... normal penetration with the sharp indentor was largely independent of the penetration direction. In contrast, the crater volume produced by the blunt indentor was increased markedly by non-normal penetration at small penetration depths, because the threshold penetration for chip formation decreased...

... ABSTRACT ABSTRACT Chip formation in rock under a line load and in front of a drag bit cutter is numerically investigated. Analysis is accomplished by a special purpose interactive graphics finite element code, SICRAP, written for the simulation of mixed mode crack propagation under linear...

... penetration, it was reasoned that chip formation and removal in the narrower slot might be more effectively resisted by an "arch effect" since the slot bottom radius is smaller relative to chip size. Indeed, there was some visual indication of such behavior. This hypo- thesis is further suggested by noting...

... reservoir geomechanics single-pair bit chip formation hydraulic fracturing strength spall fracture Upstream Oil & Gas Sandia laboratory sandstone Spark Drilling compressive wave Drilling fracture limestone hole axis Reservoir Characterization Berea sandstone mechanism spark...