In-situ Measurement of Damage Evolution in Shocked Magnesium as a Function of Microstructure

This work investigates the nucleation and evolution of spall-induced void damage in magnesium of varying microstructure, using an in-situ, absorption contrast imaging approach. Damage and failure in ductile metals is characterized by nucleation, growth, and coalescence of voids. The underlying mechanisms and kinetics that control void nucleation and growth have been linked to material microstructure, but the specific controlling mechanisms associated with these processes are not understood.  This lack of understanding is in part related to a deficiency in experimental techniques that allow for direct quantitative and statistically relevant observations of void nucleation and early-stage growth.   In this work, we close this gap by performing in-situ direct imaging of void onset and growth at unprecedented spatial resolution for the first time. 

 

Our experimental results establish that microstructure plays a significant role in damage onset and evolution. Different primary failure mechanisms are activated depending on the sample microstructure, which we demonstrate leads to a clear difference in void shape and propagation which are not captured by traditional spall measurement approaches. Furthermore, we show for the first time the direct measurement of experimental void growth rates. The insights provided by our work can be applied to the refinement of existing analytical damage models and the development of new, superior damage models.