HIGH VELOCITY BRITTLENESS AND HIGH VELOCITY DUCTILITY OF STRUCTURAL SOLIDS

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1. The system for the characterization of materials in high velocity tension that can give the dynamic tensile stress-strain diagrams up to complete breaking, in the strain rate range up to lx10^4/s was established, basing upon the "one bar method" formulae proposed by Kawata et al. The effective time duration ranges up to 1160 microsecond, the longest record in the world.2. The data on complete tensile stress-strain raletion in 10^3/s range and the phenomena of the velocity brittleness and high velocity ductility were clari-fied for various categories of solids: pure metals, alloys, composites, polymers, and ceramics.3. Pure metals: (1) Generally speaking, obtained wide results support well crystal lattice systems effect on high velocity brittleness proposed by Kawata in 1978. (2) Pure iron show drastic high velocity brittlness. And this seems the fundamental behaviour of BCC metals. This property should be suppressed in practical structural materials. (3) The flow stress of OFHC copper shows clear upper deviation from log strain rate proportionality in 10^3/s range in tension, suggesting the transition of deformation mechanism to visous type from thermal activation type.4. In the categories of alloys, composites, polymers and ceramics, also, many ramarkable results on high velocity brittleness and high velocity ductility were obtained. Some examples are: remarkable high velocity ductility of GFRP, incres-ing of absorbed energy of PC in 10^3/s range, high velocity ductility of Pyrex glas fiber, extreme high velocity brittleness of PET and Nylon 12 etc.5. Details should be referred to the 39 papers published shown in Full Report.