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Reliability investment and life-cycle cost
996
World Abstracts on Microclectronics and Reliabilil~
of dormancy failures modes and their impact upon flight test assessment follows.
Establishing realistic requirements for reliability, maintainability, and built-in-test. R. C. TRAKAS. Proc. a. Reliab. Maintainab. Syrup. 103 (1984). Steps have been taken within the Naval Air Systems C o m m a n d to provide a repeatable, logical approach to establishing realistic requirements for reliability, maintainability and built-in-test (BIT). This approach prevents problems on programs under development where failure to meet specified requirements in the areas of reliability, maintainability, and BIT could be attributed to establishment of arbitrary, unrealistic requirements with little or no basis in fact. The approach taken ensures the proper relationship between the program thresholds within the Navy and the contractually specified requirements. This provides for a cost-effective and realistic method for ensuring that adequate inherent reliability, maintainability and BIT capabilities are designed into the equipment to meet the stated operational requirements.
Field data: the final measure. HAROLD S. BALABAN and RICHARD A. KOWALSKI. Proc. a. Reliab. Maintainab. Syrup. 123 (1984). This paper examines causes for differences between field reliability measurements and estimates obtained from equipment predictions or development tests. It describes several characteristics of field data collection systems that affect the utility of the resulting data. Finally, it presents both graphic and analytic techniques for analyzing field reliability data to identify failure occurrence trends.
Cost savings by establishing life limits. WILLIAM IRELAND. Proc. a. Reliab. Maintainab. Symp. 72 (1984). There is often a tendency in engineering to be overly cautious without due cause. This can be very expensive when establishing life limits on components of mechanical systems, whether repairable or not. When one considers military systems this m a y mean tax dollars into the scrap bucket prior to realizing the inherent life left in a part or system. This paper discards the often used "I feel good about this number" in favor of a budget conscience and statistically accurate method to obtain the life limit from a given set of data and hence, lower system operating costs. The technique applied is known as the E N T R O P Y method and the results can be cost savings.
Reliability-growth programmes for undersea communication systems. ROBERT H. MURPHY. IEEE Trans. Reliab. R-32 (3), 240 (August 1983). This paper deals with the unique problems encountered when managing reliability growth programmes on expensive capital equipment components destined for use in a relatively inaccessible environment. Continuous operation of these components in predominantly non-redundant configurations is required for up to 25 years: and repair costs and/or lost revenues incurred by single failures at any time during this period can a m o u n t to several $100000. After a brief review of the history and philosophy of reliability growth programmes on components for coaxial cable systems, the planning, development and implementation of reliability assurance procedures for undersea systems designed for 1.3 g m optical transmission at 280 Mbit/s are addressed. The challenge involved in proving electro-optic and electronic components suitable for undersea optical P C M systems is not to be underestimated. Even in a relatively benign environment, these systems have specific problems with respect to operating temperatures, voltage stresses, heat dissipation factors, and the lack of escape routes for trapped contaminants. The components themselves are not only relatively new, or just emerging from the development phase, they also demand innovative reliability assessment techniques because of the inadequacy of traditional methods of accelerated testing. This paper gives an insight into some of these problems from a reliability management viewpoint. It
is increasingly evident that QC and RA programme leadclship cannot now, if it ever could, be accomplished with¢)ut detailed knowledge of sophisticated component design. A rigorous training in semiconductor and passive device physics, failure analysis, statistical quality control and reliability prediction techniques is essential for this exacting role. It is also certain that undersea communications syslcms cannot be developed on the basis of combining constant failure rate characteristics, as has been the wont of professional/military equipment analysts since long before MILHDBK-217 was a gleam in its creators' eyes. A simple analogy is that every bath-tub has a plug-hole. This plughole is situated just before the steeply rising portion, and is where companies are likely to go if they ignore wear-out failures in the context of inaccessible systems!
Quality circles--an experience in Jyoti Limited. A. V. DANDEKAR. QR d. (India), 107 ISeptember 1983). In this paper the processes needed and difficulties experienced in starting Quality Circles in the plant as well as the training given are explained. With support from all management staff the team spirit developed, and the results obtained through the circles formed and functioning both a m o n g management and among operatives are discussed.
