Recent advances in non-destructive evaluation (NDE) technologies have led to improved methods for quality control, in-service inspection and the development of new options for material diagnostics. Detailed defect sizing and characterization has become the major objective of much NDE work underway today. To address this challenge, the NDE community has turned to a combination of multiple mode inspections and computer-aided data analyses.
NDE is generally used to assess the integrity of a system or component without compromising its performance. NDE uses sensors to acquire information about these objects and perform modeling, analysis, and conversion of the information into materials and defect parameters for performance and in-service life prediction. The inspection of in-service systems can also be complicated by the fact that these systems often operate at relatively high temperature in a closed mode.
When several inspection techniques can be used, the choice of a specific schedule will depend on the accuracy and cost of the inspection, balancing the money spent on safety measures with the business return of the system being maintained. The accuracy of a given technique must also be sufficient to detect defects considerably smaller than those which could result in failure because these defects can grow in size between inspections. A cheaper and less accurate technique used frequently could be equivalent cost wise to a more expensive and more accurate technique used less frequently leading, however, to greater reliability, as illustrated by a figure of merit. However, regardless of which technique has been chosen, the critical decision remains to decide on the frequency of application. This decision depends on three factors:
The extent of damage that might remain invisible to the technique;
The rate of damage occurrence with time;
The extent of damage the structure can tolerate.
See also: Corrosion detection, NDE techniques, Selection of inspection points, Risk-based inspection, Maintenance revolution, Maintenance strategies