Development of residual stress measurement apparatus by neutron diffraction and its application to bent carbon steel

To establish the measuring technique of neutron diffraction for the internal residual stress distribution in a structural component, a neutron diffraction apparatus was designed and manufactured in Japan Research Reactor No.3 (JRR-3). At the first step of measurement, basic characteristics of the diffractometer was evaluated. The incident neutron beam flux was 104 n/cm2/s and the Full Width at Half Maximum (FWHM) of diffracted neutron profile was about 0.3 degree. This indicates that the manufactured neutron diffractometer is capable for the residual stress measurement. As the first application of the neutron diffraction measurement, the residual stress distribution in plastically bent carbon steel plate was measured. A typical compressive-Tensile-compressive-Tensile residual stress pattern in the tangential direction in the bent plate was confirmed. The maximum stress near the surface was about 180 MPa. This means that the technique for residual stress measurement by neutron diffraction method can be established in Japan. © 2021 Society of Materials Science Japan. All rights reserved.