Reliability investment and life-cycle cost. JAMES K. SEGER. IEEE Trans. Reliab. R-32 (3), 259 (August 1983). The reliability of avionic equipment profoundly influences life-cycle cost; the level of reliability attained largely depends upon the investment in reliability programs during development. As more investment is made in reliability improvement, some cost elements increase and others decrease. These opposing cost trends yield a unique m i n i m u m life-cycle cost (LCC). In order to find the level of investment in a reliability improvement program that minimizes LCC, the Reliability Investment Optimization (RIO) model has been developed. It identifies, for a particular avionic system, the level of reliability investment that minimizes the LCC of the equipment. This model employs a reliability-growth relationship based on the Duane model. The RIO model uses this reliability growth pattern to compute LCC as a function of M T B F (mean time between failures) where LCC comprises: (1) research, development, test and evaluation (RDT&E), (2) procurement, and (3) operations and support (O&S). The RIO model uses s u m m a r y level data that are appropriate for the timeframe of its most advantageous use, i.e. prior to detail design of the system. The degree of accuracy for the input parameters need not be high because results arc not very sensitive to data accuracy. The model's results thus are quite stable. The RIO model was designed with avionic systems in mind. However. the model applies to a wider range of systems. Certain assumptions should be particularly scrutinized in extending usage beyond avionics, e.g., Poisson demand assumption versus a wearout failure pattern (failure rate increases over time), scheduled maintenance, and LCC element breakdown. Some important recommendations for further investigaqon are listed. The reliability program should be broken into its major tasks and related individually to LCC. The use of built-in test and fault tolerance concepts should be reflected in the reliability program and LCC. The impact of reliability improvements upon system availability should be ewduatcd with a view toward estimating the number of systems needed to attain a constant mission capability and the cost consequences of higher reliability's reducing system population.
Management of logistic support costs in the equipment acquisition phase. DWIGHT E. COLLINS. IEEE Trans. Reliab. R-32 (3), 264 (August 1983). In recent years, a management concept known as design-to-cost has been implemented with considerable success by the US Department of Defense (DoD). Under this concept, a variety of system and ec!uip-
World Abstracts on Microclectronics and Reliabilil~
of dormancy failures modes and their impact upon flight test assessment follows.
Establishing realistic requirements for reliability, maintainability, and built-in-test. R. C. TRAKAS. Proc. a. Reliab. Maintainab. Syrup. 103 (1984). Steps have been taken within the Naval Air Systems C o m m a n d to provide a repeatable, logical approach to establishing realistic requirements for reliability, maintainability and built-in-test (BIT). This approach prevents problems on programs under development where failure to meet specified requirements in the areas of reliability, maintainability, and BIT could be attributed to establishment of arbitrary, unrealistic requirements with little or no basis in fact. The approach taken ensures the proper relationship between the program thresholds within the Navy and the contractually specified requirements. This provides for a cost-effective and realistic method for ensuring that adequate inherent reliability, maintainability and BIT capabilities are designed into the equipment to meet the stated operational requirements.
Field data: the final measure. HAROLD S. BALABAN and RICHARD A. KOWALSKI. Proc. a. Reliab. Maintainab. Syrup. 123 (1984). This paper examines causes for differences between field reliability measurements and estimates obtained from equipment predictions or development tests. It describes several characteristics of field data collection systems that affect the utility of the resulting data. Finally, it presents both graphic and analytic techniques for analyzing field reliability data to identify failure occurrence trends.
Cost savings by establishing life limits. WILLIAM IRELAND. Proc. a. Reliab. Maintainab. Symp. 72 (1984). There is often a tendency in engineering to be overly cautious without due cause. This can be very expensive when establishing life limits on components of mechanical systems, whether repairable or not. When one considers military systems this m a y mean tax dollars into the scrap bucket prior to realizing the inherent life left in a part or system. This paper discards the often used "I feel good about this number" in favor of a budget conscience and statistically accurate method to obtain the life limit from a given set of data and hence, lower system operating costs. The technique applied is known as the E N T R O P Y method and the results can be cost savings.
