The Spallation Of Ductile Metals Under Loading Of Electric Gun Driven Metallic Flyers

SRI-NAG(Nucleation And Growth) model was a recognized model in ductile materialspall behavior research. The NAG model coefficients were always regard as constants, but themicrovoids distribution at super high strain rates connoted the nucleation coefficients beingsensitive with strain rates. Exploring the rule of nucleation coefficients will be a possible wayapproach microvoids nucleation mechanism.OFHC Cu and pure Cu incipient spalled under～10⁵s^-1strain rates electric gun driven twostage flyer impacts loading. The microvoids number density and porosity of recovery sampleswere statistically analyzed. According to the photos and statistical data, microvoids nucleatedat the grain boundary, or in the grain around voids of radius greater than tens of millimeters.Nucleation of microvoids were sensitive with the shockwave amplitude, and insensitive withthe pulse duration; but growth of microvoids, on the contrary, insensitive with the shockwaveamplitude, sensitive with the pulse duration. Shapes of microvoids in OFHC Cu and pure Cuare in difference. OFHC Cu target spalled under electric gun driven driven two stage metalflyer impact loading, the velocity profiles of rear surface were measured by VISAR. The spallstrength and debris size are according with the reported data and wave propagation law.One dimensional shockwave code SSS was adapted to simulate the number density andporosity of incipient spalled OFHC Cu and pure Cu sample at the range of 10⁴-10⁵s^-1. TheNAG model coefficients were acquired, the nucleation coefficient was sensitive with thepurity of sample. Simulation results were in according with the velocity profiles of rearsurface, as the equation of state, constitutive relations and the evolution law of microvoidswere well adopted.