Fragment Size Distribution for Ice Particle Impacts on a Glass Plate

Abstract

This work presents the results of an experimental study of ice particle impacts on a flat glass plate. The experiment was conducted at the Ballistics Impact Laboratory of NASA Glenn Research Center. The main objective of the experiment was to gain understanding about the modifications needed to the experimental configuration for a future parametric study at a larger range of values for particle diameters and other parameters. This was achieved by studying the effect of the velocity of an impacting ice particle on the post-impact fragment size and distribution for a reduced range of impacting particle diameters. Pre-impact particle diameter and velocity data were captured with a high-speed side camera. Post-impact fragment data were captured in a single frame with a 29-megapixel camera located above and normal to the target. Repeat runs were conducted for ice particles with diameters ranging from 1.7 to 2.9 millimeters, impacting at velocities between 39 and 98 meters per second. The fragment areas were measured, and the corresponding equivalent diameters and histogram distributions were calculated. Analysis of the data showed that the average equivalent diameter for the fragments in a run was an order of magnitude smaller than the diameter of the impacting ice particle. The histograms for equivalent diameter distribution were non-normal with long tails, with most of the fragments having equivalent diameters concentrated toward the minimum value of the fragment size that could be resolved. Factors affecting the accuracy of the data during the digital imaging analysis were identified. Needed modifications to the setup to handle small size ice particles and other testing conditions were also identified. at a given pressure Test = A series of experimental runs at the same tank pressure and with similar ice particle diameter for ice particles of similar diameter. Each test contained 10 runs. Tests were conducted for tank pressures of 3, 5, 7, 9, 11, 13, 15, 17, and 20 psi. At each pressure, for each run, the image of the expanding fragments was segmented, and the area of each fragment was calculated. For each fragment, the diameter of a circle with the same area was calculated and called “the equivalent diameter”. For a given run, the average of the fragment