Cohesive Bulk Research Articles

Theories on channeling: Reviewed and compared with experiments

Discharge of a cohesive bulk solid from a plug-flow bin is (too) often interrupted by the development of a stable channel within the bulk solid. In thi Experiments have been performed using different bins and bulk solids. In contrast to what is generally assumed, these experiments showed that critical

The influence of consolidation on shear test results

Measurements of the yield behaviour of a cohesive bulk solid in the Jenike shear tester are normally done in two steps. First, pre-shearing to a steady state yielding, and secondly, shearing under a lower normal stress to establish the shear stress at incipient failure. Due to the limited strain of the sample in this apparatus, the material must be consolidated in an earlier stage. This is done by the twisting action of a loaded cover, at which the vertical load and the amount of twists are chosen such that a suitable stress—strain curve will be obtained in the pre-shearing stage. The ratio n between the vertical load during consolidation and pre-shearing, respectively, can have a strong impact on the results. In this article, results of measurements with various n-values are given, leading to a variation in shear stress levels for both steady state and incipient failure. This can be explained by variations in the real normal stresses on the shear plane, which can substantially deviate from the externally applied normal stresses, due to contact between ring and base. To establish the real normal stress on the plane of shear, a somewhat modified shear tester was used. Furthermore, measurements were performed where the contact between ring and base was avoided by a removeable pair of half-rings. The results of those measurements and the implications for the derived quantities are amply discussed, resulting in some recommendations for a more reliable testing procedure.

Non-spill discharge characteristics of bucket elevators

One of the well-known disadvantages of a simple type bucket elevator is still the backflow or spill. The accordingly lower capacity and increased power consumption are not always the worst consequences, provided that the boot does not become too full. With the considerable heights of modern bucket elevators, up to 225 ft and over, serious damaging of the conveyed material, an intensified noise level and increased wear can be far more inconvenient. The discharge of the buckets has been recognised as an extremely complicated phenomenon which strictly speaking cannot be analysed theoretically. This holds even more for free-flowing materials. Nevertheless, an analytical approximation has been worked out for the relatively simple case of cylindrical buckets filled with cohesive bulk material, to start with. With the developed approximative theory a spill-free combination of the relevant parameters has been found.

The electronic theory of III-V and II-VI tetrahedral compounds. I. Crystal energy and bulk modulus

The electronic theory of III-V and II-VI tetrahedrally covalent compounds is presented using a perturbation treatment based on a model potential. In the theory, according to the Jones-zone scheme of Heine and Jones (1969) the higher-order terms with respect to the pseudopotential are considered. Numerical results for the cohesive energy and bulk modulus for these crystals such as AlSb, GaP, GaAs, GaSb, InP, InAs, InSb, ZnS, ZnSe, ZnTe and CdTe are in good agreement with the observed data.

On the influence of different statistical exchange approximations on a pseudopotential calculation of the cohesive energies, structures and bulk properties of magnesium and aluminium

On the influence of different statistical exchange approximations on a pseudopotential calculation of the cohesive energies, structures and bulk properties of magnesium and aluminium