Application of Neutron Stress Measurement Method without Stress-Free Lattice Constant to Practical Material
Hiroshi SUZUKI, Atsushi MORIAI, Nobuaki MINAKAWA and Yukio MORII
Abstract:In a conventional method of a neutron stress measurement, it is required to know the stress-free lattice constant accurately in order to calculate lattice strains. A new stress measurement method, which does not need the lattice constant of the strain-free material, was proposed. In this study, this proposed method was applied to evaluate the residual stress distributions in welded sample. Utilizing Neutron Diffractometer for Residual Stress Analysis (RESA) in JRR-3 (Japan Research Reactor-3) at Japan Atomic Energy Research Institute (JAERI), the distribution of lattice constant of welded sample was measured by using the coupon samples which was cut from the welded sample. The measured lattice constant was increasing near the weld zone since the martensitic transformation occurred in heat affected zone (HAZ). On the other hand, the lattice constant distribution which was measured by using our proposed method showed an increase as close to the weld zone, and the absolute value of the lattice constant was almost the same as the lattice constant of the coupons. Therefore, it is possible to predict the lattice constant by using our proposed method even if the lattice constant distribution is existed in the materials. The residual stress distributions were evaluated by using conventional method and our proposed method. As a result, the residual stress distributions decided by our proposed method almost agreed with those measured by conventional method. This proposed method can be applied to determination of the residual stress states in the samples with the complex residual stress states. Key Words:Neutron diffraction, Residual stress, Stress measurement, Lattice constant, Welding