Papers by Keyword: Steel P91

Abstract: In this paper there has been presented a new quantitative criterion of the end of a low-cycle fatigue test conducted in the conditions of fixed amplitude loads. In this criterion there is used an analytical description of the parameters of the hysteresis loop and the number of cycles till the fracture. The conducted experimental verification of this criterion enabled to obtain satisfactory results. In the paper it has been stated that the presented criterion can have a special application in the case of tests of metal materials in an elevated temperature.

Abstract: In this paper there have been presented the results of low-cycle fatigue tests of steel P91 samples in the conditions of isothermal fixed amplitude loads as well as loads with a temperature change. Fixed amplitude isothermal loads were conducted on five levels of full strain and in two temperatures T1=20°C and T2=600°C. In the paper there has been found a significant influence of the sequence of temperature changes on the cyclic properties after the temperature change and on the fatigue life. The conducted experimental verification of the Palmgren-Miner hypothesis proved its influence on the temperature changes during the tests.

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.