The first research objective (RO1) is to develop an aggregated database of creep and creep-fatigue validation data from existing datasets for P91 steel and 316 stainless steel. An extensive database of creep, stress relaxation, monotonic tensile, fatigue, and creep-fatigue experimental data will be collected. The second research objective is to employ the RO1 database to benchmark existing creep and creep-fatigue models in a variety of finite element models. RO2 will involve the investigation into the data fitting and parameter extraction using both analytical as well as a novel multi-objective optimization approach (MACHO). Using the guidelines resulting from RO1 and RO2, a component designer will be able to easily select the best constitutive model(s) and experimental datasets for an intended design.