Strain Analysis in Geological Materials Using Neutron Diffraction and AE Signal Measurement at J-PARC/BL19 "TAKUMI"

Abstract

Acoustic emission (AE) is defined as a transient elastic wave generated by the rapid release of energy within a material. Crack initiation, phase transition and rupturing in rock materials are all detectable with the measurement of AE signals, and therefore such measurement helps to understand the underlying mechanism (s) of macroscopic deformation. In this study of the deformation mechanism (s) of rock samples, simultaneous measurements of the neutron diffraction pattern and AE signals were performed using the Engineering Materials Diffractometer TAKUMI at the Japan Proton Accelerator Research Complex (J-PARC). Two types of rock sample were tested in the experiments: sandstone and carbonate rock. A discrepancy was found between macroscopic strain (measured by strain gauge) and lattice strain (measured by neutron diffraction), and AE signals that would be generated by grain slip and pore collapse in rock samples were detected. Macroscopic strain in the rock samples was associated not only with lattice strain but also with mineral grain slip and pore collapse within the rock. The combination of AE signal measurements and neutron diffraction is an effective tool for investigating the deformation mechanisms of rock materials.