Study on structural design method by inelastic analysis(1); Investigation of design procedure

kasahara, Naoto; Ando, Masanori

Application of 'design by inelastic analysis' is expected to the rational structural design of fast reactor components where creep deformations occur due to elevated temperature operations. A main difficulty of the inelastic analysis method is a dependency of its solution to analysis methods such as constitutive equations. This study revealed that a dependency of ratchet strains on constitutive equations increases when an elastic follow-up factor or a primary stress enhances. It was also clarified that dependencies of strain ranges and fatigue damages on constitutive equations increase when an elastic follow-up factor increases, but they are rather insensitive to a primaly stress. Furthermore, it became evident. from the systematic investigations of dependencies on constitutive equations, that structures have elastic follow-up characteristics described by relaxation locus, which is insensitive to constitutive equations. Based on the above results, the authors have proposed an inelastic design approach. The first step of the approach is the evaluation of elastic follow-up characteristics and primary stresses by creep analyses with classical constitutive equations. The next step is the selection of constitutive equations that give conservative solutions under certain elastic follow-up characteristics and primary stresses. The third step is the detailed inelastic analyses with selected constitutive equations.