Thermal Behaviour of a Slipping Wet Clutch Contact

Wet clutches are used in automatic transmissions to enable gear changes and also to reduce energy loss in the torque converter. These friction devices are susceptible to stick–slip effects, which result in the vehicle giving an unsteady ride. Stick–slip effects can be avoided by ensuring the wet clutch and lubricant combination produces a friction coefficient that increases with sliding speed. Although wet clutches have been studied throughout the industry for many decades, the mechanism of the generated friction is still not fully understood. It is known that, because of the fibrous nature and thus very large roughness of friction material, the overall contact between clutch plates actually consists of many small, independent, contact units, which are the sites of the generated friction. Some authors have suggested that a temperature rise due to friction either at these contact units or of the overall clutch plate may be important in controlling friction behaviour. In this study, the flash temperatures at the contact units formed in the wet clutch contact have been measured using an infrared camera. Three friction materials have been tested. It was found that measured flash temperature in a pure sliding system similar to that present in a slipping clutch remain well below 5 °C, and are therefore unlikely to play a major role in the observed friction-speed dependency of slipping wet clutches at speeds below 2 m/s.     

Use of FIB to Study ZDDP Tribofilms

Focussed ion beam milling (FIB) followed by TEM has been used to study ZDDP tribofilms on rubbed steel surfaces. It has been found that the impact of high energy platinum and gallium ions during FIB causes significant morphological and structural changes to the uppermost 30–50 nm of a ZDDP tribofilm. This can be prevented by the low energy deposition of a quite thick gold layer prior to installation of the sample in the FIB facility. This problem, and its solution, have been quite widely reported in the non-tribology literature but have not previously been highlighted in the application of FIB to study tribological surfaces. It has also been found, using this gold pre-deposition method, that the bulk of the ZDDP tribofilm studied has a polycrystalline structure.     

需求弹性对发电系统可靠性的影响

在电力市场环境下,由于负荷需求弹性的存在,面对电价的波动,用户可适时调整负荷计划,改变实际负荷曲线,从而直接影响发电系统可靠性的计算。构筑考虑需求弹性的电价负反馈模型,通过对IEEE30节点系统进行计算,研究了需求弹性对发电系统可靠性的影响,也即对电源充裕度的影响。     

Additive-additive and additive-surface interactions in lubrication

Combinations of additives are often found to exhibit antagonistic or synergistic effects compared to the performance of the individual additives. This paper reviews the state of knowledge concerning such effects. Direct interactions, where two additives combine at a molecular level, are distinguished from complementary or exclusary effects where the individual contributions of separate additives enhance or reduce overall performance but with no direct interaction. Additive interactions take place in solution and at surfaces, and both are discussed.     

Development of laboratory tests to predict the lubricity properties of diesel fuels and their application to the development of highly refined diesel fuels

In the last few years there has been an increasing requirement for the provision of environmentally benign diesel fuels. However, the introduction of such fuels into service has been associated with high levels of field failure of rotary distribution fuel pumps due to wear. This is because the refining processes necessary to produce ecologically acceptable fuels result in greatly reduced levels of sulphur compounds, aromatics, and polar material, many of which are potential lubricity agents. This paper describes the development of bench test methods to evaluate diesel fuel lubricity and thus enable the identification of appropriate ‘solutions’. It has been found that the key to obtaining good correlation between field experience and bench tests is (1) to reproduce the thermal conditions present in operating pump contacts and (2) to ensure that the same mechanisms of wear operate in the bench test as in the pump environment. The physical and chemical processes involved in the lubrication of fuel pumps and the influence of temperature on these processes are outlined. As a result of the work described in this paper, effective additive solutions have been discovered for controlling the failure of diesel fuel pumps in the field and a provisional ISO (ISO/TC 22 / SC 7 M595: ‘Diesel engines - diesel fuel - performance requirement and test method for assessing fuel lubricity’) and CEC test method for assessing diesel fuel lubricity has also been developed.     

