Science and Technology of Energetic Materials

Vol.69, No.4 (2008)

Research paper

Mechanical changes in metals caused by transmission of explosive shock waves and a consideration to fragmentation energy in cylinder explosions
Tetsuyuki Hiroe, Kazuhito Fujiwara, Hidehiro Hata, and Kenjiro Watanabe


Explosive driven fracture such as fragmentation or spallation in a structural body will be preceded by a strong compression process, and precompression effects on the state of the material are clearly important to understand the following shock-induced damages or failures. In this study, incident shock waves in plate specimens of 304 stainless steel and aluminum alloy A5052 were generated by plane detonation waves in the high explosive PETN initiated using wire-row explosion techniques, and the compressed specimens were successfully recovered without severe damages due to tensile stress states with use of momentum trap method. A hydro code, Autodyn-2D was applied to determine test conditions: thicknesses of explosives, air-layer attenuators as necessary, specimens and momentum traps and to evaluate experimental results, simulating time-histories of stress waves in the layers of the test assembly. Microhardness distributions in crosssections, tensile strength, fracture ductility and flow stresses were measured for the recovered specimens, using miniature tensile and compression test pieces machined from them. They were compared with those of specimens from unloaded virgin plates, revealing significant increase of hardness, tensile strength and flow stresses and unique changes of elongation and ductility for shocked specimens depending on the intensities of the transmitted compression waves and the materials. The results were effectively applied to take the precompression effects into consideration of the strain-rate dependency of fragmentation energy values derived from the previous explosion tests for cylinders of the same materials using a fragmentation model.

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Mechanical properties, Shock wave transmission, Momentum trap, Cylinder explosion, Fragmentation energy.  

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