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Reliability and Maintainability Symposium, 2007. RAMS '07. Annual

Date 22-25 Jan. 2007

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  • 2007 Proceedings - Annual Reliability and Maintainability Symposium

    Page(s): c1
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    Freely Available from IEEE
  • 2007 Proceedings - Annual Reliability and Maintainability Symposium

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  • 2007 Proceedings - Annual Reliability and Maintainability Symposium

    Page(s): i
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    The following topics were dealt with:reliability analysis; fault trees; software reliability; failure analysis; probabilistic distribution; risk management. View full abstract»

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  • Copyright & reprint permission

    Page(s): ii
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  • Symposium Management Committee

    Page(s): iv
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  • Past Symposia & General Chairs

    Page(s): v
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  • The R.A. Evans - P.K. McElroy Award for the 2006 Best Paper

    Page(s): vi - xi
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  • Tutorial Sessions

    Page(s): xii
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    First Page of the Article
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  • Technical program sessions and moderators

    Page(s): xiii - xiv
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    First Page of the Article
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  • Technical papers

    Page(s): xv - xix
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    First Page of the Article
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  • Modeling Expert Judgment for Reliability Prediction - Comparison of Methods

    Page(s): 1 - 6
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    This paper presents an introduction into methods for representing and modeling expert judgment for reliability prediction in early stages of product development process. It provides a survey of required inputs and resulting outputs of the single approaches. The problem of handling uncertainties in early design stages will be exemplified by means of the evaluation of reliability for the software portion in mechatronic systems. In this context we show the influence of uncertainty and present an approach which enables the comparison of several concepts in early development stages based on expert judgment. View full abstract»

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  • Reliability analysis of phased-mission systems: a correct approach

    Page(s): 7 - 12
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    At the 2006 RAMS Conference, a paper entitled Reliability analysis of phased-mission systems: a practical approach was presented. This paper established an alleged novel and simple approach to reliability analysis of phased-mission systems. The technique presented in that paper transformed a phased-mission system into several nonphased systems, thus allowing for each phase to be analyzed independently. The paper then presented a method for combining the individual results into a composite solution that spanned all the phases of the system in question. Unfortunately, we discovered that the paper contained grave errors in its methodology, leading the authors to draw inaccurate conclusions. The paper determined a reliability time function for each phased topology, which were then combined into a so-called exact solution. This approach did not take into account the critical question of what happened to the system in the previous phases. Our paper demonstrated a mathematically accurate solution for the main example of the previously presented paper in addition to a simulation solution to verify our own methodology. Moreover, our paper presents a solution for the examples shown in the previous paper that are mathematically intractable. In summary, the ultimate objective of this paper is to correct the errant phased-mission methodology presented at the last RAMS Conference. View full abstract»

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  • Realistic reliability requirements for the stresses in use

    Page(s): 13 - 16
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    This paper discusses, with examples, dependency of the reliability estimates or requirements on the use environments, including the details of reliability changes of electronic and mechanical components as a function of environmental and operational stresses as well as of their duty cycle. It also provides a discussion of the fundamental differences between the product validation and reliability demonstration or assessment. The paper shows how the same product used in a different location of a system, e.g. vehicle, or in merely different orientation that affects its natural heat transfer, can have a very different reliability estimate. For that reason, the reliability requirements or goals need to be tailored for the product actual expected use. The reliability details such as dependency on the product use cannot be numerically tailored at all times for all locations and details of use, especially contractually. Therefore specification of reliability requirements in a form of a reliability range in average and or a minimum reliability in the harshest use profile is needed rather than as a fixed numerical value. The most excessive environmental and operational stresses are not expected be constant and always present when the product is in actual use; they are expected to be present for only a fraction of the life time, thus the knowledge of the use profile is essential to prepare analysis or design an accelerated reliability life test is specifically important. This analysis along with the reliability demonstration/growth test needs to be tailored to cover the use with the aggressive, normal, and light stresses dependent on the percent time spent in those environments, and with realistically expected stresses of the product during those times. To determine realistic and effective reliability goals or requirements, it is necessary to have in mind the manner how an item will be used and also the environments or locations of its use. Specifying a value of a required MTT- - F or MTBF may introduce unwanted problems, as they are average values and, just as reliability is, are highly dependent on the item's use its operational and environmental stresses and also of life or product use duration. It is more appropriate to specify minimum reliability value for the aggressive use in the harshest environment that the product might be used. This is even more important in cases where a product, besides electronics, contains mechanical components where and MTTF is just an average value calculated from the stress/strength criteria and resultant reliability. View full abstract»

