Creep small-punch testing and its numerical simulations

Comparison of results of creep small-punch tests (SPTs) on miniaturized discs with results of their simulation by means of finite element method (FEM) is presented. Advanced heat-resistant chromium steel of type P91 was selected for the investigations. Two basic creep constitutive models, i.e. the Norton power-law and the exponential relationship were applied in the FEM. Parameters of both relationships were determined from stress dependences of minimum creep rate of conventional creep tests at 873 K. Two principally different FE models of the SPT were applied. The first model considers only simple boundary conditions as supports and an assumption of pressure load without the specific puncher shape; the second model includes contact elements taking in account the surface friction between all contact surfaces. Results of our numerical analyses are compared with experimental results. Results of modeling allow better understanding of the specimen behavior at higher strain rates and to estimate the influence of the contact surface friction at elevated temperatures.