Effect of local anisotropy on fatigue crack initiation in a coarse grained nickel-base superalloy

In the present work, theoretical approaches, based on grain orientation dependent Young's modulus and Schmid factor are used to describe the influence of local grain orientation on crack initiation behaviour of the coarse grained nickel base superalloy René80. Especially for strongly anisotropi...

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Bibliographic Details
Published inarXiv.org
Main Authors Engel, Benedikt, Beck, Tilmann, Moch, Nadine, Gottschalk, Hanno, Schmitz, Sebastian
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 06.06.2018
Subjects
Amplitudes
Anisotropy
Computer simulation
Crack initiation
Crack propagation
Crystal structure
Elastic properties
Fatigue failure
Fracture mechanics
Grain orientation
Low cycle fatigue
Modulus of elasticity
Nickel base alloys
Parameters
Plastic deformation
Shear stress
Superalloys
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Summary:In the present work, theoretical approaches, based on grain orientation dependent Young's modulus and Schmid factor are used to describe the influence of local grain orientation on crack initiation behaviour of the coarse grained nickel base superalloy René80. Especially for strongly anisotropic crystal structures with large grain size, such as the investigated material, the local elastic properties must be taken into account for assessment of fatigue crack initiation. With an extension of Schmid's law, the resulting shear stress amplitude, which triggers local cyclic plastic deformation, can be calculated depending on local Young's modulus and Schmid factor. A Monte Carlo simulation with 100,000 samples shows how random grain orientation affects these parameters. Furthermore, the product of Young's modulus and Schmid factor (called \(E\cdot m\)) is used as a parameter to determine how grain orientation influences resulting shear stress amplitude for given total strain amplitude. In addition to the theoretical work using that approach, this model is also validated using isothermal LCF experiments by determining local grain orientation influence on the crack initiation site using SEM-EBSD analyses.
ISSN:2331-8422