Optimum Simple Step-Stress Plans for Accelerated Life Testing

This paper presents optimum plans for simple (two stresses) step-stress tests where all units are run to failure. Such plans minimize the asymptotic variance of the maximum likelihood estimator (MLE) of the mean life at a design stress. The life-test model consists of: 1) an exponential life distribution with 2) a mean that is a log-linear function of stress, and 3) a cumulative exposure model for the effect of changing stress. Two types of simple step-stress tests are considered: 1) a time-step test and 2) a failure-step test. A time-step test runs a specified time at the first stress, whereas, a failure-step test runs until a specified proportion of units fail at the first stress. New results include: 1) the optimum time at the first stress for time-step test and 2) the optimum proportion failing at the low stress for a failure-step test, and 3) the asymptotic variance of these optimum tests. Both the optimum time-step and failure-step tests have the same asymptotic variance as the corresponding optimum constant-stress test. Thus step-stress tests yield the same amount of information as constant-stress tests.     

Optimum Censored Accelerated Life Tests for Normal and Lognormal Life Distributions

This paper presents optimum accelerated life test plans for estimating a simple linear relationship between a stress and the median of product life which has a s-normal or lognormal distribution when the data are analyzed before all test units fail. Also, plans with equal numbers of test units at equally spaced test stresses are compared with the optimum plans. The plans are illustrated with a temperature-accelerated life test of electrical insulation.     

一种步进应力加速寿命试验数理统计分析法

本文提出了处理步进应力加速寿命试验的“时间等效”数学模型,并用它把寿命分布服从对数正态分布(或威布尔分布)、有m步的一次步进应力加速寿命试验变为有m级应力的恒定应力加速寿命试验来分析处理.并且推导出了它们之间的变换计算公式.用本法处理质子轰击隔离WC56型砷化镓场效应管步进应力加速寿命试验,获得了满意的结果.     

Accelerated Life Testing?Step-Stress Models and Data Analyses

This paper presents statistical models and methods for analyzing accelerated life-test data from step-stress tests. Maximum likelihood methods provide estimates of the parameters of such models, the life distribution under constant stress, and other information. While the methods are applied to the Weibull distribution and inverse power law, they apply to many other accelerated life test models. These methods are illustrated with step-stress data on time to breakdown of an electrical insulation.     

竞争失效产品步进加速寿命试验的优化设计

对weibull分布竞争失效产品的步进加速寿命试验进行优化设计,首先选取产品正常应力下中位寿命的极大似然计估渐近方差的估计值作为优化目标函数,并对优化目标函数进行统计推断.然后利用目标函数的连续性,提出基于离散数据的函数拟合方法,将试验优化设计转化为显函数的约束极值求解问题,同时将智能优化算法应用到步进加速寿命试验的优...     

光模块加速寿命试验最佳测试温度的确定方法

为了确定小型可热插拔式(SFP)光模块寿命试验所需的最短时间,提出了基于加速因子最大化的最佳测试温度的确定方法。首先,利用阿伦尼斯模型证明了温度的选择不会改变寿命预测结果,并讨论了加速因子取极大值的条件。然后利用步进温度实验获得的驱动电流随测试温度变化的曲线给出了最佳测试温度的确定方法。最后,计算分析表明由于驱动电流受温度的影响,在最佳测试温度下进行光模块寿命试验仍然很困难。     

Optimal Step-Stress Accelerated Degradation Test Plan for Gamma Degradation Processes

Step-stress accelerated degradation testing (SSADT) is a useful tool for assessing the lifetime distribution of highly reliable products (under a typical-use condition) when the available test items are very few. Recently, an optimal SSADT plan was proposed based on the assumption that the underlying degradation path follows a Wiener process. However, the degradation model of many materials (especially in the case of fatigue data) may be more appropriately modeled by a gamma process which exhibits a monotone increasing pattern. Hence, in practice, designing an efficient SSADT plan for a gamma degradation process is of great interest. In this paper, we first introduce the SSADT model when the degradation path follows a gamma process. Next, under the constraint that the total experimental cost does not exceed a pre-specified budget, the optimal settings such as sample size, measurement frequency, and termination time are obtained by minimizing the approximate variance of the estimated MTTF of the lifetime distribution of the product. Finally, an example is presented to illustrate the proposed method.      

指数分布步加试验的贝叶斯估计

给出了一种基于Gibbs抽样、CE模型下指数分布场合步进应力加速寿命试验的贝叶斯估计.通过模拟例子表明贝叶斯估计比极大似然估计更加有效.     

基于LSM的红外LED加速寿命试验数据的统计分析

利用最小二乘法(LSM)完成了红外发光二极管(LED)恒定与步进应力加速寿命试验数据的统计分析,并自行开发了可视界面和通用性强的寿命预测软件.数值结果证实了红外LED的寿命服从对数正态分布以及加速寿命方程完全符合逆幂定律,并精确地计算出预测该器件寿命所用到的关键性参数,从而使其在很短的时间(1000h)内估算寿命成为可能.     

