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Dynamic models for statistical inference from accelerated life tests
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World Abstracts on Microelectronics and Reliability
cannot be characterized as a constant failure-rate process during any significant segment of the life of the device. This paper provides an overview of the state-of-the-art in generating analytical models for fatigue life estimation due to mechanical wear-out and to critically examine the applicability of these models in the reliability prediction of electronic packages. Statistical precision and robustness of the AMSAA continuous reliability growth estimators. TARIQ ZIAD and PAUL M. ELLNER. Proc. .4. Reliab. Maintainab. Syrup., 210 (1990). The statistical precision and robustness study of the. AMSAA continuous reliability growth estimation procedure investigates the relative error distribution of the MTBF estimator. The study also addresses how this distribution is influenced when the failure data are generated from a finite number of configurations rather than from the AMSAA continuous failure rate curve. This methodology can be used to calculate the required test time associated with an idealized planning curve to achieve a specified precision with a given probability.
A Bayesian methodology for assessing reliability during product development. S. KAPLAN, G. D. M. CUNHA, A. A. DYKESand D. SHAVER.Proc. A. Reliab. Maintainab. Syrup., 205 (1990). Classical techniques for the assessment of reliability point estimates and reliability growth have been moderately successful when applied to a weapon system with "reasonable" reliability requirements and extensive data available for making the assessment. Today's weapon systems no longer reflect that environment. This paper addresses two issues of specific concern to the defence acquisition community: (1) how does one develop a reasonably accurate assessment of reliability in a small sample environment? and (2) in the absence of extensive testing, how does one assess the impact of corrective action on reliability growth? A stepwise process is described for analyzing failure data derived from various sources (subassembly level, system level [factory], system level [field] and operational testing). Bayes theorem is applied in a sequential manner to the various levels of testing. The prior distribution and updating procedure at each level involve using engineering judgement to evaluate the relevance of the various kinds of tests, the significance of failures observed, and the effectiveness of corrective actions. The application of the Bayesian process sets the language and format that provides a framework for gathering, organizing and incorporating the expert knowledge and consensus of the entire engineering team into the assessment of reliability growth. The process is shown by example to be workable in practice and is considered invaluable for the following reasons: (1) Assessments of reliability are derived with a concomitant measure of uncertainty. (2) All available data are incorporated in their proper perspec-/fve. (3) Problem areas are identified. (4) Potential impact of corrective action is assessed.
information carrying capacity. These Lightguide cables' design and failure mechanisms are drastically different from the conventional coaxial cables, therefore detailed investigation into the reliability of these lightguide cables is needed for product assurance. In this paper, the reliability of a typical lightguide cable will be analyzed by first identifying its failure mechanisms. Then theoretical calculations combined with empirical data will be used to describe these failure mechanisms.
Developing criteria for determining corrective action thresholds during reliability verification testing (RVT). DAVID T. TYLER, KALMANJ. GYIMESI and ROBERT L. VIENNEAU. Proc. A. Reliab. Maintainab. Syrup., 76 (1990). During reliability demonstration testing, corrective actions may be initiated after a given number of failures in a single failure mode. This policy could be adopted because items failing often in the same mode are usually indicative of a design flaw. This paper derives a formula for the expected number of corrective actions under such a policy. It is assumed that modes fail independently, each mode fails as a homogeneous Poisson process, and the distribution of modes is Pareto. Given these assumptions, the distribution of the time to corrective action is derived for a single mode. These mode results are then combined to obtain system results. Finally an approximation is made at the system level to obtain useful results.
Analysis of reliability block diagrams with multiple blocks per component. ROBERT F. FORCHE. Proc. `4. Reliab. Maintainab. Syrup., 145 (1990). Reliability block diagrams (RBD) used for reliability analyses consist of a single block in the diagram for each hardware or software component. This paper describes a practical reliability analysis method for a RBD in which some components appear more than once in the diagram, i.e., have multiple blocks. The reliability analysis method for a RBD with multiple blocks must include the effect of the multiple blocks or the resulting downtime can be significantly underestimated. An example is given to show the effect of including and not including the multiple block effect in the reliability analysis.