Reliability-growth programmes for undersea communication systems. ROBERT H. MURPHY. IEEE Trans. Reliab. R-32 (3), 240 (August 1983). This paper deals with the unique problems encountered when managing reliability growth programmes on expensive capital equipment components destined for use in a relatively inaccessible environment. Continuous operation of these components in predominantly non-redundant configurations is required for up to 25 years: and repair costs and/or lost revenues incurred by single failures at any time during this period can a m o u n t to several $100000. After a brief review of the history and philosophy of reliability growth programmes on components for coaxial cable systems, the planning, development and implementation of reliability assurance procedures for undersea systems designed for 1.3 g m optical transmission at 280 Mbit/s are addressed. The challenge involved in proving electro-optic and electronic components suitable for undersea optical P C M systems is not to be underestimated. Even in a relatively benign environment, these systems have specific problems with respect to operating temperatures, voltage stresses, heat dissipation factors, and the lack of escape routes for trapped contaminants. The components themselves are not only relatively new, or just emerging from the development phase, they also demand innovative reliability assessment techniques because of the inadequacy of traditional methods of accelerated testing. This paper gives an insight into some of these problems from a reliability management viewpoint. It
is increasingly evident that QC and RA programme leadclship cannot now, if it ever could, be accomplished with¢)ut detailed knowledge of sophisticated component design. A rigorous training in semiconductor and passive device physics, failure analysis, statistical quality control and reliability prediction techniques is essential for this exacting role. It is also certain that undersea communications syslcms cannot be developed on the basis of combining constant failure rate characteristics, as has been the wont of professional/military equipment analysts since long before MILHDBK-217 was a gleam in its creators' eyes. A simple analogy is that every bath-tub has a plug-hole. This plughole is situated just before the steeply rising portion, and is where companies are likely to go if they ignore wear-out failures in the context of inaccessible systems!
Quality circles--an experience in Jyoti Limited. A. V. DANDEKAR. QR d. (India), 107 ISeptember 1983). In this paper the processes needed and difficulties experienced in starting Quality Circles in the plant as well as the training given are explained. With support from all management staff the team spirit developed, and the results obtained through the circles formed and functioning both a m o n g management and among operatives are discussed.
Reliability investment and life-cycle cost. JAMES K. SEGER. IEEE Trans. Reliab. R-32 (3), 259 (August 1983). The reliability of avionic equipment profoundly influences life-cycle cost; the level of reliability attained largely depends upon the investment in reliability programs during development. As more investment is made in reliability improvement, some cost elements increase and others decrease. These opposing cost trends yield a unique m i n i m u m life-cycle cost (LCC). In order to find the level of investment in a reliability improvement program that minimizes LCC, the Reliability Investment Optimization (RIO) model has been developed. It identifies, for a particular avionic system, the level of reliability investment that minimizes the LCC of the equipment. This model employs a reliability-growth relationship based on the Duane model. The RIO model uses this reliability growth pattern to compute LCC as a function of M T B F (mean time between failures) where LCC comprises: (1) research, development, test and evaluation (RDT&E), (2) procurement, and (3) operations and support (O&S). The RIO model uses s u m m a r y level data that are appropriate for the timeframe of its most advantageous use, i.e. prior to detail design of the system. The degree of accuracy for the input parameters need not be high because results arc not very sensitive to data accuracy. The model's results thus are quite stable. The RIO model was designed with avionic systems in mind. However. the model applies to a wider range of systems. Certain assumptions should be particularly scrutinized in extending usage beyond avionics, e.g., Poisson demand assumption versus a wearout failure pattern (failure rate increases over time), scheduled maintenance, and LCC element breakdown. Some important recommendations for further investigaqon are listed. The reliability program should be broken into its major tasks and related individually to LCC. The use of built-in test and fault tolerance concepts should be reflected in the reliability program and LCC. The impact of reliability improvements upon system availability should be ewduatcd with a view toward estimating the number of systems needed to attain a constant mission capability and the cost consequences of higher reliability's reducing system population.
Management of logistic support costs in the equipment acquisition phase. DWIGHT E. COLLINS. IEEE Trans. Reliab. R-32 (3), 264 (August 1983). In recent years, a management concept known as design-to-cost has been implemented with considerable success by the US Department of Defense (DoD). Under this concept, a variety of system and ec!uip-