基于Matlab的序加试验数据的改进处理方法

利用Matlab编程工具,提出温度作为加速应力的序加试验数据的改进处理方法.改进后的方法采用序进温度应力加速样品老化,基于参数退化数据提取失效激活能和寿命外推所需要的参数,无需待样品完全丧失功能即可停止试验,从而提高试验效率.试验数据处理结果表明,新方法得到的样品平均寿命与多年来统计的现场数据一致,验证了该方法的正确性.通过与原方法进行比较,验证了新方法具有简便、高效的特点.     

基于步进加速退化试验的某型电连接器可靠性评估

某导弹电连接器属于高可靠性、长寿命产品,在短时间内很难获取其失效数据。为了评估其可靠性,在分析其失效机理的基础上设计了步进应力加速退化试验,通过分析加速退化数据外推出产品在正常工作应力水平下的可靠度函数。试验中,以电连接器的接触电阻作为性能参量,选取温度作为加速应力。数据分析时利用Wiener随机过程对样品退化进行建模,为了提高模型参数的估计精度,采用极大似然法对所有性能退化数据进行整体统计推断。结果表明,提出的基于加速退化数据分析的方法实用、有效,实现了某导弹电连接器的可靠性评估并可为其他高可靠性产品的可靠性评估工作提供参考。     

高加速寿命试验和高加速应力筛选技术

文中简单介绍高加速寿命试验和高加速应力筛选（HALT＆HASS）技术,重点从其原理、试验方法阐述该技术如何缩减研发时间与成本,达到提高产品可靠性和增强市场竞争力的目的。     

Graphical Analysis of Accelerated Life Test Data with the Inverse Power Law Model

In this paper, graphical methods are presented for analyzing accelerated life test data with the inverse power law model, when all test units are run to failure. The inverse power law model is described, and graphical methods for estimating its parameters from such complete data are given. These methods are illustrated with accelerated test data on time to breakdown of an insulating fluid. While the methods are presented with the inverse power law model, they can be used for analyzing many other accelerated life test situations. These methods are presented so that they can be used by individuals with a limited statistical background.     

Graphical Analysis of Accelerated Life Test Data with a Mix of Failure Modes

An accelerated test of a product under high stress yields life data that are extrapolated to estimate the life distribution at low stress. When the data contain competing failure modes, the dominant modes under high stress may not dominate under low stress. This has made experimenters doubt the validity of tests yielding such data. This expository paper presents new graphical methods for estimating: 1) a separate relationship between life and stress for each failure mode, 2) the life distribution at low stress when all modes act, and 3) the life distribution that would result if certain modes are eliminated. Data from a temperature-accelerated life test of electrical insulation illustrate the methods.     

Analysis of Accelerated Life Test Data?Least Squares Methods for the Inverse Power Law Model

This expository paper presents simple least squares methods for analyzing accelerated life test data with the inverse power law model, when all test units are run to failure. These methods are illustrated with accelerated test data on time to break-down of an insulating fluid.     

Likelihood Inference for Life Test Data

This paper reviews the basic ideas of likelihood inference and applies them to some reliability and life testing problems connected with the exponential distribution. Various censoring schemes are considered and the likelihood approach is shown to provide a unified framework for treating exact solutions to estimation, prediction, and population-comparison problems. These solutions are provided in a well defined but non-probabilistic form. The classical s-confidence procedures depend strongly on imaginary exact repetitions of the form of the experiment being analyzed. This is often unrealistic and impractical. The data on hand can be directly analyzed by examining the likelihood function.     

Probability Limits for Life Test Data

In this paper a general theory for constructing probability limits for life test data is briefly discussed. It is then applied to a set of life test data to determine which of three specified Weibull distributions give the best fit.     

LED可靠性评估的加速寿命试验设计方法

介绍了一种关于发光二极管（LED）可靠性评估的加速寿命试验设计方法。通过这个方法,在针对LED的性能退化现象和运行不稳定问题进行加速试验设计时,可以在已知目标可靠度和置信度的前提下,定量地确定满足可靠性要求的试验用样本量、加速应力水平以及试验时间。同时,用于发光二极管加速寿命试验的基本设计思想,可以广泛地应用于常见电子元器件的器件产品质量认证或可靠性评估等试验设计中。     

大功率LED加速寿命试验及问题分析

采用国家标准(GB1772)规定的电子元器件加速寿命试验方法,选择了工作环境温度作为加速应力,设计了四个应力等级的大功率LED加速寿命试验方案并进行试验.试验结果为每个应力等级下的失效模式有2～3种,不同应力级别确定的激活能有一定的差异.通过对金丝引线球焊处开裂、金属化层失效等主要失效机理的产生原因以及温度、电流密度之间关系分析,认为基于Arrhenius模型进行大功率LED加速寿命试验存在不足和缺陷,不能准确地预测稳态温度下的LED寿命,应当对Arrhenius模型进行修正.