November 14, 1998
Modified September 30, 1999
Pelcin's research focused on the creation of glass flakes in a controlled environment. These flakes were largely created by dropping steel balls on the glass cores. While holding the physical properties of glass constant, he varied the external platform angle (EPA), the angle of blow (AOB), indenter (hammer) force, indenter properties, and core morphologies (edge or face). The following image displays a small portion of his work which are the flakes from edge cores having an EPA of 55 degrees.
In the image, each colored diamond represents a flake and its mass is plotted against its theoretical platform thickness (TPT). These flakes were created under various load conditions and indenter properties. However, only the AOBs, delineated by the colors, had any appreciable effect on the outcome of the flake mass.
The reader will note that the flakes tend to align into two lines which converge at a TPT of two (2) millimeters and zero mass. The upper line passes through a mass of 40 grams and a TPT of 23 millimeters and consists mostly of flakes created by AOBs of 70 degrees and lower. The lower line passes through 20 grams at a TPT of 23 millimeters and is generally made up of flakes created by AOBs of 85 degrees and above. These two lines represent the energy-rich (upper) and energy-poor (lower) flakes.
On closer inspection, the 70 degree AOB created energy-rich flakes up to approximately a TPT of 28 millimeters. Above this thickness the mass of the flakes suddenly decreases and falls on the energy-poor flake line. At AOBs above and below 70 degrees the transition from energy-rich to energy-poor appears to be occurring at smaller TPTs than at 70 degrees. Therefore, it appears from this data that if one desires to make big energy-rich flakes from a core with a platform angle of 55 degrees, one would cause the AOB to be 70 degrees.
When I saw this data the first time I was intrigued. I was glad to see there was a trend between TPT and flake mass because I would have expected this. If there had been no correlation, I would have been disturbed. The real surprise was that there were two correlations. I never would have guessed this would be the case. To me, these two types of flakes that transition into each other is the most interesting finding in Pelcin's research.