D30燃料在载货汽车上的应用研究

在SXQ4181G载货汽车上开展了燃用D30(二甲醚与柴油质量分数比3∶7)燃料的动力性、燃料经济性和排放特性的试验研究。针对D30燃料的特性,改造了原车燃料供给系统和优化了喷油泵及喷油器参数后,进行了发动机台架试验和整车道路试验。结果表明,燃用D30燃料的动力性与原柴油机相当,经热值修正后的当量燃料消耗率有所改善;NOx排放下降(低转速时尤其明显);HC排放有所降低,CO排放没有明显变化,烟度在全转速范围内大幅度下降。     

Examining the theoretical–empirical inconsistency on stationarity of shipping freight rate

As market price, shipping freight rates should in theory be stationary, but most empirical tests have found them to be non-stationary. To examine the causes of this theoretical–empirical inconsistency, we investigate the sensitivities of the stationarity of shipping freight rates from two perspectives: sample length and sample window. Longer samples are found not sufficient to make them stationary. Instead, sample windows separated by structural breaks are tested as stationary. Moreover, freight rates are found to have entered into a new phase since the 2008 financial crisis. This study contributes to the literature on the stationarity of shipping freight rates by providing an explanation for the theoretical–empirical inconsistency.     

铝合金点焊接头疲劳性能研究及寿命分析

为了支持多环形纹路表面电极帽式铝合金点焊接头在车辆正向开发中的设计应用,设计并开展了一系列的铝合金点焊接头疲劳试验研究和疲劳寿命预测方法研究。过程中获得了点焊接头的载荷-寿命对应关系,总结了铝合金点焊接头疲劳强度受载荷方向、母材强度及厚度等因素影响的普遍规律,分析了铝合金点焊接头的疲劳失效破坏模式,并提出了评价铝合金点焊接头疲劳寿命的S-N曲线,可以有效指导铝合金点焊接头的抗疲劳设计开发工作。     

Vibration analysis of continuous maglev guideway considering the magnetic levitation system

The dynamic interaction between moving vehicles and two-span continuous guideway was discussed. With the consideration of the magnetic levitation system, the maglev vehicle/guideway dynamic interaction model was developed. Numerical simulation was performed to understand dynamic characteristics of the guide- way used in practice. The results show that vehicle speed, span length and primary frequency of the guideway have an important influence on the dynamic responses of the guideway and there is no distinct trend towards resonance vibration when f1 equals 1.0. The definite way is to control the impact coefficient and acceleration of the guideway. The conclusions can serve the design of high speed maglev guideway.     

斜连杆裂解工艺分析

介绍了柴油机斜连杆裂解工艺.研究了斜连杆较大外形尺寸对裂解连杆锻后控制空冷及裂纹扩展的影响及其结构不对称性对启裂的影响,分析了斜连杆在裂解试验和小批量试生产中出现的质量问题,并利用ABAQUS有限元对53D斜连杆进行了裂解启裂模拟.依据模拟结果提出了提高斜连杆裂解质量、优化斜连杆裂解工艺参数的合理建议.     

插电式燃料电池轿车的建模与仿真

简述了插电式燃料电池轿车的结构,重点介绍其各主要部件的模型结构和建模原理,最后在Matlab平台上将所建的整车模型与整车控制策略模型进行联合仿真,仿真分析结果验证了整车模型的正确性和整车控制策略的有效性.     

应用连续热驱法研析隧道水泥衬砌之拉力强度与破裂韧度受热的影响

隧道火灾可能毁损隧道衬砌支撑,造成隧道坍塌。通过对热损分布关系进一步了解,有助于在灾前提高材料的防火性能设计,并在灾后较精准的预测其损害范围,进而降低修缮成本。以往的研究都采用个别式热损试样准备法,无法准确预测没有试验数据的结果,故本研究提出连续热驱试样准备法,从而得出连续性的试验数据。本研究研析水泥砂浆受连续热损后,其拉力强度及破裂韧度与温度的相互关系。藉由试验结果,除可获得较为精确的预测方程外,并以Log Log交点法得到相对合理与准确的临界热损温度(540~550 ℃),以期为隧道火灾防范提供参考。     

橡胶元件在汽车悬架中的应用分析

介绍了橡胶元件在汽车悬架中的应用现状,分析了橡胶衬套力学特性的理论研究方法和试验技术,并对某汽车悬架橡胶衬套进行了有限元分析和试验验证。阐述了橡胶衬套对汽车平顺性、操纵稳定性及高频NVH特性的影响,并通过实例讨论了橡胶衬套对悬架运动学性能的作用和衬套刚度优化方法。指出,需进一步研究橡胶元件对汽车高频动态性能的影响。     

发动机结构噪声的计算机仿真分析

以一台四缸发动机为例,应用计算机仿真技术分析了发动机的结构振动噪声。首先建立发动机总成有限元模型,通过模态分析,为发动机的结构修改提供依据。根据车用发动机的实际使用工况,在不同转速及爆发压力下对其进行动力学计算,得到发动机的表面振动速度级。通过改进发动机结构,使发动机的表面振动速度级降低了5.6dB(A)。     

Comparison analysis of efficiency between double-synchronous step-down-stress and step-up-stress accelerated life tests

Double-crossed-step-stress (DCSS) accelerated life test (ALT) method is widely used for estimating the lifetime of products with high reliability and long lifetime. In order to further reduce the test time and test cost, a double-synchronous-step-stress (DSSS) ALT method which combines a double-synchronous-step-down-stress (DSSDS) ALT method and a double-synchronous-step-up-stress (DSSUS) ALT method is proposed. The accelerated stresses decrease and increase in a synchronous way with one step in the DSSDS-ALT and DSSUS-ALT methods, respectively. Monte Carlo method is adopted to simulate the two methods, and the validity and efficiency of them are demonstrated by the simulation results. In addition, a comparison analysis of efficiency between DSSDS-ALT method and DSSUS-ALT method is carried out. The result shows that the DSSDS-ALT method compared with the DSSUS-ALT method can significantly improve the test efficiency under the same test condition.