Improving "MIL-HDBK-217 Type" models for mechanical reliability prediction. E. HAROLD VANNOY. Proc. A. Reliab. Maintainab. Syrup., 341 (1990). For some time, there has been a desire to have "MIL-HDBK-217 Type" reliability prediction models for mechanical products. Several models of this type have been proposed. The usefulness of these models is limited because they do not adequately account for the fact that most mechanical products have a failure rate which is not constant with time. This paper suggests a combination of the "MIL-HDBK217 Type" reliability prediction model and Weibull distribution techniques which will account for the fact that the failure rate varies with time. Techniques to determine the main population Weibull parameters from a hazard plot are also discussed.
Dynamic models for statistical inference from accelerated life Undersea lightguide cable reliability analyses. PERCYS. Wu. Proc. .4. Reliab. Maintainab. Symp., 157 (1990). Product assurance for undersea cable is a must for long term cost savings because the cost of repair for undersea cable is very high, in the order of one million dollars for each repair operation. In the past, coaxial cables have dominated the undersea communication systems with their demonstrated capabilities for long system life. With the advent of optical fiber, an emerging technology in the communications field, undersea communication systems are changing from coaxial cable to lightguide cable, which has optical fiber as the transmission medium for higher transmission rate and more
tests. THOMAS A. MAZZUCHI and REFIK SOYER. Proc. A. Reliab. Maintainab. Syrup., 67 (1990). In this paper, we present a new approach for inference from accelerated life tests. Our approach is based on a dynamic linear model which arises naturally from the accelerated life testing problem and uses linear Bayesian methods for inference. The advantage of the procedure is that it does not require large number of items to be tested and that it can deal with both censored and uncensored data. Furthermore, the approach produces closed form inference results. We illustrate the use of our approach with some actual accelerated life test data.
World Abstracts on Microelectronics and Reliability
cannot be characterized as a constant failure-rate process during any significant segment of the life of the device. This paper provides an overview of the state-of-the-art in generating analytical models for fatigue life estimation due to mechanical wear-out and to critically examine the applicability of these models in the reliability prediction of electronic packages. Statistical precision and robustness of the AMSAA continuous reliability growth estimators. TARIQ ZIAD and PAUL M. ELLNER. Proc. .4. Reliab. Maintainab. Syrup., 210 (1990). The statistical precision and robustness study of the. AMSAA continuous reliability growth estimation procedure investigates the relative error distribution of the MTBF estimator. The study also addresses how this distribution is influenced when the failure data are generated from a finite number of configurations rather than from the AMSAA continuous failure rate curve. This methodology can be used to calculate the required test time associated with an idealized planning curve to achieve a specified precision with a given probability.
A Bayesian methodology for assessing reliability during product development. S. KAPLAN, G. D. M. CUNHA, A. A. DYKESand D. SHAVER.Proc. A. Reliab. Maintainab. Syrup., 205 (1990). Classical techniques for the assessment of reliability point estimates and reliability growth have been moderately successful when applied to a weapon system with "reasonable" reliability requirements and extensive data available for making the assessment. Today's weapon systems no longer reflect that environment. This paper addresses two issues of specific concern to the defence acquisition community: (1) how does one develop a reasonably accurate assessment of reliability in a small sample environment? and (2) in the absence of extensive testing, how does one assess the impact of corrective action on reliability growth? A stepwise process is described for analyzing failure data derived from various sources (subassembly level, system level [factory], system level [field] and operational testing). Bayes theorem is applied in a sequential manner to the various levels of testing. The prior distribution and updating procedure at each level involve using engineering judgement to evaluate the relevance of the various kinds of tests, the significance of failures observed, and the effectiveness of corrective actions. The application of the Bayesian process sets the language and format that provides a framework for gathering, organizing and incorporating the expert knowledge and consensus of the entire engineering team into the assessment of reliability growth. The process is shown by example to be workable in practice and is considered invaluable for the following reasons: (1) Assessments of reliability are derived with a concomitant measure of uncertainty. (2) All available data are incorporated in their proper perspec-/fve. (3) Problem areas are identified. (4) Potential impact of corrective action is assessed.
