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Research Papers: Materials and Fabrication

Finite-Element Analysis of Waspaloy Using Sinh Creep-Damage Constitutive Model Under Triaxial Stress State

[+] Author and Article Information
Mohammad Shafinul Haque

Department of Mechanical Engineering,
University of Texas El Paso,
500 West University Avenue,
El Paso, TX 79902
e-mail: mhaque@miners.utep.edu

Calvin Maurice Stewart

Department of Mechanical Engineering,
University of Texas El Paso,
500 West University Avenue,
El Paso, TX 79902

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received November 3, 2015; final manuscript received January 29, 2016; published online February 23, 2016. Assoc. Editor: Haofeng Chen.

J. Pressure Vessel Technol 138(3), 031408 (Feb 23, 2016) (9 pages) Paper No: PVT-15-1246; doi: 10.1115/1.4032704 History: Received November 03, 2015; Revised January 29, 2016

The creep deformation and damage evolution of nickel base superalloy (Waspaloy) at 700 °C are studied using the classic Kachanov–Rabotnov (KR) and a recently developed Sin-hyperbolic (Sinh) model. Uniaxial creep deformation and Bridgman rupture data collected from literature are used to determine the model constants and to compare the KR and the Sinh solutions. Finite-element (FE) simulations on a single eight-node element are conducted to validate the accuracy of the FE code. It is observed that KR cannot predict the creep deformation, damage, and rupture life of nickel base superalloys accurately using one set of constants for all the stress levels. The Sinh model exhibits a superior ability to predict the creep behavior using one set of constants for all the stress levels. Finite-element analysis (FEA) on 3D Bridgman notched Waspaloy specimen using the Sinh model is conducted. The results show that the Sinh model when combined with a representative stress equation and calibrated with experimental data can accurately predict the “notch effect” observed in the rupture life of notched specimen. Contour plots of damage evolution and stress redistribution are presented. It is demonstrated that the Sinh model is less stress sensitive, produces unconditional critical damage equal to unity at rupture, exhibits a more realistic damage distribution around the crack tip, and offers better crack growth analysis than KR.

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Figures

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Fig. 1

Bridgman notched specimen

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Fig. 2

Minimum creep strain rate using the Norton power (KR) and McVetty (Sinh) law of Waspaloy at 700 °C (log scale)

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Fig. 3

Sinh and KR model rupture life fitting of Waspaloy at 700 °C (log scale)

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Fig. 4

Sinh model analytical damage and prediction curve of Waspaloy at 700 °C

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Fig. 5

KR model analytical damage and prediction curve of Waspaloy at 700 °C

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Fig. 6

Eight-node single element with boundary constraint

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Fig. 7

Creep deformation of the KR and Sinh model of Waspaloy at 700 °C. Note that at experimental rupture life, the KR damage is way below unity. KR rupture life predictions are highly inaccurate.

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Fig. 8

KR model damage is below unity at 100% strain deformation

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Fig. 10

Sinh damage at 250 MPa and 700 °C: (a) 50 hrs, (b) 200 hrs, (c) 400 hrs, (d) 600 hrs, (e) 700 hrs, and (f) 832 hrs

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Fig. 11

Notch-strengthening effect of Sinh model at different alpha

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