Research Papers

Efficient Methodologies for Determining Temperature-Dependent Parameters of a Ni-Base Superalloy Crystal Viscoplasticity Model for Cyclic Loadings

[+] Author and Article Information
M. M. Kirka, D. J. Smith

The George W. Woodruff School
of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332

R. W. Neu

The George W. Woodruff School
of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332;
Materials Science and Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332
e-mail: rick.neu@gatech.edu

1Corresponding author

Contributed by the Materials Division of ASME for publication in the JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY. Manuscript received August 27, 2013; final manuscript received June 10, 2014; published online July 9, 2014. Assoc. Editor: Mohammed Zikry.

J. Eng. Mater. Technol 136(4), 041001 (Jul 09, 2014) (10 pages) Paper No: MATS-13-1154; doi: 10.1115/1.4027857 History: Received August 27, 2013; Revised June 10, 2014

The prediction of temperature-dependent fatigue deformation and damage in directionally solidified and single-crystal nickel-base superalloy components used in the hot section of gas turbine engines requires a constitutive model that accounts for the crystal orientation in addition to the changing deformation mechanisms and rate dependencies from room temperature to extremes of the use temperature (e.g., 1050 °C). Crystal viscoplasticity (CVP) models are ideal for accounting for all of these dependencies. However, as the models become more physically realistic in capturing the true cyclic deformation mechanisms, increases the requirements to achieve an accurate model calibration. As a result, CVP models have yet to become viable for life analysis in industry. To make CVP models an industry relevant tool, the calibration times must be reduced. This paper explores methods to reduce the calibration time. First, a series of special calibration experiments are conceived and conducted on each relevant orientation and microstructure. Second, a set of parameterization protocols are used to minimize parameter interdependencies that reduce the amount of iteration required during the calibration. These experimental and calibration protocols are exercised using the CVP model of Shenoy et al. (2005, “Thermomechanical Fatigue Behavior of a Directionally Solidified Ni-Base Superalloy,” ASME J. Eng. Mater. Technol., 127(3), pp. 325–336) by calibrating a directionally solidified Ni-base superalloy across an industry relevant temperature range of 20 °C to 1050 °C.

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Fig. 1

Strain history for a Ni-base superalloy efficient calibration experiment in the strain rate sensitive regime capturing the mechanical response of multiple deformation mechanisms

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Fig. 2

Cylindrical dog-bone specimen drawing with dimensions in mm

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Fig. 3

Iterative procedure used in calibrating material parameters for isothermal and temperature-independent behavior

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Fig. 4

Determination of the hardening exponent, n2 through fitting of a power law trend line to experimental data

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Fig. 5

Calibration of γ·oi to experimental data at 1050 °C

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Fig. 6

Calibration of Qo, Do, and Bo after iteration

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Fig. 7

Comparison of the spliced polynomials to the values of hχ determined through isothermal fitting, where C0 and C1 continuities are maintained at the transition from the solid to the dotted line

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Fig. 8

Stress–strain response: comparison of the experimental data (left) with CVP model predictions (right) at half-life for in-phase TMF in the [001] material orientation under in-phase TMF conditions, R = 0, 100–850 °C, Δmech = 1.1%

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Fig. 9

Stress–strain response: comparison of the experimental data (left) with CVP model predictions (right) at half-life for out-of-phase TMF in the [001] material orientation under out-of-phase TMF conditions, R = –, 100–850 °C, Δmech = 1.1%




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