Benchmarking of Compression Testing Devices in Snow

Abstract

Traction testing of tires for 'severe snow use' certification is performed according to ASTM F1805 in the Unites States and Canada. The ASTM standard provides guidelines for the preparation and compaction of the snow required for the testing and its evaluation using the CTI (Compliance Testing Incorporated) penetrometer. However, the CTI penetrometer provides a measure of the degree of compactness of the snow. From a computational perspective, this information in itself is not sufficient for modeling and/or validation of a snow model for virtual snow traction testing, which is important in the design stage of tires. This work attempts to compare the relative compression testing performance of three devices, namely a CTI penetrometer (rounded cone tip impactor), a standard Clegg Hammer (flat surface impactor), and an in-house developed device inspired by the Russian Snow Penetrometer (cone tip impactor). The approach used here includes a comparison of the available direct and indirect outputs of all the devices and a statistical analysis of these. The observed differences may be due to differences in the mass and drop height between the devices. The findings of this work provide a baseline for further research into the optimal mass and drop height for the evaluation of compacted snow properties. From a modeling perspective, the values generated using the Clegg impact hammer could be useful. However, it tends to underestimate the elastic modulus, when its results are compared to the laboratory technique, and to overestimate the ram resistance when compared to the in-house device. Further improvements to the in-house device may improve its ability to measure the snow properties most relevant to the modeling of snow.