Integration of a Time Varying Probability of Detection (POD) Model for Structural Integrity

Abstract

The objectives of this paper are to assess the impact of a time varying Probability of Detection (POD) model for structural integrity, and to develop an analysis process to define the limits of variability for the time varying POD model based on the computed risk of a typical structural location and the associated costs. To derive the time varying POD model, this paper will first discuss the role of POD in the current risk assessment methodology and the process for developing a POD model by using the MIL-HDBK-1823A standard for both traditional non-destructive evaluation/inspection (NDE/NDI) and in-situ sensor-based inspection methods. From the developed POD model, the false call rate and its relationship with the threshold damage index value will also be examined. An analysis process will be designed to find the optimal balance between in-situ sensor replacement frequency, upfront design costs (sensor reliability), and the impact of a degraded POD system on the risk analysis (e.g., increased probability of failure estimates). This process can be used to define the limits of variability for a time varying POD model for a given situation. Examples will be shown which demonstrate the implications of time varying POD capability on structural integrity by using the proposed analysis process.