THE MECHANICAL THRESHOLD OF DYNAMICALLY DEFORMED COPPER AND NITRONIC 40

Measurements of the mechanical threshold, or threshold stress, are reported on quasi-statically and dynamically deformed copper and Nitronic 40. Results for copper show that the increase of the threshold stress with strain rate is similar to that of the flow stress. In Nitronic 40 the results show that the ratio of the flow stress to the threshold stress is approx.0.6. Both results indicate that the increased rate sensitivity found in these materials at high strain rates is not due to the predominance of a viscous drag deformation mechanism, as has been previously suggested.