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Reliability, IEEE Transactions on

Issue 5 • Date Dec 1991

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Displaying Results 1 - 19 of 19
  • Optimum simple step-stress accelerated life-tests with competing causes of failure

    Publication Year: 1991 , Page(s): 622 - 627
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    Optimum simple step-stress accelerated life tests (ALTs) for products with competing causes of failure are presented. The life distribution of each failure cause, which is independent of the others, is assumed to be exponential with a mean that is a log-linear function of the stress, and a cumulative exposure model is assumed. Optimum plans for time-step and failure-step ALTs are obtained which minimize the sum over all failure causes of asymptotic variances of the maximum likelihood estimators of the log mean lives at design stress. The competing causes of failure affect the optimum test plan only through the product of two ratios-the ratio of the sums of the mean lives and the ratio of the sums of the failure rates over all failure causes at low and high stress levels. The effect of this product (of two ratios) is studied View full abstract»

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  • Material failure mechanisms and damage models

    Publication Year: 1991 , Page(s): 531 - 536
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    This work introduces a tutorial series on material failure mechanisms and damage models to familiarize nonspecialists with the fundamentals of failure mechanisms in engineering assemblies. Since failure is a complicated concept, four simple conceptual models for failure are discussed: stress-strength, damage-endurance, challenge-response, and tolerance-requirement. The specific failure mechanisms depend on material or structural defects, damage induced during manufacture and assembly, and on conditions during storage and field use. Conditions that affect the state of an item are broadly termed stresses (loads), e.g., mechanical stress and strain, electrical current and voltage, temperature, humidity, chemical environment, and radiation. The effects of stresses are influenced by geometry, constitutive and damage properties of the materials, manufacturing parameters, and the application environment View full abstract»

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  • Observation of electromigration at low temperature

    Publication Year: 1991 , Page(s): 524 - 530
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    Electromigration and mean time-to-failure were investigated for unglassed thin Al stripes over the temperature range of 223 K to 347 K. Thermal effects are minimized by sinking heat from the linestrip through the substrate to a miniature cryogenic refrigerator. This test technique allows the investigation of structure and current interactions while suppressing the effects of an added temperature factor. The circuit was stressed by direct current densities greater than 4×106 A/cm2. Electromigration damage was induced in a test stripe at temperatures near 0°C. For the temperature range of 347 K to 267 K, an activation energy of 0.30 eV was calculated, indicating that surface migration is the dominant failure mechanism. For temperatures between 267 K and 223 K, a calculated activation energy of 0.12 eV suggests a different failure mechanism, which was subsequently identified as stripe separation from the substrate View full abstract»

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  • A reliability model for connector contacts

    Publication Year: 1991 , Page(s): 513 - 523
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (900 KB)  

    Connector contacts have a typical end-of-life behavior during accelerated life testing. A model that predicts the change in resistance (ΔR) for an aging contact is developed based on that behavior. The model shows that the duration of accelerated life tests can sometimes be reduced by up to 50%, resulting in substantial time and cost savings. Analysis of the model leads to several unexpected conclusions. For example, the evaluation of contact reliability, using ΔR as a parameter, does not agree with a time-to-failure approach in which each individual contact is assumed to have a specific failure time. The agreement is restored by the use of change in conductance (ΔG) ratios. The use of ΔG by itself leads directly to the conclusion that contact reliability evaluated at some point in a contact's life explicitly depends on the resistance of the contact when it was put into use View full abstract»

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  • An explicit solution for the number of minimal p-cutsequences in a consecutive-k-out of-n:F system

    Publication Year: 1991 , Page(s): 553 - 554
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    R.C. Bollinger and A.A. Salvia (see ibid., vol. R-34, p. 43-5, Apr. 1985) proposed an approach to study the failure-time distribution of a consecutive-k-out-of-n:F system by studying the number of minimal p-cutsequences. They gave recursive equations to compute this number for independent identically distributed components. It is shown that the recursive equations have an explicit solution View full abstract»

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  • Reliability assessment based on accelerated degradation: a case study

    Publication Year: 1991 , Page(s): 499 - 506
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    An analysis strategy (experimental and analytic) for extracting reliability information from the measured degradation of devices subjected to elevated stress is described. The strategy is applied to the estimation of the reliability of an integrated logic family that is a component of a new generation of submarine cables. The experiment consisted of monitoring several electrical parameters while aging the devices under elevated temperature. The authors model changes observed in one of these electrical parameters (propagation delay) and identify and quantify various sources of variability observed in the data. These models are used to predict (with 95% confidence) that a randomly selected device operating at 40°C will see a change of no more than 2 ns in propagation delay in 25 yr, the lifetime of a submarine cable. An analysis of the degradation rate leads to the conjecture that the observed change in propagation delay is due to the diffusion of impurities (Na) through the bulk of the oxide layer (SiO2) View full abstract»

