Reducing the Logistics Burden for the Army After Next Doing More with Less (1999) / Chapter Skim
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7 Reliability Concepts
7 Reliability Concepts
Pages 110-127
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From page 110... ...
This chapter describes the reliability concepts and technologies needed to develop AAN mission-reliable systems. LOGISTICAL IMPLICATIONS OF HIGHT,Y RELIABLE SYSTEMS Improving the reliability of the systems used by an AAN battle force will have a multiplier effect on reducing logistics demands.
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From page 111... ...
(A catastrophic failure is a failure that requires that the item, component, or system be rebuilt or replaced.) 111 For a combat operation to accomplish its objectives, all systems taken into the area of operations must be close to fully operational and require neither repair nor maintenance throughout the period of the operation.
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From page 112... ...
simpler planning requirements to ensure that the BUSE can sustain the war-fighting operations. AAN Mission Reliability Versus Ultrareliability The discussion above shows how the reliability for AAN missions, or ANN mission reliability, can be analyzed into specific reliability requirements for systems, such as pulse reliability and fast refit.
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From page 113... ...
Three approaches can be used to ensure that AAN mission reliability (and related RAMD qualities) receives appropriate consideration along with other performance objectives.
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From page 114... ...
Designing candidate AAN system concepts to meet AAN mission reliability requirements will require the following extensions of current capabilities and design approaches: M&S systems must be adequate at every level in the hierarchy at which "designing for reliability" is done, from the top level of force-on-force engagement down to the lowest level at which the reliability of design options is evaluated. Metrics for reliability at each level must be defined in terms of operational requirements, so that reliability can be assessed objectively at that level.
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From page 115... ...
For the sake of simplicity note that the top two engagement levels are not shown. Also, the requirements and metrics for other performance goals (left side of Figure 3-1)
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From page 116... ...
Because AAN mission reliability is a cumulative outcome of complex system-level behaviors, it will be helpful to consider the necessary capabilities of each M&S system type described in Chapter 3 to provide a reasonable simulation for assessing reliability. For example, at each of the three engagement levels shown in Figure 3-l (forceon-force, multiple systems with operators, and single system with operator)
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From page 117... ...
Less obvious perhaps is that the appropriateness of the reliability measures at one level is determined by the performance properties at the next higher level to achieve the reliability characteristics required there. This linkage of the reliability measures at a given level to the required performance characteristics for reliability at the next higher level makes it possible for assessable reliability requirements to "flow down" from mission-specific, functional requirements (like pulse reliability or rapid refit)
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From page 118... ...
, but valid data on even well established properties that affect reliability may not be available to the designer. For AAN mission reliability to be analyzed objectively and reasonably, modelers will need sound data for all design options of potential interest and for all properties that significantly affect the reliability metrics at each mode!
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From page 119... ...
With rigorous adherence to good systems engineering practices, a performance goal like mission reliability, which is a global property of overall system performance across a system's mission profile, can be achieved. AAN mission reliability can only be assured if the trade-offs inherent In creating a novel and complex product that can be fielded by 2025 maintain adequate levels of mission reliability.
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From page 120... ...
An equally valid approach from the standpoint of systems engineering is for designers to re-examine the performance requirements, including the reliability requirements, at each level in the M&S environment from the top down, to see if any can be relaxed without sacrificing the essential requirements for the system to do its job (i.e., top-down reduction of functional requirements)
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From page 121... ...
mechanisms offailure modeling, to relate structural failure modes at one level in the M&S hierarchy to physical properties at the next lower level materials selection and materials design to provide new options (and inputs at the level of component design and analysis) in the M&S hierarchical environment prognostics (the design and application of prognostic sensing technology)
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From page 122... ...
Given the importance of energy management in reducing logistics burdens (see Chapter 4) , many AAN vehicles or other systems will require high-horsepower engines that operate at high fuel efficiencies throughout the range of operating conditions required for AAN mission scenarios.
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From page 123... ...
how failure modes are affected by materials with different structural patterns at different spatial scales (ranging from atomic to micron scaler, as opposed to materials with bulk properties dete~ined predominantly by their atomicscale structure. Materials Selection for Improved Reliability If all of the performance requirements, including the reliability metrics, for component-level models of an AAN system cannot be met with standard materials,
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From page 124... ...
As materials science develops better tools for modeling the performance characteristics of materials based on their underlying structures, and as methods for forming materials with novel structures, particularly at very fine scales, are improved, an even more innovative approach may become possible. The component designer may be able to call on the materials designer to design a new material to meet the performance requirements for a particularly demanding application.
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From page 125... ...
Although prognostics is not a substitute for AAN mission reliability, it is clearly a complementary technology. SCIENCE AND TECHNOLOGY INITIATIVES TO ACHIEVE AAN MISSION RELIABILITY Based on the preceding analyses of the role of reliability (and related concepts, such as maintainability, availability, and durability)
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From page 126... ...
models incorporated into the M&S environment that can represent the system properties and environmental conditions that affect AAN mission reliability requirements, (2) measurable reliability-related requirements defined for the models at each level in the M&S hierarchy, (3)
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From page 127... ...
selecting or designing alternatives for materials that can meet AAN requirements, including reliability requirements, that familiar materials cannot meet, and (3) using embedded prognostic sensing technology in designing structures and components.
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