Monitoring microstructural evolution of alloy 617 with non-linear acoustics for remaining useful life prediction; multiaxial creep-fatigue and creep-ratcheting
- Pennsylvania State Univ., State College, PA (United States); Nuclear Energy University Programs
- North Carolina State Univ., Raleigh, NC (United States)
- Tuskegee Univ., Tuskegee, AL (United States)
The research built upon a prior investigation to develop a unified constitutive model for design-by-analysis of the intermediate heat exchanger (IHX) for a very high temperature reactor (VHTR) design of next generation nuclear plants (NGNPs). Model development requires a set of failure data from complex mechanical experiments to characterize the material behavior. Therefore uniaxial and multiaxial creep-fatigue and creep-ratcheting tests were conducted on the nickel-base Alloy 617 at 850 and 950°C. The time dependence of material behavior, and the interaction of time dependent behavior (e.g., creep) with ratcheting, which is an increase in the cyclic mean strain under load-controlled cycling, are major concerns for NGNP design. This research project aimed at characterizing the microstructure evolution mechanisms activated in Alloy 617 by mechanical loading and dwell times at elevated temperature. The acoustic harmonic generation method was researched for microstructural characterization. It is a nonlinear acoustics method with excellent potential for nondestructive evaluation, and even online continuous monitoring once high temperature sensors become available. It is unique because it has the ability to quantitatively characterize microstructural features well before macroscale defects (e.g., cracks) form. The nonlinear acoustics beta parameter was shown to correlate with microstructural evolution using a systematic approach to handle the complexity of multiaxial creep-fatigue and creep-ratcheting deformation. Mechanical testing was conducted to provide a full spectrum of data for: thermal aging, tensile creep, uniaxial fatigue, uniaxial creep-fatigue, uniaxial creep-ratcheting, multiaxial creep-fatigue, and multiaxial creep-ratcheting. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Optical Microscopy were conducted to correlate the beta parameter with individual microstructure mechanisms. We researched application of the harmonic generation method to tubular mechanical test specimens and pipes for nondestructive evaluation. Tubular specimens and pipes act as waveguides, thus we applied the acoustic harmonic generation method to guided waves in both plates and shells. Magnetostrictive transducers were used to generate and receive guided wave modes in the shell sample and the received signals were processed to show the sensitivity of higher harmonic generation to microstructure evolution. Modeling was initiated to correlate higher harmonic generation with the microstructure that will lead to development of a life prediction model that is informed by the nonlinear acoustics measurements.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (United States); North Carolina State Univ., Raleigh, NC (United States); Tuskegee Univ., Tuskegee, AL (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE). Nuclear Energy University Program
- DOE Contract Number:
- AC07-05ID14517
- OSTI ID:
- 1214660
- Report Number(s):
- DOE/NEUP--10-915; 10-915
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ACOUSTIC MONITORING
AGING
CORRELATIONS
CREEP
DEFECTS
DYNAMIC LOADS
FAILURES
FATIGUE
FORECASTING
HARMONIC GENERATION
INCONEL 617
MAGNETOSTRICTION
MECHANICAL TESTS
MICROSTRUCTURE
NONDESTRUCTIVE ANALYSIS
NONLINEAR PROBLEMS
OPTICAL MICROSCOPY
PIPES
PLATES
RATCHETING
SCANNING ELECTRON MICROSCOPY
SENSITIVITY
SERVICE LIFE
SHELLS
STRAINS
TEMPERATURE RANGE 1000-4000 K
TIME DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
TUBES