Fragmentation in the Expanding Ring Experiment

Ever since the inspiring work of Mott [

1

] on the explosive fragmentation of shells, the expanding ring test has been used as an effective tool for evaluating the dynamic constitutive and failure behavior of materials at strain rates of about 10

4

s

−1

. Due to the complexity of the experimental configuration used in the expanding ring test, very few experimental results are available in the literature. A large database collected by Grady and Benson [

2

], which shows that the ring fails by generating a large number of localized necking deformation and a number of fractures at the neck points, has served as the main benchmark for analytical and numerical investigators. Two different points of view are prevalent in the literature, one is based on a statistical approach following on Mott and the other based on the growth of perturbations that localize deformation into necks (see for example, Guduru and Freund, [

3

]). Both approaches provide realistic predictions of the statistics of the fragmentation and its dependence on the rate of loading; hence additional experimental investigations that are instrumented to identify the appropriate necking and fragmentation mechanisms at these strain rates to are essential.