MULTIAXIAL EXPERIMENTATION ON CREEP-FATIGUE-RATCHETING BEHAVIOR OF INCONEL 617

Open Access
Author:
Sengupta, Mainak
Graduate Program:
Engineering Mechanics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 12, 2011
Committee Members:
  • Clifford Jesse Lissenden Iii, Thesis Advisor
  • Charles E Bakis, Thesis Advisor
  • Reginald Felix Hamilton, Thesis Advisor
Keywords:
  • creep
  • multiaxial experimentation
  • fatigue
  • ratcheting
Abstract:
Materials play an important role in human society and find uses in diverse areas like load–bearing structures, semiconductors and biological applications. High-temperature nuclear–power reactors are one of these applications that require novel materials for extreme environments. High-temperature nuclear reactors are predicted to provide higher efficiency and cleaner power for society. Inconel 617 is one of the candidate materials for constructing components of high-temperature reactors. Considerable time and effort must be spent in order to understand the viscoplastic behavior of the material before it can be put into use. Material behavior depends on temperature, loading rate, loading paths and other factors. This thesis presents multiaxial experimental results for Inconel 617 specimens using an axial-torsion test machine. Multiaxial experiments were conducted on Inconel 617 tubular specimens for two non-proportional loading paths, MR1 and MR2, at two different temperatures, 950℃ and 850℃, and at two different strain rates, 0.1%/s and 0.04%/s. The MR1 experiment was controlled in steady axial stress and cyclic shear strain. The MR2 experiment was a bow-tie path controlled in cyclic axial stress with holds at maximum and minimum stress and cyclic shear strain. These tests simulated creep-fatigue-ratcheting behavior in Inconel 617. These results will aid in the development of unified constitutive models, so that nuclear components can be designed for longer operational lives. The higher temperature tests led to more plastic strain accumulation and lower stress levels in the specimen. The higher loading rates led to higher stress levels and lower plastic strain for the MR1 experiments. The behavior of Inconel 617 for the MR1 and MR2 loading paths is significantly different.