Seminar | ISE Graduate Student Colloquium: Amir Asgharzadeh

Title: Multiscale modeling of metallurgical and mechanical characteristics of tubular material undergoing tube hydroforming and subsequent annealing processes

Presenter: Amir Asgharzadeh

Committee Members: Profs. Farhang Pourboghrat, Michael Groeber, and Alan Luo

The microstructural characteristics of materials such as grain topology, spatial arrangement of grains, and precipitation have a significant influence on the mechanical properties. These properties could be subjected to significant changes during post-deformation annealing process, depending on various in-situ and post-process parameters. To evaluate the mechanical performance of materials, it is important to obtain a deep knowledge of metallurgical events taking place during the annealing process. Because of the time-consuming and costly experimental procedures required for this investigation, derivation of various models at different length scales (from nano- to macro-scale) and subsequent incorporation of the attained data in a multiscale modeling setup is of great importance. The established multiscale model would act as a virtual testing toolbox for prediction of the mechanical and metallurgical properties of the material undergoing complex thermo-mechanical conditions.

In this project, a hierarchically coupled cellular automata (CA) model, crystal plasticity finite element method (CPFEM), and transient thermal finite element (FE) model is developed to predict the softening kinetics of the bulged steel tube during the non-isothermal annealing. Through the developed model, the kinetics of softening mechanisms including static recovery (SRV) and static recrystallization (SRX), as well as the recrystallization texture are predicted. Later, the Johnson-Mehl-Avrami-Kohnogorov (JMAK) model based on the predicted SRX data is developed to interpret the recrystallization behavior of the material. To perform this study, diverse experimental tests including tube hydroforming (THF), annealing, uniaxial tensile test, hardness test, as well as microstructure observations through optical microscopy and Electron Backscatter Diffraction (EBSD) tests on steel tube are performed. The obtained experimental data are utilized to calibrate and verify the implemented CPFEM model for simulation of THF process, thermal FE model for prediction of the local temperature over the annealing time, and CA algorithm for modeling of the softening kinetics and texture evolution throughout the annealing process.