Comprehending the dynamic indentation response of elasto-viscoplastic materials

There is a growing interest in dynamic indentation due to its capacity to characterize the high strain rate mechanical response of small volumes of materials. Our objective is to understand the dynamic indentation response of elasto-viscoplastic materials and explore the extent to which this response can be employed to characterize both strain rate-sensitive mechanical properties and the high-rate performance of materials. Characterizing the strain rate-sensitive mechanical response of materials at high strain rates is essential for a wide range of applications, including understanding ballistic and other impact events. Such an understanding will also enable small-scale, high-throughput characterization of the strain rate-sensitive mechanical response of materials, thus accelerating the materials characterization and discovery process. In this work, we investigate the influence of indentation loading rate, material properties, constitutive response, and indenter geometry on the dynamic hardness of materials. Specifically, we analyze dynamic indentation using a conical indenter, employing both finite element calculations and an analytical cavity expansion model. Our findings indicate that, for low to moderately high indentation loading rates, dynamic hardness correlates with the materials’ strain rate-sensitivity. However, at high indentation loading rates, dynamic hardness is influenced by both indentation depth and indentation strain rate, while at ultra-high indentation loading rates, it primarily depends on the indentation loading rate itself. Additionally, we will present a set of non-dimensional parameters designed to normalize the effects of indenter geometry and indentation depth alongside these results.