Cast iron plasticity

The cast iron plasticity constitutive model is used to model the elastic-plastic behavior of gray cast iron.

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Cast iron plasticity

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In tension gray cast iron is more brittle than most metals. This brittleness is attributed to the microstructure of the material, which consists of a distribution of graphite flakes in a steel matrix. In tension the graphite flakes act as stress concentrators, leading to an overall decrease in mechanical properties (such as yield strength). In compression, on the other hand, the graphite flakes serve to transmit stresses, and the overall response is governed by the response of the steel matrix alone.

The above differences manifest themselves in the following macroscopic properties: (i) different yield strengths in tension and compression, with the yield stress in compression being a factor of three or more higher than the yield stress in tension; (ii) inelastic volume change in tension, but little or no inelastic volume change in compression; and (iii) different hardening behavior in tension and compression. It is commonly accepted (Hjelm, 1992, 1994) that a Mises-type yield condition along with an associated flow rule models the material response sufficiently accurately under compressive loading conditions. This assumption is not true for tensile loading conditions: a pressure-dependent yield surface with nonassociated flow is required to model the brittle behavior in tension. The model is described in detail in the remainder of this section.