Test on Evaluation Method for Biodegradability of Lubricants

Using carbon tetrachloride （CCl4） as extraction agent, the activated sludge from Tianjin Jizhuangzi Sewage Treatment Plant as inoculum, the test study on biodegradability of lubricants was carried out. The test flasks containing the mineral medium, the test oil and the inoculum were placed in incubation together with flasks containing poisoned blanks for periods of 0 and 21 days, respectively. Flasks containing the reference materials in place of the test oil were run in parallel. At the end of the incubation period, the contents of the flasks were subjected to sonic vibration, and were acidified and extracted by using CCI4. The extracts were then analysed by infra-red （IR） spectrometer to measure the maximum absorption of the C-H stretch of CH2-CH3 band at wavelength of 2 930 cm^-1. The absorption values were used to calculate the residual oil contents of the poisoned and test flasks. Consequently the biodegradability of the test oil was calculated. The test results indicate that the differences in the biodegradability of test materials in different tests are within 5.5%, and consistent with the data described in Coordinating European Council （CEC） L-33- A-93. The biodegradability of lubricants can be evaluated by this method effectively.

Comparison of Final Drive GearLubricant Field Results to Laboratory Tests

To meet the increasing needs to move goods and materials, transportation vehicles are logging an increasing number of kilometers each year. With increasing use of these vehicles comes the need to conserve fuel to save money and to conserve resources. New engines, transmissions and axles are being developed to further conserve fuel and to provide more efficient power sources. Southwest Research Institute, a leader in global automotive research, regularly performs tests to evaluate the power and fuel economy improvement of drive train hardware and lubricants. The Institute has recently provided services to design, develop, and perform test verification of a dynamometer stand that is capable of evaluating the efficiency of axle lubricants in heavy-duty use.

Investigation of the friction coefficient evolution and lubricant breakdown behaviour of AA7075 aluminium alloy forming processes at elevated temperatures

The lubricant behaviour at elevated temperatures was investigated by conducting pin-on-disc tests between P20 tool steel and AA7075 aluminium alloy. The effects of temperature, initial lubricant volume, contact pressure and sliding speed on the lubricant behaviour(i.e. evolutions of the coefficient of friction(COF) and the breakdown phenomenon) were experimentally studied. The evolutions of COF at elevated temperatures consisted of three distinct stages with different friction mechanisms. The first stage(stage Ⅰ) occurred with low friction when the boundary lubrication was present. The second stage(stage Ⅱ) was the transition process in which the COF rapidly increased as the lubricant film thickness decreased to a critical value. In the final plateau stage(stage Ⅲ), lubricant breakdown occurred and intimate contact at the interface led to high friction values. At the low friction stage(stage Ⅰ), the value of COF increased with increasing temperature. The increase in temperature, contact pressure and sliding speed as well as the decrease in initial lubricant volume accelerated the lubricant breakdown.

Impact of lubricant traction coefficient on cage's dynamic characteristics in high-speed angular contact ball bearing

In this paper,the formulas of elasto-hydrodynamic traction coefficients of three Chinese aviation lubricating oils,4109,4106 and 4050,were obtained by a great number of elastohydrodynamic traction tests.The nonlinear dynamics differential equations of high-speed angular contact ball bearing were built on the basis of dynamic theory of rolling bearings and solved by Gear Stiff（GSTIFF） integer algorithm with variable step.The impact of lubricant traction coefficient on cage＇s dynamic characteristics in high-speed angular contact ball bearing was investigated,and Poincare map was used to analyze the impact of three types of aviation lubricating oils on the dynamic response of cage＇s mass center.And then,the period of dynamic response of cage＇s mass center and the slip ratio of cage were used to assess the stability of cage under various working conditions.The results of this paper provide the theoretical basis for the selection and application of aviation lubricating oil.

Calculation of flash temperature for hybrid ceramic ball bearing lubricated with solid

The scuffing behavior of hybrid ceramic bearing lubricated with solid is greatly affected by the contact flash temperature. Formulas are dedused using Lee’s asperity flash temperature method, to calculate the flash temperature of ball bearing lubricated with solid. The maximum flash temperature is calculated for hybrid ceramic ball bearings. The results show that under given conditions, the flash temperature of inner race is higher than that of outer race, the flash temperature of the hybrid ceramic bearing is sensitive to the load, rotational speed and race curvature. The flash temperature of inner race at 20 000 r/min is 66 9% more than that that at 11 000 r/min, and with the load changing from 1.1 kN to 2 kN, the flash temperature inner race goes up to 165 7%. Very common for high speed ball bearings, when curvature coefficients of both inner and outer race change from 0 515 to 0 56, the inner race flash temperature decreases from 421 446℃ to 56 2℃.

