Strain hardening effect on ductile tearing under small scale yielding plane strain conditions
(2025) Journal of the Mechanics and Physics of Solids β Vol. 202, p. 106171 (2025)
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Nguyen, Van Dung 
- Abstract
- finite element approach using an advanced nonlocal Gurson model. A focus is put on considering high strain hardening exponent π up to 0.5, while classical literature is often limited to π = 0.2, in order to encompass materials like stainless steels as well as several modern TRIP-TWIP alloys and high entropy alloys. First, π½2 plasticity-based simulations are performed to set the static crack reference. These simulations provide a hint about the origin of the increase of fracture toughness with increasing π, connected to much smaller finite strain zones at a given loading level quantified by the value of the π½ integral. In addition, it is found that above π βΌ 0.3, the opening stress does not attain a maximum value at a distance equal to one to two crack openings but keeps increasing towards the surface of the blunted crack tip. Then, Gurson-based simulations are used to determine the π½π curve for different π and initial porosity, and associated quantities related to crack initiation such as π½πΌπ , critical crack tip opening displacement πΏπ , and fracture process zone length. As already found in earlier studies, both π½πΌπ and πΏπ increase with increasing π, although the effect is much more marked on π½πΌπ . The origin of this first-order effect is unraveled by looking at the stress triaxiality, damage, and plastic strain fields. Even though the near crack tip stress triaxiality increases with π, the associated lower plastic strain at a fixed distance to the crack front leads to much lower void growth rates and delays void coalescence. As a important side result, the simulations appear very sensitive to an accurate fine-tuning of the adjustment factors entering the Gurson model at high strain hardening, pointing towards the intrinsic limitations of the model when π is large. This study confirms the interest in developing alloys with large strain hardening capacity, not only with respect to tensile properties but also in view of enhancing the ductile fracture toughness
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Citations
Besson, J., Pardoen, T., Nguyen, V. D., & Kaniadakis, A. (2025). Strain hardening effect on ductile tearing under small scale yielding plane strain conditions. Journal of the Mechanics and Physics of Solids, 202, 106171. https://doi.org/10.1016/j.jmps.2025.106171 (Original work published 2025)