Konstitutiver Lebensdauerzähler

FKM 2006
Issue No. 292
Project No. 254

Abstract:
Constitutive 1 D equations for the description of the cyclic and creep rupture-free behavior of creep-resistant power plant steels.
The cyclic creep and creep rupture behavior under isothermal and anisothermal rectangular cyclic loading without and with compression phase was investigated experimentally and theoretically on a series of characteristic creep-resistant steels used in power plant, turbine and high-temperature plant construction. Using the example of the forged steel / melt X12CrMoWVNbN10-1-1 / 1A / uA1, it could be shown that the selected constitutive material model has the potential to be applied to aninisothermal, overelastic, time-dependent and, at the same time, no-control stresses with predominant creep damage. This was done in the verification experiments carried out in the project with conclusive results, even with multi-axial loading in notch specimens. In the recalculation of the strain-controlled, isothermal tests with an operationally similar rotor cycle, the deformation behavior during the first cycles could be described well so far. In future, a corresponding approach is to be developed for time-dependent calculations, which should result in significantly shorter calculation times. Furthermore, the applicability of phenomenological approaches to lifetime calculation from previous work to the modern power plant steels X12CrMoWV- NbN10-1-1, 23CrMoNiWV8-8, GX12CrMoWVNbN10-1-1, G17CrMoV5-10, X10CrMoVNb9-1 and X11- CrMoWVNbN9-1-2, which are currently the focus of attention, could be demonstrated up to the upper application temperature in each case. The experimental data basis is formed by tests on smooth and notched samples up to approx. 3000h running time with high-resolution deformation measurement. The comparison of the experimentally determined fracture time with the calculated fracture time determined using the service life fraction rule confirms the applicability of the present materials with the same evaluation of compressive and tensile stresses. Finally, phenomenological service life calculations were carried out on the basis of the experimentally determined stress curve of the anisothermal, strain-controlled tests with creep fatigue loading close to operation. The critical service life consumption due to creep and fatigue damage accumulated for these tests to values just below one with predominant material exhaustion due to creep damage. Overall, this work contributes to an improved characterization of component behavior against the background of more heavily loaded high-temperature components with increasingly flexible operating modes. The objective of the research project has been achieved. Scope of report:
69 p., 51 fig. and 13 tab., 100 Start of work:
01.01.2002 End of work:
30.06.2005 Funding body:
AVIF-No. A174 Research center:
Institute for Materials Science Technical University of Darmstadt Prof. Dr.-lng. C. Berger Dr.-Ing. A. Scholz Processor and author:
Dipl.-lng. A. Simon Chairman of the working group:
Dr.-lng. M. Reigl, ALSTOM (Schweiz) AG