Computer simulation of microstructures evolution for three-high cross-rolling of hollow steels
Based on the rigid-plastic finite element method (FEM), an investigation on three-high cross-rolling of hollow steels was carried out in this study. The numerical model coupled thermal, mechanical and microstructural phenomena, in which some empirical recrystallization mode were obtained using the Gleeble-3500 thermomechanical simulator. The distributions of different field-variables, including temperature, strain and grain size, were obtained by FEM simulation. After different mandrel diameters were calculated, the investigation obtained the effect of microstructures evolution and compared the grain size between no mandrel and different mandrel diameters.
Numerical Prediction of Austenite Grain Size in Round-Oval-Round Bar Rolling
In bar or rod rolling process, improvement of mechanical properties of the hot rolled products requires numerical prediction of austenite grain size (AGS) for better controlling the microstructural evolution. In this study, a fully three-dimensional finite element (FE) program, which can simulate three-dimensional deformation and heat transfer was integrated with an AGS evolution model available in the literature. It was applied to a four-pass round-oval-round rolling sequence to characterize the AGS distributions depending on the change of roll gap and rolling speed. The predicted AGS distribution obtained from the FE based approach was compared with that obtained from the approximate analytical approach based on elementary theory of plasticity, developed for practical purpose. It was found out that reducing roll gap and increasing the rolling speed leads to fine and uniform grain distribution and recrystallization behavior divided into meta-dynamic and static recrystallization region, respectively. In addition, AGS predicted from the approximate analytical approach was in agreement with that from the FE based approach, but showed discrepancies at higher rolling speed conditions investigated in the present work.
Towards a Formalisation of Justification and Justifiability
We introduce the logic QKD S which is a normal multi-modal logic over finitely many modalities that additionally supports bounded quantification of modalities. An important feature of this logic is that it allows to quantify over the information components of systems and, hence, can be used to derive justifications. We compare the proposed logic with Artemov’s justification logic and also report on a prototypical implementation of a satisfiability solver of this logic and show some examples.