Multiscale Residual Stress Evaluation of Engineering Materials/Components Based on Neutron and Synchrotron Radiation Technology

Multiscale residual stress exists throughout the manufacturing process of engineering components, from design and production to processing and servicing. This stress can impact the machining accuracy, structural load capacity, and fatigue lifespan of these components. Therefore, accurate measurement and regulation of residual stress are critical for ensuring the longevity and reliability of engineering components. However, precise characterization of residual stress is challenging owing to its multilevel and cross-scale distribution traits and dynamic evolution under various conditions, such as temperature and load. Compared with laboratory X-ray measurement methods, neutron diffraction (ND), synchrotron-based high-energy X-ray diffraction (HE-XRD), and synchrotron-based X-ray microbeam diffraction (mu-XRD) techniques offer increased penetration depth and better time and spatial resolutions. In addition, the ability to attach environmental devices enables nondestructive and accurate in situ characterization of three types of residual stresses: macroscopic residual stress, intergranular or interphase microscopic stress, and intragranular ultramicroscopic stress. ND is currently the only nondestructive method capable of accurately measuring three-dimensional (3D) stress at centimeter-level depths within engineering components. HE-XRD, due to its high flux, excellent collimation, and millimeter-level penetration depth for metals, can be utilized for in situ studies of intergranular and interphase stress evolution and partitioning during deformation. The mu-XRD employs a submicron focused beam and differential aperture technology to analyze depth information of a sample. By conducting point-by-point scanning, it can capture 3D distribution of microscopic stress inside a single grain. Furthermore, our group has developed a novel method and device for depth stress characterization based on differential aperture technology under synchrotron-based high-energy monochromatic X-ray transmission geometry, and can measure stress gradients with high precision from the surface to the interior of engineering materials at millimeter-level depths. This study presents the measurement principles, application ranges, and applications of the above-mentioned multiscale stress characterization technologies based on the neutron/synchrotron facilities as well as envisaging the future development of related technologies.