ON WEAR AS A MECHANISM OF GRANULE ATTRITION

Mechanisms of granule or agglomerate attrition are studied in the light of the principles of fracture mechanics. Fracture properties are measured for agglomerated systems including both glass beads bound by polymeric binders and pesticide products. In the present work, the sizes of typical granules are less than the critical specimen sizes capable of gross fracture, as calculated from fracture theory. This implies that the mode of granule attrition is primarily one of erosion or abrasive wear and not gross fracture. Previous abrasive wear research is reviewed, with the aim of establishing the dependence of agglomerate bar wear on material properties. Idealized bar agglomerates are studied, as they allow convenient characterization of the dependence of granule erosion on material properties. Bar wear rates are found to parallel results from the ceramics wear literature. In particular, wear rate is found to have a similar but somewhat different dependence on fracture toughness than the work of Mullier et al.4, where both fluid-bed granule erosion rate and wear of bar agglomerates were found proportional to 1/K(c).