Processing and Probability Analysis of Pulsed Terahertz NDE of Corrosion under Shuttle Tile Data
This paper examines data processing and probability analysis of pulsed terahertz NDE scans of corrosion defects under a Shuttle tile. Pulsed terahertz data collected from an aluminum plate with fabricated corrosion defects and covered with a Shuttle tile is presented. The corrosion defects imaged were fabricated by electrochemically etching areas of various diameter and depth in the plate. In this work, the aluminum plate echo signal is located in the terahertz time-of-flight data and a threshold is applied to produce a binary image of sample features. Feature location and area are examined and identified as corrosion through comparison with the known defect layout. The results are tabulated with hit, miss, or false call information for a probability of detection analysis that is used to identify an optimal processing threshold.
Directed Design of Experiments for Validating Probability of Detection Capability of NDE Systems (DOEPOD)
The capability of an inspection system is established by applications of various methodologies to determine the probability of detection (POD). One accepted metric of an adequate inspection system is that there is 95% confidence that the POD is greater than 90% (90/95 POD). Directed design of experiments for probability of detection (DOEPOD) has been developed to provide an efficient and accurate methodology that yields observed POD and confidence bounds for both Hit‐Miss or signal amplitude testing. Specifically, DOEPOD demands utilization of observance of occurrences. Directed DOEPOD does not assume prescribed POD logarithmic or similar functions with assumed adequacy over a wide range of flaw sizes and inspection system technologies, so that multi‐parameter curve fitting or model optimization approaches to generate a POD curve are not required.
Time-domain terahertz spectroscopy of bioagent simulants
In this work, we present initial results of time-domain Fourier transform spectroscopy in the THz frequency range (from 0.5 to 4 THz) of bio-agent simulants. Also shown are spectra acquired with conventional FT-IR spectroscopy. The potential promise and limitations of the technique will be discussed for stand-off detection of biological threat agents.