Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the effect of stress dependent interparticle friction in direct shear
  tests   Contact friction is a key influence factor for the shearing behaviour of
granular media. In the discrete element method (DEM) contact friction is
usually modelled with Coulomb's law assuming a constant interparticle friction
coefficient. From tribology it is known that friction is influenced by several
factors, e.g., temperature, normal stress, surface condition, etc. None of
these influences can be modelled with the constant interparticle friction
coefficient from Coulomb's law. For a given granular material (particle shape
distribution), the usage of constant interparticle friction in DEM models
generally results in constant bulk friction coefficients in the simulation of
direct shear tests. While this is frequently seen in experiments with
equi-sized spherical particles, papers exist in literature which report a
stress dependency of bulk friction for non-spherical particles of certain
materials. In this work, a stress dependency of bulk friction is obtained by
introducing a model for stress dependent interparticle friction in DEM
simulations. For validation experimental results of direct shear tests
conducted on single or paired glass beads are used. While the bulk friction of
paired spheres clearly decreases with increasing normal stress, it is nearly
constant for single spheres. DEM simulations with the stress dependent
interparticle friction are in good accordance with the experimental results of
both single and paired spheres. A comparison with simulations, using constant
interparticle friction, clearly shows the advantage of the proposed model.

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The categories of this paper are: math
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The categories of this paper are: q-bio
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The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: astro-ph
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: eess
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The categories of this paper are: adap-org
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex