Human error analysis of a standby redundant system with arbitrarily distributed repair times

This paper presents human error analysis of a (two units working and one on standby) system with arbitrarily distributed repair times. The supplementary vairables method is used to develop the system availability expressions. A general formula for the system steady-state availability is developed when the failed system repair times are gamma distributed. Time-dependent availability, system reliability with repair, mean time to failure and variance of time to failure formulae are developed for some particular cases. Selective plots are shown to demonstrate the impact of critical human error on system availability and reliability.     

Comparative redundancy, an alternative to triple modular redundant system design

A new scheme for implementing highly reliable digital systems is proposed. The method has a circuitry overhead which is comparable to that of the triple modular redundancy (TMR) scheme, although it is shown to have a reliability, and more importantly a mean time to failure, improvement well beyond that expected from the standard TMR systems. The reliability and mean time to failure are both developed from a discrete state, continuous time, Markov model of the new system. The results for the reliability and mean time to failure characteristics for this new design of system, termed comparative redundancy, are compared to both TMR and a single unit.     

基于随机Petri网的通信网络性能评价

利用Petri网的动态描述能力,将Petri网应用到通信网动态可靠性分析上。通过分析网络故障的起因,把故障原因抽象为三个子故障系统。根据故障产生、消解的随机性,运用SPN建模,然后运算求解,得到网络可靠度的表达式。最后通过实例验证了方法的正确性。     

Reliability evaluation of systems with critical human error

This paper presents four mathematical models to evaluate reliability of redundant systems with critical human error. Equations for system reliability, state probabilities and mean time to failure are developed. System reliability and mean time to failure plots are shown.     

Stochastic analysis of a general standby system with constant human error and arbitrary system repair rates

This paper presents a mathematical model for performing reliability and availability analyses of a general standby system with constant human error and common-cause failure rates. In addition, system repair times are assumed arbitrarily distributed. Markov and supplementary variable techniques were used to develop equations for the model. The method of linear ordinary differential equation is developed to obtain the general expressions of the steady state availability. The Laplace transform technique was used to obtain the system time-dependent availability, reliability and mean time to failure expressions.     

Inspection frequency and availability of emergency equipment

A mathematical model has been developed which permits the investigation of the influence of human error during an inspection procedure on the availability of equipment used in emergency conditions. Two types of human error are considered: an error to detect failure of the equipment and an error which causes an inadvertent failure of the equipment during the inspection. The human reliability model based on THERP method is developed in the paper. Various levels of dependence between consecutive tastes are considered. An optimal inspection interval is found for exponential distribution of time to failure.     

Reliability test and failure analysis of high power LED packages

A new type application specific light emitting diode(LED) package(ASLP) with freeform polycarbonate lens for street lighting is developed,whose manufacturing processes are compatible with a typical LED packaging process.The reliability test methods and failure criterions from different vendors are reviewed and compared.It is found that test methods and failure criterions are quite different.The rapid reliability assessment standards are urgently needed for the LED industry.85℃/85 RH with 700 mA is used to test our LED modules with three other vendors for 1000 h,showing no visible degradation in optical performance for our modules,with two other vendors showing significant degradation.Some failure analysis methods such as C-SAM,Nano X-ray CT and optical microscope are used for LED packages.Some failure mechanisms such as delaminations and cracks are detected in the LED packages after the accelerated reliability testing.The finite element simulation method is helpful for the failure analysis and design of the reliability of the LED packaging.One example is used to show one currently used module in industry is vulnerable and may not easily pass the harsh thermal cycle testing.     

Reliability and availability analysis of transit systems

This paper presents three newly developed Markov models representing on-surface transit systems. Transit system reliability, steady-state availability, mean time to failure (MTTF) and variance of time to failure formulas are developed. Selective plots are shown for each model. These plots clearly exhibit the impact of various parameters on transit system reliability, steady-state availability, and MTTF.     

竞争硬故障与软故障失效模式产品的可靠性分析

根据系统可靠性理论,考虑到硬故障和软故障两种竞争失效模式对产品失效的影响,对传统的可靠性分析方法进行了扩展。研究了满足硬故障和软故障竞争失效规则的产品可靠性函数和失效率函数。并通过不同的失效模式之间的关系。得到产品在不同的硬、软故障模式下的失效分布函数。另外还给出一个简单的算例来说明该分析方法的应用。该分析方法可能更符合机电产品的失效规律。     

Reliability Object Model Tree (ROM-Tree): A system design-for-reliability method

Designing complex systems that satisfy reliability requirements is a challenge because of complex assembly structures and logical connections, numerous components and associated failure modes, limited reliability data or prediction models, and multi-disciplinary considerations. To overcome these difficulties and to design reliable systems in a systematic way, we have developed a system design-for-reliability (SDfR) method, called Reliability Object Model Tree (ROM-Tree). The developed ROM-Tree consists of: (1) a new reliability analysis structure, (2) reliability metrics, and (3) reliability activities. ROM-Tree is demonstrated through a case study in electronic system designs. Results show that the ROM-Tree method is useful in supporting SDfR in a unified way.     

高密度陶瓷倒装焊封装可靠性试验开路后的失效定位

陶瓷材料具有优良的综合特性,被广泛应用于高可靠微电子封装.陶瓷倒装焊封装的特殊结构使得对其进行失效分析相较其他传统封装形式更为困难.针对一款在可靠性试验中发生开路的高密度陶瓷倒装焊封装器件,制定了一套从非破坏性到破坏性的试验方案对其进行分析.通过时域反射计(TDR)测试排除了基板内部失效的可能性,通过X射线(X-ray)检测、超声扫描显微镜(SAM)和光学显微分析初步断定失效位置,并最终通过扫描电子显微镜和X射线能谱仪实现了对该器件的准确的失效定位,确定失效位置为基板端镀Ni层.该失效分析方法对其他陶瓷倒装焊封装的失效检测及分析有一定的借鉴意义.     

