Impact of micro-scale residual stress on in-situ tensile testing of ductile cast iron: Digital volume correlation vs. model with fully resolved microstructure vs. periodic unit cell

Abstract

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Relation between microstructural heterogeneities and damage mechanisms of a ferritic spheroidal graphite cast iron during tensile loading

“…Over the last years, noticeable efforts to improve the understanding about the relation between the microstructural heterogeneities and mechanical properties of spheroidal graphite cast iron (SGI), particularly for ferritic SGI grades, were undertaken. The analyses involved experimental and computational approaches where different assumptions about graphite nodule distributions, loading conditions, ferritic grain size, among others, were done 1–19 . However, because of the marked heterogeneous nature of SGI added to the complex experimental procedures involved, there is an incomplete understanding about the specific role of each microstructural heterogeneity on the damage mechanisms acting during different stages of the material failure and consequently, on the resulting mechanical properties.…”

“…In this context, the role of the graphite nodule on the SGI mechanical properties has been evaluated by different authors 1,2,5,6,12,17 . Despite the application of different assumptions, most recent studies agree that the graphite nodules should not be accounted as a spherical void, particularly at the beginning of the elastoplastic macroscopic behaviour 11,17,19 . The mechanical properties of the graphite nodule and its damage mechanisms for different loading conditions were also investigated.…”

“…The results show that the thermal contraction mismatch between the graphite nodule and the metallic matrix during solid‐state cooling leads to a complex residual stress state along the microstructure, particularly near the graphite particles. However, this complex residual stress state is relevant at small strains only 19,22 …”

Analysis of the Correlation between Micro-Mechanical Fields and Fatigue Crack Propagation Path in Nodular Cast Iron

“…The graphite nodules were assumed to behave linearly elastically. Their highly inhomogeneous and anisotropic internal structure was accounted for by means of the approach described in detail in [35]. The overall idea is that each nodule is divided into an external shell and a core.…”

“…The values of the transversely isotropic elastic moduli used for the core and of the isotropic elastic moduli used for the external shell of the nodules are listed in Table 1, whereas the corresponding values of the thermal expansion coefficients as functions of temperature can be found in the supplementary data. A thorough explanation for the choice of these parameters can be found in [35].…”