Cyclic-loading Induced Lattice-Strain Asymmetry in Loading and Transverse Directions
- ORNL
- University of Tennessee, Knoxville (UTK)
Cyclic-loading effects on a nickel-based superalloy are investigated with in-situ neutron-diffraction measurements. The thermoelastic-temperature evolution subjected to cyclic loading is estimated based on the lattice-strain evolution. The atomic thermoelastic responses are compared with the measured bulk temperature evolution. Two transitions in the temperature-evolution are observed. The first transition, observed with the neutron-measurement results, is associated with the cyclic hardening/softening-structural transformation. The second transition is observed at larger number of fatigue cycles. It has a distinct origin and is related to the start of irreversible structural transformations during fatigue. A lattice-strain asymmetry behavior is observed. The lattice-strain asymmetry is quantified as a grain-orientation-dependent transverse/loading parameter (P-ratio). The P-ratio parameter evolution reveals the irreversible plastic deformation subjected to the fatigue. The irreversible fatigue phenomena might relate to the formation of the microcracks. At elevated temperatures the cyclic hardening/softening transition starts at lower fatigue cycles as compared to room temperature. A comparison between the room-temperature and the elevated-temperature fatigue experiments is performed. The P-ratio parameters show the same irreversible trends at both the room and the elevated temperatures.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1038787
- Journal Information:
- Metallurgical and Materials Transactions A, Vol. 43A, Issue 5; ISSN 1073-5623
- Country of Publication:
- United States
- Language:
- English
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