Study and Development of a Screener Test for Fuel Economy Passenger Car Motor Oil

Fuel economy regulations have been issued in many countries to save energy,and it is one of the most essential performance requirements for Passenger Car Motor Oil(PCMO) this decade.The performance is also important to reduce green house gas(GHG) emissions.Automotive,Oil and Additive industries have been developing fuel economy tests in fired engine for PCMO.The ASTM 5 Car test was started in 1982 and ASTM Sequence Ⅵ series test was also developed by the industries as one of fuel economy tests after the 5 Car test.However,the fired engine(combustion) test condition is more complicated and the combustion mode in engine introduce high variability into a fuel economy measurement.Screening by bench testing is complicated by the difficulty to reproduce friction conditions of all of engine parts.Based on the background,a motored engine friction torque test(MEFT) was developed as one of the solutions for fuel economy screening test.Using a newly developed MEFT,key additive chemistries were evaluated and compared in the test,and it distinguished the differences in additive chemistries,in addition to those in viscosity and friction modifiers.The Sequence Ⅵ-D FEI 1(Seq.Ⅵ-D FEI 1) and chassis dynamometer vehicle tests were also conducted in this study,and the test data has shown an excellent correlation among MEFT,Seq.Ⅵ-D FEI 1 and chassis dynamometer vehicle tests.

Determination of the Friction Coefficient in the Flat Strip Drawing Test

Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces were tested under similar contact conditions regarding contact area, normal pressure, sliding speed, lubricant and surface characteristics to calculate the friction coefficient between the tool surface and a high strength low alloy steel sheet HSLA 380. The results showed that friction coefficient varies over a wide range with different lubricating conditions and different sliding velocities. For some sliding velocities, the coefficient of friction is stable and low, while for others it is unstable and higher. Results of the experiments reveal that this novel tribotester is a very useful tool to evaluate and compare the friction between steel sheet and tool surfaces in alloyed steel for cold working applications. The outcomes have only small dispersion within the different test series, which indicates a stable process with good repeatability. The test method enables comparison of different surface finishes and treatments, lubricants and coatings in terms of friction and galling under conditions similar to those found in sheet metal forming processes. The four different types of surfaces considered for this study were grinded, polished, nitrided and quenched/tempered. The main difference among the tested tools in this work was the surface roughness, which was found to have a strong influence on friction.

Experimental Study on Vibration Control of Offshore Wind Turbines Using a Ball Vibration Absorber

To minimize the excessive vibration and prolong the fatigue life of the offshore wind turbine systems, it is of value to control the vibration that is induced within the structure by implementing certain kinds of dampers. In this paper, a ball vibration absorber (BVA) is experimentally investigated through a series of shake table tests on a 1/13 scaled wind turbine model. The reductions in top displacement, top acceleration, bottom stress and platform stress of the wind turbine tower system subjected to earthquakes and equivalent wind-wave loads, respectively, with a ball absorber are examined. Cases of the tower with rotating blades are also investigated to validate the efficacy of this damper in mitigating the vibration of an operating wind turbine. The experimental results indicate that the dynamic performance of the tested wind turbine model with a ball absorber is significantly improved compared with that of the uncontrolled structure in terms of the peak response reduction.

Precision loss of ball screw mechanism under sliding-rolling mixed motion behavior

The sliding-rolling mixed motion behavior degrades the ball screw’s precision at different levels.Based on the sliding-rolling mixed motion between ball and screw/nut raceway,the ball screw’s precision loss considering different given axial loading and rotational speed working conditions was investigated.Since creep and lubrication relate to sliding and rolling motion wear,the creep and lubrication characteristics are analyzed under different working conditions.Besides,the precision loss was calculated considering the sole influence of sliding behavior between ball and screw and compared with the results from other current models.Finally,research on precision loss owing to the sliding-rolling mixed motion behavior was realized under given working conditions,and suitable wear tests were carried out.The analytical results of precision loss are in good agreement with the experimental test conclusions,which is conducive to better predicting the law of precision loss in stable wear period.

Application of Automated Ball Indentation for Property Measurement of Degraded Zr2.5Nb

In this work, Automated Ball Indentation (ABI) technique is based on load controlled multiple indentations (at a single penetration location) of a polished surface by a spherical indenter (0.7 to 1.46 mm) and indentation depth is progressively increased to a maximum user specified limit with intermediate partial unloading. This technique permits measurement of yield strength, stress-strain curve, strength coefficient and strain hardening exponent. ABI Testing was carried out on samples of Zr-Nb2.5 (Pressure Tube Material) with different heat treatment conditions in which temperature was varying (550 degree to 900 degree and retention time was varying 0.5 to 6 hour and furnace cooled. For all these test material and conditions, the ABI derived results were in very good agreement with those from conventional standard test methods.

