Role of pre-existing dislocations on the shock compression and spall behavior in single-crystal copper at atomic scales

Large-scale molecular dynamics simulations are carried out to investigate the role of pre-existing dislocation loops on the shock-induced deformation and spall behavior of single-crystal Cu microstructures. This study investigates the role of loading orientation and initial density of pre-existing dislocations on the decay behavior of the Hugoniot elastic limit (HEL) as well as the damage nucleation and growth behavior during spall failure of single-crystal Cu systems. The results suggest that the presence of pre-existing dislocation loops results in a decrease of the shock wave velocity and a substantial decay of the HEL values. The increased decay behavior is attributed to the decrease in the density of Shockley partials at the shock front as the shock wave travels through the metal as compared to defect-free initial single-crystal microstructures. Similarly, the presence of pre-existing dislocations is observed to result in increased values for the spall strength as compared to defect-free initial single-crystal microstructures wherein a higher density of dislocations results in the nucleation of a larger number of smaller voids. The decay behavior of the HEL values is observed to have a power-law dependence on the shock propagation distance with the initial dislocation density as a parameter. Similarly, a power-law dependence is also proposed for the number of voids nucleated at the spall plane with a dependence on the size of the voids as well as the initial density of dislocations. The evolution of microstructure (dislocation densities and voids) for the various loading orientations and initial densities of dislocations is discussed.

Automated summary

The study found that pre-existing dislocation loops in single-crystal Cu systems result in decreased shock wave velocity and a substantial decay of the Hugoniot elastic limit (HEL) values, but also increase spall strength. The decay behavior of HEL values and the power-law dependence of the number of voids on shock propagation distance and initial dislocation density were observed.