高速动车组减振器载荷特征研究

减振器的主要功能是提供阻尼力以衰减和抑制车辆系统振动,对高速动车组动力性能有十分重要的影响。既有研究主要将减振器处理为阻尼力以研究车辆系统动力性能,极少从动力学和结构可靠性角度关注减振器自身承受的载荷。制作某型高速动车组转向架抗蛇行减振器、轴箱减振器、二系横向和垂向减振器测力元件,在大同-西安高速线路上测试并获得该型动车组运行过程中四种减振器载荷引起的应变信号。对测试数据进行处理和分析,获得高速动车组运行工况下四种减振器载荷的时间历程,分析减振器载荷的时域和频域特征。采用雨流计数法统计减振器载荷峰谷值和频次,获得不同速度等级下载荷分布。结果表明,高速动车组抗蛇行减振器载荷最大、二系横向减振器载荷最小。轴箱减振器相对速度最大、二系横向减振器相对速度最小。减振器载荷总体上呈正态分布,而且一般有列车运行速度越高减振器载荷越大。列车正线行驶时曲线半径对轴箱减振器、二系垂向减振器以及二系横向减振器载荷影响不明显,列车速度和线路小半径曲线对抗蛇行减振器载荷影响明显。     

应用于万能铣床的自动滚齿系统设计

介绍了一种在万能铣床上实现滚齿加工的自动化系统。该系统以单片机作为核心控制单元,利用光电编码器采集滚刀及工件转速信息,通过控制器控制工件与滚刀比例同步运转,从而实现铣床上的滚齿加工。其软件设计采用了PID算法,根据所测滚刀转速对工件转速进行实时偏差调节,从而保证了滚刀与工件恒定的转速比关系。实践证明,本系统工作稳定、可靠,能很好地满足中小型机械加工企业齿轮加工的要求。     

韧性材料的几种断裂形式及判据讨论

考察几种韧性材料的复合型断裂试验过程，用传统强度理论思想认定启裂位置与启裂方向，通过对不同物理机制的断裂形式变化规律的研究，判定韧性材料的主要断裂形式有三类，以空穴成核、扩张、聚合为主导机制的正拉断，和以局部剪切带形成、发展为主导机制的两种不同类型的剪切断裂。局部大塑性变形的出现在材料内引起损伤，空穴的聚合或局部剪切带的出现仅发生在载荷达到某一临界值时。导致材料断裂发生的根本因素，是危险点上某应力参数达到了材料的断裂临界值，以此对不同断裂形式的断裂判据进行讨论，提出新的韧性断裂判据。     

Reliability prediction of the fatigue life of a crankshaft

Crankshaft, the core element of the engine of a vehicle, transforms the translational motion generated by combustion to rotational motion. Its failure will cause serious damage to the engine so its reliability verification must be performed. In this study, the S-N data of the bending fatigue limit of a crankshaft are derived. To evaluate the reliability of the crankshaft, reliability verification and analysis are performed. For the purpose of further evaluation, the bending test of the original crankshaft is carried out, and failure mode analysis is made. The appropriate number of samples, the applied load, and the test time are computed. On the basis of the test results, Weibull analysis for the shape and scale parameters of the crankshaft is estimated. Likewise, the B10 life under 50% of the confidence level and the MTTF are exactly calculated, and the groundwork for improving the reliability of the crankshaft is laid. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Do-Hyun Jung received his B.S. and M.S. degrees in Mechanical Engineering from Ajou University in 1988 and 1990, respectively. He then obtained his Ph.D. degree from Changwon National University in 2006. Dr. Jung is currently an Adjunct Professor at the School of Mechanical Engineering of Sunmoon University, Korea. He also manages the Reliability Application Research Center of the Reliability Division of KATECH. Dr. Jung’s fields of study include fatigue, reliability, and remanufacturing issues.     

