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Open AccessArticle

Effect of Grain Size and Surface Roughness on the Normal Coefficient of Restitution of Single Grains

1
School of Geosciences, Mewbourne College of Earth and Energy, University of Oklahoma, Norman, OK 73069, USA
2
Department of Architecture and Civil Engineering, City University of Hong Kong, Yeung Kin Man Academic Building, Blue Zone 6/F, Kowloon, Hong Kong, China
*
Author to whom correspondence should be addressed.
Materials 2020, 13(4), 814; https://doi.org/10.3390/ma13040814
Received: 28 December 2019 / Revised: 27 January 2020 / Accepted: 5 February 2020 / Published: 11 February 2020
(This article belongs to the Special Issue Surface and Interface Engineering)
The coefficient of restitution (COR) represents the fraction of pre-collision kinetic energy remained after the collision between two bodies. The COR parameter plays an important role in the discrete numerical analysis of granular flows or the design of protective barriers to reduce flow energy. This work investigated the COR for grain-block type impacts through comprehensive experiments using a custom-built impact loading apparatus. Glass balls of three different sizes were used as grains. The impact experiments were performed on three different types of materials as base blocks, namely brass, granite and rubber. Experiments on the brass block showed a decrease in COR values with increasing grain size. On the contrary, impacts on granite and rubber blocks showed an increase in COR values with increasing grain size. Additionally, the effect of surface roughness on the COR was investigated. It was revealed that the increase in surface roughness of either the grain or the block reduced the COR values due to the increased plastic deformations of surface asperities. View Full-Text
Keywords: coefficient of restitution; glass balls; granite; rubber; roughness coefficient of restitution; glass balls; granite; rubber; roughness
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Sandeep, C.S.; Luo, L.; Senetakis, K. Effect of Grain Size and Surface Roughness on the Normal Coefficient of Restitution of Single Grains. Materials 2020, 13, 814.

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