Snow is a complex material that is difficult to characterize especially due to its high compressibility and temperature-sensitive nonlinear viscoelasticity. Snow mechanics has been intensively investigated by avalanche and army researchers for decades. However, fewer research studies have been published for compacted snow, commonly defined as snow with a density in the range of 370-560 kg/m3. From a mobility perspective, the tires are the primary point of force and motion generation and their interaction with the terrain causes an increased reliance on the skill of the driver for safer mobility. Thus, standards like ASTM F1805 are implemented for the evaluation of winter tires which can be used in harsh conditions like ice and snow.
This work focuses on evaluating the prior efforts performed for the measurement of snow properties. In addition, analysis using regression models and principal component analysis is performed to understand the extent to which specific measurements related to snow affect the traction of the tire. It was found that the compressive and shear properties of snow contribute more than 90% to the variation in the traction coefficient of a tire when evaluated on a compacted snow domain per ASTM F1805.
Identification of this phenomenon allowed the enhancement of an existing device that can be used for measuring the compaction and shear properties of snow. The device hence conceptualized was manufactured in-house and tested at the Smithers Winter Test Center to benchmark against existing devices available commercially. Further, a more analytical method for evaluating the resistive pressure for the penetration of the device was formulated. Based on this, a possible framework for the determination of the bevameter parameters using measurements of the new device has been proposed which needs to be validated experimentally and computationally. / Doctor of Philosophy / Winter tires sold in North America require prior evaluation according to a standard namely the ASTM F1805 to bear the 'mountain-snowflake symbol' for severe snow usage. The standard specifies the conditions for evaluating a prototype winter tire and the necessary track preparation methodologies. However, the computational model of a track used for such a certification is not found in the literature causing the manufacturing of such winter tires to be more of a 'trial-and-error' process.
The main objective of this investigation is to assess earlier studies of snow characteristics. Additionally, analysis employing regression models and principal component analysis was conducted to comprehend the extent to which particular measurements connected to snow affect the traction of the tire. When tested using an ASTM F1805-compliant compacted snow domain, it was discovered that the compressive and shear properties of snow account for more than 90% of the variation in the traction coefficient of a tire.
The discovery of this phenomenon made it possible to improve a tool for assessing the compaction and shear characteristics of snow. The device that was conceptualized was manufactured internally and put to the test at Smithers Winter Test Center to compare it to other devices that were already on the market. Further, a new analytical method for evaluation of the resistive pressure to the device was developed. Using measurements from the new device, a method to utilize the devised output parameters as inputs and for the validation of a computational snow model is proposed.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/118281 |
| Date | 05 March 2024 |
| Creators | Shenvi, Mohit Nitin |
| Contributors | Mechanical Engineering, Sandu, Corina, Untaroiu, Costin D., Taheri, Saied, Hardy, Warren Nelson |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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