基于力的存在性与可行性的夹紧力变向增量递减规划算法

根据工件的静力平衡条件与工件-装夹元件之间接触力的方向约束,建立工件装夹方案的力学模型。进一步结合线性规划技术,构建力的存在性分析模型及其求解方法,实现夹紧力是否有解的判断。针对夹紧力有解这一条件,由装夹方案力学模型与线性规划技术推导出力的可行性分析模型及其判断标准,实现给定的夹紧力是否合理的判断。考虑夹紧力的取值范围,以一定步长正向从最小值开始取值,根据当前值与上一次取值之间可行性的差异,确定下一次取值的步长及其方向;若可行性相同则以相同步长继续正向取值,否则以一半步长、反向取值,直至步长的绝对值在阈值范围之内,构建夹紧力变向增量递减的规划算法。该算法将连续型的夹紧力设计问题转化为离散型,不仅利于计算机实现夹紧力的自动化设计,而且还适合于形状复杂的工件。     

The study on pressure oscillation and heat transfer characteristics of oscillating capillary tube heat pipe

In the present study, the characteristics of pressure oscillation and heat transfer performance in an oscillating capillary tube heat pipe were experimentally investigated with respect to the heat flux, the charging ratio of working fluid, and the inclination angle to the horizontal orientation. The experimental results showed that the frequency of pressure oscillation was between 0.1 Hz and 1.5 Hz at the charging ratio of 40 vol.%. The saturation pressure of working fluid in the oscillating capillary tube heat pipe increased as the heat flux was increased. Also, as the charging ratio of working fluid was increased, the amplitude of pressure oscillation increased. When the pressure waves were symmetric sinusoidal waves at the charging ratios of 40 vol.% and 60 vol.%, the heat transfer performance was improved. At the charging ratios of 20 vol.% and 80 vol.%, the waveforms of pressure oscillation were more complicated, and the heat transfer performance reduced. At the charging ratio of 40 vol.%, the heat transfer performance of the OCHP was at the best when the inclination angle was 90°. the pressure wave was a sinusoidal waveform, the pressure difference was at the least, the oscillation amplitude was at the least, and the frequency of pressure oscillation was the highest.     

Non-singular tool path planning by translating tool orientations in C-space

This paper discusses the singular problem in five-axis machining of freeform surfaces. At first, the generating mechanism of the singularities is studied on the unit sphere in the P-system. Then a new method is developed to avoid the singularities by translating the tool orientations in the configuration-space (C-space) at the time just after the initial cutter locations have been generated for a cutter contact (CC) trajectory on the surface. The tool orientation vectors of the initial cutter locations are projected onto the C-space, forming the orientation polyline. In the C-space, a taper circle is defined. The singularities are detected by contact checking between the orientation polyline and the taper circle. Once they contact, the orientation polyline is translated by a minimum translating vector to avoid the contact. The minimum translating vector is picked on the offset polyline of the original orientation polyline. After that, the translated orientation polyline is inversed to calculate the optimized cutter locations in the P-system. The benefit of avoiding singularities at the tool path planning stage is that the original CC points on the CC trajectory are respected. The developed method is programed and tested through contrastive experiments. Results show that the optimized cutter locations can effectively avoid the singularities.     

Compensation of nonlinear dynamics for energy/phase control of hopping robot

Hopping height control is one of the difficult problems in legged control. Many kinds of research employ a leg spring for the supplement of energy, and model the robot as a spring-mass model. Feedback linearization enables to cancel the nonlinear terms theoretically. However, it is difficult to identify the nonlinear terms including the parameters precisely in the real world.This paper nominalizes the robot dynamics as the desired spring-mass system applying a disturbance observer. In order to realize the desired characteristics of the spring and the mass, the disturbance including the nonlinear terms is rejected firstly by a disturbance observer. To make the mass in the workspace as constant, the nominal inertia of the disturbance observer in the joint space is varied. Next, by adding the desired virtual elastic force, the robot dynamics is nominalized as the desired spring-mass system.Based on the nominalized spring-mass dynamics, hopping-height control using energy/phase control is implemented. While energy control is often used for hopping height control, the energy/phase control enables the hopping-height control and the spring-mass oscillation simultaneously.Constant hopping-height and stepwise hopping height are realized experimentally through the proposed control method. The simulations in the case of the ideal dynamics are also conducted for comparison.     

