Scheduled maintenance has been utilized in rotorcraft industry to sustain structural integrity and reliability of dynamic components throughout the service life. However, inspection schedules are often too simplistic, e.g., use equal intervals, which tend to be overly conservative causing significant maintenance burden and cost. In the current approach, the inspection interval is determined by the typical material data, expected value of crack growth rate, anticipated usage and applied load (with embedded conservatism). To incorporate the effect of Non-Destructive Inspection (NDI), a characteristic value representing typical inspection capability, a NDi, is considered and used as the "initial" crack size for damage growth life prediction. To compensate for the inherent randomness associated with damage progression, the estimated average damage growth life is further divided by a safety factor, typically ranging from 3 to 4. This adjusted damage growth life is defined as the inspection interval. Although the outlined approach has been widely used in the industry, there are several folders of drawbacks. First of all, the approach is based on average behavior of Fatigue Crack Growth (FCG). While a safety factor is employed to make further adjustment, its value may not be fully justified and often results in excessive conservatism. In addition, there is no justification to use a single characteristic value representing the capability of a NDI. Therefore, the lack of rigorous statistics to address uncertainties in damage progression and inspection capability limits the applicability and creditability of the current approach. In general, the inspection plan obtained from the aforementioned approach results in many unnecessary inspections. In this paper, a technical approach that addresses the inherent scatter of damage progression and incorporates the reliability model of specific inspections is presented to assess DT risk and determine the optimal inspection schedule. The approach incorporates effects of various uncertainty sources and associated risk of excessive damage progression, capability of inspection, and quality of repair into the process of structural reliability assessment and subsequent inspection planning and maintenance decision. The methodology is demonstrated through a case study for a rotorcraft dynamic component. Baseline risk assessment has been established and various POD models and inspection options are considered. An optimal inspection plan is established. These results highlight the technical capabilities and application potential of developed DT risk assessment and inspection schedule optimization framework in risk management and CBM decision making.


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    Title :

    Optimization of inspection planning for probabilistic damage tolerance design


    Additional title:

    Optimierung der Inspektionsplanung für den Entwurf wahrscheinlichkeitstheoretischer Schadenstoleranzen


    Contributors:
    Zhao, J. (author) / Wu, Justin (author) / Urban, M. (author) / Tristch, Douglas (author)


    Publication date :

    2011


    Size :

    14 Seiten, 20 Bilder, 3 Tabellen, 8 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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