Experimental and Numerical Investigations of Cerchar Scratching Rock Interaction

Abstract

This paper presents Cerchar scratch tests performed on sandstone samples with a constant thrust force of 70 N. The scratch test is reproduced using discrete element method (DEM) models. Simulated scratching force–(depth-) displacement curves evolve in the same way as those of experimental results. Numerical scratching force is also comparable with laboratory results. All these accordance indicate that the presented model can represent the experiments. Microscopic observation of the scratch indicates pullout of grains and the associated tensile failure dominates the scratching process. Particle detachments and microcrack development in numerical simulations also verified this tensile-dominated failure mode. Compared with reported rock cutting studies with fixed cutting depth mode, the cutting force shows a much smaller variation in this fixed thrust force mode. This finding indicates that the applied thrust force plays a significant role in the cutting process, rock failure, and the tool–rock interaction. Factors that may result in a much larger scratch depth in simulations are carefully discussed. A parametric study was conducted to investigate the effect of scratching velocity, amplitudes of indentation velocity, particle sizes, and applied thrust load on the scratch behavior.