Abstract
Taylor impact tests involving the collision of a cylindrical sample with an anvil are widely used to study the dynamic properties of materials and to test numerical methods. We apply a combined experimental-numerical approach to study the dynamic plasticity of cold-rolled oxygen-free high thermal conductivity OFHC copper. In the experimental part, impact velocities up to 113.6 m/s provide a strain up to 0.3 and strain rates up to 1.7 × 104 s−1 at the edge of the sample. Microstructural analysis allows us to find out pore-like structures with a size of about 15–30 µm and significant refinement of the grain structure in the deformed parts of the sample. In terms of modeling, the dislocation plasticity model, which was previously tested for the problem of a shock wave upon impact of a plate, is implemented in the 3D case using the numerical scheme of smoothed particle hydrodynamics (SPH). The model includes an equation of state implemented in the form of an artificial neural network (ANN) and trained according to molecular dynamics (MD) simulations of uniform isothermal stretching/compression of representative volumes of copper. The dislocation friction coefficient is taken from previous MD simulations. These two efforts are aimed at building a fully MD-based material model. Comparison of the final shape of the projectile, the reduction of the sample length and increase in the diameter of the impacted edge of the sample confirm the applicability of the developed model and allow us to optimize the model parameters for the case of cold-rolled OFHC copper.
Highlights
Dynamic strength and plasticity of metals are relevant to a wide range of civilian and defense applications and continue to attract the attention of researchers
The existing experimental methods of dynamic testing cover a wide range of strain rates up to 109 s−1, which is already attainable for direct simulations by molecular dynamics (MD), while most practical problems correspond to somewhat lower strain rates
We applied a combined experimental-numerical approach to study the dynamic plasticity of cold-rolled oxygen-free copper with high thermal conductivity (OFHC) copper
Summary
Dynamic strength and plasticity of metals are relevant to a wide range of civilian and defense applications and continue to attract the attention of researchers. The existing experimental methods of dynamic testing cover a wide range of strain rates up to 109 s−1, which is already attainable for direct simulations by molecular dynamics (MD), while most practical problems correspond to somewhat lower strain rates. The widely used split Hopkinson pressure bar (Kolsky bar), [14,15,16] provides more moderate strain rates up to about 103–104 s−1. The flying-wheel machine can be used to attain the strain rates of about 102–103 s−1 [17]. Taylor impact tests combine large non-uniform strains and large strain rates in the range
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