This paper proposes a new 2D continuous-discontinuous heat conduction model to simulate heat transfer and thermal cracking in fractured quasi-brittle materials by combining with mechanical ...calculations of the Finite-Discrete Element Method. By updating the sharing relationship of the nodes at the cracks, the model can accurately predict the temperature evolution, crack propagation and considers the effect of cracking on heat conduction. We verified the correctness of the continuous-discontinuous heat conduction model using examples of heat conduction in a continuum, media with single or multiple cracks, thermal deformation problems, and cracking induced by temperature gradient and thermal mismatch. The numerical results indicate that the continuous-discontinuous heat conduction model well reflects the effect of crack propagation on heat conduction and the discontinuity of temperature across the cracks. It provides a powerful tool for studying the whole process and mechanism analysis of thermal cracking of quasi-brittle materials.
Rock slope failure is particularly detrimental to the safety of human life and engineering infrastructure. The pre-existing discontinuities in the jointed rock slopes play a key role in the slope ...stability, and the destabilization process often related to the complex interaction between the discontinuities and the intact rock bridge. Understanding the failure mechanism and accurately predicting the failure process are essential for the safety of jointed rock slopes. In this paper, a jointed rock slope analysis model (Y-slopeJ) is developed to evaluate the stability state and simulate the progressive failure process of jointed rock slopes based on the combined finite-discrete element method (FDEM). The accuracy and robustness of the proposed model are validated by numerical tests. Then this Y-slopeJ is applied to investigate the failure mechanism and failure process of rock slopes with various types of discontinuities, with an emphasis on crack initiation, propagation and coalescence. This work proposed a promising tool in understanding and predicting the progressive failure process of jointed rock slopes.
It is well known that kaolinite platelets readily aggregate into ‘stacks’, having face-to-face contact. The traditional view of kaolin has been that the platelet faces are negatively charged and the ...edges are positively charged in an acidic environment, but that some attraction between faces may exist at some close range of approach. Particle-scale simulations in this paper show that this is insufficient to explain aggregation during sedimentation. Recently it has been established that the silica and alumina faces of kaolinite platelets have opposite charges in acidic conditions, and taking these findings into account, discrete element simulations are presented which replicate and explain the face-to-face aggregation that occurs during sedimentation. The results demonstrate the importance of correctly modelling the interactions between the various surfaces of individual platelets in any particle-based model.
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•Using Discrete Element Method to model kaolinite platelets.•Each platelet has 3 distinct surfaces: silica face, alumina face, edge.•Different interactions used between different surfaces.•Using multifaceted interactions controls ability to aggregate/flocculate.
A surface mesh represented discrete element method (SMR-DEM) for granular systems with arbitrarily shaped particles is presented. The particle surfaces are approximated using contact nodes obtained ...from surface mesh. A hybrid contact method which combines the benefits of the sphere-to-sphere and sphere-to-surface approaches is proposed for contact detection and force computation. The simple formulation and implementation render SMR-DEM suitable for three-dimensional simulations. Furthermore, GPU parallelization is employed to achieve higher efficiency. Several numerical examples are presented to show the performance of SMR-DEM. It is found that on the particle level the method is accurate and convergent, while on the system level SMR-DEM can effectively model particle assemblies of various regular and complex irregular shapes.
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•A SMR-DEM for particlesof arbitrarily complex shapesis presented.•A hybrid contact method allowing simple and efficient contact detectionis proposed.•The SMR-DEMprovides results well corroborated byresults from the literature.•The computational cost of SMR-DEM is independent of the particle shape.
From its inception, the combined finite discrete element method has used a distributed potential contact force algorithm to resolve interaction between finite elements. The contact interaction ...algorithm relies on evaluation of the contact force potential field. The problem with existing algorithms is that the potential field introduces artificial numerical non-smoothness in the contact force. This work introduces a smooth potential field based on the finite element topology, and a generalized contact interaction law is constructed on top of the smooth potential field. A number of validation cases for the proposed algorithm, considering different shapes of discrete elements, are presented, and detailed aspects of the proposed contact interaction law are tested with numerical examples.
The authors examine carbene ligands in surface chemistry with regard to stabilization of discrete elemental allotropes to modification of nanoscale and bulk substrates.
In numerical simulations of the blast furnace, the discrete element method (DEM) is a quite novel method. The accuracy of physical parameters of the method is a key issue for the reliability of the ...results. In this study, we first measured the parameters describing the interaction between pellets, sinter and coke, as well as between these three materials and a steel plate. The experimentally determined parameters include the Young's modulus, Shear modulus and Poisson's ratio, particle density, coefficient of restitution, as well as coefficients of static and rolling friction. The coefficients of rolling friction of non-spherical particles were obtained by comparing the repose angle of bulk materials in experiment and simulation. After these calibration steps, the DEM parameters were validated by a comparison of free surfaces of the conical piles formed in simulations and experiments. The experimental and calculated results show good agreement, which demonstrates that the measured DEM parameters are of sufficient accuracy to be used in simulation of burden distribution and descent in the blast furnace.
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•DEM physical parameters of pellet, sinter and coke are measured and validated.•A simple device is made to measure coefficient of friction combined.•DEM parameters were validated by the comparison of simulations and experiments.
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•Tribocharging models often depend on ill-defined or poorly quantified parameters.•An effective empirical model parameter evaluation method is presented and validated.•The efficacy of ...2D/3D DEM models using these parameters is compared and evaluated.•2D and 3D models simulate successfully tribocharging due to single contacts.•Only 3D models agree experimental data in complex (multi-particle/contact) systems.
Many discrete element method (DEM) tribocharging models presented in the literature rely on ill-defined or poorly quantified charging parameters. This work presents a straightforward experimental method to quantify key parameters, namely the charge transfer limit, Γ, and the charging efficiency, κc. These parameters are then used in both 2D and 3D DEM simulations to evaluate the applicability of faster 2D models to tribocharge modelling. Both the 2D and 3D models are found to perform well against the experimental data for single-contact and single-particle, multi-contact systems. However, the 2D model fails to produce good agreement with experimental data for multi-contact, multi-particle systems. This approach for determining experimentally the parameters for the DEM tribocharging model is found to be effective and produces good agreement between simulated and experimental data. This method will improve and simplify the DEM modelling of triboelectric charging in dry material handling processes.
The construction of an underground opening leads to changes in the in situ stress regime surrounding the excavation. The opening influences the rock mass owing to the redistribution of the stresses ...and results in the disturbance of the surrounding ground. At great depths, massive to slightly or moderately fractured rock masses are usually encountered, and under high stresses, they are more likely to behave in a brittle manner during an excavation. While constitutive models have been developed and proposed for the numerical simulation of such excavations using continuum mechanics, this brittle response cannot be simulated accurately enough, since the material behaviour is governed by fracture initiation and propagation. On the contrary, discontinuum approaches are more suitable in such cases. For the purposes of this paper, the brittle behaviour of hard, massive rock masses and the associated spalling failure mechanisms were simulated by employing a finite–discrete element method (FDEM) approach using Irazu software. The generated numerical model was utilized to replicate field conditions based on the observations at the Atomic Energy of Canada Limited (AECL) Underground Research Laboratory (URL) test tunnel located in Pinawa, Manitoba, Canada. The model results are compared with field observation data to explicitly demonstrate the suitability of the method.
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