Optimizing the Voce–Chaboche Model Parameters for Fatigue Life Estimation of Welded Joints in High-Strength Marine Structures

Abstract

This work studies the Voce–Chaboche (V–C) material model parameter optimization for high-strength steel welded joints subjected to cyclic loading. The model parameters of each material zone in a S690 steel butt-welded joint were determined using an optimization algorithm based on the Newton trust region (NTR) method and an accumulated true strain parameter. The model parameters were fitted to stress–strain histories from uniaxial strain-controlled cyclic tests. To validate the model, fully-reversed variable amplitude fatigue experiments were performed under load control. The experimental results were then compared to numerical results from a finite element analysis. When the elastic modulus is optimized as a V–C parameter, the results indicate that the V–C model slightly underestimates the strain range, leading to conservative fatigue life estimates. However, the results can be improved by using an elastic modulus obtained experimentally. In this case, the resulting material model slightly overestimates the strain range, leading to a non-conservative, but more accurate, fatigue life estimation. It can be concluded that the NTR-based accumulated true strain approach successfully determined the V–C model parameters for different material zones in the welded joint, and closely estimated the strain range and the fatigue life for a variable amplitude load history.

Computational Methods of the Identification of Chaboche Isotropic-Kinematic Hardening Model Parameters Derived from the Cyclic Loading Tests

“…Figure 12. The comparison between experimental and numerically-generated curves for the procedure proposed by Santus et al [40] for 𝜀𝜀 = ±1% (a) and the fitting to the last stabilized cycle (b) methods has been tested [53][54][55][56]. The optimization technique using the least-square approach is proposed here.…”

Local relaxation of residual stress in high-strength steel welded joints treated by HFMI

“…The calibrations considered the first five hysteresis loops up to reaching stability. Young's modulus was pre-defined from the first tensile load of the test data [25] and not considered an optimization parameter, which better estimates crack initiation life for high-strength steel welded joints when little plasticity is involved [29]. As shown in Table 2, the cyclic test data for HAZ material show high hardening behavior after the first cycle, reflecting larger values of isotropic hardening parameters compared to others.…”

Investigation of Chaboche and Bouc–Wen Parameters of Quenched and Tempered Steel and Comparison of Model Predictive Capabilities

“…Focusing on only a plain specimen under uniaxial loading, the incremental plastic strain tensor is given in Equation (7), whereas the backstress tensor is reported in Equation (8) for each backstress component.…”

“…It was introduced by Chaboche [5], extending the Armstrong and Frederick model [6] by adding multiple backstress components with different properties. It can also be efficiently combined with the isotropic hardening rule proposed by Voce [7], as in [8][9][10], and both hardening rules are implemented in Ansys commercial finite element software [11]. The combination of a CKH model and Voce isotropic hardening model results in the Chaboche isotropic kinematic hardening (CIKH) model.…”