A Computer Code for Aerial Magnetic Soundings of Layered Media

An iterative algorithm is described to solve the inverse problem of stratified media using magnetic field data collected in aerial surveys. An airborne antenna sends downwards magnetic fields at several frequencies, and an airborne antenna detects the secondary magnetic fields. The input data for the inversion algorithm are the complex ratios between the secondary and primary magnetic fields at different frequencies. The algorithm selects one value for each unknown in ranges where the solution is likely to lie. Complex residuals between experimental and estimated data are computed. A cost function is defined as the summation of the absolute values of the real parts of the residuals added to the summation of the absolute values of the imaginary parts of the residuals. A value of the cost function is computed for the selected set of values of the unknowns. All such procedures are repeated for other sets of values of the unknowns. Such sets span the ranges of values where the solution is deemed to lie. The solution in the first iteration is the set of values of the unknowns that relates to the minimum computed value of the cost function. In each subsequent iteration, a minimization of the cost function is performed around the solution estimated in the immediately preceding iteration. The final solution relates to the minimum value of the cost function over all the iterations. The inverse problem is solved without recourse to either analytical or numerical computation of derivatives. This provides stability and simplicity to the algorithm. The MATLAB code of the algorithm is set forth. The code is assessed using field data from two aerial magnetic surveys.     

重型燃气轮机叶片离心载荷下应力特性的研究

针对重型燃气轮机叶片疲劳寿命研究的需要,通过设计和搭建的全尺寸叶片疲劳试验装置,模拟离心载荷工况下的低周疲劳试验,开展离心载荷下叶片应力分布和疲劳寿命预测的研究。该全尺寸叶片疲劳试验装置能够模拟低周疲劳中的等效离心载荷工况,为叶片试验提供必要的条件和手段。同时,对叶片进行网格划分和有限元仿真计算后,得到叶片Von mises应力分布结果,发现叶身应力最大处位于中部偏下边缘薄壁侧。然后将有限元仿真及应力试验相结合,提出叶片疲劳试验的离心载荷等效方法。在此基础上完成叶片的动应力试验,获得应力时间历程数据,并且给出离心载荷应力谱。结果表明,叶身中部边缘的应力水平最高,动应力谱幅值与频数概率的分布服从6阶麦克劳林拟合函数,用等效离心载荷疲劳寿命进行叶片寿命预测的结果是偏安全的,该结论可作为优化设计和试验研究的参考依据。     

焊点对于汽车B立柱刚度影响的数值分析

汽车B柱是车身结构中非常重要的安全件,要求其具有很高的刚度,点焊是B柱组装过程中的必要工序,点焊焊点的间隔距离对汽车B立柱刚度也有着明显影响。本研究应用CATIA三维造型软件对国产某小型轿车的侧面碰撞关键部件B立柱进行了三维建模,并用大型通用有限元软件ABAQUS对其进行了碰撞计算分析,研究了焊点分布与间隔距离对B立柱结构刚度的影响。结果表明,B柱刚度随焊点间距的增加而降低,当焊点的间距为70mm左右时,汽车B立柱刚度表现较好,而焊点间距小于70mm时B柱刚度上升不明显,考虑到经济性及工艺可行性,B柱焊点间距应该控制在70mm左右。     

基于激光扫描的环形锻件径向尺寸测量方法

在环形锻件环轧成形过程中,径向截面尺寸数据在很大程度上影响着环形锻件的锻造精度。由于轧制环境的复杂性以及高强度的噪声干扰,扫描数据量很大,据此测量得到的径向尺寸精度较低,因此,提出了一种环形锻件径向截面尺寸测量新方法。对激光扫描数据建立信息空间集合,并以连续的同心圆划分信息空间;根据信息空间内各区域间的信息关系,引入一致连续性系数并结合梯度下降法来求解待定系数;根据扫描数据点密度设定精简比率,结合精简比率与待定系数来确定每一同心圆各部分需要保留的点数,删去其余点及两同心圆相交部分的重复点;重复上述方法遍历激光扫描数据,对环形锻件的径向截面激光扫描数据进行处理。将该测量方法应用在实验中,从处理后的激光扫描径向截面形线数据中提取径向截面各尺寸数据,将处理前后所测得的数据与真实值进行对比,发现处理后得到的数据精度更高,误差更小,证明了该方法的可行性。     

