PSI - Issue 35

Orhun Bulut et al. / Procedia Structural Integrity 35 (2022) 228–236

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Orhun Bulut et al. / Structural Integrity Procedia 00 (2021) 000–000

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(a) Engineering stress-engineering strain curves of specimens having t / d below 3 (b) Engineering stress-engineering strain curves of specimens having t / d above 3

Fig. 5: Engineering stress-engineering strain curves for specimens having di ff erent t / d ratios.

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Engineering Stress (MPa)

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t/d ratio

Fig. 6: Flow stress values at %10 displacement of specimens having di ff erent t / d ratios.

changes dramatically for these specimens. Moreover, the most important reason is that in the calculations the same hardening parameters are used for each specimen. Yet, while specimens with t / d > 1 have the same mean grain size, the specimens with t / d < 1 show decreasing grain size behavior with decreasing t / d ratio. If hardening parameters were adjusted according to the grain sizes, or if a size dependent crystal plasticity model was employed, which would lead to a harder response, then the results would be similar for t / d < 1 to the experimental observations. The flow stress response shows a steep increase for t / d between 1 and a critical value compared to the response at higher t / d ratios which converge to polycrystalline behavior. Fig. 6 shows that the critical value corresponds to around 2. Between 1 and the critical value, the numerical study resulted in a similar trend with the experimental results. Starting from t / d = 1, as the ratio is increased, the grain boundaries parallel to the loading direction start to emerge. These GBs contribute to the resistance of the material to plastic deformation. The di ff erence between