Warm Compaction Process of P/M Steels by Orthogonal Testing Method

In order to achieve higher density of P/M steels using the die wall lubrication compacting method or powder lubricant in warm compaction process, the influence of different process parameters on the green density of warm compacted samples was studied. According to the orthogonal test method, the authors systematically study the influence of the different compaction pressure, condition of lubrication and compaction temperature on the green density of the sample in the warm compaction process, and put forward the optimal process parameter of warm compaction experiment. It is found that, a high compaction pressure （≥700 MPa）, die wall lubrication combined with a small amount of internal lubricants, and fitting compaction temperature by different condition of lubrication, are the optimal parameters in warm compaction process.

An Analysis of Physical Fitness Differences in Soccer,Handball,and Basketball

This study focuses on the evaluation of the differences of physical fitness among soccer players, handball players, and basketball players, and the investigation of the physical fitness structures of those players. The participants consisted of 160 elite players selected from university teams. Fourteen tests related to health and motor fitness were conducted. The results were subjected to a multivariate analysis of variance (MANOVA) to test the mean vector differences among the three groups of different sport. Nine out of the fourteen tests were of significantly discriminating results regarding to different group, which include side step, abdominal strength, shuttle running, 100m running, pull-up, 1,500m running, trunk flexion, grip strength and broad jump, as determined by a stepwise regression approach. MANOVA showed that there was a significant difference (p<0.001) of the mean vectors of the 9 tests among the three events. Discriminant function analysis showed that three discriminant functions were significant, whose correctness was testified by the classification analysis to be over 80.2%. It is demonstrated that elite handball players are good at agility, elite soccer players are speedy, and successful basketball players apparently possess preeminent muscular strength and endurance.

Single Bout of Resisted Exercises Using Physioball on Random Blood Sugar on a Female Type II Diabetes Mellitus

Lowering of random blood sugar on a female obese diabetic subject is the core of this case report. Single bout of high intensity exercises using Physioball helps to induce confidence in the subject.

考虑弹流润滑效应的三点接触球轴承刚度特性分析

为获得润滑状态下三点接触球轴承更为准确的刚度特性,应考虑弹流润滑效应对轴承刚度的影响。文中基于拟静力学模型考虑高速离心力和陀螺力矩效应,根据给定轴承的结构参数和工况,计算滚动体与内外圈的法向接触载荷和各部件的运动速度。将拟静力学模型的计算结果和润滑介质参数代入弹流润滑模型,求解出滚动体与内外圈之间的压力分布和油膜厚度分布。进一步研究了转速、轴向载荷和润滑油的初始黏度对油膜压力和最小油膜厚度的影响。基于弹流润滑理论分析了转速和轴向载荷对轴承接触刚度、油膜刚度及综合刚度的影响。结果表明:转速的提高会大幅增加润滑油膜的整体厚度;润滑油初始黏度的增大会增加油膜厚度;随着轴承转速的提高,轴承的整体轴向刚度和轴向油膜刚度减小;随着轴向载荷的增大,轴承轴向刚度和轴向油膜刚度增大,且差值变化不大。

石墨烯纳米颗粒参数对角接触球轴承油气润滑特性的影响

为探究高速旋转状态下油气负载石墨烯润滑特性,以B7003C轴承为研究对象,通过有限元软件建立其三相润滑流场的数值模型,考虑石墨烯纳米颗粒参数对润滑的影响,观察润滑油和石墨烯纳米颗粒在轴承腔内的分布和变化,结果表明:轴承腔内石墨烯润滑油的体积随时间延长而增大,一段时间后润滑油总体积与分布状态在轴承腔内随时间脉动循环;石墨烯质量分数增加改变了基础油的润湿性,增大了相同工况下轴承腔内油的含量,进而改善了轴承润滑状态;石墨烯纳米颗粒在轴承腔内的运动轨迹和分布与其粒径尺寸有关,小粒径石墨烯扩散速度更快,主要参与钢球与内沟道润滑,更易从轴承腔入油口一侧溢出;大粒径石墨烯主要参与钢球与外沟道润滑,更易从油气入口侧进入轴承腔内参与润滑。

