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The reliability-design engineer relationship
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WORLD ABSTRACTS ON M I C R O E L E C T R O N I C S AND R E L I A B I L I T Y
*Probabilistie reliability: An engineering approach. M. L. SHOOMAN,McGraw Hill, 1968. 524 p. 116 Refs. Reliability concepts and approaches are related to basic probability mathematics in a textbook for college and industrial courses. Probability and differential equations are reviewed, as are set theory, continuous and discrete random variables, moments, Markow models and estimation theory. Combinatorial reliability is treated, including series and parallel configurations, general techniques and various models. Catastrophic-failure models consider treatment of failure data, failure modes, hazard rate and failure density, and hazard models. Approximation and bounds, general approaches to computation, and computer methods of analyzing system reliability are described. Methods of reliability improvement considered are systems design and component improvement, redundancy in digital systems and standby redundancy, the human operator as an adaptive controller, and repairable systems. Drift failures, component tolerances, and parameter variations are discussed in terms of deterministic and probabilistic approaches, approximation techniques, and applications to circuits and control system analysis. Reliability physics models and statistical parameter estimation are reviewed; and analog computations, numerical analysis and digital computation, some useful integrals, and number of Monte Carlo trials are presented. *The Methods of reliability. W. B. ROSSNAGEL,1968 Prod. Ass. Conf. Tech. Exhibition, Long Island, N.Y., June 7-8 (1968), Transactions, p. 259. Prediction and analysis, design and specification reviews, drawing review and sign-off, test procedure review and sign-off, failure analysis, and corrective action are discussed as the major portions of a reliability program. Ground rules are presented which include specific methods for achieving an effective reliability program; and problem situations that could arise are cited; and 10 guidelines for corrective action are included. Other activities considered to be part of the reliability program are listed as training, configuration control, vendor control and audit.
Wanted--Realistic Alternatives to MIL-STD-781. P. B. BRIGHAM,Proc. 1969 Ann. Syrup. Reliab., Chicago, January 21-23 (1969), p. 280. We have been a long time selling the idea that reliability is a design parameter as real as weight, velocity, or power output; that reliability is a design discipline. To effectively control design reliability we have developed elaborate methods and amassed an impressive body of data to predict and evaluate reliability during design. We have also attempted with much less success, to demonstrate, i.e. measure, this elusive quantity. Since a quantity that is predictable must be amenable to measurement, when we fail to measure reliability we love credibility. MIL-STD-781 established a standardized set of methods for reliability demonstration and they work well--but not for all equipment and not for MTBF's which force extended testing. As systems (and their missions) become increasingly complex and our capability to build reliable hardware increases, we have increasing difficulty using MIL-STD-781 test methods. Where MIL-STD-781 is readily applied, the penalty for failure may force an impossibly high design reliability goal, thus creating a situation in which the demonstration requirement, not the mission, sets the design reliability goal. This paper will discuss some specific problems with MIL-STD-781 demonstrations and propose some useful alternatives. *The reliability-design engineer relationship. M. TRIEB, 1968 Prod. Ass. Conf. Tech, Exhibition, Long Island, N.Y., June 7-8 (1968), Transactions, p. 1. Relationship between reliability and design engineering is discussed, emphasizing the need for subtle reliability control over design functions. It is shown that the way to control the design function is to make the design engineer dependent upon the services provided by the reliability group. Close contact between personnel representing the two groups is considered a must, as is design know-how among personnel representing the reliability group. *Using cost data to optimize reliability. K. WEIR, 22rid Am. Soc. Quality Control, Ann. Tech. Conf., Philadelphia, May 6-8 (1968), Transactions, p. 491 (A68-31438). Outline of methods amenable to computer solution for generating system reliability models and optimizing them with respect to another system parameter. A simple reliability model which represents a nonseries, parallel, or series-parallel configuration is considered in order to demonstrate the optimization technique. Although the discussion is restricted to optimization of the cost variable, weight, schedule, or volume could have been chosen as easily.
