Publications (6)1.93 Total impact

  • D.E. Mortin · J.G. Krolewski · M.J. Cushing
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    ABSTRACT: The assumption of the constant failure rate can lead to excessive costs and nonoptimum design decisions. As this paper shows, simply summing constant failure rates can produce results which are highly inaccurate. Highly inaccurate results can introduce significant error in decisions made in everything from product design to logistics support requirements such as spares and maintainers. The authors argue that if a shift is made from reliability accounting tasks to reliability engineering analysis, the ability to address hazard rates versus time based on root-cause failure mechanisms will become cost-effective and can become an integral part of the concurrent engineering approach to product development. The notion of the constant failure rate should no longer be accepted as a rule. Instead, statistical distributions and assumptions must be shown to be appropriate every time they are used. Simplicity alone is not a sufficient reason to use any given methodology or approach
    No preview · Conference Paper · Feb 1995
  • D.E. Mortin · M.J. McCarthy · D.M. Querido · P.M. Ellner
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    ABSTRACT: This paper presents an overview and a discussion of the methodology used in the AMSAA Subsystem Reliability Growth Planning Model (SSPLAN). SSPLAN is used to develop subsystem reliability growth planning curves that, with a specified probability, demonstrate a system mean time between failure (MTBF) objective with a specified level of confidence. The model uniquely determines the subsystem growth test times either by minimizing reliability testing costs or by using a specified allocation of the system-level failure intensity among the individual subsystems. SSPLAN provides a means to develop subsystem testing plans which will cost effectively demonstrate a system MTBF goal prior to system-level testing. Although additional failure modes will likely appear during system integration, a structured subsystem testing program will eliminate or reduce many failure mechanisms, and result in less system-level testing, since the initial system MTBF will be increased. The model can also serve as a means for prime contractors to integrate the reliability growth activities of their subcontractors. The model is currently under consideration as a management tool for structuring a reliability subsystem test program for two major Army weapon systems
    No preview · Conference Paper · Feb 1994
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    ABSTRACT: Two general approaches are available for assessing reliability of electronics during design: device failure-rate prediction, physics-of-failure. This article broadly compares these two approaches in a way that is readily understandable by the wide range of readers concerned with the design, manufacture, and support of electronic equipment. The most prominent device failure-rate prediction methodology, US Mil-Hdbk-217, does not provide the designer or manufacturer with any insight into, or control over, the actual causes of failure since the cause-and-effect relationships impacting reliability are not captured therein. Mil-Hdbk-217 does not address the design & usage parameters that strongly influence reliability; this problem results in an inability to tailor a Mil-Hdbk-217 prediction using these key parameters. Physics-of-failure methodology is an approach to design, reliability assessment, testing, screening, and stress margins that uses knowledge of root-cause failure mechanisms to prevent product failures through robust design & manufacturing practices. This approach proactively incorporates reliability into the design process by establishing a scientific basis for evaluating new materials, structures, and electronic technologies. This approach encourages innovative, cost-effective design through realistic reliability assessment.
    No preview · Article · Jan 1994 · IEEE Transactions on Reliability
  • D.E. Mortin
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    ABSTRACT: A methodology is described for evaluating the logistical supportability of complex systems. Specifically, the supportability of the US Army's mobile subscriber equipment (MSE) is described. MSE is a good example of a complex military system which employs many continuity-of-operations (CONOPS) features, i.e. system networking, component redundancy, and functional bypass capabilities. The MSE supportability analysis determined that the additional procurement of specific spare parts could greatly increase MSE performance. The MSE analysis provided a means to increase the expected call-completion rate of the Army's primary corps and division common-user voice-communication system significantly. The increased cost associated with acquiring the additional spares was virtually negligible when compared to the MSE procurement cost
    No preview · Conference Paper · Feb 1990
  • W. Hughes · M.M. Kim · R.M. McGauley · D.E. Mortin · G.A. Serabo
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    ABSTRACT: The authors describe level-of-repair analyses for four major US Army weapon/communication systems using the Optimum Supply and Maintenance Model (OSAMM). The four systems are: Single Channel Objective Tactical Terminal (SCOTT); Global Positioning System (GPS); Single Channel Ground and Airborne Radio System (SINCGARS); and Hawk guided missile. The analyses compare the costs associated with a strict two-level maintenance concept with the resulting costs of other maintenance alternatives (e.g. three- and four-level, with and without screening). The authors identify the sensitivity of the resulting cost to such factors as inaccurate built-in test (BIT); TMDE (test measurement and diagnostic equipment) costs, including test program sets; provisioning levels and supply support measures, including number and placement of test equipment and maintenance personnel; and the impact of repair vs. discard. The cost of each policy is assessed not only in terms of dollars, but also in terms of operational availability and system readiness
    No preview · Conference Paper · Oct 1989
  • David Edward. Mortin
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    ABSTRACT: Thesis (Ph. D.)--University of Maryland, College Park, 1999. Thesis research directed by Dept. of Materials and Nuclear Engineering. Includes bibliographical references (leaves 144-154).
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