Ultra high speed full-field strain measurements on spalling tests on concrete materials

Abstract

This paper presents the use of an ultra high speed camera in conjunction with full-field measurements (grid method) to measure strain fields in a concrete specimen submitted to a spalling test (inertial tensile test). A Shimadzu camera is used to capture the images with a time resolution of 2 microseconds. Strain and acceleration fields are then obtained by spatial and temporal differentiation. It is then shown how the data can be used in the Virtual Fields Method to identify Young's modulus using the acceleration forces as a distributed volume load cell. The identified modulus values are consistent with expected values and the onset of damage can be detected as a sudden decrease in Young's modulus. This is a first step towards better description of damage at high strain rate in such brittle materials using full-field measurement approaches.