含石墨烯油气润滑的角接触球轴承腔热流数值分析

为更有效地降低大功率高速电主轴用高速角接触球轴承腔温度,对含石墨烯的油气润滑影响轴承腔热流特性的规律进行分析。基于流体力学守恒方程,建立了高速角接触球轴承腔体内压缩气体、润滑油和石墨烯颗粒形成的气液固三相流热流分析数学模型。通过数值模拟分析了不同速度压缩气体状态下油气通道中的石墨烯润滑油环状流形成条件、轴承腔内石墨烯润滑油流场速度,以及石墨烯颗粒分布与轴承腔温度场的关系。结果表明,石墨烯润滑油速度与压缩气体速度之比为1∶10时,油气通道中会形成石墨烯润滑油环状流,使高速角接触球轴承腔具有良好的润滑效果;高速运转工况下,轴承腔内石墨烯的分布状态同时受离心力与滚珠高速自旋的影响,而且石墨烯颗粒分布越密集,该区域的温度越低;石墨烯润滑油在滚珠与内圈接触区域流速越大,表面换热系数越高,该区域散热越快,为石墨烯油气润滑更好地降低高速角接触球轴承温度、保障轴承正常工作提供了理论依据。

喷嘴位置对轴承腔内油气润滑两相流的影响

基于气液两相流理论,采用多重坐标系法构建角接触球轴承数值计算模型,分析不同喷嘴位置和转速下轴承腔内油相体积分数、保持架表面及轴承内外圈的油气分布特性。结果表明:在轴承低转速下,正面供油时轴承腔内油相体积分数及其周向分布的波动大于背面供油;正面供油时保持架下表面会产生润滑油的积聚,造成润滑油无法及时通过出口排出,而背面供油时润滑油在保持架表面的油相分布更均匀;正面供油时内圈左面油相体积分数较高,外圈油相分布变化较大,而背面供油时内圈右面、中间面及外圈中间面油相体积分数较高。不同转速下喷嘴位置对腔内油相分布的影响也不同,低转速下正面供油时腔内油相体积分数更高,高转速下喷嘴位置对轴承腔内油相分布的影响较小,润滑油在轴承腔内分布较为均匀,保持架下侧未见明显的润滑油积聚。

联合载荷作用下精密轴系角接触球轴承钢球与保持架动力学行为分析

针对联合载荷作用下精密轴系角接触球轴承钢球与保持架的相互作用行为,基于滚动轴承动力学理论建立了精密轴系动力学分析模型,分析了转速、载荷、轴承结构参数对钢球与保持架动力学行为的影响,并通过保持架转速试验验证了模型的准确性,结果表明:力矩载荷对钢球与保持架动力学行为的影响程度较径向载荷明显;在径向载荷作用下,当转速小于40000 r/min时钢球与保持架的作用力随轴向预紧力增大而增大,当转速大于40000 r/min时钢球与保持架的作用力随轴向预紧力增大先减小后增大;在力矩载荷作用下,钢球与保持架的作用力随着力矩载荷的增大先增大再减小而后急剧增大;增大保持架兜孔间隙与外沟曲率半径系数有利于减小钢球与保持架的作用力。

角接触球轴承内圈织构设计及对油气润滑两相流的影响

针对角接触球轴承油气润滑中内圈润滑油含量少和保持性差的问题,提出在轴承内圈滚道设计圆凹坑形表面织构的润滑增效方法。基于气液两相流模型和多重参考系方法,建立内圈织构化角接触球轴承腔内油气两相流数值分析模型,分析内圈织构对轴承油气两相流动及润滑增效的影响。结果表明:织构化轴承可以显著提高润滑油在内圈的保持量,同时改善轴承腔内润滑油分布不均的状况;在微织构附近油气两相流动更不规则,所产生的压力梯度和速度梯度有利于提高气液两相膜的承载力;随着轴承转速的升高,内圈织构润滑增效效果相对减弱;随着供油量的增加,内圈织构润滑增效效果更加显著。

再成形(Re-Balled)焊球阵列封装的焊球强度评估

近年来,许多国家禁止在电子产品中铅的使用,但是一些特定产品拥有豁免权。拥有豁免权的电子产品生产厂商面临含铅元器件供应缺乏的现状,因此生产厂商开始寻求利用焊球再成形技术把焊球阵列封装中的无铅焊球转变为锡铅焊球。焊球再成形技术曾经被用于元器件的回收再利用,但是关于焊球再成形元器件的可靠性信息十分有限。介绍了利用焊球再成形技术使无铅焊球阵列封装转变为锡铅焊球阵列封装。两种焊球去除方法和两种焊球再贴装方法分别用于实现从无铅焊球到锡铅焊球的转变,用以调查再成形工艺对于封装质量的影响。热时效试验以及焊球强度评估用于检测焊球再成形工艺过程。