Genetic algorithm based optimization of Chaboche kinematic hardening parameters along with the validation of FE model through characterized crack initiation

In the context of electro-mobility for commercial vehicles, the failure analysis of a low voltage (LV) connector panel in a DCDC converter is crucial, particularly regarding crack initiation at the interface of busbar and plastic component. This analysis requires a thorough understanding of thermo-mechanical behavior under thermal cyclic loads, necessitating kinematic hardening material modeling to account for the Bauschinger effect. As low cycle fatigue (LCF) test data is not available for thermo-plastic composite material Ultramid A3U44G6, we have adopted a novel approach of determining non-linear Chaboche Kinematic Hardening (CKH) model parameters from monotonic uniaxial temperature dependent tensile test data of Ultramid A3U44G6. In this proposed work a detailed discussion has been presented on manual calibration and Genetic Algorithm (GA) based optimization of Chaboche parameters. Due to lack of fiber orientation dependent test data for Ultramid A3U44G6, here von Mises yield criteria based non-linear CKH model is implemented as a macro-mechanical phenomenological model based on test data with random fiber orientation. After material modelling as described above the thermo-mechanical finite element (FE) simulation has been conducted on LV connector panel assembly with temperature cycling from -40⁰C to 80⁰C. The assembly under consideration is composed of signal pins, busbars, insert mold and outer connector body of plastic PA66-GF25 (Ultramid A3U44G6). It is observed from the simulation result that though the equivalent plastic strain is much higher at 80⁰C in comparison to the same at -40⁰C, the equivalent von Mises stress is comparatively lower at 80⁰C than at -40⁰C because of Bauschinger effect while reversing load, which in turn validates the implementation of proper kinematic hardening material model to address the physical phenomenon. Finally, the FE model is validated through characterized crack initiation site in the plastic component comparing with equivalent plastic strain and von Mises stress evaluated from simulated result.