https://popups.uliege.be/esaform21/index.php?id=3945 Index terms fr 0 https://popups.uliege.be/esaform21/index.php?id=3869 The integration of forming in the fatigue modelling of cold-formed components significantly improves the predictive accuracy of the estimated life. The current study investigated the fatigue behaviour of a bent specimen made from a 5 mm thick, S900MC high strength steel plate. Because of its superior static and dynamic strength, this grade is progressively used for hollow cold-formed sections in mobile applications. However, it exhibits a strong stress saturation as well as limited formability. In this regard, a finite element modelling framework was adopted from previous research and further developed to integrate bending in the fatigue modelling and life estimation procedure. However, this framework currently ignores the possible influence of kinematic hardening and associated Bauschinger effect. For this reason, a numerical study was performed that compares isotropic with kinematic hardening for this specific application. First, the characteristic behaviour of these models was verified in a virtual tension-compression test. Subsequently, they were implemented in forming simulation followed by fatigue loading. Herein, the stress-strain evolution was investigated and a multi-axial fatigue criteria was used to map the sensitivity of the estimated life to the type of hardening. In general, the stress that entered the fatigue calculation was at least 21% lower for the kinematic model. As a result, a significant increase of 65% was observed for the estimated fatigue life, yielding a better comparison with experimental data. Mon, 29 Mar 2021 14:52:43 +0200 Thu, 08 Apr 2021 21:11:43 +0200 https://popups.uliege.be/esaform21/index.php?id=3869 https://popups.uliege.be/esaform21/index.php?id=2403 Modern pipeline steels exhibit complex microstructures that cause mechanical anisotropy in various respects. For instance, strain path effects under non-monotonic loadings are exceptionally pronounced in these steels. Crystallographic texture and morphological anisotropy are the main contributors to strength and hardening directionality in pipeline steels under monotonic loading. In contrast, the dislocation substructure is seen as the primary source for Bauschinger and cross effects during complex non-monotonic loading, e.g. during pipe forming. The Bauschinger effect for example may arise from pile-ups formed at obstacles such as intragranular shear bands, and homo- or heterophase boundaries. The dislocation-based model by Peeters et al. [Acta Mater., 49 (2001), pp. 1607-1619] developed for coarse-grained ferritic steel allows for complex strain path effects through the accumulation of dislocations at micro-shear bands. However, it struggles to reproduce the large Bauschinger effect of ~250MPa in fine-grained bainitic pipeline steel [Bönisch et al., Procedia Manuf., 47 (2020), pp. 1434-1441]. Considering the microstructural differences between the two steel varieties, a promising way to improve the model predictions - especially for the Bauschinger effect - is to incorporate dislocation interactions with phase and/or grain boundaries. In the present work, we introduce this approach and demonstrate the basic capabilities of such a grain boundary-extended Peeters model. By accounting for the formation of pile-ups at grain boundaries the Bauschinger effect is enlarged. Furthermore, by explicitly considering the grain boundary spacing, the model can deliver grain size (Hall-Petch) strengthening. Tue, 23 Mar 2021 18:22:40 +0100 Mon, 29 Mar 2021 19:56:15 +0200 https://popups.uliege.be/esaform21/index.php?id=2403