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  • Electronic failures and monitoring strategies in automotive control units

    Page(s): 17 - 21
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    A widely spread and required risk analysis method in automotive industry is the FMEA (failure mode and effects analysis). However, it can be shown, that with the help of the FMEA, the complex relations of drive and monitoring strategies for example in engine, transmission and/or general automotive control units, cannot be completely treated. In order to show and to implement the new legal requirements, the increased complexity, the cross linking of the developed systems and, last but not least, the shortened development times, a new procedure was created. The new procedure enables, by a two-phase layout, the assisting of the implementation of drive and monitoring strategies in automotive control units and the illustration of possible failure functions in software, electronics, mechanics and their interactions to other systems. Furthermore it allows the definition of adequate failure reactions to prevent, to minimize and/or to keep the vehicle in stable and secured working conditions. It is now possible, under consideration of the defined measures, to demonstrate the potential of improvement, i.e. the decrease of the assessment value of the severity and the connected failure effect in a traceable way and to allow a suitable risk prioritization in an FMEA. View full abstract»

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  • What is 217Plus/sup TM/ and Where Did It Come From?

    Page(s): 22 - 27
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    In June, 2005 the DoD contract for the Reliability Information Analysis Center (RIAC), formerly known as the Reliability Analysis Center (RAC), was awarded to a five member team comprised of Wyle Laboratories, Quanterion Solutions, the Center for Risk and Reliability at the University of Maryland, the Penn State University Applied Research Laboratory (ARL), and the State University of New York Institute of Technology (SUNY-IT). While the Center name and contractor change have been confusing to the R&M community-at-large, even more confusing has been the introduction of the DoD-funded 217Plustrade methodology and reliability prediction software tool by the RIAC to replace the DoD-funded PRISMreg tool introduced under the "old" RAC. In July 2006, RIAC released 217Plustrade as the successor to the DoD-funded, Defense Technical Information Center (DTIC)-sponsored Version 1.5 of the PRISMreg software tool. The RIAC release of 217Plustrade supplemented the six original component models with six new component models connectors, inductors, optoelectronic devices, relays, switches and transformers. Also, for the first time, the 217Plustrade models and methodology were published in the RIAC's "Handbook of 217Plus Reliability Prediction Models". The handbook, in a MIL-HDBK-217 style format, details the 217Plustrade methodology and models as a more current replacement for the early-90's vintage MIL-HDBK-217. The RIAC charter as a DTIC-sponsored Information Analysis Center (IAC) ensures that DoD funding will continue to support the data collection/analysis and modeling activities that are planned for future 217Plustrade releases and enhancements. This paper describes the evolution, and some of the technical detail, behind the RIAC's 217Plustrade methodology. View full abstract»

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  • A diagnostics design decision model for products under warranty

    Page(s): 28 - 33
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    Warranty obligations in product service involve additional costs to the manufacturers. Building diagnostic features into a product can reduce the warranty costs because of; 1) fewer visits needed by warranty service representatives (through self-guided user repairs for simple problems) and 2) shorter service times (via reduced diagnostic time) for each failure. However, this approach increases the cost of the product and is worthwhile only if the reduction in the expected warranty cost is more than the additional costs incurred. This paper develops models to evaluate diagnostic design decisions for products under warranty from the manufacturer's point of view. The roles and influence of the key parameters and decision variables based upon the consideration of uncertainty are explored. Numerical examples are given to illustrate the proposed models. View full abstract»

