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Research Papers: Theoretical Applications

Constitutive Models in Simulating Low-Cycle Fatigue and Ratcheting Responses of Elbow

[+] Author and Article Information
T. Hassan

Department of Civil, Construction,
and Environmental Engineering,
North Carolina State University,
Raleigh, NC 27695-7908
e-mail: thassan@ncsu.edu

M. Rahman

Department of Civil, Construction,
and Environmental Engineering,
North Carolina State University,
Raleigh, NC 27695-7908

1Corresponding author.

2Present address: Areva, Inc., Charlotte, NC 28262.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received April 28, 2014; final manuscript received November 8, 2014; published online March 23, 2015. Assoc. Editor: Wolf Reinhardt.

J. Pressure Vessel Technol 137(3), 031002 (Jun 01, 2015) (12 pages) Paper No: PVT-14-1075; doi: 10.1115/1.4029069 History: Received April 28, 2014; Revised November 08, 2014; Online March 23, 2015

As stated in the sister article that the objective of this study was to explore the low-cycle fatigue and ratcheting failure responses of elbow components through experimental and analytical studies. Low-cycle fatigue and ratcheting damage accumulation in piping components may occur under load reversals induced by earthquakes or thermomechanical operations. Ratcheting damage accumulation can cause failure of components through cracking or plastic buckling. Hence, design by analysis of piping components against ratcheting failure will require simulation of this response with reasonable accuracy. In developing a constitutive model that can simulate ratcheting responses of piping components, a systematic set of elbow experiments involving deformation and strain ratcheting were conducted and reported in the sister article. This article will critically evaluate seven different constitutive models against their elbow response simulation capabilities. The widely used bilinear, multilinear, and Chaboche models in ansys are first evaluated. This is followed by evaluation of the modified Chaboche, Ohno–Wang, modified Ohno–Wang, and Abdel Karim–Ohno models. Results from this simulation study are presented to demonstrate that all the seven models can simulate the elbow force response reasonably. The bilinear and multilinear models can simulate the initial elbow diameter change or strain accumulation, but always simulate shakedown during the subsequent cycles when for some of the cases the experimental trends are ratcheting. Advanced constitutive models like Chaboche, modified Chaboche, Ohno–Wang, modified Ohno–Wang, and Abdel Karim–Ohno can simulate many of the elbow ratcheting responses well, but for some of the strain responses, these models simulate negative ratcheting, which is opposite to the experimental trend. Finally, implications of negative ratcheting simulation are discussed and suggestions are made for improving constitutive models ratcheting response simulation.

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References

Figures

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Fig. 1

(a) Photograph of the elbow specimen and test setup showing actuator and load cell of the universal testing machine and (b) sketch of the elbow specimen and test boundary conditions (dimensions are in mm) (from Ref. [67])

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Fig. 2

Model parameter determination and material response simulations with bilinear and multilinear models, (a) uniaxial hysteresis curve, (b) axial strain ratcheting rate from uniaxial experiment, and (c) circumferential strain ratcheting rate from biaxial experiment

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Fig. 3

Model parameter determination and material response simulations with Chaboche and modified Chaboche models, (a) uniaxial hysteresis curve, (b) axial strain ratcheting rate from uniaxial experiment, and (c) circumferential strain ratcheting rate from biaxial experiment

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Fig. 4

Model parameter determination and material response simulations with Ohno–Wang and modified Ohno–Wang models, (a) uniaxial hysteresis curve, (b) axial strain ratcheting rate from uniaxial experiment, and (c) circumferential strain ratcheting rate from biaxial experiment

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Fig. 5

An example (mesh 1) of the FE meshes in Table 1 used in the mesh optimization study and boundary condition (B.C.) used in the analysis

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Fig. 6

Circumferential strain ratcheting simulation at flank and intrados for mesh optimization study

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Fig. 7

Simulations with bilinear and multilinear models, (a) force-displacement (P-δ) hysteresis loop, (b) flank to flank diameter change mean (ΔDmx), (c) flank circumferential strain amplitude (εaθ), (d) flank circumferential strain mean (εmθ), (e) extrados circumferential strain mean (εmθ), and (f) intrados axial strain mean (εmx) as a function of loading cycle (N)

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Fig. 8

Simulations with Chaboche and modified Chaboche models, (a) force-displacement (P-δ) hysteresis loop, (b) flank to flank diameter change mean (ΔDmx), (c) flank circumferential strain amplitude (εaθ), (d) flank circumferential strain mean (εmθ), (e) extrados circumferential strain mean (εmθ), and (f) intrados axial strain mean (εmx) as a function of loading cycle (N)

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Fig. 9

Simulations with Ohno–Wang and modified Ohno–Wang models, (a) force-displacement (P-δ) hysteresis loop, (b) flank to flank diameter change mean (ΔDmx), (c) flank circumferential strain mean (εmθ), and (d) intrados axial strain mean (εmx) as a function of loading cycle (N)

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Fig. 10

Simulations with Ohno–Wang and Abdel Karim–Ohno models, (a) force-displacement (P-δ) hysteresis loop, (b) flank to flank diameter change mean (ΔDmx), (c) flank circumferential strain mean (εmθ), and (d) intrados axial strain mean (εmx) as a function of loading cycle (N)

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