Lateral cracking and crushing

Under combined stresses, the normal condition in an industrial crushing situation, many cracks will be initiated and propagate in a direction perpendicular to the local tensile stress but, sooner or later, they run into a region of compression, which stops further crack growth [B.12]. Therefore, the highest number of cracks will be initiated and cause failure near the point(s) of energy input. Also, if primary fractures relieve the... 

Considering the mechanisms listed above it is perhaps easiest to visualize (1) if we are dealing with an ideally brittle solid, for then the energy consumed is equal to total new surface area produced multiplied by the specific surface energy. Three components are present in this assessment. First, as Figure 2.18 shows, the pivot makes an indent similar to a Vickers diamond. Therefore there is the same projected area. Second, depending upon the load, there will be production of the median vent crack into the solid whereas the lateral vent cracks are not produced until the load is removed. Therefore, rocking the pendulum produces only one set of cracks which produce new surface. And, finally, as the pivot rocks and to some extent processes, crushed debris is produced. 

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