A study on life evaluation & prediction of railway vehicle contactor based on accelerated life test data

In this recent tendency, an accelerated life test (ALT) is used to evaluate stability and reliability of machinery parts and systems for short periods. As ALT is performed by applying high stress compared to normal use conditions in a short time, we can rapidly evaluate the life of the machinery and obtain reliability values. In this paper, we conduct the accelerated life test for a railway vehicle contactor, constructing the real-time monitoring system. Based on ALT data, we can determine the contactor's failure mode and mechanism, and estimate reliability values. Consequently, we will examine the method of evaluating the life of railway vehicle contactors through an estimation of the interesting value - relationship between life and stress, mean time to failure (MTTF), percentile B100P life etc. in normal use conditions.     

串并联系统可靠度置信区间估计

针对复杂系统可靠性试验非常少甚至没有做的情况，提出了基于单元信息进行可靠性综合的方法。该方法不需假设系统或单元产品的寿命服从某一分布，减少了因寿命分布选择不当所造成的可靠性和方差的误差。在获得单元可靠性的均值和方差的基础上，利用系统可以分解为单一的串联或并联关系，通过逐步综合获得复杂系统的可靠性均值和方差估计值。利用系统信息熵原理，将部件的试验数据折合为系统的试验数据，获得系统的子样数。由此提出了小子样下的系统可靠性置信区间估计新方法，该方法只假设系统可靠性估计服从正态或对数正态分布。新方法使用限制少，计算简单，适用于系统数据较少的可靠性分析。     

基于定时测试的综合应力加速寿命试验方案优化设计

针对定时测试综合应力加速寿命试验设计问题,就恒定应力加速寿命试验方法,根据所提出的加速寿命试验方案优化设计的准则和方法,以产品在正常工作应力水平时寿命估计值的方差最小为目标,在确定了每个应力水平组合下定时测试时间获取方式后,以各加速因子的试验应力水平、各次试验的试样分配比例及各次试验的截尾时间为设计变量,应用极大似然估计理论,建立了定时测试综合应力加速寿命试验方案优化设计的数学模型.对航天电连接器的定时测试综合应力加速寿命试验方案优化设计的结果表明,经过优化以后的定时测试试验方案不仅可以提高试验数据的估计精度、减少试验次数,而且还可以在相同置信度下减少试验所需的样本数量,并能够缩短试验时间.     

基于设备状态振动特征的比例故障率模型可靠性评估

基于概率统计的传统可靠性评估方法一般依赖于失效寿命数据。但失效寿命数据需要通过寿命试验和加速寿命试验获取,对于大量的实时工作设备采用这种方法是不适宜的。这种情况下,基于设备状态的性能退化数据能够提供可靠性评估的重要信息。在集成失效数据可靠性建模技术和基于设备状态的振动信号特征提取的基础上,提出设备状态振动特征的比例故障率模型可靠性评估的新方法。该方法可以把底层信息(如设备运行状态特征的方均根、峭度)与高层信息(如可靠性统计学)之间建立联系,适合设备运行可靠性参数的估计,并能够提供有效的可靠性评估,为设备以可靠性为中心的基于状态的预防维修提供技术支持。通过在铁路机车轮对轴承上的应用实例说明该方法的合理性和有效性。     

Accelerated life testing of nano ceramic capacitors and capacitor test boards using non-parametric method

Engineers are searching for a reliable method to determine the time-to-failure (TTF) data of the electronic systems as cheaper as possible. Reliability plays a vital role in electronic devices marketing & sales, product quality, etc. Accelerated Life Test (ALT) and Highly Accelerated Life Testing (HALT) are the latest methodology in the field of life testing of engineering systems. The ALT can be conducted at higher stress level to generate more failure data within short duration of time. The parametric method and non-parametric method are used to convert the accelerated test condition to actual condition. In this paper, the most widely used C0G and X7R nano ceramic capacitor is selected to generate the time-to failure data at accelerated condition and non-parametric method is used to convert the accelerated condition data into actual condition.     

Identifying joints from measured reflection coefficients in beam-like structures with application to a pipe support

The properties of joints in mechanical systems are notoriously uncertain causing corresponding uncertainty in the systems’ dynamic responses. A piping system is one such example where an accurate knowledge of joint properties is useful for the purposes of structure-borne sound transmission, fatigue considerations and structural health monitoring. This paper presents an inverse technique that is applicable to joint estimation in one-dimensional structures such as a pipe. Measured wave reflection coefficients are used which have several advantages over modal information. First, they characterise just the joint and adjacent pipes and are independent of the rest of the built-up system. Second, they are potentially more sensitive to the joint parameters in question than are modal parameters.The method is illustrated by means of an experimental case study featuring a straight pipe suspended by a cantilevered hanger. The stiffness and inertia of the hanger are accurately identified from measured data at frequencies significantly higher than the fundamental modes of the structure.     

