With the recent advancements in laser technology, the use of the laser as a measurement tool has become more widespread. Currently, research is underway in which a semiconductor laser diode is being used to measure the radial strain of a plastically deforming test specimen at the Naval Surface Warfare Center Dahlgren Division (NSWCDD). This particular application involves the use of a 670 nanometer (nm) wavelength laser diode and 25 megahertz (MHz) optical detector in lieu of conventional electrical resistance strain gages to measure specimen true strain in the split Hopkinson pressure bar (SHPB), a compressive stress testing apparatus capable of generating strain rates up to 10{sup}4s{sup}(-1). Preliminary data has shown that, for incompressible materials, this optical method of strain measurement results in increased resolution, bandwidth and signal-to-noise ratios such that identification of both the elastic and plastic deformation regimes is possible. In addition, peak specimen strains and strain rates can be resolved. Finally, this study will show that the use of the optical method of strain measurement improves the precision of the SHPB experiment by ridding the experiment of the errors associated with the electrical resistance strain gage.
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