利用声发射技术在线判断涂层开裂,并通用透射电子显微镜（TEM）分析了试验前后涂层内部微观结构,研究了喷涂层疲劳磨损裂纹的扩展行为。结果表明：制备的涂层致密,结合状态良好,主要相为铁素体,同时存在大量的非晶-纳米晶相,利用声发射技术能够表征涂层的临界失效状态,其内部疲劳磨损裂纹主要以韧性穿晶断裂的形式扩展。     

非稳态弹流润滑状态下滚动体-滚道摩擦副的动力特性研究

针对滚动体-滚道摩擦副,建立了点接触非稳态弹流润滑数学模型,利用FFT技术和半解析算法数值求解了接触体在自由振动过程中油膜压力和膜厚的变化,同时结合有阻尼系统的自由振动模型,给出了预测点接触摩擦副动力特性的方法,在较宽的载荷和速度范围内分析了接触副的等效刚度系数和阻尼系数的变化.结果表明：根据接触副的实际工作载荷和速度所确定的无量纲自然频率来进行非稳态弹流的计算所得到的膜厚结果更接近实验值;在接触体的振动过程中油膜的压力和厚度在平衡位置附近上下波动,且由于润滑油膜的作用接触体的振动幅值逐渐减小;刚度系数随载荷参数的增加而增加,随速度参数的增加而减小,而阻尼系数的变化规律较复杂,在不同的载荷和速度范围内呈现出不同的变化趋势.     

RV减速器主支撑角接触球轴承混合润滑分析

针对RV减速器角接触球轴承承受预紧力、轴向力和径向力等联合外载荷作用的工况,分析得出了内、外圈滚道接触界面的接触区几何参数和接触载荷.在此基础上,综合考虑了角接触球轴承的接触区宏观几何、接触载荷、真实表面粗糙度、瞬态效应等因素,建立了角接触球轴承混合润滑数学模型,分析了在不同工况下角接触轴承的润滑状况及表面以下应力分布.结果表明:随着载荷的不断增加,钢球与内圈沟道之间的油膜厚度会不断减少,导致干接触面积迅速扩大,接触点表面以下最大应力增大;转速的增加会使油膜变厚,干接触面积缩小.该结果对角接触球轴承的实际工程应用具有重要借鉴意义.