PSI - Issue 71

Shreebanta Kumar Jena et al. / Procedia Structural Integrity 71 (2025) 34–41

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2.4.2. Calibration of Chaboche parameters & cyclic stress-strain response This type of behaviour requires a common set of non-linear kinematic hardening parameters (three decomposed Chaboche material model) to simulate post- yield behaviour under cyclic conditions. The Chaboche material model constants were calibrated from test hysteresis loops under axial strain amplitudes of ±1.0%. The calibrated constants ( ( ) ( ) for 1≤ ≤3 ) were used to verify the simulated hysteresis loops with corresponding test responses. The test and simulated hysteresis loops compare well for pure axial and pure torsion loading conditions for different strain amplitudes (the saturated cyclic yield strength of the corresponding strain amplitude was varied manually). The calibrated Chaboche parameters are given in Table 1. Additionally, typical comparison of the cyclic stress strain curve obtained from the test as well as from FE analyses using the calibrated Chaboche material model for pure axial loading conditions is shown in Figure 5. Table 1 . Material parameters used for present FE analyses

(a) Figure 5. Comparison of monotonic and cyclic as well as stress-strain curves obtained using the Chaboche model.

E (GPa) (--) (1) 203 0.3 7.05×10 5

(MPa) (1) (--) (2) (MPa) (2) (--) (3) (MPa) (3) (--) (MPa) 10500 1×10 5 725 6500 0 158.25( ) 0.325 Here, %.

Parameter ( )

Value ( ) : saturated cyclic yield strength

Similar to the Masing idealizationidealisation studies, calibration of the cyclic plasticity material model parameter and validation of these calibrated parameters for different loading conditions have also been extensively carried out by Arora et al. (2021). 2.5. Validation of Chaboche material model parameter The suitability of three decomposed Chaboche’s non -linear kinematic hardening model has been checked with respect to test results for unnotched tube specimens for the same grade of C-Mn steel. For this, tests on unnotched tube specimens have been conducted under pure axial, pure torsional and in-phase axial torsional loading condition. Additionally, Finite Element Analyses (FEA) have also been used to model and simulate the same experimental conditions. Continuum three-dimensional twenty noded brick element with full integration scheme has been considered for elastic-plastic FE calculations.

(a) (d) Figure 6. (a) unnotched tube FE model with mesh, comparison of the test vs. elastic-plastic FE simulated loop using the Chaboche material model for unnotched tube specimens: (b) axial loading condition (c) torsional loading condition (d) in-phase axial-torsional loading condition. (b) (c)