Applied Mechanics and Materials Vols. 488-489

Abstract: When diagnosing mechanical faults using multi signal features, in order to keep the most efficient signal features and eliminate redundant ones, and make the mechanical fault diagnosis achieve a balance between computational complexity and diagnostic accuracy, a redundant features eliminating method based on k-means clustering was proposed. By optimizing the result of k-means clustering we obtained weights of all the inputted features, after setting appropriate threshold, compare it with all feature weights, eliminate those features whose weight is smaller than the threshold. After compared this method with some advanced methods, it shows that when using the SVM multi-classifier for mechanical fault diagnosis, this method produces a higher accuracy; and since eliminating part of features, it makes the time needed for diagnosis shorter.

Abstract: The axial buckling threshold force of continuous welded rail (CWR) depends on lateral stability of railway track. The conventional CWR buckling models are based on track static parameters and behavior. In this paper, a dynamic finite element model for investigating the relationship between the rail nature frequencies and the critical buckling axial force of CWR track is presented. This model consists of rails, sleepers and foundation, and covers factors of interest such as track curvature, supporting distance between adjoining sleepers. With the new dynamic model, numerical computations and analyses are performed. The correlations among the critical axial force of rail, the lateral stability and the nature frequencies of CWR track are studied. The computational results of the new dynamic model show a great agreement with the field testing results.

Abstract: In this paper, the effects of continuously regenerating trap (CRT) after-treatment system on performance, fuel efficiency and regulated gas emissions from a turbocharged electronically controlled high pressure common rail diesel engine that meets China-V regulation have been investigated. The test results revealed that: the power and torque of diesel engine after the installation of CRT after-treatment system declines slightly, which is limited to 2%, and the rise in brake specific fuel consumption is around 2%. At the same time, the emission of CO decreased significantly by 86% to 94%, NOx also reduced slightly by 8% to 12%. However, the emission of HC dropped at part loads and rose at full load modes since the original engine emission is already quite low.

Abstract: The buckle propagation phenomenon in offshore pipelines is an important subject of ocean engineering. The local buckling will easily propagate along the pipeline if the external hydrostatic pressure is high enough. The buckle propagation will seriously hinder the transmission of the oil. This paper focuses on the numerical calculation of buckle propagation pressure using ABAQUS software.

Abstract: Wide-band planar microstrip balun implemented with simplified composite right/left-handed (SCRLH) structure is presented in this letter. The proposed balun consists of a wide-band Wilkinson power divider and a broadband 180° phase shifter based on SCRLH structure. The new design was simulated and validated by the measurement. In the experimental results, within the frequency range from 3.1 to 8.3 GHz (91.2%), the measured return losses of the unbalanced and balanced ports are greater than 10 dB, and the balanced ports isolation is below 15 dB. The measured amplitude and phase difference between the two balanced ports are within ±0.6 dB and ±50, respectively, over the operating frequency band.

Abstract: In this paper, the finite method is applied and ABAQUS software is used, the vortex flow field is loaded as boundary condition of wraps. The stress and deformation in scroll under the action of gas pressure, temperature load and both of them is analyzed, the stress distribution and deformation of wraps in different shaft rotation angles is discussed, the stress distribution and deformation discipline of wraps are also respectively obtained. The results show that the overall stress and deformation in scroll are the largest when compression chamber is moving near the vent position and the thermal deformation is the main factor of affecting the overall deformation of scroll.

Abstract: Cold starting test of a high pressure common rail diesel engine was conducted on an engine test bench simulating plateau environment with high altitudes and low temperature. A comprehensive study of cold starting and idling performance was investigated under plateau ambient temperature of-35°C to-10°C and altitude ranged from 2km to 4km. Results show that, without inlet air heating, during engine starting up under different altitude at-10°C, average inlet temperature and pressure can drop slightly and idling rotating speed exhibits strong fluctuation. By heating up inlet air for 60 seconds, the inlet temperature shows statistically linear growing trend in the first 8 heating seconds, during which period averaged inlet temperature rises to 12.4°C, thus obviously lifting up intake temperature, improving engine starting up performance and reducing rotating speed fluctuation. At high altitude and cold plateau conditions, by prolonging the air heating time solely has limited effects on reducing engine starting up time or improving cold starting performance, nor can rotating speed fluctuation been effectively reduced. When ambient temperature reaches-30°C, by heating up inlet air for the same specified time interval, an average of temperature rise of 2.4°C can be obtained for altitude step increase of 1 kilometer, but cold starting up performance has not been therefore significantly improved.

Abstract: The difficulty to simulate the complex loads in the fatigue analysis of excavator working device results in great error in the result, so a research method of fatigue life of working device that was completely driven by real loads was proposed. With a 20t excavator as the research object, a kinetic model of excavator working device was established using the D-H method. According to the hydraulic cylinders pressure and displacement data in the process of digging recorded by the sensors, the real working loads of booms hinge points were obtained combining the equation of forces. The life contour of boom was obtained by the fatigue analysis of boom using software MSC.Fatigue. The minimum fatigue life is 16.8 years, and the result of the study provides basis for designing excavator working device structure.

Abstract: This paper mainly talks about the Covariance Analysis Describing Equation Technique (CADET), which is used for the improved proportional guidance law. Firstly, the principle of this method is introduced. Secondly, the related conclusion and validation of Gaussian assumption is analyzed. Thirdly, an improved augmented proportional navigation guidance law (APNG) is analyzed by this method. Finally, the higher guidance accuracy of this improved APNG is demonstrated by stimulated experiments.

Abstract: Previous papers which researched the effects of spray angle were mainly focused on the influence of spray angle on the performance and emissions of diesel engine. Few papers clarified the effect of spray angle on the airflow in detail. Airflow and turbulence have a significant influence on the combustion and distribution of emissions.The effects of spray angle on the flow, combustion and emissions of diesel engine were studied in this paper by a numerical simulation method. The results indicated that the spray angle had an obvious impact on the vortex and turbulence. The distribution of high temperature areas and emissions depend on the vortex and turbulence. With the increase of spray angle, the maximum cylinder pressure and temperature increase gradually. The heat release rate increases with the increase of spray angle. The CO and soot emissions were the lowest when the spray angle is 155°, however, the NO_x emissions was the highest at that spray angle.