Abstract
A testing device has been developed to study the dynamic compressive behaviour of a quasi-brittle material under confining pressure. At the opposite of similar studies conducted with SHPB tests, this one is achieved with a crossbow system. This direct impact device is composed of a hurled mass and a measuring output bar. Moreover, a specific confinement system is developed. The specimen is confined laterally by a thin metallic sleeve and axially between two metallic plugs [1, 2]. A metallic part gathers the confining cell and the output bar together, and guides the whole during compression. High-speed camera is used to follow the cell compression, and an image post-treatment is realised. The axial strain is consequently obtained from the displacement between the input and the output plugs. In addition, the confining pressure is calculated using the ring expansion and the material constitutive law. Finally, strain gauges on the output bar are used to determine specimen axial stress. Different projectile masses, specimen diameters and ring thicknesses were tested in order to get specimen strain up to failure associated for different constant confinements. Finally, the device allows obtaining different strain rates with various confining pressures.
Highlights
For an application on a charged polymeric specific material, the CEA Le Ripault and the Ecole Centrale Nantes studied the realisation of a dynamic compressive test on cylindrical specimen, with high-pressure confinement, allowing the measurement of stress and strains in the material
We conceive a test on crossbow system [8], including a possibility of strain measurement by correlated pictures of a thin metallic sleeve during the test
The energy is produced by the impact of a 44 kg mass, moving at a speed of 4.8 m/s on a test mechanism, which is mounted on a Hopkinson bar
Summary
For an application on a charged polymeric specific material, the CEA Le Ripault and the Ecole Centrale Nantes studied the realisation of a dynamic compressive test on cylindrical specimen, with high-pressure confinement, allowing the measurement of stress and strains in the material. Chen and Ravichandran [1, 3] use a plastic metallic sleeve on a ceramic test specimen. The specimen is cooled and the sleeve heated. This operation causes a confinement pressure, function of sleeve material and thickness, and relative diameter dimension. They determine this pressure by considering elastic law for the test specimen, and elasto-plastic perfect for the sleeve. They considered a thin sleeve thickness in front of the ray of the test specimen in order to simplify their expressions
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