Techniques for calibration of hailpad material



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Because of their simple design and low costs, hailpads are, to this date, an essential instrument in the field of hail-related research. Hail research is an area that experiences growing interest and a field that investigates one of the most expensive and devastating weather phenomena known to humankind. Hailpads are plates of extruded polystyrene covered by thin paint or foil, mounted to a frame. They can be placed in fields or on roofs and serve as a data collection tool for hail impacts. Impacting hail leaves dents behind, and those dents can be measured and used to gather more information on a hailstorm. To obtain information on hailstone sizes based on the impact diameters, it is often impossible to use the actual hailstones as a comparison because they are melted or otherwise destroyed before a hailpad is recovered. Therefore, hailpad material is calibrated using the impacts of spheres of a different material. Because of its widespread accessibility, this material is often steel. An assumption made in those calibration procedures is that a sphere creates equal diameter dents if it impacts the hailpad with the same kinetic energy. This research aims to answer whether this assumption of equal kinetic energy and sphere size resulting in equivalent dent sizes is correct. Observation and analysis in forensic engineering suggest that there are different damage potentials for ice and steel. This research shows a statistically significant difference in dent sizes for different materials that impact a hailpad with the same kinetic energy. It also draws relationships between the other materials and the influence of the projectiles' varying impact angles on the hailpad.

Embargo status: Restricted until 06/2026. To request the author grant access, click on the PDF link to the left.



Hail, Hailstone, Terminal Velocity, Testing, Impact, Velocity, Styrofoam