Abstract
A comparison is made of the ductility limits of one mild (normal) and two high-tensile strength shipbuilding steels with an emphasis on stress state and loading path dependency. To describe the ductile fracture behavior of the considered steels accurately, an alternative form of ductile fracture prediction model is presented and calibrated. The present fracture model combines the normalized Cockcroft–Latham and maximum shear stress criterion, and is dependent on both stress triaxiality and Lode angle parameter. The calibrations indicate that, depending on the hardening characteristics of the steels, ductile fracture behavior differs considerably with stress state. It is demonstrated that the adopted fracture model is able to predict the ductile fracture initiation in various test specimens with good accuracy and is flexible in addressing the observed differences in the ductile fracture behavior of the considered steel grades.
Highlights
Ductile fracture resistance is an important structural performance requirement for the steel components of naval structures
The failure initiation results have been correlated through stress triaxiality and equivalent plastic strain [6,7], and micro-mechanism based models by McClintock [4]
Among the three steel grades, the ductility limits of normal-strength steel, grade A, showed a relatively low Lode angle dependence which could be best described by a fracture locus similar to the Cockcroft–Latham model
Summary
Ductile fracture resistance is an important structural performance requirement for the steel components of naval structures. Xue [19] developed a Gurson-type model that included the void shearing mechanism because of the Lode angle effect Based on these recent developments, a dozen empirical or phenomenological uncoupled ductile fracture models that incorporate the Lode angle effect and address fracture due to shear-dominated stress states were proposed recently [20,21,22,23,24,25,26,27]. Despite their ease of calibration and good prediction capability for certain ranges of stress states, MSS and CL criteria lack mathematical flexibility, yielding high calibration errors in general It was noted by Park et al [28] that the extension of the CL model by combining it with MSS criterion may provide a flexible alternative format, as demonstrated by Gruben et al [37]. The predictive capabilities of the presented fracture model are evaluated for marine structural steels
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