Strain rate effects on fracture behavior of austempered ductile irons

Abstract

In this work, the mechanical behavior of the austempered ductile iron (ADI) JS/1050-6 was investigated, with particular attention to the strain rate effects on the material ductility. Tensile tests at different strain rates (up to 10 3 s −1) and temperatures (ranging from 213 to 343 K) were performed. Samples with different geometries, smooth and round notched bars, were used to evaluate the effect of the stress triaxiality level on the strain at fracture. For each configuration, the evolution paths of stress and strain were extracted in the point where failure is expected performing numerical analyses at the continuum scale. Stress histories were used as input in a micromechanics analysis aimed to analyze the heterogeneous state of stress, determined by the presence of the graphite nuclei, under the different loading conditions obtained in the experiments. The main result is that, under dynamic conditions, the stress field redistribution, due to the adiabatic condition, postpones the failure occurrence, regardless temperature and strain rate effects on the matrix ductility.

ADI 1050-6 Mechanical Behavior at Different Strain Rates and Temperatures

“…Even if the mechanism behind the criterion formulation, of frictional sliding between material particles, is not pertinent to the ADI deformation process, the Mohr-Coulomb criterion has the twofold Materials Science Forum Vol. For nodular cast irons, the pressure dependence is caused by the different morphology of the matrix debonding from the graphite nodule under different stress triaxiality levels [6]. FE-based micromechanical analyses proved to be very effective in giving the resulting macroscopic properties from known characteristics at the microscale [7].…”