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UNIAXIAL COMPRESSION DENSITY

A bulk material underlie various external forces. At storing a bulk material in a silo, the pressure to which the bulk material is exposed increases with increasing depth. With increasing depth, the pressure on the bulk material is larger and the packing density of the particles increases (the density of the bulk material increases).

The change in the packing density of the particles has a great influence on the behavior of the bulk material. With smaller particle spacing, the contact surfaces between the particles are larger and the influence of the forces between the individual particles is increased.

The bulk density (ρb) describes the ratio of the mass (m) of the bulk material to volume (V). The density of a bulk material at a pressure of P = 0 is called as bulk density (ρb0). Especially with cohesive materials, the resulting bulk density is not completely reversible and has a hysteresis.

At filling a container or mass flow in the shaft and if no shear movement has taken the bulk material, the bulk material is subject to uniaxial compression. By shearing a reorientation of the particles to each other is possible, so that sets a usually higher density.

During measuring of the yield locus, we measure the density simultaneously under the influence of pressure and shear stress. Even if the DIN only considers uniaxial compaction, both types of compaction can be used in the automatic evaluations.

 

 

EXAMPLE FOR EVALUATION OF RESULTS OF THE DENSITY MEASUREMENT

 


EVALUATION REPORT DENSITY
file nameDE1a.de
date03 May 2016
material validation powder
operator MB
client shear-test.com
note 

device shear-test.com ST200AUTO
shear cell ST30.cel 

  

ρ(σ) = 22.649 * ln( σ ) + 428 kg/m³


ρ0ρ(1kPa)ρ(5kPa)ρ(10kPa)ρ(15kPa)ρ(20kPa)ρ(30kPa)ρ(40kPa)ρ(50kPa)
[kg/m³][kg/m³][kg/m³][kg/m³][kg/m³][kg/m³][kg/m³][kg/m³][kg/m³]
428 585 621 637 646 652 662 668 673

 

density measurement graph

 

Measurements and evaluations of physical properties of powders and bulk solids yield locus