This book presents the proceedings of the 9th International Conference on Mechanical Stress Evaluation by Neutron and Synchrotron Radiation which was hosted by the South African Nuclear Energy Corporation (Necsa) SOC Limited in cooperation with the International Atomic Energy Agency (IAEA). The conference topics included deformation & modeling, processing & welding, techniques & instruments, mechanical methods vs. diffraction, microstructure & characterization, surface modification & coatings, 3D/4D characterization and fatigue, creep & plasticity.