Strain Rate and Stress-State Dependence of Gray Cast Iron

Abstract

An investigation of the mechanical strain rate, inelastic behavior, and microstructural evolution under deformation for an as-cast pearlitic gray cast iron (GCI) is presented. A complex network of graphite, pearlite, steadite, and particle inclusions was stereologically quantified using standard techniques to identify the potential constituents that define the structure–property relationships, with the primary focus being strain rate sensitivity (SRS) of the stress–strain behavior. Volume fractions for pearlite, graphite, steadite, and particles were determined as 74%, 16%, 9%, and 1%, respectively. Secondary dendrite arm spacing (SDAS) was quantified as 22.50 μm ± 6.07 μm. Graphite flake lengths and widths were averaged as 199 μm ± 175 μm and 4.9 μm ± 2.3 μm, respectively. Particle inclusions comprised of manganese and sulfur with an average size of 13.5 μm ± 9.9 μm. The experimental data showed that as the strain rate increased from 10−3 to 103 s−1, the averaged strength increased 15–20%. As the stress state changed from torsion to tension to compression at a strain of 0.003 mm/mm, the stress asymmetry increased ∼470% and ∼670% for strain rates of 10−3 and 103 s−1, respectively. As the strain increased, the stress asymmetry differences increased further. Coalescence of cracks emanating from the graphite flake tips exacerbated the stress asymmetry differences. An internal state variable (ISV) plasticity-damage model that separately accounts for damage nucleation, growth, and coalescence was calibrated and used to give insight into the damage and work hardening relationship.

The Effects of Heat Treatment on the Microstructure and Tensile Properties of an HPDC Marine Transmission Gearcase

“…The ASTM Standard E562-02 [23] was used for statistically estimating the volume fraction of the identifiable phases. The volume fraction is determined assuming that the area fraction is equivalent to the volume fraction for the randomly distributed particles [23,24]. The volume fraction of the phases of interest and the observed porosities in the as-cast component are summarized in Table 3.…”

Three-dimensional coupled thermo-mechanical analysis for fatigue failure of a heavy vehicle brake disk: Simulation of braking and cooling phases

“…Gray cast iron shows brittle behavior in tension and a ductile behavior during compression. 36 So, this model is based on a yield function dependent on the maximum principal stress during tension loadings, and the Von Mises yield criterion during compression. The hardening of gray cast iron is independent of tension and compression.…”

Strain rate sensitivity and toughness behaviour of ductile iron under specific loading

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