A 316 stainless steel rod impacts with a rigid flat: Theory, experiment, and numerical simulation

A slender rod suffers global vibration in impact. In this study, we present the experimental, numerical, and theoretical studies of the axial responses of a 316 stainless steel rod during vertical impact with a rigid flat. Combining the contact models and the one-dimensional (1D) wave equation, we first develop a semi-analytical vertical impact model for the rods based on a unified theoretical framework, which considers different geometries of the impacting end including the hemispherical nose, the truncated conical nose, and the flat end. Furthermore, we perform free-drop experiments on these rods and numerical simulations to verify the theoretical models. The results show that the strain-rate effect hardens the rod nose and should not be ignored even at a velocity as low as a few meters per second. After the proposal of a dynamic correction factor to adjust the quasi-static contact model, the theoretical, numerical, and experimental results agree well with one another. Also, the three-dimensional (3D) FEM simulations show that the slight deviations between the experimental and the predicted results are due to the slight obliqueness of the rods in the drop. Additionally, we leverage the theoretical tool and FEM simulations to compare the mechanical responses of rods with different impacting ends, and suggestions about the selection of rod noses are obtained.