WORLD ABSTRACTS ON M I C R O E L E C T R O N I C S AND R E L I A B I L I T Y
*Probabilistie reliability: An engineering approach. M. L. SHOOMAN,McGraw Hill, 1968. 524 p. 116 Refs. Reliability concepts and approaches are related to basic probability mathematics in a textbook for college and industrial courses. Probability and differential equations are reviewed, as are set theory, continuous and discrete random variables, moments, Markow models and estimation theory. Combinatorial reliability is treated, including series and parallel configurations, general techniques and various models. Catastrophic-failure models consider treatment of failure data, failure modes, hazard rate and failure density, and hazard models. Approximation and bounds, general approaches to computation, and computer methods of analyzing system reliability are described. Methods of reliability improvement considered are systems design and component improvement, redundancy in digital systems and standby redundancy, the human operator as an adaptive controller, and repairable systems. Drift failures, component tolerances, and parameter variations are discussed in terms of deterministic and probabilistic approaches, approximation techniques, and applications to circuits and control system analysis. Reliability physics models and statistical parameter estimation are reviewed; and analog computations, numerical analysis and digital computation, some useful integrals, and number of Monte Carlo trials are presented. *The Methods of reliability. W. B. ROSSNAGEL,1968 Prod. Ass. Conf. Tech. Exhibition, Long Island, N.Y., June 7-8 (1968), Transactions, p. 259. Prediction and analysis, design and specification reviews, drawing review and sign-off, test procedure review and sign-off, failure analysis, and corrective action are discussed as the major portions of a reliability program. Ground rules are presented which include specific methods for achieving an effective reliability program; and problem situations that could arise are cited; and 10 guidelines for corrective action are included. Other activities considered to be part of the reliability program are listed as training, configuration control, vendor control and audit.
Wanted--Realistic Alternatives to MIL-STD-781. P. B. BRIGHAM,Proc. 1969 Ann. Syrup. Reliab., Chicago, January 21-23 (1969), p. 280. We have been a long time selling the idea that reliability is a design parameter as real as weight, velocity, or power output; that reliability is a design discipline. To effectively control design reliability we have developed elaborate methods and amassed an impressive body of data to predict and evaluate reliability during design. We have also attempted with much less success, to demonstrate, i.e. measure, this elusive quantity. Since a quantity that is predictable must be amenable to measurement, when we fail to measure reliability we love credibility. MIL-STD-781 established a standardized set of methods for reliability demonstration and they work well--but not for all equipment and not for MTBF's which force extended testing. As systems (and their missions) become increasingly complex and our capability to build reliable hardware increases, we have increasing difficulty using MIL-STD-781 test methods. Where MIL-STD-781 is readily applied, the penalty for failure may force an impossibly high design reliability goal, thus creating a situation in which the demonstration requirement, not the mission, sets the design reliability goal. This paper will discuss some specific problems with MIL-STD-781 demonstrations and propose some useful alternatives. *The reliability-design engineer relationship. M. TRIEB, 1968 Prod. Ass. Conf. Tech, Exhibition, Long Island, N.Y., June 7-8 (1968), Transactions, p. 1. Relationship between reliability and design engineering is discussed, emphasizing the need for subtle reliability control over design functions. It is shown that the way to control the design function is to make the design engineer dependent upon the services provided by the reliability group. Close contact between personnel representing the two groups is considered a must, as is design know-how among personnel representing the reliability group. *Using cost data to optimize reliability. K. WEIR, 22rid Am. Soc. Quality Control, Ann. Tech. Conf., Philadelphia, May 6-8 (1968), Transactions, p. 491 (A68-31438). Outline of methods amenable to computer solution for generating system reliability models and optimizing them with respect to another system parameter. A simple reliability model which represents a nonseries, parallel, or series-parallel configuration is considered in order to demonstrate the optimization technique. Although the discussion is restricted to optimization of the cost variable, weight, schedule, or volume could have been chosen as easily.