The response of natural rocks and concrete-like composites to dynamic loading was studied by measuring the passage of stress waves in ballistically-suspended Hopkinson bars. The substances considered include various plutonic rocks exhibiting a wide spectrum of grain sizes, as well as sedimentary, volcanic and structural materials, the latter consisting of combinations of Portland cement and special types of igneous aggregates. Transient loading was accomplished by the central longitudinal impact of a 1/2-in. diameter steel sphere at projectile velocities ranging up to 10,000 in/sec. The shape and velocity of propagation of the symmetric components of the resultant pulses were recorded at various stations along the bars by means of surface strain gages or sandwiched quartz crystal pressure transducers. The metamorphosis of the transient served as the basis for the delineation of the macroscopic behavior mechanisms of these materials. Results both from a single wave passage and from records involving multiple reflections indicate that some rocks exhibited virtually no change in pulse shape, while attenuation in increasing degree was observed in the volcanic materials with no noticeable alteration in wave profile. On the other hand, pulse propagation in a sandstone revealed a significant change in pulse shape. The artificial composites behave similarly to conventional concrete, with only minor amounts of attenuation and no dispersion of the transient. Static properties of the various specimens were examined both in the unshocked and shocked state, revealing little difference in all but one case, namely diorite; mechanical tests and petrographic examination of such samples showed significant deterioration in the physical characteristics as a consequence of wave passage.
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