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Probabilistic Modeling of Slip System-Based Shear Stresses and Fatigue Behavior of Coarse-Grained Ni-Base Superalloy Considering Local Grain Anisotropy and Grain Orientation

1
Gas Turbine and Transmission Center Research Center (G2TRC), University of Nottingham, Nottingham NG7 2RD, UK
2
Department for Technology & Innovation, Gas and Power Division, Siemens AG, Huttenstraße 12, 10553 Berlin, Germany
3
Institute of Materials Science and Engineering, TU Kaiserslautern, 67663 Kaiserslautern, Germany
4
School of Mathematics and Science, Bergische Universität Wuppertal, 42119 Wuppertal, Germany
*
Author to whom correspondence should be addressed.
Metals 2019, 9(8), 813; https://doi.org/10.3390/met9080813
Received: 26 June 2019 / Revised: 17 July 2019 / Accepted: 20 July 2019 / Published: 24 July 2019
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
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Abstract

New probabilistic lifetime approaches for coarse grained Ni-base superalloys supplement current deterministic gas turbine component design philosophies; in order to reduce safety factors and push design limits. The models are based on statistical distributions of parameters, which determine the fatigue behavior under high temperature conditions. In the following paper, Low Cycle Fatigue (LCF) test data of several material batches of polycrystalline Ni-base superalloy René80 with different grain sizes and orientation distribution (random and textured) is presented and evaluated. The textured batch, i.e., with preferential grain orientation, showed higher LCF life. Three approaches to probabilistic crack initiation life modeling are presented. One is based on Weibull distributed crack initiation life while the other two approaches are based on probabilistic Schmid factors. In order to create a realistic Schmid factor distribution, polycrystalline finite element models of the specimens were generated using Voronoi tessellations and the local mechanical behavior investigated in dependence of different grain sizes and statistically distributed grain orientations. All models were first calibrated with test data of the material with random grain orientation and then used to predict the LCF life of the material with preferential grain orientation. By considering the local multiaxiality and resulting inhomogeneous shear stress distributions, as well as grain interaction through polycrystalline Finite Element Analysis (FEA) simulation, the best consistencies between predicted and observed crack initiation lives could be achieved. View Full-Text
Keywords: LCF; René80; Probabilistic modeling; slip system-based shear stresses; probabilistic Schmid factors; polycrystalline FEA; anisotropy; Ni-base superalloy LCF; René80; Probabilistic modeling; slip system-based shear stresses; probabilistic Schmid factors; polycrystalline FEA; anisotropy; Ni-base superalloy
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Engel, B.; Mäde, L.; Lion, P.; Moch, N.; Gottschalk, H.; Beck, T. Probabilistic Modeling of Slip System-Based Shear Stresses and Fatigue Behavior of Coarse-Grained Ni-Base Superalloy Considering Local Grain Anisotropy and Grain Orientation. Metals 2019, 9, 813.

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