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A THEORETICAL STUDY OF THE SHOCK WAVE ORIGIN OF SHATTER CONES.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO
Shatter cones are striated, conical structures usually found in fine-grained, homogeneous rocks. The investigation resulted in the development of a theory which predicts that conical fracture surfaces will be produced as the result of the interaction of a shock wave with a small obstacle. The obstacle is a region of anomalous density andor compressibility in the transmitting medium. The shock wave must have the property that the amplitude of the compressive stress at and behind the front must be equal to the yield strength of the transmitting medium. A theoretical derivation of the stress distribution which results from the interaction of the shock wave and the obstacle demonstrated that a conical fracture surface should be produced. This fracture surface is shown to be an almost perfect pair of cones whose axis of symmetry is parallel to the direction of propagation of the shock wave. At a distance of several obstacle radii, the flanks of the cones are inclined at an angle of 45 degrees to the axis of revolution. This result is independent of the composition of the transmitting medium or the obstacle. There is reason for believing that the cone whose apex points in the direction of shock propagation will be smaller that its companion which points toward the source and in some cases may not exist at all.