A rocking spelling test to characterize the crack velocity in concrete

Abstract

The dynamic crack velocity is a key-parameter involved in the micro-mechanics based modelling of the tensile damage of geomaterials under impact loading. However, because of technical difficulties, very few experimental methods have been proposed in the literature. In this work, a new set-up is presented based on spalling tests. A compressive pulse is transmitted to a parallelepipedic specimen by means of a Hopkinson bar. It is reflected as a tensile wave on the opposite free surface of the sample. A short notch is used to trigger a single crack whereas a larger notch provides a rocking effect of the rear part of the specimen. This experimental configuration has been optimized using numerical simulation analysis. Finally, a series of tests have been conducted on dry and wet concrete. Crack gauges and ultra-high speed camera coupled to Digital Image Correlation have been used to determine the crack speed in this material.