| hysteresis | Incomplete recovery of shape on the relaxation of stress. i.e. A partial elastic recovery inhibited by a degree of permanent deformation. |
| IBC | Intermediate bulk container. |
| intensity of variation | The degree to which a variation of a physical property deviates from defined bounds, the average value of a batch or from adjacent product, whichever is significant. (See Scale of scrutiny and Scale of variation). |
| interstice | The space between particles in a mass. (See preferred term void). |
| interstitial | Occurring in the space between the particles of composition. |
| isotropic | Pertaining to axial directional differences. This applies to individual particles, their structure in a bulk arrangement of particles, to stresses and to strains. A sphere is isotropic, whereas elongated particles and flakes are not. Fluids are, whilst wood, by virtue of its grain, is not. Strain, Shear and uniaxial compaction are essentially anistotropic (non-isotropic) processes that produce anistropic states in the bulk material. The feature is relevant to both the preparation and loading of a sample of bulk material for testing, as the failure conditions depend upon how the bulk will shear. This in turn depends on the orientation of the constituents of the particulate structure in relation to the direction of stresses that produced the specific state of the bulk and the direction of stresses applied to cause the bulk to fail. The isotropy of a particulate structure is essentially disturbed when shear takes place. |
| Jenike, Andrew | See Appendix II. (Recommended reading). |
| laminar flow | Flow in which the head loss is proportional to the first power of the velocity. It is characterised by the lack of turbulence. |
| latex particles | Particles of natural latex or other polymer; usually spherical and of a narrow size range; often used for calibration purposes. |
| liquefaction | The process whereby a powder bed is transformed from a solid state to a liquid state, usually as a result of the restructuring of particles in a fully saturated bed to a higher packing density arrangement or the introduction of excess fluid. Additional fluid separates the particles, whereas closer particle packing allows the pore pressure of the incompressible fluid to support the applied stresses. Either change relaxes the particle-to particle contact pressure and resulting in a much greater freedom for the particles to shear with little resistance. Fluidisation is an equivalent process with a gas, instead of a liquid, providing the void pressure to reduce the contact pressure between particles. |
| Log-normal distribution | A distribution which results in a straight line when a cumulatively quantity on a probability axis is plotted against particle size on a logarithmic axis. |
| measuring range | The range over which an instrument as set-up can give results within a specified uncertainty. (Note: – Some instruments have many measuring ranges). |
| micrometre (μm) | One millionth part (10-6) of a metre. |
| micron | (See micrometre) |
| monolith | A block of material; a very large particle. |
| nanometre (nm) | One thousand millionth part (10-9) of a metre. |
| nano technology | The study of particles in the size region of one nanometre or less. (This is an area of intense interest because of some useful physical characteristics of ultra fine particles, such as their large surface area in relation to mass). |
| normal distribution | A distribution which results in a straight line when cumulative quantity on a probability axis is plotted against particle size on a linear axis. |
| normal stress | The stress acting at 90 degrees to the considered plane. (usually that of shear failure). |
| particle | A discrete piece of matter. |
Glossary of Terms in Powder & Bulk Technology
1.3 General Terms
Page 4 of 7
