Hopkinson techniques for dynamic recovery experiments

Abstract

Novel techniques are introduced to render the classical split Hopkinson bar apparatus suitable for dynamic recovery experiments, where samples can be subjected to a single pulse of pre-assigned shape and duration, and then recovered without any additional loading, for post-test characterization; i. e., techniques for fully controlled unloading in Hopkinson bar experiments. For compression dynamic recovery tests, the new design generates a compressive pulse trailed by a tensile pulse (stress reversal), travelling toward the sample. Furthermore, all subsequent pulses which reflect off the free ends of the two bars (incident and transmission) are rendered tensile, so that the sample is subjected to a single compressive pulse whose shape and duration can also be controlled. For tension recovery experiments, the new design provides for trapping the compression pulse reflected off the sample, and the tensile pulse transmitted through the sample. In addition, a sample can be subjected to compression followed by tension, and then recovered, allowing the study of, e. g. the dynamic Bauschinger effect in materials.

Dynamic compressive strength of silicon carbide under uniaxial compression

“…In particular, it is important to ensure that a uniform state of stress is attained along the length of the sample. Hence, the following further modifications are made [10]: 1. A thin copper cushion is placed at the impact end of the incident bar.…”

Influence of Damping Ring Material on Dynamic Tensile Tests

“…In the beginning of 90s, a method to interrupt Hopkinson experiments was developed by Nemat-Nasser et al [25], which was based on the absorption of the reflected waves for controlling the deformation level of the specimen. Ma et al [26] developed a high-speed tensile facility to interrupt the fracture tests for pure copper specimen at different levels of elongation.…”

Constitutive response of welded HSLA 100 steel

“…For q 1 0/q 2 0/q 3 0/1, the Gurson Á/Tvergaard model [27] reduces itself to the Gurson model [28]. For the description of a uniaxial-loading test, the dependencies between the stress tensor invariants and axial stress are used in the form (s z is the stress along the loading direction):…”

“…The dynamic tension tests were carried out on a modified Hopkinson tension bar using a momentum trap for reflected compressive waves [28]. The principle and the configuration of the dynamic Hopkinson tension bar are shown in Fig.…”