Evaluation of cutting fragments in relation to force dynamics in actuated disc cutting

Abstract

Actuated disc cutting (ADC) is one of the latest developments in rock cutting. While there have been significant developments in understanding its mechanics, the ADC induced rock fragmentation remains poorly understood. In efforts to improve the current understanding, this paper evaluates the cutting fragments and the relationship between fragments and force dynamics. Rock cutting tests were performed on two types of sedimentary rocks using a CSIRO customized ADC unit, known as Wobble. Wobble is equipped with force, torque, and displacement transducers to monitor the cutting process. This paper studied the dynamics of force signals, and as a result of these analyses, the concept of chipping to the crushing ratio ( Rcc) was introduced. The force drop distribution was also evaluated together with the specific energy (SE). The rock fragments generated were examined through two sets of the laser-scanning machine. Characterization of rock fragments explored the particle size distribution, fractal dimension (Ds), and coarseness index (CI) based on the fragment minimum width. Evaluation of the distribution profile indicated both force drops and fragment sizes follow a type of distribution known as Generalized Extreme Value (GEV) distribution. GEV is often associated with brittle failure of a structure. Correlation analyses further emphasised the previous observations that ADC key variables—the geometry factor ε, the actuation factor 2πυ, and the penetration rate p, are the major controlling factors of Rcc, SE, Ds, and CI.