Comparison between linear and non-linear fracture mechanics analysis of experimental data for the ductile superalloy Haynes 230

With increasing use of renewable energy sources, an industrial gas turbine is often a competitive solution to balance the power grid. However, life robustness approaches for gas turbine components operating under increasingly cyclic conditions are a challenging task. Ductile superalloys, as Haynes 2...

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Veröffentlicht in:Journal of engineering for gas turbines and power 2016, Vol.138 (6), p.062101
Hauptverfasser: Ewest, Daniel, Almroth, Per, Sjödin, Björn, Leidermark, Daniel, Simonsson, Kjell
Format: Artikel
Sprache:eng
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Zusammenfassung:With increasing use of renewable energy sources, an industrial gas turbine is often a competitive solution to balance the power grid. However, life robustness approaches for gas turbine components operating under increasingly cyclic conditions are a challenging task. Ductile superalloys, as Haynes 230, are often used in stationary gas turbine hot parts such as combustors. The main load for such components is due to nonhomogeneous thermal expansion within or between parts. As the material is ductile, there is considerable redistribution of stresses and strains due to inelastic deformations during the crack initiation phase. Therefore, the subsequent crack growth occurs through a material with significant residual stresses and strains. In this work, fatigue crack propagation experiments, including the initiation phase, have been performed on a single edge notched specimen under strain controlled conditions. The test results are compared to fracture mechanics analyses using the linear ΔK and the nonlinear ΔJ approaches, and an attempt to quantify the difference in terms of a life prediction is made. For the tested notched geometry, material, and strain ranges, the difference in the results using ΔK eff or ΔJ eff is larger than the scatter seen when fitting the model to the experimental data. The largest differences can be found for short crack lengths, when the cyclic plastic work is the largest. The ΔJ approach clearly shows better agreement with the experimental results in this regime.
ISSN:0742-4795
1528-8919
DOI:10.1115/1.4031712