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Friatest: Simulation of the comminution test


Synthetic diamond grit producers and users developed several methods to measure the impact strength of the grits they produce or use.

A widespread approach, also adopted by the FEPA, consists of putting a few carats of diamond grits in a capsule, together with a steel ball, and of shaking it a number of times in order to subsequently measure the damage caused to the grits.

The best known representative of this way of testing diamond grit friability is the Friatester device developed by the De Beers group.

Such tests are often used blindly, without wondering about the physics behind.

For a better understanding of the motion of the steel ball in the capsule and of the effect of variations in the machine parameters, we developed a simple model for this motion, with as main output the energy transfer from the ball to the diamond grits. The equations are solved numerically.

The results are a nice example of the fact that, even in such a simple dynamic system, chaotic motion is possible in some parameter ranges.


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