Reliability testing of flexible printed circuit-based RF MEMS capacitive switches

In this paper, reliability results of a novel type of electrostatically actuated RF MEMS capacitive switches developed by our group are discussed. The test setup used for reliability testing consists of the capacitive MEMS switch under test connected in series with a resistor. A specified actuation waveform is applied to the switch and the voltage waveform across the resistor is continuously recorded. The recorded waveform aids in identifying short, open, or stiction failure of the switch. Further, the waveform recorded can be analyzed to study the degradation, reliability, and lifetime characteristics of the switch. The proposed method has been used to study the reliability, failure, and hold-down test characteristics of flexible circuit-based RF MEMS switches. Reliability testing up to 75 million operations has been carried out for flexible circuit-based RF MEMS switches.     

Reliability analysis of networks with human errors: A block diagram approach

This paper presents an approach for performing reliability analysis of bridge and parallel-series networks with critical and non-critical human errors. Reliability and mean time to failure formulas are developed for exponential and Rayleigh distributed failure times. Selective plots are shown for demonstrating the effect of human errors on system reliability and mean time to failure. Equations for estimating a number of units in series, parallel, series-parallel and parallel-series networks are presented.     

Reliability and availability analysis of a system with warm standby and common cause failures

This paper presents reliability and availability analyses of a two unit parallel system with warm standby and common-cause failures. The standby and switching mechanisms are subject to failure. The failed system repair times are assumed to be arbitrarily distributed. Expressions for Laplace transforms of system state probabilities, steady state system availability, system reliability, and mean time to failure are developed.     

基于故障物理的电子产品可靠性仿真分析方法

基于故障物理的电子产品可靠性仿真分析方法首先对产品进行故障模式、机理与影响分析（FMMEA）,得到所有潜在故障点的故障模式、机理与对应的物理模型.利用产品材料、结构、工艺、应力等参数建立产品的仿真数字模型,并进行应力分析,利用概率故障物理（PPoF）模型进行损伤分析,得到各潜在故障的寿命分布.最后利用时间竞争的原理对其进行数据融合,得到产品故障率、平均故障间隔时间（MTBF）等可靠性指标.通过某型单板计算机的可靠性仿真过程说明了该方法的实施流程.这种基于故障物理的可靠性仿真的方法从微观角度将可靠性与产品的结构、材料及所承受的应力联系在一起,有助于发现产品的薄弱环节并采取切实有效的措施,是目前基于手册数据的可靠性预计方法的有益补充.     

Local Polynomial Fitting in Failure Rate Estimation

The failure rate function is one of the most important functions in reliability analysis as it addresses concepts such as scheduling, maintenance, improved system design, cost analysis, etc. Kernel-based estimation of the failure rate function imposes minimal assumptions on the data, and thus offers large flexibility. Therefore, it is very helpful in reliability analysis where the shape of the failure function is a primary target. However, standard kernel estimates are biased more than usual in the endpoints. Motivated by the advantages that the local linear fitting method provides for estimation of densities near the boundary, we employ the technique to the failure rate setting. We show that it produces estimators that have the same amount of boundary bias as in areas outside the boundary. The mean square error properties of the method are demonstrated, and a practically useful procedure for automatic smoothing parameter selection is developed, and studied both theoretically, and by simulations. The result is displayed graphically by distributional, and real life data.     

System Reliability in the Presence of Common-Cause Failures

This paper presents a method for calculating the reliability of a system depicted by a reliability block diagram, with identically distributed components, in the presence of common-cause failures. To represent common-cause failures, we use the Marshall & Olkin formulation of the multivariate exponential distribution. That is, the components are subject to failure by Poisson failure processes that govern simultaneous failure of a speciflc subset of the components. The method for calculating system relability requires that a procedure exist for determining system reliability from component reliabilities under the statistically-independent-component assumption. The paper includes several examples to illustrate the method and compares the reliability of a system with common-cause failures to a system with statistically-independent components. The examples clearly show that common-cause failure processes as modeled in this paper materially affect system reliability. However, inclusion of common-cause failure processes in the system analysis introduces the problem of estimating the rates of simultaneous failure for multiple components in addition to their individual failure rates.     

Evaluation of a dynamic reliability problem based on order ofcomponent failure

A dynamic reliability problem is considered where system components are operating in time. A general framework for analyzing the relationship of prior information and variance of a Monte Carlo estimator is developed. The variance of an estimator based on less prior information is less than that of an estimator based on more prior information. The first application derives a sequential destruction method as a special case in this general framework. The method uses the order of component failure as prior information instead of the time to failure of components. The second application shows that the use of less prior information than the order of component failure can circumvent difficulties faced by a state transition method. A numerical example is presented     

Reliability modeling of on-surface transit systems with human errors

This paper presents two newly developed Markov models representing on-surface transportation systems subject to hardware failures and human errors. Transit system reliability, steady state availability, mean time to failure (MTTF) and variance of time to failure formulas are developed. Selective plots are shown for each model.     

Proportional difference estimate method for bimodal and multimodalfailure distributions

Peaks appear after proportional differentiation of cumulative distribution functions of Weibull and lognormal distributions. The characteristic parameters can be extracted from the proportional difference peaks because these peaks are related to the characteristic parameters directly. On this basis, a simple method known as the proportional difference estimate (PDE) method for determining the characteristic parameters of multimodal failure distributions was developed. This method can be applied to microelectronics dielectric and interconnect reliability studies