Particulates and powders constitute over 75% of material feedstock in industry. Many of these solids exhibit complex cohesive behaviour, leading to handling problems including arching and rat-holing in silo discharge. It is generally recognised that the cohesive strength of a bulk solid is dependent on the prior consolidation stress exerted on the solid. Such cohesive behaviour must be investigated if a numerical model depicting these powder flow problems is to be successful. This presentation describes the development of a DEM model coupled with a calibration methodology to produce quantitative predictions of powder flow problems.

A new contact model was devised to account for the stress history dependent

frictional-adhesive behaviour. The model used a bi-linear hysteretic spring to model elastic-plastic permanent contact deformation and a single adhesive force parameter which was defined as a function of the maximum contact overlap for each contact. The model was used to predict the uni-axial unconfined loading to failure of a bulk solid that has been subjected to increasing consolidation stress levels.

The results show that the adhesive frictional model can capture the failure mode

(hardening followed by softening at larger strains) and also the stress dependent

cohesive strength that is often observed in industrial solids.