The effects of dilatancy in composite assemblies as micropolar continua

AbstractA smoothed particle hydrodynamics code based on micropolar continua for geomaterials is developed for problems involving large deformation and shear strain localization. Two typical geotechnical problems, i.e., biaxial compression test and sand column collapse, are simulated using classical and micropolar model to demonstrate the performance of the newly proposed method. A parameter study is given on the scale effect in the micropolar continua.

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Comparative 3D DEM simulations of sand–structure interfaces with similarly shaped clumps versus spheres with contact moments

Acta Geotechnica ◽

10.1007/s11440-021-01255-0 ◽

2021 ◽

Author(s):

A. Grabowski ◽

M. Nitka ◽

J. Tejchman

Keyword(s):

Particle Shape ◽

Friction Angle ◽

Rigid Wall ◽

Numerical Results ◽

Contact Forces ◽

Interface Roughness ◽

Interface Shear ◽

Dem Simulations ◽

Micropolar Continua ◽

Interface Behaviour

AbstractThree-dimensional simulations of a monotonic quasi-static interface behaviour between initially dense cohesionless sand and a rigid wall of different roughness during tests in a parallelly guided direct shear test under constant normal stress are presented. Numerical modelling was carried out by the discrete element method (DEM) using clumps in the form of convex non-symmetric irregularly shaped grains. The clumps had an aspect ratio of 1.5. A regular grid of triangular grooves (asperities) along the wall with a different height at the same distance was assumed. The numerical results with clumps were directly compared under the same conditions with our earlier DEM simulations using pure spheres with contact moments with respect to the peak and residual interface friction angle, width of the interface shear zone, ratio between grain slips and grain rotations, distribution of contact forces and stresses. The difference between the behaviour of clumps and pure spheres with contact moments proved to be noticeable in the post-peak regime due to a different particle shape. The rolling resistance model with pure spheres was proved to be limited for capturing particle shape effects. Three different boundary conditions along the interface were proposed for micropolar continua, considering grain rotations and grain slips, wall grain moments and wall grain forces, and normalized interface roughness. The numerical results in this paper offer a better understanding of the interface behaviour of granular bodies in DEM and FEM simulations.

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Multiscale Analysis of Materials with Anisotropic Microstructure as Micropolar Continua

Lecture Notes in Mechanical Engineering - Proceedings of XXIV AIMETA Conference 2019 ◽

10.1007/978-3-030-41057-5_64 ◽

2020 ◽

pp. 796-806

Author(s):

Nicholas Fantuzzi ◽

Patrizia Trovalusci

Keyword(s):

Multiscale Analysis ◽

Micropolar Continua

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Renewal of basic laws and principles for polar continuum theories (I) —Micropolar continua

Applied Mathematics and Mechanics ◽

10.1007/bf02438100 ◽

2003 ◽

Vol 24 (10) ◽

pp. 1119-1125 ◽

Cited By ~ 12

Author(s):

Dai Tian-min

Keyword(s):

Micropolar Continua ◽

Continuum Theories

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Scale Effects in Orthotropic Composite Assemblies as Micropolar Continua: A Comparison between Weak- and Strong-Form Finite Element Solutions

Materials ◽

10.3390/ma12050758 ◽

2019 ◽

Vol 12 (5) ◽

pp. 758 ◽

Cited By ~ 11

Author(s):

Lorenzo Leonetti ◽

Nicholas Fantuzzi ◽

Patrizia Trovalusci ◽

Francesco Tornabene

Keyword(s):

Finite Element ◽

Scale Effects ◽

Kinematic Model ◽

Elastic Response ◽

Actual Behavior ◽

Orthotropic Composite ◽

Additional Degree ◽

Micropolar Continua ◽

Orthotropic Composites ◽

Micropolar Materials

The aim of the present work was to investigate the mechanical behavior of orthotropic composites, such as masonry assemblies, subjected to localized loads described as micropolar materials. Micropolar models are known to be effective in modeling the actual behavior of microstructured solids in the presence of localized loads or geometrical discontinuities. This is due to the introduction of an additional degree of freedom (the micro-rotation) in the kinematic model, if compared to the classical continuum and the related strain and stress measures. In particular, it was shown in the literature that brick/block masonry can be satisfactorily modeled as a micropolar continuum, and here it is assumed as a reference orthotropic composite material. The in-plane elastic response of panels made of orthotropic arrangements of bricks of different sizes is analyzed herein. Numerical simulations are provided by comparing weak and strong finite element formulations. The scale effect is investigated, as well as the significant role played by the relative rotation, which is a peculiar strain measure of micropolar continua related to the non-symmetry of strain and work-conjugated stress. In particular, the anisotropic effects accounting for the micropolar moduli, related to the variation of microstructure internal sizes, are highlighted.

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