A comparative study on the restrictions of dynamic test methods

Abstract

Abstract. Dynamic behavior of materials is investigated using different devices. Each of the devices has some restrictions. For instance, the stress-strain curve of the materials can be captured at high strain rates only with Hopkinson bar. However, by using a new approach some of the other techniques could be used to obtain the constants of material models such as Johnson-Cook model too. In this work, the restrictions of some devices such as drop hammer, Taylor test, Flying wedge, Shot impact test, dynamic tensile extrusion and Hopkinson bars which are used to characterize the material properties at high strain rates are described. The level of strain and strain rate and their restrictions are very important in examining the efficiency of each of the devices. For instance, necking or bulging in tensile and compressive Hopkinson bars, fragmentation in dynamic tensile extrusion and petaling in Taylor test are restricting issues in the level of strain rate attainable in the devices.

Development of material strength and failure models for structural simulation of metallic shock tube diaphragms

“…This is an advantage over most explicit techniques for determining the Johnson Cook constants as high strain rate effects are often simply extrapolated from experimental data that has generally only been found at low to medium strain rates [47]. Gathering results using this technique requires creating an optimisation process to update the JC material constants intelligently after each iteration [48].…”

“…As discussed before, this testing technique requires an iterative optimisation process to run and modify simulations. Taylor Anvil tests are a commonly used technique to determine Johnson Cook parameters [47] [39] however they require cylindrical specimens and the X3 diaphragm is too thin to produce a cylindrical specimen.…”