Characterization and modeling of damage behavior of a casting aluminum wheel considering inhomogeneity of microstructure and microdefects

Abstract

For a meaningful description of casting processes on component behavior, the inhomogeneities of the microstructure, microdefects, and mechanical properties including damage behavior in a casting aluminum wheel were experimentally characterized. Both effects of microstructure/microdefects and stress state on damage behavior were determined by performing smooth and notched tensile tests and torsion tests on specimens extracted from different positions. The distribution of microstructure and microdefects in the cast wheel and the corresponding effects on damage development were analyzed using metallography, 3D X-ray CT, and SEM. Casting simulations were performed to determine distributions of local parameters like solidification time, secondary dendrite arm spacing (SDAS), and porosity. It is clear that the ultimate strength and elongation decrease with increasing porosity and SDAS. A material model describing the influence of porosity on flow stress and a damage model describing the relationships of fracture strain with porosity and triaxiality were developed based on the experimental and numerical results. The correlations of yield stress and elongation with porosity were applied to calibrate the models. Additionally, the influence of stress triaxiality on fracture strain was determined using torsion and notched tensile tests for selected porosities and the corresponding inverse simulations. Simulations of the different specimen tests with the developed material model and damage model could satisfactorily describe the experimental results. This method builds a good basis for coupling between casting simulation and structural simulation to optimize manufacturing processes and develop lightweight products. Improving the precision of microdefect calculation in casting simulations and applying of a stochastic model in structural simulations are important future works.