Spray jet penetration and distribution of modulated liquid jets in subsonic cross-flows

Modulated liquid jets injected into subsonic cross-flows are empirically studied by using a mechanical liquid jet modulation apparatus. Experimental investigations were conducted using water over a range of cross-flow velocities from 5 m/s to 143 m/s and with modulated liquid jet frequencies from 35.7 Hz to 166.2 Hz and so on. PDPA(phase Doppler particle anemometry) was employed to measure droplet diameter and velocity with various spray cross-sections from Z/d=20 to Z/d=60. The spray structure, penetration depth, SMD(Sauter mean diameter), volume flux and velocity characteristics of modulated liquid jets injected into cross-flows were examined. As oscillation of the periodic pressure that could make liquid jet moved up and down in cross-flow field, the mixing process was facilitated. This phenomenon has the advantage of mixing the spray concentration from the center area to the outer area. Also, a bulk liquid jet puff was detected in the upper field of the liquid jet surface. The modulation effect appears significant in the extent of the spray oscillation. The correlation equations for the liquid jet boundary of the upper and lower regions which related to the Strouhal number have been presented to predict the spray structure under modulation conditions. Because of the modulation frequency, an inclination of averaged SMD for the structured layer was evanescent which contributed to the promotion of the macroscopic spray mixing process. Cross-sectional characteristics of SMD had the same tendency over a range of various modulation frequencies. As the modulation frequency increased, the region of volume flux distribution also increased.     

Development and application of VPG simulation technique based on equivalent virtual road profile

A Virtual Proving Ground (VPG) is a vehicle simulation environment used for evaluating durability of the suspension elements. Among the components that comprise the VPG system, the tire model with its complex nonlinear characteristics has most significant impact on the credibility of the estimated durability. This research proposes a method for generating an equivalent road profile as a way to compensate for the limits involved in modeling details of the tire characteristics. The method first identifies the frequency response function from the road heights to the spindle forces, which would contain rich information on the tire’s effect on the vehicle dynamics. Then it back-calculates a road profile using this model and the spindle force measurement. Finally the solution is updated iteratively until it yields the spindle forces close to their measured values. Using the proposed method, an equivalent road profile was successfully generated from a spindle force measurement collected from a physical durability test. In order to investigate validity of the proposed method, durability analysis was performed for a suspension component — a lower control arm. From the preliminary VPG simulation results, it was confirmed that the estimated fatigue life agreed well with the estimation based upon the force measurement.     

伊利的世博营销

正如一切始于世博会的名言所说,历届世博会向世界展示了新的发明创造、新的技术和世界各国比较独特的产品.1889年巴黎世博会使埃菲尔铁塔成为最具吸引力的世界奇迹;1915年的世博会见证了中国茅台酒一捧成名的传奇;魔方在1982年世博会上引发了人们的头脑风暴,在全球累计销量超过1亿只;2005年日本爱知世博会使丰田机器人吸引了全世界的眼球……     

Piezoelectric study for a three-phase composite containing arbitrary inclusion

This paper analyzes a coated inclusion of arbitrary shape embedded in an infinite plate subjected to anti-plane mechanical and in-plane electrical loadings. Based on the methods of complex variable, conformal mapping, Faber series and Laurent series, the complex potential for each component can be expressed in series form with unknown coefficients. The continuity conditions of the interfaces are used to build up a set of linear equations to determine the unknown coefficients. The exact solutions are obtained after the complex potentials are solved. By truncating the infinite system of linear equations at finite N terms, some numerical examples are provided to show the effect of the material mismatch and the shape of inclusion on the interfacial stress and elastic field. The accuracy of the linear systems is also discussed in the article.     

The effect of a multistep deep-drawing process with circular and rectangular shapes on the deformation of AZ31 magnesium sheets

This study has mostly focused on the forming limit, microstructural change, and anisotropy that arise from rectangular and circular deep drawing of magnesium sheets. Moreover, this study predicts the change in the material thickness and the forming depth at the first forming process that produces the rectangular cup by the deep drawing of the rectangular blank. Further, by using the rectangular cup that is formed by the first forming process, when the circular and square cups in the rectangular cup are simultaneously manufactured in the so-called second forming process, the effect of the clearance between the die and punch on the change in the product thickness according to forming depth associated with microstructural analysis is investigated. The forming temperature is optimized to maximize formability. The results obtained in this study are utilized as data for predicting the die clearance and the change in the thickness.     