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  • Confidence bounds for Pr{X>Y} in 1-way ANOVA random model

    Publication Year: 1991 , Page(s): 537 - 540
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    Approximate confidence bounds for reliability, R=Pr{X >Y|X,Y}, are obtained, where X and Y are independent normal (Gaussian) random variables, and X and Y are vectors of measurements for X and Y, respectively. Balanced 1-way ANOVA (analysis of variants) random effect models are assumed for the populations of X and Y. Confidence bounds are derived for R under three cases for standard deviations, σx and σy. An example shows how the results are used View full abstract»

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  • A probabilistic foundation for vagueness and imprecision in fault-tree analysis

    Publication Year: 1991 , Page(s): 563 - 571
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (740 KB)  

    Fault tree and reliability analyses frequently must rely on imprecise or vague input data. A theoretical framework, based on Dempster-Shafer theory (DST), that accommodates this vagueness and shows how imprecision can give rise to false-negative and false-positive inferences is proposed. DST assigns upper and lower bounds for the probability on elements of the state space. The author focuses on two consequences of vagueness: (1) the influence of imprecise or fuzzy input data on the parameters of the model to be observed, and (2) the result of sensory-device failures or of leaving out relevant variables that can cause false-negative and false-positive inferences. Imprecise input data are modeled through a three-valued logic derived from DST `probability' assignments. False-negative and false-positive signals are illustrated by incorporating this information in an additional parameter that is coupled, with a Boolean AND gate, to each rule of the fault tree. The computational simplicity of incorporating DST probability assignments and the advantages of DST for reliability analyses are shown View full abstract»

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  • Estimators for type-II censored (log)normal samples

    Publication Year: 1991 , Page(s): 547 - 552
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Three common estimators for the parameters of the log-normal distribution are evaluated for censored samples. Correction factors which eliminate essentially all the bias, and formulas for the standard deviations of the estimators, are presented. It is reported that the Persson-Rootzen estimators are about as good as the maximum-likelihood estimators, without the penalty of requiring iterative (computer) optimization. Also, the estimators resulting from (least squares) fitting a line to the plot of log lifetimes on normal (Gaussian) probability paper are reasonably good. Formulas are given for obtaining these latter estimators without actually plotting the points. The author simulated 5 k to 30 k samples (more samples for smaller N for each case) and calculated the following: the means, standard deviations, and third moments of each estimator; correlations between the two members of each pair; comparisons between the estimators; and simple corrections to improve the performance of the estimators View full abstract»

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  • Bayes estimation of hazard and acceleration in accelerated testing

    Publication Year: 1991 , Page(s): 615 - 621
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    In accelerated life testing, the time transformation function θ(t) is often unknown, even if that function is assumed to be linear. If θ(t) is known, data in the accelerated condition can be adjusted to provide information about the failure time distribution in the use condition. If θ(t) is unknown, the usual estimation procedures require data from the use condition as well as data from the acceleration condition. In this work it is assumed that the uncertainty about θ can be modeled by a prior distribution, chosen from the truncated Pareto family of distributions, and that the uncertainty in λ, the failure rate, can be modeled by a prior distribution from the gamma family. Under these assumptions, the posterior distributions and their first two moments are provided for both λ and θ. Thus, this complete Bayes approach to accelerated life testing with the assumed model allows the adjustment of data taken in the accelerated condition to provide the user with the important estimates in the use condition. The results are illustrated by examples View full abstract»

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  • Voting mechanisms in distributed systems

    Publication Year: 1991 , Page(s): 593 - 600
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    It is shown how voting mechanisms can be exploited to improve the reliability of decisions in a distributed system. A model of decision making in which several processors (nodes) are assigned to work independently on various aspects of a problem and each returns a binary answer to a coordinator node is assumed. The coordinator combines the answers, using a voting mechanism to arrive at a final answer. Two issues are addressed: (1) if the reliability of each node is known, then by assigning suitable votes to the various nodes it is possible to maximize the probability of a correct decision by the coordinator; and (2) if a cost vs. reliability function for each node is known, then it is possible to determine a best operating point for each node so as to minimize the total cost of the computation. Algorithms for minimizing the cost were designed and tested, and conditions under which savings can be realized were identified View full abstract»

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  • Estimating the reliability of electrical connectors

    Publication Year: 1991 , Page(s): 507 - 512
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    Some current approaches to estimating the reliability of electrical contacts and connectors are discussed. These approaches center on the statistical analysis of test data and address the active degradation mechanisms, the determination of appropriate environmental tests with corresponding acceleration factors and exposures, the statistical analysis appropriate for the test data, and the establishment of appropriate acceptance criteria. Each of these issues is treated separately. Multiposition connectors and Mil-Hdbk-217 are discussed. The authors deprecate reliability predictions based on generic databases and failure rate models, such as Mil-Hdbk-217, and describe instead what should constitute a reliability qualification program View full abstract»

