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Granular Materials Powder Metallurgy
Published in Leo Alting, Geoffrey Boothroyd, Manufacturing Engineering Processes, 2020
A granular material is a mixture of solid grains or particles possibly of varying sizes. Each grain or particle may be a combination of smaller units, for example, the crystals in metal grains. Granular materials are generally used for one or more of the following reasons: The particular material is only available or can only be produced in the granular state.The desired properties (porosity, combination of materials, etc.) can only be obtained from granular materials.Manufacture of the product is cheaper than by other methods.Small components are difficult to produce by other methods.
Transport and Storage of Food Products
Published in Dennis R. Heldman, Daryl B. Lund, Cristina M. Sabliov, Handbook of Food Engineering, 2018
The coefficient of friction between granular materials is equal to the tangent of the angle of internal friction of the material. The angle of repose is the angle made by a material with respect to the horizontal when piled. While it is generally assumed that the angle of friction and the angle of repose are approximately equal, for some materials, such as sorghum, the magnitudes of the two angles can be different (Mohsenin, 1986). There are two angles of repose, a static angle of repose taken up by a granular solid that is about to slide upon itself, and a dynamic angle of repose that arises in all cases where the bulk of the material is in motion, such as during discharging of solids from bins and hoppers.
Sound propagation in dense granular materials
Published in Y. Kishino, Powders and Grains 2001, 2020
Granular materials are ubiquitous in nature and involved in a wide range of industrially important operations and processes, such as agriculture, pharmaceutics and construction. They also play an important role in many geological processes on much larger scale. On the other hand, the study of granular media is of great scientific interest (Jaeger et al, 1996; de Germes 1999). In a static assembly of cohesionless grains, photoelastic visualizations (Dantu, 1957; Travers et al 1987) and computer simulations (Radjai et al, 1996) have shown very inhomogeneous spatial distributions of contact forces between particles, organized along force chains which may extend over a scale much larger than the grain diameter. These force chains carrying most of the forces in the system involve only a small fraction of the total number of grains. For grains made of a hard material (e.g. glass), the deformation at the (hertzian) contact between its constituent grains is extremely small compared to its grain size. One anticipates that the nature of these contacts is very fragile, and any external disturbance (thermal or mechanical) incompatible with the force chains structure will lead to the irreversible rearrangement of the granular system (Liu 1994; Vanel et al 1998). In addition to the elastic continuum description (Savage 1998; Eveques & de Gennes 1998), some new constitutive laws have been proposed recently to describe the static force transmission along the privileged force paths within granular systems and the instability of the force networks (Bouchaud et al 1995; Cates et al 1998; Coppersmith et al 1996). However, several basic points about this issue remains to be clarified (de Gennes 1999).
Prediction of shear strength for granular material under the effect of liquid-powder binder using a PSO–RBF neural network model
Published in Particulate Science and Technology, 2023
Muhammad Waryal Dahri, Mingxi Zhou, Zihua Liu
Granular materials are collections of microscopic particles visible to the naked eye, such as glass beads or sand (Mitarai and Nori 2006). Granular materials exhibit complex shear deformation characteristics similar to solids and liquids. A previous study observed that granular materials have much more complex elastoplastic and viscous behaviors compared with finer particle materials (Jeong and Park 2019). Wet granular materials differ from dry ones in that the grains are large enough for colloidal forces to be negligible. On the grain scale, this cohesion is caused by the wetting liquid’s lower pressure than the surrounding atmosphere, which effectively attracts the wet grains to one another. The wetting liquid forms isolated bridges connecting pairs of grains in contact or separated by a short distance in the so-called pendular regime for low liquid contents. These liquid bridges transmit an attractive capillary force depending on grain geometry, bridge volume, and interfacial tension (Badetti et al. 2018).
Scale-up in Turbula® mixers based on the principle of similarities
Published in Particulate Science and Technology, 2020
Claire Mayer-Laigle, Cendrine Gatumel, Henri Berthiaux
Granular materials are present in numerous processes, in all industrial sectors. In many of them, mixing or premixing of dry particles is a critical step since it controls the properties of the finished product (color, taste, bioavailability of a drug) (Shenoy et al. 2015). It can influence the downstream steps (Zhou and Morton 2012), as for example, in dry lubrication processes (Suzuki et al. 2015). At the process scale, granular materials can be seen as a state of matter at the crossroad between the solid and the liquid states (Redaelli et al. 2017). Granular materials appear as a multitude of grains, behaving as a solid in isolated form and exhibiting internal discontinuities, according to the size, the shape, and the nature of the interactions (Shah et al. 2017). These discontinuities induce a partial transmission of the stresses during the process, making the behavior of the raw material difficult to describe, flowing sometimes as a liquid or aggregating under the form of clusters (Savage 1984).
DEM analysis of granular crushing during simple shearing
Published in Marine Georesources & Geotechnology, 2018
Sihong Liu, Yishu Wang, Chaomin Shen
Most granular materials occurring in nature and engineering application are composed of particles with a broad range of sizes. Some research indicates that a uniformly graded granular material exhibits more crushing than a well-graded material with the same maximum particle size (Lade, Yamamuro, and Bopp 1996; Nakata, Hyodo et al. 2001). To reflect a more realistic grain crushing phenomenon, the generation of a specimen with a broad range of sizes is important in DEM simulations. At present, the DEM specimens generated are mostly composed of particles with some specific sizes. For example, Jiang, Konrad, and Leroueil (2003) proposed a multi-layer with under compaction method to generate homogeneous DEM specimens, in which the particle size distribution (PSD) was first discretized into several “classes,” defined over subintervals, and the particles in each class had the same size. Voivret et al. (2007) proposed a space-filling method to build densely packed specimens of prescribed polydispersity for DEM studies, in which a similar particle size generation technique was adopted. Since the current methods as mentioned above cannot generate the DEM specimen with a smooth and continuous PSD, a new technique is presented in this study, in which the PSD is replaced with a probability density function (PDF).