Tap Testing

  Using the CATT

  Sample Data
   & Images

  Data Analysis





Advanced Structural Imaging, Inc.
 1502 Duff Avenue, Ames, IA 50011

Computer-Aided Tap Tester (CATT)

Data Analysis

As mentioned previously, the CATT collects quantitative data relating to the surface stiffness of the structure. This data can be used to make engineered decisions. In the inspection of a structure for flaws and damages, the decision to repair, scrap, or put the structure back in service is often based on a number of factors, including the number of defects present, the size of each defect, the combined area of the defects, and the proximity of the defects with each other. With the CATT system, such information is readily contained in the images it generates. The system affords the user opportunities to input an accept/reject criterion, and provides a thresholded image (go/no-go image) and a detailed defect analysis. The analyzed results list the number of defects detected, the size and location of each defect, and the combined defective area as a percentage of the area inspected. This convenient and useful feature of the CATT gives the user the ability to objectively evaluate the condition of a structure as soon as the test is completed.

The first images below, shows a CATT scan of a hail damaged area of a composite aircraft component. In this image, the contact time of the instrumented tap probe is plotted. Red, yellow and green areas indicate that the contact time was longer than it was for the blue areas. Areas of lower stiffness result in a longer contact time and, in fact, the contact times can automatically be converted to stiffness values by the CATT software. In the second image, the system was told to plot in red those areas with a contact time above a certain threshold value. Areas in red would be indicative of a damaged area. From this image, the system can calculate the number of damaged areas, the area of each defective area and the total amount of damaged area within the scanned area. The defect summary information is summarized in a table as shown below.