Utilizing the Explicit Finite Element Method for Studying Granular Flows

Kabir, M. A.; Lovell, Michael R.; Higgs, C. Fred

doi:10.1007/s11249-007-9285-y

Cited by 32 publications

(19 citation statements)

References 18 publications

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“…A 3D computer simulation [21,22] was proposed to study granular flow regimes undergoing shear in a parallel-plate configuration with the particular interests by using the discrete element method (DEM). And the DEM can be combined with continuum model to simulate more complex granular flow [23,24].…”

Section: Introductionmentioning

confidence: 99%

Effects of Sliding Velocity and Normal Load on Tribological Characteristics in Powder Lubrication

et al. 2011

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The antifriction ability of powder lubrication and the state of powder layer are strongly related to the service conditions. Therefore, the effects of sliding velocity and normal load under powder lubrication were studied using a face-to-face contact tribometer. In our work, some graphite, a widely used solid lubricant, was introduced into the frictional interface in the state of free powder. Varying friction coefficient and temperature rise were recorded online. The powder layer formed on the frictional surface of the bottom samples was observed by an optical microscope after tests. The comparative research demonstrated the tribological characteristics of powder lubrication are similar to that of polytetrafluoroethylene coating. Besides, the powder lubrication provides longer lubrication life, although the powder was difficult to seal and control during the tests. Within the proper range of sliding velocities and normal loads, the powder layer dynamically formed on the contact surface of the bottom samples, which resulted in the self-replenishing and oil-free lubrication. The powder layer inclined to deteriorate under lower velocity and higher load. The tests with higher velocity exhibited lower friction coefficient and higher temperature rise. The tests with lower load exhibited higher friction coefficient and lower temperature rise. The state of powder layer included typically four stages such as the full layer, the partial detachment, the serious detachment, and the complete destruction. The damage degree of powder layer is not in proportion to the friction coefficient or the temperature rise due to the particularity of powder lubrication.

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Section: Introductionmentioning

confidence: 99%

Effects of Sliding Velocity and Normal Load on Tribological Characteristics in Powder Lubrication

et al. 2011

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“…Kabir et el modeled particle flow in a shear cell using explicit FEM and compared the results with DEM code [45,46]. The drawback with the combined FEM/DEM approach is the requirement of significant computational resources which has limited the application to mostly 2D problems, though 3D problems have also been considered [47,48].…”

Section: Combined Fem/dem Approachmentioning

confidence: 99%

Mechanics of light weight proppants: A discrete approach

Kulkarni¹,

Ochoa²

2012

Composites Science and Technology

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Proppants are a specific application of granular materials used in oil/gas well stimulation. Employment of hard and soft particle mixtures is one of the many approaches availed by the industry to improve fracture resistance and the stability of the granular pack in the hydraulic fracture. Current industrial practices of proppant characterization involve long term and expensive conductivity tests. However, the mechanics governing the proppant pack response, in particular the effects due to material, shape and size of particles on the pack porosity, stiffness and particle fragmentation are not understood clearly.The present research embodies analytical and experimental approach to model hard (ceramic) and soft (walnut shell and/or pure aluminum) proppant mixtures by taking into account polydispersity in size, shape and material type of individual particles.The hydraulic fracture condition is represented through confined compression and flowback loads. The particle interactions clearly illustrate changes in pore space as a function of pressure, mixture composition and friction. Single particle compression tests on individual particles are carried out to obtain mechanical properties which are incorporated into the finite element models and are further correlated with the compression/crush response of the mixture. The proppant pack stiffness and particle fragmentation depends strongly on the mixture composition as illustrated in the models and experiments. The flowback models demonstrated that the formation of a stable arch is essential to pack stability. Additional variables that enhance flowback resistance are identified as; addition of softer particles to a pack, softer rock surfaces and higher interparticle friction. The computational studies also led to the discovery of better, and more iv efficient pack compositions such as -short and thin pure Al needles/ceramic and the pistachio shells/ceramic mixtures. These analytical results have generated great interest and are engaged in the design of experiments to formulate future proppant pack mixtures at Baker Hughes Pressure Pumping, Tomball, TX. v

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“…More details about this FEM approach can be found in works by the authors. 28,29 B. FEM modeling procedure…”

Section: A the Explicit Fem Modeling Approachmentioning

confidence: 99%

Contact stress analysis of lightly compressed thin films: Modeling and experimentation

Terrell

Kabir

Higgs

2009

Journal of Applied Physics

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Although a number of models have been developed to describe the contact between nominally smooth surfaces, very few of these models have been validated with experiment. Therefore, in this study, an asperity-scale experimental contact measurement was conducted and compared to the predictions of two contact models. The experimental component of this study involved a flat diamond punch tip on a nanoindenter, which was used to compress a thin film that was lithographically patterned into isolated raised squares. This experimental method was developed in order to measure the predominantly elastic load response of the surface asperities on one of the isolated raised topography islands. The experimental measurements were compared to the predicted load responses of an existing analytical contact model as well as a finite element contact model that incorporated the topography of the raised island into its formulation. The predictions of both the models were shown to have reasonable agreement with the experimental data. The modeling results were also used to provide greater depth of insight into the physics of the flat punch compression.

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Utilizing the Explicit Finite Element Method for Studying Granular Flows

Cited by 32 publications

References 18 publications

Effects of Sliding Velocity and Normal Load on Tribological Characteristics in Powder Lubrication

Effects of Sliding Velocity and Normal Load on Tribological Characteristics in Powder Lubrication

Mechanics of light weight proppants: A discrete approach

Contact stress analysis of lightly compressed thin films: Modeling and experimentation

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