Numerical Investigation of the Cushion and Size Effects During Single-Particle Crushing via DEM
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ISSN 1860-2134
Numerical Investigation of the Cushion and Size Effects During Single-Particle Crushing via DEM Du-min Kuang1
Zhi-lin Long1
Rui-qi Guo1 Jie Wang1
Piao-yi Yu1
Xu-tong Zhou1
(1 College of Civil Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China)
Received 9 November 2019; revision received 19 August 2020; Accepted 30 August 2020 c The Chinese Society of Theoretical and Applied Mechanics 2020
ABSTRACT This paper uses the discrete element method to model the size and cushion effects during single-particle crushing tests. We propose simplified numerical modeling to examine the effects of particle size and coordination number on particle breakage behavior. We validate the proposed modeling by comparing the numerical results with the experimental data reported in the literature, in terms of the variability of particle tensile strength and axial force–displacement responses. Based on the numerical results, it is clear that a larger particle size entails a higher tensile strength with a larger discreteness. In addition, the characteristic tensile strength increases linearly with an increasing coordination number. Moreover, smaller particles are more susceptible to the cushion effect than larger particles. The numerical results also indicate that an increasing coordination number induces a more ductile mode of failure. Based on these results, we propose an empirical equation for calculating tensile strength, incorporating both the cushion effect and the size effect.
KEY WORDS Particle breakage, Cushion effect, Size effect, Discrete element method
1. Introduction Crushable granular materials such as rock blocks, sand particles, and ballasts are widespread in nature and commonly used in engineering practice. The mechanics of particle breakage depend on various factors (e.g., particle shape, size, and coordination number), among which the particle size and coordination number are particularly important [1–3]. Many researchers have investigated the effects of these factors on particle breakage behavior [4–7]. Cheshomi et al. [8] performed single-particle crushing tests on microcrystalline limestone particles, observing that tensile strength increases as particle size decreases. The single-particle crushing tests on coal particles, performed by Zhong et al. [9] and Wang et al. [10], provided similar results. In addition, it has been found that high coordination numbers can effectively prevent the breakage of particles [5, 11, 12]. This phenomenon can be explained by the nearly isotropic compressive stress state of larger particles caused by the high coordination numbers derived from the surrounding smaller particles. This “cushion effect” [13–16] reduces the likelihood of the larger particle breaking. Tsoungui et al. [16] performed oedometric compression tests on molding plaster disks and observed that small particles are more likely to break than larger ones during the loading process. McDowell and Bolton [5] observed that fine particles can be crushed successively under increasing loading stres
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