新疆东天山灵北地区康南岩体岩石学#br# 特征及其构造意义

研究区位于新疆东天山觉罗塔格造山带吐哈盆地以南百灵山以北,多年来对于研究区古生代构造背景的认识受前人热议,存在争议。通过对研究区新发现基性岩体的岩石、地球化学特征与构造背景进行探讨,以期为大区域构造背景的研究提供一定的数据支持。主量元素研究表明,康南岩体具有高Mg、Fe,低Al的特征,说明研究区基性侵入岩为碱性岩石系列。微量元素测试结果表明具有同源演化的特征,Rb、Hf元素亏损较为严重。K、Ba、P、Sm富集明显,Tb、Nb、Ti表现为弱异常,在稀土元素球粒陨石标准化配分模式图中Eu的负异常不明显,表现为弱的正异常, Yb+Nb-Rb构造环境判别图解中样品落在“后碰撞”环境内,以上特征说明具有岛弧花岗岩的基本特征。岩性为深灰绿色弱蚀变细粒橄榄辉绿岩。     

驾驶员座椅悬架系统主动控制研究与仿真分析

针对车辆座椅悬架系统,建立电控空气弹簧悬架座椅系统的车辆-座椅三自由度物理模型和数学模型,以路面信号为激励源,应用随机线性二次型最优控制理论(LQG),根据系统性能要求选取合适的频率加权系数,设计出控制系统的最优反馈规律,并在MATLAB中对该模型进行仿真.结果表明:这种控制策略对路面激励通过车辆系统传递到驾驶员座椅的振动控制具有更好的适应性,能有效降低驾驶员所承受的垂直振动加速度.     

SYNERGISTIC EFFECT OF VITAMIN B1 ON SANITIZER AND DISINFECTANT TREATMENTS FOR REDUCTION OF BACILLUS CEREUS IN RICE

The synergistic bactericidal effects of vitamin B₁ (thiamine dilauryl sulfate) and the efficacy of commercial sanitizers for minimization of Bacillus cereus contamination in cooked rice were investigated. Sanitizer-treated rice exhibited a greater reduction than water-treated rice, while sanitizer-treated rice with Vitamin B₁ produced an even greater reduction. The treatments for B. cereus in rice included (1) 100 ppm hydrogen peroxide with 500 ppm vitamin B₁; (2) 200 ppm hydrogen peroxide with 100 ppm vitamin B₁; (3) 400 ppm hydrogen peroxide; (4) 50 ppm chlorine with 500 ppm vitamin B₁; (5) 60 ppm chlorine with 300 ppm vitamin B₁; (6) 70 ppm chlorine with 100 ppm vitamin B₁; (7) 80 ppm chlorine; and (8) 100,000 ppm ethanol with 500 vitamin B_1. All treatments completely eliminated B. cereus in rice. The sensory properties of all sanitizer-treated cooked rice did not differ significantly from the same properties for water-treated cooked rice.

PRACTICAL APPLICATIONS

The prevalence of Bacillus cereus in rice and rice products has been documented and control of the growth of B. cereus in rice is an important consideration. The results obtained from this study can be of use to rice producers in the manufacture of safe products. Although chemical disinfectants can be used to reduce the amount of B. cereus in rice, vitamin B₁ can also be used as an effective additive that reduces the amount of disinfectant use via a synergistic antimicrobial effect. The increasing use of chemical disinfectants for safety in the food industry can be reversed using our method.     

茶叶辐照的热释光分析研究

不采用二次辐照,将TL 分析法应用于辐照茶叶的定性鉴定。分离并收集茶叶中黏附的硅酸盐,采用热释光剂量仪测量获得硅酸盐的热释光发光曲线,比较未辐照与辐照不同剂量茶叶的热释光发光曲线的积分强度、峰值和峰值温度等特征参数。未辐照茶叶的热释光发光曲线的积分强度小于50、峰值小于0.4、峰值温度大于260℃;反之,辐照茶叶的热释光发光曲线的积分强度大于50000、峰值大于600、峰值温度位于160～190℃。TL 分析法能判别出茶叶的辐照与否,尤其对不能满足参比剂量辐照条件的样品很有帮助。