Papers by Author: Karel Milička

Abstract: The FEM modeling of small punch tests on miniaturized thin discs (SPT) of two heat resistant steels was performed. The FE models did represent the creep SPT, i.e. tests with constant acting force. It was shown that different values of the surface friction coefficient used in the calculations have significant impact on the calculated stress and strain state and consequently on the deformed shape of the disc. Thus, the surface friction coefficient should be considered one of the key factors for any correct correlation of SPT and uniaxial creep test results. Proper attention must be paid to the friction conditions during the long term creep deformation. An attempt to define simple approach how to relate the SPT with uniaxial tests is suggested. Some of the calculated results are compared with experiment.

Abstract: Conventional uniaxial creep tests on massive specimens and small punch creep tests on thin discs were performed on P91 steel at temperatures from 823 to 873 K. The shapes of corresponding time dependences, i. e., creep curves and time dependence of the disc deflection, are very similar. A simple linear relationship between the applied stress in creep tests and the acting force in small punch tests leading to identical times to rupture was empirically derived. The proportionality factor reaches a value close to values observed in other creep-resistant ferritic steels.