FREE DROP IMPACT DATA ACQUISITION USING DIGITAL IMAGE CORRELATION

Radioactive materials are widespread throughout our everyday activities and are used in many different types of industries. There are about 3 million shipments of radioactive materials that occur each year in the United States. Because radioactive materials are so widespread, safety and security are top priorities for the Package Testing Program (PTP) at Oak Ridge National Laboratory (ORNL), and effective and accurate data collection methods are imperative. The packaging used to carry nuclear materials is subjected to rigorous tests to verify its durability. One such test is the free-drop test. Impact data are often collected through an accelerometer attached to the test unit. Unfortunately, these devices are easily broken in the testing environment and are expensive to procure, install, and post process. Digital image correlation (DIC) using high-speed images offers a non-contact alternative. DIC is an optical method that employs image registration techniques to accurately measure changes in images. To verify the suitability of the cameras and process, a test weight was dropped from various heights, and the impact acceleration was derived using DIC. This paper compares the results with data from the attached accelerometer. A total of nine drop tests were performed with three different image capture rates (frames per second) and from three different package drop heights. An ANSYS LS-Dyna model was also used to determine theoretically predicted deceleration rates for comparison with the DIC and accelerometer data.