Plate-impact-driven ring expansion test (PIDRET) for dynamic fragmentation

Abstract

A new experimental set-up mounted at the muzzle of a singlestage gas gun has been designed in order to study the fragmentation of metallic rings under dynamic radial expansion. This concept takes advantage of the quasi-incompressibility of HDPE whose radial flow under plate impact-like loading is used to apply a pressure boundary condition at the ring’s inner surface. For the experimental configurations considered in the present work, the average strain rate in the ring reaches values close to 104 s-1. The repeatability and the reliability of the experiments are verified for rings made of steel and aluminium.

The effect of initial texture on multiple necking formation in polycrystalline thin rings subjected to dynamic expansion

“…The ring expansion experiment developed by Niordson (1965) has become a reference benchmark problem to investigate dynamic necking localization and fragmentation of ductile metallic materials. The test consists of a thin circular specimen with square/rectangular cross-section which is expanded radially at high strain rates using electromagnetic loading schemes, explosive charges or mechanical loading systems such as gas guns (Fyfe and Rajendran, 1980;Goto et al, 2008;Wood et al, 2021;Gant et al, 2021), so that multiple necks are formed throughout the circumference of the sample at large strains, leading to the final fragmentation of the ring. The principal advantage of the rapidly expanding ring experiment -in comparison with the tensile impact testing of linear specimens (slender bars)-is that the radial symmetry of both specimen and loading nearly eliminates the propagation of stress waves along the hoop direction of the sample before necking localization, thus revealing the true dynamic properties of the material.…”

The effect of initial texture on multiple necking formation in polycrystalline thin rings subjected to dynamic expansion

“…The ring expansion experiment developed by Niordson (1965) has become a reference benchmark problem to investigate dynamic necking localization and fragmentation of ductile metallic materials. The test consists of a thin circular specimen with square/rectangular crosssection which is expanded radially at high strain rates using electromagnetic loading schemes, explosive charges or mechanical loading systems such as gas guns (Fyfe and Rajendran, 1980;Goto et al, 2008;Wood et al, 2021;Gant et al, 2021), so that multiple necks are formed throughout the circumference of the sample at large strains, leading to the final fragmentation of the ring. The principal advantage of the rapidly expanding ring experiment -in comparison with the tensile impact testing of linear specimens (slender bars) -is that the radial symmetry of both specimen and loading nearly eliminates the propagation of stress waves along the hoop direction of the sample before necking localization, thus revealing the true dynamic properties of the material.…”