Application of equi-potential lines method for accurate definition of the deforming zone in the upper-bound analysis of forward extrusion problems

Prediction of the optimal pressure is one of the objectives in the die design for the extrusion process. In this study, the concept of Equi-Potential Lines (EPLs) was applied for an accurate definition of the deforming zone in the upper-bound solution of the extrusion process. To implement the concept for the extrusion process, the initial and final shapes were considered and two different potentials were assigned to these. Then, the EPLs were drawn between the two shapes while minimizing the work path from the initial billet to the desired final shape. Bilinear, cubic Bezier, and polynomial curves were used for the definition of the deforming zone. It was shown that the coefficients of cubic Bezier curve could be replaced by the values obtained from the EPLs method. Moreover, accurate 3D streamlines representing material flow path in the deforming zone were obtained from the present method. Finally, forming pressures in the extrusion process were computed using the proposed geometry. To show the effectiveness of the proposed method, the estimated values were compared with experimental results. It was shown that the proposed method had a remarkable agreement with the experimental results.     

环境胁迫响应的潜在故障适应性修复方法

工业生产系统在运行过程中不可避免地要面临各种环境因素的随机波动,由此会引起系统性能波动而造成设备故障发生。以运行阶段系统所处的环境因素为研究对象,对环境因子和环境敏感系统进行说明,并对温度、湿度、振动等环境胁迫因子对设备系统性能的影响进行分析。针对环境敏感系统提出环境胁迫响应模型：在环境胁迫条件下,系统性能下降处于潜在故障状态时,利用传感器对环境因子进行监测,并根据监测数据构建转录因子阵列和状态酶阵列,转录因子启动环境修复方案并配合状态酶调控其运行程度进行环境适应性修复,避免潜在故障持续造成功能故障,保障系统的正常运行。通过对空分流程进行模拟,验证了该模型方法的有效性。     

正交轴色谱仪设计与样机研制

以正交轴色谱仪为对象,研究结构设计与样机研制。首先,根据设计要求对其进行结构设计,综合出合适的机械构型并根据动量矩定理对其进行动力学分析,得出驱动力矩;然后,对机械构型进行模态分析,得出机械构型的薄弱环节;最后,针对薄弱环节进行结构优化,在此基础上搭建物理样机,并通过相关的实验测试来分析样机的分离效率及其影响因素。结果表明:在一定范围内,随转速的增加,样机的固定相保留率增大,分离效率增高,当转速达到800 r/min时,固定相保留率最大,当转速超过800 r/min时,固定相保留率减小,分离效率降低,而当样机转速一定时,样机中液体的流速越大,固定相保留率越低。     

基于 RP-EKF 的无人机动力系统参数辨识

针对无人机动力系统电池电压波动导致系统噪声大、辨识结果精度低的问题,本研究提出了一种基于反向预测-增广卡尔曼滤波(RP-EKF)的无人机动力系统参数辨识方法。首先构建增广参数矩阵,将压降噪声模型考虑入辨识环节,其次提出反向预测卡尔曼滤波算法,设定新息平方比阈值,计算原始预测新息平方与反向预测新息平方的比值,通过对比预测新息比与阈值完成过程噪声调整并实现估计模型修正。实验结果表明,本文提出的基于RP-EKF的参数辨识方法,平均误差为39.22 rpm,均方根误差为55.85 rpm,平均相对偏差为0.85%,相比于最小二乘算法与卡尔曼滤波算法,本文方法辨识结果平均误差分别提高41.51%和22.26%,均方根误差提高49.63%和13.0%,平均相对偏差提高41.7%和22.7%。本文提出的算法拥有更高的辨识精度。     

Identification of acoustic wave propagation in a duct line and its application to detection of impact source location based on signal processing

