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    Identification of Constitutive Model Parameters for Nimonic 80A Superalloy
    (Springer India, 2018) Korkmaz, Mehmet Erdi; Verleysen, Patricia; Guenay, Mustafa
    Nimonic 80A is a nickel-chrome superalloy, commonly used due to its high resistance against creep, oxidation, and temperature corrosion. This paper presents the material constitutive models of Nimonic 80A superalloy. Johnson-Cook (JC) and modified JC model is preferred among the different material constitutive equations (Zerill Armstrong, Bodner Partom, Arrhenius type) due to its accuracy in the literature. Three different types of compression tests were applied to determine the equation parameters. Firstly, quasi-static tests were performed at room temperature. These tests were conducted at 10(-3), 10(-2), and 10(-1) s(-1) strain rates. Secondly, compression tests were performed at room temperature at high strain rates (370-954 s(-1)) using the Split-Hopkinson pressure bar. Finally, compression tests were performed at a temperature level from 24 to 200 degrees C at the reference strain rate (10(-3) s(-1)). Johnson-Cook and modified JC model parameters of Nimonic 80A were determined with the data obtained from these tests, and they were finally verified statistically.
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    Investigation of tensile Johnson-Cook model parameters for Nimonic 80A superalloy
    (Elsevier Science Sa, 2019) Korkmaz, Mehmet Erdi; Gunay, Mustafa; Verleysen, Patricia
    Developing high temperature technology increases the need for high temperature resistant materials. Nimonic 80A alloy is generally preferred due to its high creep resistance, oxidation resistance and high resistance to high temperature corrosion. The study determines the tensile constitutive equation (JC parameters) of Nimonic 80 A superalloys. Johnson Cook (JC) model is preferred amongst the various material constitutive equations (Zerille Armstrong, Bordner Partom, JC model). Three different kinds of tensile experiment were performed to identify the model parameters. These are quasi-static tensile experiments applied at room temperatures. These experiments were carried out at 0.001, 0.01 and 0.1 s(-1) strain rates. Therefore, the reference strain rate for all experiments was selected to be 10(-3). As a second test, tensile experiments were conducted at room temperature at high strain rates (10(2)-10(3) s(-1)) using the Split Hopkinson pressure bar (SHPB). Lastly, tensile experiments were conducted at high temperatures (300-900 degrees C) at 0.001 s(-1). It was observed whether all tests are compatible with each other or not, and so five Johnson-Cook (JC) parameters of Nimonic 80 A alloy were identified via the data found from the experiments. After determination of parameters, tensile test simulations by finite element method (FEM) were performed in ANSYS Workbench. As a result, the accuracy of the JC parameters is verified since there is a deviation of %2.84 between the experimental and the simulation results. (C) 2019 Elsevier B.V. All rights reserved.