The use of a railgun facility for dynamic fracture of brittle materials

Linear electromagnetic acceleration has a wide range of applications. Among them are applications in the field of materials science where relatively small, inexpensive systems can be of high value. For instance, it was shown recently at the French-German Institute of Saint Louis (ISL), France, that the symmetric Taylor test - a method to investigate the deformation behaviour of specimens at high deformation rates- can be realized with higher precision than attainable with other acceleration methods by using a railgun with velocity control. In this work, we present another example for an application of a railgun in the field of materials science, namely the study of impact phenomena and terminal ballistics. One of the major advantages of railgun technology is that the acceleration profile can be well defined at velocity ranges from very low speeds (< 10 m/s) up to more than 2000 m/s - for one and the same launcher. Moreover, the geometry of a railgun projectile can be round, rectangular or, as in the case discussed here, hexagonal. Finally, electromagnetic acceleration does not require the use of propellants, which in the case of impact experiments could lead to complications - at least for the experimental application presented. The quest is to study the ejecta field of fractured brittle materials at moderate impact velocities (< 500 m/s). It transpires that a railgun can be a valuable tool for such investigations. Using high-speed cameras and novel data processing methods ejecta distribution-velocity relations are explored. Our contribution describes the experimental setup used and will introduce some of the major results obtained so far.