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PM, NDI and SHM simulation platform
The simplest structural risk and reliability assessments do not require maintenance or inspection information for their analysis. Thus the failure probability simply provides an indication or a prediction of risk of failure as a function of operating hours for the given operating conditions. Structural risk and reliability methodologies can be extended for evaluating the effects of inspections on the failure probability. To allow evaluation with inspection the Inspection Probability of Detection (POD) is needed.
 

Detecting service-accumulated damage is one of the critical aspects of any probabilistic damage tolerance approach. Many factors such as part geometry, part location, the skill of the NDE equipment operator, or the environment in which the inspection takes place (PM, NDI and SHM) will significantly influence the Probability of Detection (POD) results and hence greatly affect the anticipated structural performance. Thus, the probabilistic damage tolerance approach needs to incorporate all variables associated with inspection, i .e. detected damage sizes, POD capabilities and their impact on determining the actual damage sizes present in the structure at the time of inspection.


Herein, the general framework for an inspection-based estimation of Probability of Failure (POF) is developed. This framework takes into account the influence of detection probabilities, critical damage and detection thresholds as well as the evolutionary nature of the damage accumulation process under the operational envelopes. The uncertainties inherent to any inspection event and damage growth are accounted for in an explicit way with the ability to differentiate between rates and types of appearing defects, location effects as well as combination of inspection procedures for the different areas and types of structure’s zones including variation of damage and detection thresholds. In addition, the probabilistic analysis can also utilize the distribution of actual damage sizes, which are derived in terms of the detected damage sizes and the detection capabilities at the time of inspection, in order to derive a more realistic scenario of the damage accumulation process and consequently of the residual structural capacity.

 

Thus, a Simulation Platform which incorporates information form i) Process Monitoring PM, e.g. estimates of possible defects during manufacturing based upon a validated signal analysis and relation to defect types ii) Non - Destructive Inspection NDI and iii) Structural Health Monitoring SHM, e.g. fused data from on-line systems that impart the possibility of identifying defects and their key characteristics will allow for a complete analysis of structural components and sensitivity studies related to maintenance and inspection strategies. POF assessment will also enable Inspection Interval assessment and Optimisation studies for minimum Maintenance Costs and high structural Reliability as well as fine-tuning of manufacturing and inspection processes. The theoretical basis was developed in the framework of MANHIRP project and the goal is to be extended, developed and implemented for all inspection phases in the framework of a Probabilistic Life - Cycle Management

 

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Sensor - advised Inspection interval computation is guided by POF value (blue line). Inspection events are much less compard to those computedusing typical deterministic approach. (Ref. IARCAS project)
 
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