某轿车前副车架服役载荷模拟试验加速方法研究*

服役载荷模拟试验能准确地预测零部件的疲劳寿命。为节省试验时间,急需开发出一套合理、实用的加速试验方法。重点研究在不具备结构局部应变响应,仅具备外部激励载荷如力、位移、和加速度等情况下的试验加速方法。基于修正Miner准则,以伪损伤保留比例作为小载荷删除准则,并结合疲劳数据编辑(Fatigue data editing, FDE)技术,提出一套便于工程应用的服役载荷模拟试验加速方法。以某轿车前副车架的疲劳试验为例,分别编制伪损伤保留比例为99%、95%和90%的加速谱。综合考虑各加速谱的载荷特征和加速效果,选用95%加速谱、90%加速谱和原始谱分别建立台架试验。试验结果表明两种加速谱在有效节省试验时间的同时,均获得了与原始谱相同的试验结果,且90%加速谱的加速试验效果更为显著。本方法便于工程应用,可为其他汽车零部件的服役载荷模拟试验提供参考。     

步进加速寿命试验及参数估计

阐述了加速寿命试验技术的基本原理、方法，定义了适合步进加速随机振动试验的过载系数．提出了定数截尾步进应力加速寿命试验数据的参数估计方法，在加速寿命试验具备4个假设条件的基础上建立了时间等效模型，通过结合随机振动的加速试验曲线公式建立的时间等效模型，并利用历史数据首先确定参数b，以实现各级应力下的试验时间等效折算。采用改进的极大似然法(MMLE)、最好线性不变(BLIE)和线性回归技术估计威布尔分布中的未知参数。根据随机振动试验结果对3种参数估计方法的有效性进行了分析。     

Design hazards of electrosurgical devices.

The tremendous lifesaving value of adjunct electrosurgery to the medical profession is not without potential hazards. The hazards, which can be classified as radio-frequency burn hazards, shock hazards, electrocution hazards, and explosion hazards, may result from equipment design circuitry, possible failure modes, or operator error. The three basic electrosurgery systems currently being marketed--grounded output systems, referred-to-ground output systems, and floating output systems--are described, and the hazard potential of each system, as well as the hazard potentials of modifications of these systems, are identified. The authors propose a safety system to eliminate most of the hazards cited for the other systems, recommend minimum circuit performance requirements, and evaluate an electrosurgery standard.     

基于应力波分析的状态监控与故障预测研究

随着先进的仪器测量与分析、物联网、云计算、数据挖掘、人工智能等科学技术的发展,设备状态监控和故障预测技术近年来在工业设备健康管理中起到越来越重要的作用。研究了一种基于应力波分析的状态监测与故障预测技术,通过应力波传感器对设备运动部件间的摩擦、机械冲击和动态荷载的电子信号进行检测和处理,采用专为应力波分析而开发的时域和频域特征提取软件和基于神经网络的数据融合技术,对设备状态进行定量分析,对设备故障进行准确预测,并提供设备健康诊断分析报告。运行试验表明,与振动分析等传统的状态监测方法相比,本系统能更好地实时监控设备运行情况,更早地预测故障,保证了生产安全性,降低了设备检维修成本,提高了生产效率。     

大型机泵健康监测与诊断系统设计与应用

该文着重介绍了一种自主研发的大型机泵设备健康监测与诊断系统,该系统具有数据采集、状态监测、异常报警、故障诊断等功能,能够及时、准确地推送设备的运行状态及可能存在的故障隐患,提高检修效率,延长设备寿命。以某化工厂为例,简述了该系统在工业领域中的应用。     

Urban rail track condition monitoring based on in-service vehicle acceleration measurements

Condition monitoring of railway tracks is essential in ensuring the safety of railway systems. Traditional track recording vehicles (TRV) can only carry out the track inspection in the midnight after all the service vehicles are off duty. One track line can be inspected only once or less in a month. The severe track condition degradation cannot be detected timely and there is potential safety hazard for the railway system. Therefore, the track condition monitoring based on in-service vehicle has been paid more attention in the recent years. In this paper, the track condition monitoring based on the bogie and car body acceleration measurements is presented. The track alignment information which can be derived from the bogie and car body sensor is investigated by using a mathematical model and the frequency response analysis. The track irregularities can be estimated by using the bogie and the car body acceleration sensors. The acceleration signals are preprocessing with a DC filter and a low pass filter. After that, the track alignments are obtained by double integrating the signals. Field tests are carried out in Shang Hai metro Line 1 for demonstrating the effectiveness of the proposed track inspection system.     

Multidimensional condition monitoring of machines in non-stationary operation

Many critical mechanical systems operate in a non-stationary regime (load), and many observed symptoms of its condition depend in a some way on a system load and/or environmental conditions. Hence the condition monitoring of a such systems ought to have some possibility of rescaling of observed symptoms to a standard load condition. This paper shows such a possibility of a symptoms rescaling in application to multidimensional vibration condition monitoring. It is shown on some real example of vibration condition monitoring, that rescaling of symptoms can make more reliable the assessment of current system condition, as well as its prognosis.     

