Stress-Strain Relations for Nodular Cast Irons with Different Graphite Volume Fractions under Tension and Compression

In this paper, the results of finite element analyses for nodular cast irons with different volume fractions of graphite particles based on an axisymmetric unit cell model under uniaxial compression and tension are presented. The experimental compressive stress-strain data for a nodular cast iron with the volume fraction of graphite particles of 4.5% are available for use as the baseline material data. The elastic-plastic stress-strain relation for the matrix of the cast iron is estimated based on the experimental compressive stress-strain curve of the cast iron with the rule of mixture. The elastic-plastic stress-strain relation for graphite particles is obtained from the literature. The compressive stress-strain curve for the cast iron based on the axisymmetric unit cell model with the use of the von Mises yield function was then obtained computationally and compared well with the compressive stress-strain relation obtained from the experiment. Different unit cell models with different graphite volume fractions were then developed. The computational stress-strain relations under tension and compression were then obtained for different graphite volume fractions. The different tensile and compressive curves for different graphite volume fractions are used to obtain the pressure sensitivity parameters of the Drucker-Prager yield function for nodular cast irons for simulations of fillet rolling process of crankshafts.