In situ phase contrast imaging of spall and cracking in vitreous carbon, polymethylmethacrylate, and magnesium alloys

In impact-generated compression and tension experiments, velocimetry diagnostics are used to detect dynamically created interfaces associated with material damage by observing wave interactions with free surfaces. Interpretation of these wave interactions becomes increasingly more difficult when the interfaces are sufficiently heterogeneous and oblique to the shock front. Therefore, phase contrast imaging of gas gun driven impacts has been performed at the Advanced Photon Source. Damage nucleation, propagation, and coalescence have been studied in multiple configurations for vitreous carbon, polymethylmethacrylate, and several magnesium alloys including AZ31B and AMX602. Uniaxial tension was used for obtaining spall strength and dynamic stress intensity factors. Complex tension, created from wave release off of concave and convex surfaces, was used to investigate shear dependence and stochasticity of cracking. Phase contrast images will be presented to illustrate the range of damage responses exhibited across the different classes of material in their respective microstructure and the use of concave and convex surfaces to create complex tension in planar geometries.