Novel Accelerating Life Test Method and Its Application by Combining Constant Stress and Progressive Stress

Constant stress accelerated life tests (ALTs) can be applied to obtain a high estimation accuracy of reliability measurements, but these are time-consuming tests. Progressive stress ALTs can yield failures more quickly but cannot guarantee the estimation accuracy of reliability measurements. In this paper, a progressive-constant combination stress ALT is proposed to combine the merits of both tests. The optimal plan, in which the design variables are the initial progressive stress level, the progressive stress ramp rate, the sample allocation proportion of the progressive stress and the constant stress level, is determined using the principle of minimizing the asymptotic variance of the maximum likelihood estimator of the natural log reliable life for the connectors. A comparison between the optimal PCCSALT plan and the CSALT plan with the same sample size and estimation accuracy shows that the test time is reduced by 13.59% by applying the PCCSALT.     

基于性能退化模型的万能式断路器操作附件实时剩余寿命预测

针对万能式断路器操作附件的个体差异性以及在实际使用过程中动作不频繁的特性,提出一种基于性能退化模型的万能式断路器操作附件实时机械剩余寿命(RUL)预测方法。不同于传统的RUL预测方法,该方法融合了操作附件的历史退化数据与实时更新的状态监测(CM)数据。首先,考虑到操作附件性能退化过程具有线性非单调的特点,建立基于Wiener过程的操作附件性能退化模型;其次,对操作附件的历史退化数据采用极大似然估计法和一维搜索法确定模型参数的先验分布;然后,运用贝叶斯方法并结合操作附件实时更新的CM信息对模型参数进行迭代更新;基于首达时间的概念建立了RUL预测模型,以实现对断路器操作附件实时RUL的预测。最后,通过操作附件的寿命数据对本文所提方法进行验证,结果表明本文方法不仅可实现操作附件的实时剩余机械寿命预测,同时相较于其他文献方法具有更高的预测精度。     

基于M-BUS和GPRS的热量表耐久性远程监控系统的研究

针对热量表耐久性试验,该文设计了一套基于M-BUS总线、GPRS和数据采集卡的远程自动监控系统,可实时监控试验过程,实时记录、分析被检表及管路的动态信息并进行反馈补偿,在遭遇异常情况时自动报警,实现了试验的远程自动控制和耐久性质量分析,达到了热量表耐久性试验无人值守的目的。     

混合指数分布恒定应力加速寿命试验的统计分析

提出了一种分析加速寿命试验数据的方法。当产品具有多个失效机理时,设产品的寿命服从混合分布。研究了恒定应力加速寿命试验的统计分析问题,建立了统计分析的数学模型,给出了参数估计方法和估计量的渐近性质。最后以混合指数分布为模拟例子,表明本文的模型和方法在应用上是可行的和有效的。     

机械强度有限寿命设计专家工作站软件系统

对两种机械强度有限寿命设计专家工作站软件进行了介绍。车载式工作站软件配备有６个大型软件包：数据采集软件包ＰＣＭ、可编程交互式分析软件ＰＩＡＳ、信号分析软件ＳＰＡＳＳ、计数分级软件ＫＬＡＵＳ、疲劳强度 分析软件ＦＡＴＩＭＡＳ、图形软件包ＧＯＳＹ以及可选的结构有限元分析软件Ｉ－ＤＥＡＳ。便携式工作站软件系统包括４个大型软件包、：数据采集、数据分析、数据显示、疲劳寿命分析软件，对上述软件包的功能、使用方     

Novel Accelerating Life Test Method and Its Application by Combining Constan Stress and Progressive Stress

Constant stress accelerated life tests(ALTs) can be applied to obtain a high estimation accuracy of reliability measure?ments, but these are time?consuming tests. Progressive stress ALTs can yield failures more quickly but cannot guaran tee the estimation accuracy of reliability measurements. In this paper, a progressive?constant combination stress ALT is proposed to combine the merits of both tests. The optimal plan, in which the design variables are the initial pro?gressive stress level, the progressive stress ramp rate, the sample allocation proportion of the progressive stress and the constant stress level, is determined using the principle of minimizing the asymptotic variance of the maximum likelihood estimator of the natural log reliable life for the connectors. A comparison between the optimal PCCSALT plan and the CSALT plan with the same sample size and estimation accuracy shows that the test time is reduced by 13.59% by applying the PCCSALT.     

计及湿热效应的层板复合材料疲劳寿命的试验及数据处理方法

湿热环境严重影响复合材料的物理及力学性能 ,为研究湿热效应对疲劳寿命的影响 ,建立考虑湿热影响的复合材料疲劳性能试验方法。文中以剩余强度衰减模型为基础 ,对考虑湿热效应的层板复合材料的拉—拉疲劳性能试验的全过程进行介绍 ,阐述试件准备过程、试验中测试的项目 ,详细介绍基于剩余强度衰减模型中的参数的确定以及试验中试件个数确定的计算方法 ,并且指出试验中一些必要的注意事项 ,对试验中的有关数据处理也给出相应的理论基础。以此试验方法为基础可以方便地进行疲劳寿命的预测与分析