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Bronkhorst, Curt A

Publications and source records attributed to Bronkhorst, Curt A.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Pressure and Temperature effects on the High Pressure Phase Transformation in Zirconium

At high pressure zirconium is known to undergo a phase transformation from the hexagonal close packed (HCP) alpha phase ({alpha}) to the simple hexagonal omega phase ({omega}). Under conditions of shock loading, the high-pressure omega phase is retained upon release. However, the hysteresis in this transformation is not well represented by equilibrium phase diagrams. For this reason, the influence of peak shock pressure and temperature on the retention of omega phase in Zr is explored in this study. In situ VISAR measurements along with post-mortem metallographic and neutron diffraction characterization of soft recovered specimens have been utilized to quantify the volume fraction of retained omega phase, morphology of the shocked alpha and omega phases, and qualitatively understand the kinetics of this transformation. This understanding of the role of peak shock stress will be utilized to address physics to be encoded in our present macro-scale models.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Effects of Loading Kinetics on the Shock Response of Polycrystalline Copper

The effects of loading kinetics on the damage evolution in high purity copper samples are summarized as follows: The combination of the energy supplied by the shock impulse (peak stress) and the time spent in it dissipation seem to be responsible for the characteristics of the damage fields. For an increasing coupled parameter of energy*time, more damage was predicted, as well as experimentally observed; As more energy (higher peak stress) was dissipated for longer periods of time (lower decompression rate), the damage fields evolved from early stages of damage, in the form of void nucleation and initial void growth, to the later stages of void coalescence.

36 MATERIALS SCIENCE↗