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  • Simulation and calculation of reliability performance and maintenance costs

    Page(s): 34 - 40
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    This paper provides a short description of an extensive method for simulation and calculation of reliability, availability and maintenance costs of a product (system, function, equipment, mechanism, part, etc). Our method helps the designer to determine at an early stage of the design what level of reliability performance and corrective and preventive maintenance costs can be achieved under the selected design solution, maintenance and operation strategies, and maintenance resources. The versatility of the method promotes also the introduction of expertise from areas that strongly affect the success of the design process, namely the manufacturing, testing, operation, and maintenance. RAMoptim software has been developed to implement this method. The reliability and availability obtained from RAMoptim should be compared with the requirements, set, for example, by using our allocation method RAMalloc. If these or other defined requirements have not been achieved, the designer must return to the drawing table to consider other solutions. Further, our method enables also repair time delays due to external causes. E.g., using StockOptim one can assess the delay caused by the lack of spare parts. Finally, the development of the method and the related software continues. The effect of preventive maintenance(PM) (e.g. condition monitoring and diagnostic resources) on failure tendency is a particularly important and challenging subject for further research. View full abstract»

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  • Modeling and optimization of extended warranties using probabilistic design

    Page(s): 41 - 47
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB) |  | HTML iconHTML  

    Reliability engineers and actuaries from the insurance industry are increasingly being asked to collaborate in measuring, valuing and managing risk associated with extended warranties and long term service agreements. This interaction has resulted in the development of hybrid approaches that combine methods of quantifying uncertainty in the engineering domain (probabilistic design algorithms) with models that incorporate financial risk and uncertainty (actuarial loss models). One such hybrid algorithm is described in this paper. In this approach, the reliability of a structure is computed using a analytic, time-dependent stochastic-degradation code and its long term risk is assessed using a combination of renewal and actuarial loss models. Using these techniques, products can be optimally designed to meet an acceptable probability of survival as well as a predetermined cap on probabilistic financial exposure. The methods presented in this paper can also be used to value extended warranties. The algorithm and its potential applications are illustrated through a representative case study. View full abstract»

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  • Embedded diagnostics enable military ground vehicle

    Page(s): 48 - 52
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    The DoD has initiated programs to modernize logistics practices and processes. Among them is the requirement to build and deploy autonomic logistics (AL). AL is necessary to provide a focused and tailored logistics response to area of operations (AO). It is based upon knowing status, condition and health of all combat equipment in the AO. Embedded sensors monitor levels of consumables (fuel, ammo, water) and condition (health of components, subsystems and systems) and report those through the logistics operational architecture to Global Combat Support Systems (GCSS) and Global Command Control Systems (GCCS). Autonomic logistics fills the critical gap of interpreting, assimilating and synchronizing data from individual platforms into aggregated and actionable calls for supply, support and maintenance. Embedded diagnostics plays a critical role as an enabler for autonomic logistics and is the subject of this article. View full abstract»

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  • Real time consequence engine

    Page(s): 53 - 58
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    This paper presents a brief overview of a prognostics and health management (PHM) system, the basic capabilities and architecture of the real time consequence engine (RTCE), and how the RTCE fits into a PHM system. Also, examples of consequence analysis results as applied to a past prototype development effort and the results of ongoing modification efforts to RTCE are presented. By varying operational settings, maintenance schedules, and other parameters of interest, the RTCE can be used to examine the consequences of such actions in terms of common performance metrics; such as, mean time between failures (MTBF), mean time to repair (MTTR), system availability, maintenance cost, downtime cost, etc. In its final form, the RTCE will provide the capability to evaluate the potential cost/benefit of an embedded PHM system, which is considered to be a precursor to implementing a PHM system; and, provide the capability for real-time consequence analysis, which is typically viewed as the final step in the development of a complete PHM system. View full abstract»

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  • Energetic Material/ Systems Prognostics

