Damage Dosimeter Third-Octave and Time-History RMS Values

• Activity Number: 150
• Type: Contributed
• Date/Time: Monday, August 12, 2002 : 2:00 PM to 3:50 PM
• Sponsor: Section on Physical & Engineering Sciences*
• Author(s): David Banaszak*+ and Angela Trego and Dansen Brown
• Affiliation(s): Wright-Patterson Air Force Base and The Boeing Company and Air Force Research Laboratory
• Keywords: Strain Data ; Time History ; Third Octave ; Mean ; Standard Deviation ; Root Mean Square

Abstract

The Air Force sponsored flight tests using damage dosimeters, fabricated by The Boeing Company, to measure temperature and structural dynamic strains on B-52, F-15, and C-130 aircraft. The dosimeter measurements help diagnose difficult-to-analyze structural conditions, such as acoustics and high-cycle fatigue, and support the durability patch design process to repair secondary structure cracks. The dosimeter is a rugged, small, lightweight data acquisition unit that runs autonomously off of battery power. It measures three channels of strain at a rate up to 15 kilo-samples per second and one channel of temperature at a rate of 1.3 samples per second. The dosimeter acquires data above a programmer-defined root mean square (rms) strain threshold. It is currently programmed to store 42 time-history records (0.3 seconds each) and compute and store 29,544 third-octave spectra (18 bands each) in its 4-megabyte memory. LabVIEW virtual instruments (VIs) provide a quick look at the time-history and third-octave data, and stores mean, rms, and standard deviation values into a spreadsheet. This paper compares rms values computed from third-octave data with rms values from time-history data.