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  • Optimal designs of {k,n-k+1}-out-of-n:F systems (subject to 2 failure modes)

    Publication Year: 1991 , Page(s): 559 - 562
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    The problem of achieving optimal system size (n) for {k,n-k+1}-out-of-n systems, assuming that failure may take either of two forms, is studied. It is assumed that components are independently identically distributed (i.i.d.) and that the two kinds of system failures can have different costs. The optimal k or n that maximizes mean system-profit is determined, and the effect of system parameters on the optimal k or n is studied. It is shown that there does not exist a pair (k,n) maximizing the mean system-profit View full abstract»

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  • On computing reliability-measures of Boolean circuits

    Publication Year: 1991 , Page(s): 582 - 592
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (844 KB)  

    Testability and reliability analyses of Boolean circuits require the computation of the following figures of merit: signal probability, detection probability, signal reliability, as well as signal detectability, signal maskability, and signal unreliability of two-rail and weighted self-checking circuits. The authors present a generic algorithm for computing these measures. Special cases of this generic algorithm compare very favourably with known algorithms for computing some of these measures. An asymptotic analysis of this algorithm is presented. This analysis helps one identify a nontrivial class of problem instances because of all these problems are known to be #P-hard and a polynomial-time algorithm for these problems might not exist View full abstract»

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  • Counting the number of minimum cuts in undirected multigraphs

    Publication Year: 1991 , Page(s): 610 - 614
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    The problem of counting the number of cuts with the minimum cardinality in an undirected multigraph arises in various applications, such as testing the super-λ-ness of a graph, as described by F.T. Boesch (1986), and calculating upper and lower bounds on the probabilistic connectedness of a stochastic graph G in which edges are subject to failure. It is shown that the number |C( G)| of cuts with the minimum cardinality λ(G) in a multiple graph G=(V,E) can be computed in O(|E|+λ(G)|V|2 +λ(G)|C(G)||V|) time View full abstract»

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  • Interval estimation of availability of a series system

    Publication Year: 1991 , Page(s): 541 - 546
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    For a system that consists of n independent subsystems connected in series, based on a sample of complete periods for each subsystem, an approximate interval estimate of the steady-state availability of the system is presented for three cases: when each lifetime and repair-time has an exponential distribution; when each lifetime has an exponential distribution and each repair-time has a log-normal distribution; and the case where each lifetime and repair-time has a log-normal distribution. For a large system it often costs less to test subsystems than to test the system. Consequently, it is more economical to estimate the steady-state availability of the system by using the data from each subsystem. Moreover, it is time-saving since subsystems can be tested simultaneously prior to assembly of the system. Numerical examples show good confidence bounds for the steady-state availability View full abstract»

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  • A heuristic approach to optimal assignment of components to a parallel-series network

    Publication Year: 1991 , Page(s): 555 - 558
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    In a parallel-series network the required n components are to be selected from the available m(⩾n) components and assigned to the n positions in the network with the objective of maximizing the reliability of the system. Any component can be assigned to any of the n positions, but the reliability of a component is affected by the position to which it is assigned. Obtaining an exact solution to this problem is highly complex. Therefore, a heuristic method that requires solving k(k+1)/2 classical assignment problems, where k is the number of pathsets in the network, is developed. The results of an extensive computational experiment show that the heuristic method obtains exact solutions in a vast majority of cases, and when it fails to give an exact solution, the deviation from the exact solution is small in most cases View full abstract»

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  • Estimation of network reliability using graph evolution models

    Publication Year: 1991 , Page(s): 572 - 581
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    Monte Carlo techniques for estimating various network reliability characteristics, including terminal connectivity, are developed by assuming that edges are subject to failures with arbitrary probabilities and nodes are absolutely reliable. The core of the approach is introducing network time-evolution processes and using certain graph-theoretic machinery, resulting in a considerable increase in accuracy for Monte Carlo estimates, especially for highly reliable networks. Simulation strategies and numerical results are presented and discussed View full abstract»

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  • System failure-frequency analysis using a differential operator

    Publication Year: 1991 , Page(s): 601 - 609, 614
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    A method for obtaining the failure frequency of any system whose structure function is coherent is introduced. The relationship of the availability to the failure frequency can be expressed as a unique differential operator. In this way, regardless of the form of expression, the failure frequency can be obtained by applying the differential operator to the availability expression. Some reduction techniques are shown to be useful in evaluating failure frequency by means of this differential operator. If the reduction formulas are approximate rather than exact, it is generally difficult to apply the operator. This operator is tested on a special type of approximate reduction (the quadrilateral-star transformation). A numerical example for this reduction is presented View full abstract»

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Aims & Scope

IEEE Transactions on Reliability is concerned with the problems involved in attaining reliability, maintaining it through the life of the system or device, and measuring it.

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Meet Our Editors

Editor-in-Chief
Way Kuo
City University of Hong Kong