Cohesion particles

The whole problem of computing pressure distributions in particulate packings is one of great complexity. In addition to the fact that we are unable to deal with a material whose apparent density is not uniform, we must consider added difficulties such as diffusion, sliding friction, deformation of individual particles, cohesive forces, and perhaps others. The quantitative relationships of these factors to particle size must remain empirical for the time being. In the paragraphs to follow we shall be concerned only with a limited theory of the problem of particles under pressure. 

Figure 8.46 shows the effect of crack advancement on integrity of filler particle. The advancing crack can be delayed by the pinning mechanism if stress is lower than adhesion and filler particle cohesion. If stress is higher than particle cohesion then particles may break. The... 

Conversely, Ehlermann and Schubert (1987) sustained that compressibility results from materials of different composition cannot be compared and that flowability characterization through compressibility must be made specifically for each food variety. Moreover, confined uniaxial compression is a simple compression test that provides an approximate measure of the flowability of powders. Therefore, it is not suitable for silo design but may prove to be a convenient method for process control in any food laboratory (e.g., to evaluate particle cohesion). Table II offers a range value definition for flowability classification by comparing flow function (ratio between the maximum consolidation stress and unconfined yield stress) with compressibility. 

In traditional ceramics the material to be pressed is a mix of various minerals (clays, feldspars, sands..) that have been pre-moistened homogeneously to give the clayey parts plasticity and aid inter-particle cohesion. 

The data presented in the previous chapter clearly indicate the universal importance of investigating particle cohesion under various conditions for establishing the scientific basis for explaining (and controlling) the mechanical properties of disperse systans in various natural and industrial processes. An important aspect of such investigations is the use of surface-active substances (surfectants), which at a low bulk concentration accumulate at the interfaces and radically change their properties. Before addressing specific results pertinent to the studies of contacts between particles of various natures in various surfactant solutions, let us briefly summarize the concepts of the adsorption of surfactants, primarily of the thermodynamics of adsorption. 

Here, it is worth highlighting a principally new view on the problem we are considering a thermodynamic factor. We are not focusing on the kinetic role of the DLVO potential barrier, but on its possible influence on the depth of the primary potential energy minimum of the w(h) function. That is, we are examining the role of the potential barrier on the energy of particle cohesion. 

The structure formation that takes place in disperse systems is the result of spontaneous, thermodynamically favorable processes of particle cohesion, leading to a decrease in the free energy of the system, such as particle coagulation or substance condensation at the points of particle contact. The development of spatial networks of various types is the foundation for the ability of a disperse system to transform into a material. As a result of such a transformation, the system acquires new characteristics and properties that are completely different from those in the original state. 

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