Modeling of strengthening mechanisms of surface layers in burnishing process

Abstract

In the present work, a physic-based analytical model has been developed to find the hardening mechanism contributed to surface property enhancement during burnishing process. The model takes into account the effects of grain size evolution, phase change and plasticity-induced twinning. Here, the deformation parameters were firstly modeled using the expanding cavity model and theory of incremental plasticity. Then, the strengthening mechanism are identified based on developed physics based material model. Series of experiments were carried out to confirm the hardness values obtained from the model. Finally, the developed multiphysics model were utilized to identify the influence of burnishing parameters on hardness distribution and contributed mechanisms. The obtained results indicated that the there is good agreement between the measured and predicted values of hardness. On the other hand, it was found that the twinning-induced plasticity followed by phase change (from austenite to ferrite) have more dominant influence on hardening compared to grain size evolution; however, the latter only affects the hardening up to limited depth. In addition, the burnishing depth has been identified as most influential parameter that affects hardness and hardened depth.