PSI - Issue 41

Kushal Mishra et al. / Procedia Structural Integrity 41 (2022) 248–253

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Mishra & Singh/ Structural Integrity Procedia 00 (2022) 000 – 000

Fig.2. Fracture surface of tensile test carried out at different strain rates (a,b) at strain rate of 0.0003 s -1 (c,d) at st rain rate of 0.005 s -1 (e,f) at st rain rate of 0.02 s -1 (g,h) at st rain rate of 0.2 s -1 . (a,c,e,g) shows the overall fracture surface. High magnification images of the black dotted box region in (a,c,e,g) are presented in (b,d,f,h). (b,d,f,h) are the highmagnification images of fracturesurface in crack initiation region. Fig. 3(a) shows the uniaxia l compressive stress -strain curve for specimens tested at strain rates as listed in Table 1. It is observed that the yield strength increases with strain rate. Specimens tested at higher strain rates show a higher flow s tress curve post-yield. The percentage softening post-yield also increases as strain rate increases. This is because of the localizat ion of deformation. The softening stage is immediately succeeded by the hardening stage. At high strain rates, the deformation is non-homogenous post the yield transit, and hence the deformat ion happens in local shear bands until the hardening stage is reached. At low strain rates, the shear band format ion happens throughout the materia l, and the hardening stage is reached fas ter (Morelle , 2015; Wu and van der Giessen, 1994). Hence, the softening post yielding increases with strain rate as the hardening through shear banding happens more locally in this case. From both the tensile and compressive stress -strain (Fig. 1(a) & Fig. 3(a) ) it Is observed that the Young’s modulus goes on increasing as the test strain rate increases. Fig. 3(b) presents a plot of the variation of Young’s modulus with strain rate under compressive loading. The in itia l increase in Young’s modulus is much higher with strain rate but it gradually decreases as strain rate is further increased.