生物柴油混合燃料的排放特性研究

本试验通过对燃烧生物柴油对发动机排放污染物的测量和分析,探讨了生物柴油降低柴油机排气污染物的机理。研究结果表明:在同一稳定工况下,随着生物柴油加柴油中入比例的上升,燃烧排放物中的CO和HC比柴油排放呈现线性下降,NOx排放有所上升,而CO2排放一本在同一水平。     

含氧燃料成分对柴油机排放特性影响的试验研究

将占体积比80％柴油分别与20％乙醇、20％生物柴油以及同时与10％乙醇和10％生物柴油组合成的混合燃料，在增压中冷柴油机上进行实验，分析比较其排放特性。结果表明，随着含氧燃料中乙醇比例的增大，发动机排放的HC和CO升高，碳烟降低，NOx则差别不大。     

FABRICATION AND PROPERTIES OF ANTIFERROELECTRIC RAINBOW ACTUATOR

A new type of large-displacement actuator called reduced and internally biased oxide wafer (RAINBOW) is fabricated by chemical reduction of Pb(Sn,Zr,Ti)O3(PSZT) antiferroelectric ceramics and its properties are investigated. It is found that PSZT is easily reduced and the optimal conditions for producing RAINBOW samples are determined to be 870 ℃ for 2-3 h. The antiferroelectrics- ferroelectrics phase transitions occur at lower field strength in RAINBOW actuators compared with normal PSZT actuators. Large axial displacements are also obtained from the RAINBOW actuator by application of electric fields exceeding the phase switching level. However, the field-induced displacement of the RAINBOW actuator is dependent on the manner of applying load on the samples.     

轻卡燃油滤清器支架振动分析及其优化设计

针对某轻卡燃油滤清器支架在整车道路试验中出现的开裂问题,首先采集该支架在各个路面的振动加速度,测试结果表明其中搓板路的振动加速度最大。然后将车架端作为激励点并且加载实测频域信号,基于频率响应方法对该支架进行振动分析,分析结果表明该支架在Z向的最大von Mises应力超过其材料屈服强度,位于圆管折弯处,与实际失效位置一致。最后通过Isight平台集成Catia、Hypermesh和Nastran同时采用第二代非劣排序遗传算法对该支架进行多目标优化分析,得到了圆管的最优参数,优化之后其最大应力值均低于许用应力,优化效果比较明显,均能够满足疲劳强度性能要求,与此同时其优化方案也通过了整车可靠性路试验证,因此成功解决了该开裂问题。该分析方法集成了道路测试、有限元技术、频率响应方法以及整车可靠性路试验证,对于类似支架的振动分析及其优化设计具有非常重要的实际工程应用意义并且提供了先进的参考依据。     

燃气热力性质的计算和分析

本文讨论了C－H－O－N'系燃料的燃气热力性质：提出了四种具有不同准确度的简捷计算方法;分析了现有各种近似计算方法（包括本文提出的）的准确度;总结了计算的规律。     

CALCULATION AND IMPROVEMENT OF DYNAMIC CHARACTERISTICS OF CENTRIFUGE

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电梯轿厢-导轨耦合动力系统建模及其动态特性

对电梯轿厢－导轨耦合动力系统进行分析,建立12自由度非线性振动模型。用基于状态空间的数值迭代法对模型进行求解,研究当导轨不平顺度激励强度以及轿厢运行速度等因素发生改变时,轿厢水平振动的时域和频域特性。研究成果可为导轨安装误差的合理确定提供重要理论依据,同时也将对轿厢结构的优化设计、振动控制等方面的研究起到良好的推动作用。     

PARAMETERS OPTIMIZATION OF CONTINUOUS WAVELET TRANSFORM AND ITS APPLICATION IN ACOUSTIC EMISSION SIGNAL ANALYSIS OF ROLLING BEARING

Morlet wavelet is suitable to extract the impulse components of mechanical fault signals. And thus its continuous wavelet transform (CWT) has been successfully used in the field of fault diagnosis. The principle of scale selection in CWT is discussed. Based on genetic algorithm,an opti-mization strategy for the waveform parameters of the mother wavelet is proposed with wavelet en-tropy as the optimization target. Based on the optimized waveform parameters,the wavelet scalogram is used to analyze the simulated acoustic emission (AE) signal and real AE signal of rolling bearing. The results indicate that the proposed method is useful and efficient to improve the quality of CWT.     

静压轴承自控系统动态品质的优化方法

提出带节流器的自适应性静压轴承系统动态品质的分析与优化方法,通过在系统内以不同方式引人类型各异的校正装置,可以改善轴承系统的动特性,提高主轴的回转精度。利用自控系统稳定性理论,对优化前后系统的过渡过程曲线和对数相频、幅频特性图像进行综合分析和对比,评定不同方法对轴承系统动特性改善的效果,并且对它们的应用范围作了说明,为改善主轴系统动态品质及其优化设计提供理论依据。     

不同强韧性组配的16Mn钢焊接接头的断裂性能和裂行为

对16Mn钢不同组配焊接接头的断裂性能和断裂行为进行了试验研究。认为在高应力塑性断裂和高应力脆性断裂状态下,16Mn钢接头的断裂强度为焊缝强度和接头各部分塑性变形能力所决定,提高焊缝强度以及提高焊缝和母材的塑性均有利于提高接头的抗断裂能力;在低应力脆性断裂状态下,接头的抗断裂性能是可以根据焊缝的低温冲击韧度进行评价的。焊接接头各部分塑性变形能力及其相互关系对焊接接头的断裂行为具有不可忽视的影响,是评价接头断裂性能的重要依据。     

EVALUATION AND COMPARISON OF LUBRICANT PROPERTIES IN MINIMUM QUANTITY LUBRICATION MACHINING

Minimum Quantity Lubrication (MQL) machining involves the application of a minute amount of an oil-based lubricant to the machining process in an attempt to replace the conventional flood coolant system. Understanding the correlations between fluid properties and MQL performance can help in selecting lubricants from a variety of choices without going through extensive machining tests. This study compared nine different MQL fluids in terms of their physical properties, wettability, tribological properties (lubricity and extreme pressure (EP) properties), mist characteristics and machinability to determine the correlation of measured properties and MQL drilling and reaming performance. Results show that low fluid viscosity, high mist concentration, large mist droplet diameter and high wettability were best correlated with good machinability. Although it is difficult to draw strong relationships, the optimal machining in a mild cutting condition was found with the low viscosity fluids, which may also have the highest mist concentration, largest drops and best wettability.     

裂纹起扩展阻力Ji与基本力学性能的关系

韧性裂纹开始扩展的J积分值对于韧性断裂的工程构件是一个重要的材料性能指标.统计了三个钢种两种焊缝200多个J积分值.发现当裂纹生长量Δa＜0.6 mm时,Δa与J积分值存在线性关系,可以用J=J0+K(Δa)表示,式中K=di/dΔa(Δa=a0+da),a0是J-Δa曲线与钝化线的交点.当da=0时的J值以Ji表示,它表示了韧性裂纹开始扩展时的J积分值.实验证明,只有Ji与静拉伸发生颈缩时的颈缩比功有良好的线性相关性,从而由Ji换算得KIC也应与颈缩比功线性相关(相关系数＞99%),而与静力韧度无关.而韧性裂纹开始扩展以后,各个扩展量下的JR值与静力韧度、颈缩比功无任何相关性.