SUMMARY
This report is an extension of the paper given at the AMU~ Meeting held at Princeton and includes further analysis on the application of Fracture Mechanics to the chipping experiments reported at the Annual Meeting by the workers at the University of Birmingham. In addition it has been found that the initial pessimism of finding published work on fracture under applied compressive loads was not fully justified.
Some of the ideas of Fracture Mechanics are briefly reviewed and fracture criteria for both Linear Elastic Fracture Mechanics (LEFM), which is predominantly brittle, as well as for ductile failure in the presence of extensive plastic deformation are presented. The role of plastic deformation is stressed: it governs toughness and brittle/ductile failure, characteristics. The effect of size is considered and it is shown that the observed ductility of particles of materials which may be brittle in large scale components is a logical consequence of the theory. Kendall’s work on this topic is briefly described.
It is argued that fracture mechanics can be usefully applied to particle breakage, although LEFM will be of less use than for fracture of larger samples and plastic deformation must be incorporated in the treatment. Attrition is not seen to differ mechanistically from gross fracture and will depend on the same parameters, particle shape being a significant factor in determining whether small fragments are chipped off or not. Some ideas concerning the dependence of abrasion on yield stress are discussed and it is concluded that fracture toughness and yield stress are both important governing parameters.
Finally, some suggestions for future work are presented.