Grinding Chatter Detection and Identication Based on BEMD and LSSVM

Grinding chatter is a self?induced vibration which is unfavorable to precision machining processes. This paper proposes a forecasting method for grinding state identification based on bivarition empirical mode decomposition(BEMD) and least squares support vector machine(LSSVM), which allows the monitoring of grinding chatter over time. BEMD is a promising technique in signal processing research which involves the decomposition of two?dimen?sional signals into a series of bivarition intrinsic mode functions(BIMFs). BEMD and the extraction criterion of its true BIMFs are investigated by processing a complex?value simulation chatter signal. Then the feature vectors which are employed as an amplification for the chatter premonition are discussed. Furthermore, the methodology is tested and validated by experimental data collected from a CNC guideway grinder KD4020 X16 in Hangzhou Hangji Machine Tool Co., Ltd. The results illustrate that the BEMD is a superior method in terms of processing non?stationary and nonlinear signals. Meanwhile, the peak to peak, real?time standard deviation and instantaneous energy are proven to be e ec?tive feature vectors which reflect the di erent grinding states. Finally, a LSSVM model is established for grinding status classification based on feature vectors, giving a prediction accuracy rate of 96%.     

Damage Tolerance Assessment of a Brake Unit Bracket for High-Speed Railway Welded Bogie Frames

The brake unit bracket of a bogie frame is an important load-carrying component, particularly under emergency start/stop conditions. Conventional infinite/safe life approaches provide an over-conservative recommendation for the allowable strength and lifetime, which hinders the lightweight design of modern railway vehicles. In this study, to ensure the reliability and durability of a brake unit bracket, an attempt was made to integrate the nominal stress method and an advanced damage tolerance method. First, a complex bogie frame was modelled using solid elements instead of plate and beam elements. A hot spot stress region on the bracket was found under an eight-stage load spectrum obtained from the Wuhan–Guangzhou high-speed railway line. Based on the probability of foreign damage, a semi-elliptical surface crack was then assumed for residual life assessment. The results obtained by the cumulative damage and damage tolerance methods show that the brake unit bracket can operate for over 30 years. Moreover, even if a 2-mm depth crack exists, the brake unit bracket can be safely operated for more than 2.27 years, with the hope that the crack can be detected in subsequent maintenance procedures. Finally, an appropriate safety margin was suggested which provides a basis for the life prediction and durability assessment of brake unit brackets of high-speed railways.     

基于生成对抗网络和自动编码器的机械系统异常检测

现有的机械系统智能诊断模型需要不同健康状态下大量的历史数据和相对应的标签来完成模型训练,但有些机械系统难以采集到异常样本。在无异常样本训练情况下,本文提出一种新的机械系统异常检测方法。新方法结合生成对抗网络和自动编码器,构建了一种编码-解码-再编码的网络模型。所提模型首先通过早期采集的正常样本进行训练,然后用于对未知状态的实时监测样本进行测试,输出两次编码得到的潜在特征的差异值,最后通过观察差异值的变化对系统进行监测。3组实验分析结果验证了方法的有效性。与传统方法相比,新方法检测出异常的时间更早,所得差异值指标在异常发生时幅度增加得更大,且能更稳定表征故障演化过程。     

液压软制动系统在下运式带式输送机中的应用

为了探究下运式带式输送机在不同运行工况下的制动策略，提出了液压软制动系统，通过建立数学模型对其进行分析研究，采用液压软制动作为突发断电和紧急停车的安全制动方式，解决特殊工况下的安全问题。借助Simulink和AMESim两款仿真软件对各工况下的制动过程进行了仿真研究，结合下运式带式输送机的运行特性搭建了模拟运行试验台，对所设计的制动系统进行了试验研究。结果表明：“四象限变频回馈制动+液压软制动” 的电液复合制动能够实现带式输送机在正常供电工况下的安全停车，且液压软制动系统在突发断电和紧急停车过程中有良好的制动效果，为下运式带式输送机的制动特性研究提供了借鉴。     

断带抓捕装置液压系统仿真实验研究

为实现对大运量、长距离、重载的带式输送机在工作过程中断裂的胶带进行准确、及时的抓捕，设计了一套机电液一体化的断带抓捕装置。介绍了系统的基本结构，建立了装置的液压系统模型，借助AMESim软件对其进行仿真，分析蓄能器不同参数的设定对抓捕效果的影响，同时组装搭建了断带抓捕试验台，对上述仿真结果进行验证。结果表明：25 L双蓄能器对胶带的抓捕时间较50 L单蓄能器对胶带抓捕时间短；在一定范围内，并联式蓄能器容积越小，抓捕时间越长；液压泵与蓄能器之间的安装距离也影响系统对胶带的抓捕效果，安装距离越大，抓捕时间越长。