一种用于电子远传水表机电转换可靠性试验的装置

机电信号转换可靠性是关系到直读式电子远传水表产品质量好坏的关键指标。本文研制了一套基于数字图像识别的直读式电子远传水表机电转换可靠性试验非实流自动检测装置,介绍了该装置的组成和工作原理;设计了装置的机械定位转动机构,选用西门子S7-200作为下位机控制器的核心,实现系统的运动控制;采用Delphi7.0开发上位机软件程序,实现人机交互和数据存储。     

A Universal Distribution for Component Failure Times

It is proposed to use a mixture of Weibull and exponential distributions to describe component reliability on the basis of a realistic model for resource consumption.     

Estimation of the Parameters of a Mixture of Exponential and Weibull Distributions with Progressive Censoring

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions using censored samples. Preliminary estimates obtained by graphical analysis are refined by the method of maximum likelihood. The efficiency of the method is confirmed by the results of a statistical modeling.     

性能贮存可靠性评估及贮存寿命预测方法

在介绍贮存可靠性与条件贮存可靠性的基础上,针对一次性产品的性能贮存可靠性试验的特点,提出了性能贮存可靠性评估及贮存寿命预测的基本思路和方法。通过算例说明了本文提出的评估和预测思路的可行性与合理性,同时也分析了这种贮存可靠性评估和寿命预测方法对于一次性产品的适用范围。     

Reliability analysis of electronic devices with multiple competing failure modes involving performance aging degradation

This paper presents an extension of reliability analysis of electronic devices with multiple competing failure modes involving performance aging degradation. The probability that a product fails on a specific mode is derived. Using this probability, the dominant failure mode on the product can be predicted. A practical example is presented to analyze an electronic device with two kinds of major failure modes–solder/Cu pad interface fracture (a catastrophic failure) and light intensity degradation (a degradation failure). Reliability modeling of an individual failure mode and device reliability analysis is presented and results are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

利用可靠性模型确定电子测量设备检定周期的方法

周期检定是保障计量器具能够准确可靠地开展测量活动的重要手段.检定周期的长度影响计量器具测量活动的可靠性和计量工作的经济性.本文通过建立电子测量设备测量可靠性与使用时间关系的数学模型提出了利用可靠性模型确定电子测量设备检定周期的可靠性评估法.该方法可以有效地保证电子测量设备检定周期制定的科学性.     

基于可靠性的智能电子标签壳体方案优化设计

目的为了不影响外包装的总体结构和包装方式,对安装在外包装上的电子标签进行微型化设计。同时,针对电子标签壳体可能由于外部特殊情况造成破损的情况,对其进行可靠性分析。方法通过Ansys软件对基于空间最大化原则设计的壳体的抗压、抗冲击性进行仿真分析。结果在z方向施加了2 MPa的压强下最大变形量为2.8 mm,不能满足抗压性需求,进而提出了基于结构最优化原则的壳体设计方案。经仿真分析,壳体z方向在2 MPa静压的最大变形量为0.2 mm,较优化前降低了2.6 mm。结论智能电子标签经过优化后,具有微型化、高可靠性的特点,满足系统的应用需求。     

Effect of Field Stress Variance on Test to Field Correlation in Accelerated Reliability Demonstration Testing

This paper discusses the effect of field stress variance on the value of demonstrated reliability. In many cases, the acceleration factor for a reliability demonstration test is calculated based on a high percentile field stress level, typically corresponding to severe user or environmental conditions. In those cases, the actual field reliability for the population will be higher than that demonstrated by the test. This paper presents a mathematical approach to estimating ‘true’ field reliability based on the acceleration model and stress variable distribution over the product field population. This method is illustrated by an example of automotive electronics reliability demonstration testing and has a wide range of practical applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Reliability analysis of Weibull multicomponent system with stress-dependent parameters from accelerated life data