information carrying capacity. These Lightguide cables' design and failure mechanisms are drastically different from the conventional coaxial cables, therefore detailed investigation into the reliability of these lightguide cables is needed for product assurance. In this paper, the reliability of a typical lightguide cable will be analyzed by first identifying its failure mechanisms. Then theoretical calculations combined with empirical data will be used to describe these failure mechanisms.
Developing criteria for determining corrective action thresholds during reliability verification testing (RVT). DAVID T. TYLER, KALMANJ. GYIMESI and ROBERT L. VIENNEAU. Proc. A. Reliab. Maintainab. Syrup., 76 (1990). During reliability demonstration testing, corrective actions may be initiated after a given number of failures in a single failure mode. This policy could be adopted because items failing often in the same mode are usually indicative of a design flaw. This paper derives a formula for the expected number of corrective actions under such a policy. It is assumed that modes fail independently, each mode fails as a homogeneous Poisson process, and the distribution of modes is Pareto. Given these assumptions, the distribution of the time to corrective action is derived for a single mode. These mode results are then combined to obtain system results. Finally an approximation is made at the system level to obtain useful results.
Analysis of reliability block diagrams with multiple blocks per component. ROBERT F. FORCHE. Proc. `4. Reliab. Maintainab. Syrup., 145 (1990). Reliability block diagrams (RBD) used for reliability analyses consist of a single block in the diagram for each hardware or software component. This paper describes a practical reliability analysis method for a RBD in which some components appear more than once in the diagram, i.e., have multiple blocks. The reliability analysis method for a RBD with multiple blocks must include the effect of the multiple blocks or the resulting downtime can be significantly underestimated. An example is given to show the effect of including and not including the multiple block effect in the reliability analysis.
Improving "MIL-HDBK-217 Type" models for mechanical reliability prediction. E. HAROLD VANNOY. Proc. A. Reliab. Maintainab. Syrup., 341 (1990). For some time, there has been a desire to have "MIL-HDBK-217 Type" reliability prediction models for mechanical products. Several models of this type have been proposed. The usefulness of these models is limited because they do not adequately account for the fact that most mechanical products have a failure rate which is not constant with time. This paper suggests a combination of the "MIL-HDBK217 Type" reliability prediction model and Weibull distribution techniques which will account for the fact that the failure rate varies with time. Techniques to determine the main population Weibull parameters from a hazard plot are also discussed.
Dynamic models for statistical inference from accelerated life Undersea lightguide cable reliability analyses. PERCYS. Wu. Proc. .4. Reliab. Maintainab. Symp., 157 (1990). Product assurance for undersea cable is a must for long term cost savings because the cost of repair for undersea cable is very high, in the order of one million dollars for each repair operation. In the past, coaxial cables have dominated the undersea communication systems with their demonstrated capabilities for long system life. With the advent of optical fiber, an emerging technology in the communications field, undersea communication systems are changing from coaxial cable to lightguide cable, which has optical fiber as the transmission medium for higher transmission rate and more
tests. THOMAS A. MAZZUCHI and REFIK SOYER. Proc. A. Reliab. Maintainab. Syrup., 67 (1990). In this paper, we present a new approach for inference from accelerated life tests. Our approach is based on a dynamic linear model which arises naturally from the accelerated life testing problem and uses linear Bayesian methods for inference. The advantage of the procedure is that it does not require large number of items to be tested and that it can deal with both censored and uncensored data. Furthermore, the approach produces closed form inference results. We illustrate the use of our approach with some actual accelerated life test data.