For the detection of the impact location in a pipeline system, the correlation method has been the conventional method. For the application of the correlation method, the diameter of a duct should be small so that the acoustic wave inside the duct can propagate with nondispersive characteristics, in the form of, for example, a plane wave. This correlation method calculates the cross-correlation between acoustic waves measured at two acceleration sensors attached to a buried duct. It also gives information about the arrival time delay of an acoustic wave between two sensors. These arrival time delays are used for the estimation of the impact location. However, when the diameter of the duct is large, the acoustic waves inside the duct propagate with dispersive characteristics owing to the reflection of the acoustic wave off of the wall of the duct. This dispersive characteristic is related to the acoustic modes inside a duct. Therefore, the correlation method does not work correctly for the detection of the impact location. This paper proposes new methods of accurately measuring the arrival time delay between two sensors attached to duct line system. This method is based on the time-frequency analyses of the short time Fourier transform (STFT) and continuous wavelet transform (CWT). These methods can discriminate direct waves (non-dispersive waves) and reflective waves (dispersive waves) from the measured wave signals through the time-frequency analysis. The direct wave or the reflective wave is used to estimate the arrival time delay. This delay is used for the identification of the impact location. This systematic method can predict the impact location due to the impact forces of construction equipment with more accuracy than the correlation method.     

中比转速离心泵无过载优化设计

对D450-60-10型中比转速离心泵进行无过载优化设计,原始方案采用模型换算法设计模型泵进行试验并换算得到原型泵性能,同时利用Fluent模拟得到模型泵和原型泵性能,对泵性能分析后提出基于叶片出口角、叶轮出口直径和叶轮出口宽度等结构参数的3种原型泵优化方案。结果表明:当叶片出口角β2=10°时,与β2=15°相比,功率曲线的拐点更接近额定工况点,且最大功率下降了6.78%,但会牺牲部分扬程;3种优化方案下离心泵都达到了无过载的要求,功率备用系数K均小于1.2;最佳方案(叶轮出口直径D2=0.49m,叶轮出口宽度b2=0.03m,叶片出口角β2=10°)的功率备用系数最低,为1.09,与原始方案相比,扬程和效率分别提高了6.94%、1.95%,为中比转速离心泵无过载设计提供了参考。     

Temperature and ageing condition effects on the characterization of acrylic bone cement

This study investigates the effect of the environmental temperature and ageing condition on the characterization of acrylic bone cement. The tests were performed according to ISO 5833. The testing parameters were allowed to vary within the limits defined by the standard, in order to assess their effect on the results of the test. In certain cases the tests were also performed under conditions which the standard does not provide for but which are likely to occur clinically. This investigation showed that the cement behaviour may also change in the temperature range specified in the standard. Therefore, it is deemed appropriate to correlate the curing parameters of the bone cement to the environmental temperature, performing the test at different temperatures. In this way the effect of temperature on the duration of the phases in the cement curing could be assessed. The resultant graphical representation of the effect of temperature on the duration of the phases in cement curing has direct clinical relevance. Furthermore, this study showed that the ageing conditions of the mechanically tested specimens affected the results. Hence, it is deemed advisable to modify the ageing conditions of the specimens, fixing them closer to the in vivo conditions.     

电弧增材成形单道两层熔积过程中的晶粒生长模拟

晶粒生长的数值模拟是研究复杂微观组织演变的重要手段,现有的研究较少涉及电弧增材成形中晶粒生长的数值模拟。采用有限元和元胞自动机方法建立了碳钢电弧增材成形过程的宏观传热和微观组织演变的耦合模型,模拟单道第两层熔积的熔池凝固过程中晶粒动态演变过程。模拟结果显示,单道第一层熔积熔池凝固过程中晶粒从熔合线位置形核后向熔池中心生长,在温度梯度方向与枝晶臂优先生长方向的共同作用下,枝晶呈现竞争生长,晶粒优先生长方向与温度梯度方向一致的晶粒生长更快,部分晶粒生长被抑制,最终形成交错、完全粗大的柱状晶组织,枝晶之间出现溶质富集的现象;单道第二层熔积的晶粒在上一层粗大柱状晶基础上形核并生长,随后的生长过程与第一层类似,第二层熔积时熔池温度梯度方向的改变导致晶粒的主要生长方向与第一层之间有一定夹角。与模拟相同成形工艺的成形试样金相照片验证了模拟结果。研究结果可为电弧增材成形微观组织控制以及后续工艺规划提供依据和参考。