2007 Fiscal Year Final Research Report Summary
The Changes of Mechanical Properties in Structural Materials Caused by Transmission of Strong Shock Waves and the Application to Fragmentation Modeling for Exploding Cylinders
| Project/Area Number |
17560072
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Kumamoto University |
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Principal Investigator |
HIROE Tetsuyuki Kumamoto University, Grad. Sch. of Sci. & Tech., Professor (90218826)
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| Co-Investigator(Kenkyū-buntansha) |
FUJIWARA. Kazuhito Kumamoto Univ., Grad. Sch. of Sci. & Tech., Professor (50219060)
HATA Hidehiro Kumamoto Univ., Grad. Sch. of Sci. & Tech., Assistant Prof. (30381007)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Mechanical Properties / Shock Wave Transmission / Momentum Trap / Cylinder Explosion / Fraamentation Enemy / Precomnression / Explosive Loadina |
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| Research Abstract |
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 following shock-induced damages or failures. In this study, incident shock waves in plate specimens of 304 stainless steel, aluminum alloys A5052 and A2017 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 cross-sections, tensile strength, fracture ductility ac and flow stresses cro2 at the strain of 20% 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 plates, revealing significant increase of hardness, tensile strength and flow stresses and unique changes of elongation and ductility for shocked specimens according to the amplitudes of the transmitted compression waves and the materials especially between the stainless steel and aluminum alloys. The results were effectively applied to take the precompression effects into consideration of the strain-rate dependency of fragmentation energy values r derived from the previous explosion tests for cylinders of the same materials of 304SS and A5052 using a fragmentation model proposed by Grady.
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