In this paper, reliability estimation of multicomponent system under a multilevel accelerated life testing. When the lifetime of components follows Weibull distribution, the problem of point and interval estimates are discussed from different perspectives. Under a general life-stress assumption that there are multiple nonconstant and stress-dependent scale and shape parameters, the maximum likelihood estimates of unknown parameters along with associated existence and uniqueness are established. Approximate confidence intervals are constructed correspondingly via expected Fisher information matrix. Furthermore, some pivotal quantities are constructed and alternative generalized point and interval estimates are also proposed for comparison. In addition, predictive intervals for the lifetime of the multicomponent system are discussed under classical and generalized pivotal approaches, respectively. The results show that the proposed generalized estimates are superior to the conventional likelihood approach in terms of the accuracy. A real data example is carried out to illustrate the implementations of the proposed methods.     

基于贝叶斯-GO综合法的快递配送系统可靠性研究

提出用贝叶斯-GO综合方法分析快递配送系统可靠性。首先综合考虑配送系统对时间、品质、服务可靠性的要求,详细分析配送工作流程及其影响因素,建立GO图;然后根据映射规则转换为贝叶斯网络,最后通过案例分析,利用贝叶斯网络正反向推理和敏感度分析,得到系统的薄弱环节及其主要影响因素。研究结果表明：贝叶斯-GO综合法克服了单独使用GO法逻辑运算复杂繁琐的缺点,能够快速找到快递配送系统的薄弱环节及其主要影响因素,其中收件子系统故障率最高,快递员的配送不及时、寄件损坏、丢失是主要影响因素。     

A study of time‐between‐events control chart for the monitoring of regularly maintained systems

Owing to usage, environment and aging, the condition of a system deteriorates over time. Regular maintenance is often conducted to restore its condition and to prevent failures from occurring. In this kind of a situation, the process is considered to be stable, thus statistical process control charts can be used to monitor the process. The monitoring can help in making a decision on whether further maintenance is worthwhile or whether the system has deteriorated to a state where regular maintenance is no longer effective. When modeling a deteriorating system, lifetime distributions with increasing failure rate are more appropriate. However, for a regularly maintained system, the failure time distribution can be approximated by the exponential distribution with an average failure rate that depends on the maintenance interval. In this paper, we adopt a modification for a time‐between‐events control chart, i.e. the exponential chart for monitoring the failure process of a maintained Weibull distributed system. We study the effect of changes on the scale parameter of the Weibull distribution while the shape parameter remains at the same level on the sensitivity of the exponential chart. This paper illustrates an approach of integrating maintenance decision with statistical process monitoring methods. Copyright © 2008 John Wiley & Sons, Ltd.     

医疗设备使用风险评估中的FMECA新方法

基于FMECA的风险分析方法可以帮助医疗机构更加有效地评估、控制医疗设备的使用风险。根据医疗设备的使用特点,利用模糊数学与灰色关联理论对方法进行改进,可更为客观地得出各风险模式的模糊评价结果和优先控制顺序。新方法以C臂机的风险分析为实例,说明其改进和应用过程。新方法扩展了FMECA的应用领域,为医疗设备的科学管理提供了依据。     

AZ31镁合金微结构关联的孪生形核与长大统计分析

为了揭示金属镁合金晶粒大小、晶向及晶界倾角等微结构与孪生形核及长大之间的关联性,通过EBSD技术获取大量诸如晶粒尺寸、晶向及晶界倾角等微结构以及晶内孪生形核数、孪晶厚度等数据进行统计分析。对应变为4.9%的镁合金微结构的统计分析表明:晶粒大小、晶界倾角等微结构分布基本符合概率函数Weibull分布特征;大晶粒、高Schmid因子、小角度晶界有利于孪生形核,而孪晶长大对微结构的敏感度较弱;不是所有高Schmid因子的孪生变体都能够形核长大。由对孪生形核与长大随应变递增的演化分析结果可推测:相同晶粒内,不同位置对孪晶变体的形核强度有显著影响,很显然存在其他晶内微结构如缺陷、位错密度等对孪生形核产生重要影响;然而孪晶长大更多地受到晶内存在的孪生形核数和孪晶变体类型数量的强烈影响。本工作可为发展孪生形核长大与微结构的数学关系提供试验依据。