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A study of Laser Shock Peening on Fatigue behavior of IN718Plus Superalloy: Simulations and Experiments

Chaswal, Vibhor
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368027477

Abstract Details

2013, PhD, University of Cincinnati, Engineering and Applied Science: Materials Science.
Laser shock peening (LSP) for improving fatigue life of IN718Plus superalloy is investigated. Fatigue geometry and LSP parameters were optimized using finite element method (FEM). Residual stress distributions estimated by FEM were validated using Synchrotron XRD and line focus lab XRD, and correlated with microhardness. An eigenstrain analysis of LSP induced edge deflections (measured with optical interferometry) was also conducted. Transmission electron microscopy (TEM) of single-spot LSP coupons shows sudden increase in dislocation density under LSP treated region. Total life fatigue was conducted at R=0.1 at 298K and 923K, with and without LSP. S-N curve endurance limit increases at both temperatures with FEM optimized LSP samples. Based on TEM of fatigue microstructure and LSP coupons, mechanistic description of observed fatigue improvement is attempted. Often need arises to weld components, and weld heat-affected-zone reaches near-solvus temperatures. To simulate this treatment, sub-solvus hot-rolled IN718Plus is aged at 923K. We observe precipitation of thin eta-Ni3(Al, Ti) plates after 1000 hours, making the material susceptible to cracks, and lowering fatigue life. Effect of LSP on fatigue crack growth (FCG) is studied following ASTM guidelines on M(T) geometry at R=0.1. Acceleration in FCG rate with LSP is observed for this geometry and LSP condition. Prior FEM optimization was not conducted for FCG tests, and may account for lower FCG resistance after LSP. FCG results were corroborated with COD compliance based analysis. Crack measurements were done using potential drop method, and crack closure was analyzed. Effect of LSP on overload FCG was investigated by single-cycle 100% overload followed by single-spot LSP on the crack-tip plastic zone. Crack retardation occurs after application of overload+LSP. Effective contribution of overload+LSP to crack retardation is estimated. Fractographic analysis of LSP treated fatigue samples suggests sub-surface crack nucleation, and is analyzed based on stress concentration behavior of small cracks.
Vijay Vasudevan, Ph.D. (Committee Chair)
Kristina Langer, Ph.D. (Committee Member)
Dong Qian, Ph.D. (Committee Member)
Rodney Roseman, Ph.D. (Committee Member)
Dale Schaefer, Ph.D. (Committee Member)
251 p.
Materials Science
Nickel superalloy; Fatigue and Crack Growth; Laser shock peening; Transmission electron microscopy; Synchrotron X-ray diffraction; Modeling and simulations;

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Citations

  • Chaswal, V. (2013). A study of Laser Shock Peening on Fatigue behavior of IN718Plus Superalloy: Simulations and Experiments [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368027477

    APA Style (7th edition)

  • Chaswal, Vibhor. A study of Laser Shock Peening on Fatigue behavior of IN718Plus Superalloy: Simulations and Experiments. 2013. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368027477.

    MLA Style (8th edition)

  • Chaswal, Vibhor. "A study of Laser Shock Peening on Fatigue behavior of IN718Plus Superalloy: Simulations and Experiments." Doctoral dissertation, University of Cincinnati, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368027477

    Chicago Manual of Style (17th edition)

ucin1368027477
1,750
© 2013, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.