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Description
The Chaboche kinematic hardening model provides reliable description of the cyclic-plastic behaviour of metals. However, the identification of Chaboche constants is a challenging task, which generally requires high computational cost and advanced optimization methods such as genetic algorithms, particle swarm optimization and differential evolution algorithms. Instead of using complex pointwise fitting operations, the global properties of the stabilized cycles, which are also of interest for further failure assessment, can be considered. For uniaxial cyclic-loadings, closed-form expressions can then be obtained to relate each Chaboche parameter to global properties of stabilized strain-controlled tests, such as hysteresis area, slope at the inversion points, stress range, plastic strain range and average points, and to ratcheting rate obtained from stress-controlled tests. Despite this and given the widespread use of the Chaboche model in modelling the cyclic-plastic behaviour of materials under multiaxial loading conditions, the identification of the parameters from non-uniaxial tests remain an open scientific question. This research aims to present a theoretical framework for the identification of Chaboche parameters by using the global properties of the stabilized cycles obtained through cyclic-torsional tests. In particular, this work demonstrates that low-cost mathematical expressions can be obtained even considering a biaxial loading case such as torsion. In addition, the proposed framework emphasizes that two strain-controlled tests, one symmetric ($R_{\gamma}=-1$) and one asymmetric ($R_{\gamma}\neq -1$), and one asymmetric moment-controlled test $R_\textup{M}\neq -1$ can be sufficient to identify all the parameters. These latter tests were then implemented considering thin-walled tubular specimens made of 42CrMo4, and the obtained results were compared with the corresponding ones extracted through classical uniaxial cyclic-tests. Finally, the contribution proposes mathematical expressions for further developments by using the Chaboche model to numerically describe combined torsional–tensile loadings.