MULTISCALE MODELING AND SIMULATION OF THE MECHANICAL BEHAVIOR OF THE DUAL PHASE STEELS: PARAMETRIC STUDY AND MICROSTRUCTURE OPTIMIZATION
Belgasam, Tarek M.
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The goal of this thesis is to investigate the relationship between microstructure properties and mechanical properties of dual phase (DP) steels to design advanced materials for automotive applications. In this research, a new effective analytical methodology that studies the influences and interactions of microstructure properties on the mechanical behavior of DP steels under different strain rates was developed. In this work, the plastic deformation of multiphase material with different microstructures including volume fraction and grain size of phases, and carbon content in DP steels etc., under different strain rates was investigated. First, a microstructure-based approach using a 3D micromechanical model was suggested. The 3D representative volume elements (RVEs) model that can precisely predict the mechanical behavior of DP steels under quasi-static strain rate is developed. This is followed by a methodical response surface method (RSM) to investigate the effects and interactions of microstructure parameters on the mechanical behavior of DP steels. The developed method can estimate effective microscopic parameters, as well as optimum values of microstructure features for achieving the maximum energy absorption capacity of DP steels. Through the comprehensive parametric study, it was shown that the microscopic parameters play an important role in the mechanical properties of DP steels, as well as the energy absorption capacity of material would be optimized. Second, a multiscale material and structure model using a dislocation density based nonlinear elastic-viscoplastic model was developed to predict the mechanical behavior of DP steels under quasi-static and dynamic uniaxial loading conditions. A comprehensive parametric study and microstructure optimization using RSM model were conducted on the influences and interactions of microstructure parameters in DP steels on the strength, ductility, and energy absorption capacity. It is shown that the microscopic parameters and their two-way interactions play an important role in the mechanical behavior of DP steels, as well as the strength, ductility and tensile toughness of DP steels, would be optimized. Furthermore, not only did this methodology is a powerful tool to investigate the microstructure parameters effects at various strain rate conditions and an effective optimizer tool, but it is also possible forming operations and collision-related data.