Spalling Behavior of Cu Plate Under Sliding Detonation Loading

We study the fracture behavior of a Cu plate under sliding detonation loading using wire explosion technique. Both Doppler Pins Systems (DPS) and Scanning Electron Microscope (SEM) are employed in the experiments to study the velocity of the free surface and the microstructure of the recovered samples. A novel spalling phenomenon is substantially observed. Unlike the flyer impact method, the typical spalling signals are not currently obtained in the velocity curves. But the microstructure images of recovered samples show obvious spalling characters. Several microholes are created and arranged along the direction perpendicular to the loading axis. Moreover, these holes all aline within a wide band with about 1mm width. This is quite different from the case in the flyer impact experiment, in which the microholes all aline in a very narrow region. This is caused by the complex tensile stress state in the sample initiated by the explosive loading. More interestingly, all the microholes are initiated at the grain boundary and the grain size is much smaller in the band, especially at the edge of the big holes. These results may reveal the mechanism of the nucleation and the growth process for the microholes.