Experimental and Numerical Investigations of Single Abrasive-Grain Cutting
Anderson, David James
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The cutting action of a single abrasive grain was investigated using a combination of high-speed scratch tests and finite element models. The high-speed scratch tests were unique in that the cutting conditions of a grinding operation were closely replicated. Two geometries were tested: a round-nosed stylus to approximate a 15-grit abrasive grain and a flat-nosed stylus to approximate a worn 46-grit abrasive grain. The three-dimensional finite element model was unique in that a hybrid Euler-Lagrange method was implemented to efficiently model the interaction between an abrasive grain and a workpiece. The finite element model was initially validated using indentation tests to remove the complexities of relative motion from the validation process. The validation was completed through comparisons to the experimental scratch tests. The results of the analysis revealed several key findings. Rubbing, plowing, and cutting do not display distinct transitions; rather, they coexist with different weightings depending on the scratching speed and the depth of cut. The normal forces increased for a given depth of cut as the scratching speed was increased due to strain-rate hardening of the workpiece. The tangential forces decreased for a given depth of cut as the scratching speed was increased due to a reduction in the coefficient of friction and a change in the cutting mechanics from plowing to cutting. The change in the cutting mechanics was investigated by analyzing the evolution of the scratch profiles as the depth of cut and scratching speed were changed. It was found that higher scratching speeds produced less material pile-up and this was attributed to a change in the cutting mechanics. Due to the change in the cutting mechanics, the specific energy decreased as the depth of cut and scratching speed were increased. A numerical case study revealed that reducing the grain size resulted in: lower forces, lower specific energies, and smaller volumes of subsurface stresses. The finite element model was adapted to work in conjunction with the flat-nosed stylus creating the first model capable of simulating the cutting of an abrasive grain in three dimensions.