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Research Papers

Modeling the Creep of Hastelloy X and the Fatigue of 304 Stainless Steel Using the Miller and Walker Unified Viscoplastic Constitutive Models

[+] Author and Article Information
Luis A. Varela

Department of Mechanical Engineering,
The University of Texas at El Paso,
El Paso, TX 79968
e-mail: Lavarela@miners.utep.edu

Calvin M. Stewart

Assistant Professor
Department of Mechanical Engineering,
The University of Texas at El Paso,
El Paso, TX 79968

Contributed by the Materials Division of ASME for publication in the JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY. Manuscript received June 4, 2015; final manuscript received December 13, 2015; published online January 29, 2016. Assoc. Editor: Vadim V. Silberschmidt.

J. Eng. Mater. Technol 138(2), 021006 (Jan 29, 2016) (9 pages) Paper No: MATS-15-1125; doi: 10.1115/1.4032319 History: Received June 04, 2015; Revised December 13, 2015

Hastelloy X (HX) and 304 stainless steel (304SS) are widely used in the pressure vessel and piping industries, specifically in nuclear and chemical reactors, pipe, and valve applications. Both alloys are favored for their resistance to extreme environments, although the materials exhibit a rate-dependent mechanical behavior. Numerous unified viscoplastic models proposed in literature claim to have the ability to describe the inelastic behavior of these alloys subjected to a variety of boundary conditions; however, typically limited experimental data are used to validate these claims. In this paper, two unified viscoplastic models (Miller and Walker) are experimentally validated for HX subjected to creep and 304SS subjected to strain-controlled low cycle fatigue (LCF). Both constitutive models are coded into ansys Mechanical as user-programmable features. Creep and fatigue behavior are simulated at a broad range of stress levels. The results are compared to an exhaustive database of experimental data to fully validate the capabilities and performance of these models. Material constants are calculated using the recently developed Material Constant Heuristic Optimizer (macho) software. This software uses the simulated annealing algorithm to determine the optimal material constants through the comparison of simulations to a database of experimental data. A qualitative and quantitative discussion is presented to determine the most suitable model to predict the behavior of HX and 304SS.

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References

Figures

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Fig. 1

macho material constant optimization process

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Fig. 2

Objective function evolution during optimization of Miller and Walker for HX creep

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Fig. 3

Objective function evolution during optimization of Miller and Walker for 304SS LCF

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Fig. 13

Walker hysteresis loops of 304SS LCF at 600 °C, Δε = 0.007 [21]

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Fig. 12

Walker hysteresis loops of 304SS LCF at 600 °C, Δε = 0.005 [21]

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Fig. 11

Miller hysteresis loops of 304SS LCF at 600 °C, Δε = 0.007 [21]

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Fig. 10

Miller hysteresis loops of 304SS LCF at 600 °C, Δε = 0.005 [21]

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Fig. 9

Walker creep rest stress of HX at 950 °C

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Fig. 8

Walker creep drag stress of HX at 950 °C

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Fig. 7

Walker creep deformation of HX creep at 950 °C [8]

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Fig. 6

Miller creep rest stress of HX at 950 °C

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Fig. 5

Miller creep drag stress of HX at 950 °C

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Fig. 4

Miller creep deformation of HX creep at 950 °C [8]

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