Strain rate-dependant mechanical properties of OFHC copper

The mechanical properties of high purity copper have been extensively studied in the literature, with yield and flow stresses measured as a function of strain rate, grain size, and temperature. This paper presents a comprehensive study of the strain rate and grain size dependence of the mechanical properties of OFHC copper, including an investigation of the previously observed upturn in rate dependence of flow stress at high rates of strain (≥500 s⁻¹). As well as a comprehensive review of the literature, an experimental study is presented investigating the mechanical properties of OFHC copper across a range of strain rates from 10⁻³ to 10⁵ s⁻¹, in which the copper samples were designed to minimize the effects of inertia in the testing. The experimental data from this study are compared with multiple sources from the literature varying strain rate and grain size to understand the differences between experimental results on nominally the same material. It is observed that the OFHC copper in this study showed a similar increase in flow stress with strain rate seen by other researchers at high strain rates. The major contribution to the variation between experimental results from different studies is most likely the starting internal structure for the materials, which is dependent on cold working, annealing temperature, and annealing time. In addition, the experimental variation within a particular study at a given strain rate may be due to small variations in the internal structure and the strain rate history.