Modelling of thermo-mechanical fatigue behavior in superalloys
Kadioglu, Yavuz
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https://hdl.handle.net/2142/22144
Description
Title
Modelling of thermo-mechanical fatigue behavior in superalloys
Author(s)
Kadioglu, Yavuz
Issue Date
1992
Doctoral Committee Chair(s)
Sehitoglu, Huseyin
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Engineering, Materials Science
Language
eng
Abstract
Thermo-mechanical fatigue (TMF) and isothermal fatigue (IF) behavior of coated and uncoated Mar-M247 and, uncoated Mar-M246 was studied. The Mar-M247 was coated with Alpak-S1. The coating consists of a manganese and Aluminium powder slurry that is applied by painting, dipping, or spraying with an air brush.
Thermo-mechanical experiments for coated Mar-M247 were conducted under T$\sb{\rm min}$ = 500$\sp\circ$C and T$\sb{\rm max}$ = 871$\sp\circ$C conditions. Both out-of-phase and in-phase strain-temperature phasing conditions were considered. Isothermal experiments were conducted at 500$\sp\circ$C and 871$\sp\circ$C. Comparison with the uncoated Mar-M247 showed that fatigue lives of coated material could be lower than the uncoated material and the difference was as much as four folds in some cases. For uncoated Mar-M247, only thermo-mechanical out-of-phase experiments were conducted. The temperature limit considered was T$\sb{\rm min}$ = 500$\sp\circ$C and T$\sb{\rm max}$ = 1038$\sp\circ$C. SEM, Microprobe and Auger spectroscopy were used to gain insight into oxidation effects at high temperature.
An experimental program for Mar-M246 was also carried out. Due to the coarse grained structure, the stress-strain response indicates variation from specimen to specimen in some cases. The effect of this variation on life does not appear significant, except at smaller strain ranges.
A numerical method is also developed to estimate the stress field due to a surface inhomogeneity in an elastic half space. The technique is based on Eshelby's equivalent inclusion method. The results were used in developing a life prediction methodology for the coated superalloys.
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