    Page(s): 59 - 64
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    The US military and weapons industries require their weapon systems to be reliable. As inexpensive miniaturized sensors and affordable simulation tools have become available, the prognostics method has begun to attract the attention of engineers seeking a new way to increase and optimize system reliability. This paper presents the tools currently available and being developed for prognostics of military energetic systems. Key elements of the study were assessments of available energetic material models, as well as current and future sensors for monitoring the health of energetic systems. A roadmap for developing prognostic methodologies is proposed View full abstract»

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  • Electronic Prognostics for Computer Servers

    Page(s): 65 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (286 KB) |  | HTML iconHTML  

    Electronic prognostics (EP) relates measurable precursors of failures to remaining useful life (RUL) predictions for electronic systems. When used with condition-based maintenance, EP promises to significantly increase the effective mean-time-between system failures (MTBF) by predicting and avoiding system failures (maintenance planned based on condition). Increased MTBF numbers translate into enhanced availability and better operational reliability. This is essential for building highly dependable computing systems. This paper briefly reviews the steps required for achieving successful prognostics. The lessons learned from adopting EP to the previous and current generations of enterprise computing systems have influenced the next generation computer system designs, equipping future systems with more advanced capabilities for electronic prognostics. Sun Microsystems' new continuous system telemetry harness (CSTH) coupled with advanced pattern recognition substantially increases component reliability margins and system availability goals while reducing (through improved root cause analysis) costly sources of "no trouble found" events. These "no trouble found" events have become a significant warranty-cost issue for COTS and a sparing-logistics issue for mil spec electronic systems View full abstract»

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  • Dynamic Reliability Block Diagrams VS Dynamic Fault Trees

    Page(s): 71 - 76
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    Reliability block diagrams (RBD), and fault trees (FT) are the most widely used formalisms in system reliability modeling. They implement two different approaches: in a reliability block diagram, the system is represented by components connected according to their function or reliability relationships, while fault trees show which combinations of the components failures will result in a system failure. Although RBD and FT are commonly used, they are limited in their modeling capacity of systems that have no sequential relationships among their component failures. They do not provide any elements or capabilities to model reliability interactions among components or subsystems, or to represent system reliability configuration changing (dynamics), such as: load-sharing, standby redundancy, interferences, dependencies, common cause failures, and so on. To overcome this lack, Dugan et al. developed the dynamic FT (DFT). DFT extend static FT to enable modeling of time dependent failures by introducing new dynamic gates and elements. Following this way, recently we have extended the RBD into the dynamic RBD notation. Many similarities link the DFT and the DRBD formalisms, but, at the same time, one of the aims of DRBD is to extend the DFT capabilities in dynamic behavior modeling. In the paper the comparison between DFT and DRBD is studied in depth, defining a mapping of DFT elements into the DRBD domain, and investigating if and when is possible to invert the translations from DRBD to DFT. These mapping rules are applied to an example drawn from literature to show their effectiveness View full abstract»

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  • Fault Tree Analysis Based on Fuzzy Logic

    Page(s): 77 - 82
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    Accurate assessment of system reliability with limited or insufficient statistical data is difficult. This paper presents a method which overcomes the drawbacks of traditional fault tree analysis (FTA) by using FTA based on possibilistic measures and fuzzy logic. This method is designed specifically for situations wherein reliability and safety assessment is imprecise by nature and necessary statistical data is scarce. Based on fundamentals of fuzzy logic, failure possibility is first defined and then fuzzy variables are characterized in the context of possibility theory. Next, subevents in FTA described with natural language are viewed as a collection of elastic constraints of fuzzy variables. Fuzzy rules are generated from linguistic quantification and meaning inference in fuzzy logic. Lastly, an example is used to illustrate the proposed analytical method and reasoning mechanism. Unlike previously reported fuzzy FTA or fuzzy logic-based FTA, this method is an integration of the possibilistic approach and the fuzzy logic-based reasoning approach which is of potential value for creating expert knowledge databases. It can also be applied to other aspects of reliability engineering, addressing ambiguous and subjective uncertainty problems qualitatively and quantitatively View full abstract»

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