PSI - Issue 83

Ritesh M. Patel et al. / Procedia Structural Integrity 83 (2026) 41–46

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Fayed (2018), Khan (2019). Fig.2. , Fig.3. and Fig.4. illustrates how the mode-I, mode-II and mixed mode geometrical components Y I and Y II behave with regards to the crack inclination angle for the ratios of a/R = 0.5 and S/R = 0.5 respectively. One of the main objectives of this study is to ascertain T -stress because it is a crucial component of fracture analysis. The T -stress of the SCB specimen is computed and normalized with Eq. (4).The normalized T -stress (T ∗ ) is shown in Fig. 5 and varies with the fracture inclination angle. T ∗ is found to typically grow in tandem with the fracture angle. This implies that the T - stress rises when one transitions from pure mode-I to pure mode-II. The negative sign of the T -stress found for the SCB specimens in this investigation validates the concept of stable crack formation in brittle fracture as postulated by literature Cotterell (1980). At 0 о and 43 о , pure mode-I and mode II are detected, representing pure extension and pure shear, respectively. Mode - II geometry factor (Y II ) is less sensitive to S/R than mode-I geometry factor (Y I ) . While the crack angle for pure mode-I is always zero simultaneously in pure mode- II, crack angle is dependent on a/R and S/R .

Fig. 5. Variations of Y I , Y II , T ∗ with α Fig. 6. Variations of β with α Fig. 5 shows how the biaxiality ratio (β) changes with the crack initiation angle (α) for a/R and S /R = 0.5 . In pure mode-II, the β value is always positive for large fracture angles, but in pure mode-I, it is often negative. Additionally, for specimens with a significant β value, T -stress influences mixed mode brittle fracture significantly.

5. Conclusions The findings of this investigation can be summed up as follows:

In order to examine mixed mode fracture from pure mode-I to pure mode-II, the PLA material's SCB specimen is taken into consideration. The estimated crack parameter of the fracture specimen utilizing a finite element analysis is shown to be accurate by cross-referencing it with previous research publications. These data are essential for accurately describing fracture testing, and the value of T -stress is important for the SCB specimen in mixed mode conditions. When β is low (0 о -10 о ), it displays a negative sign; when β is high (15 о - 43 о ), it displays a positive sign. The ratio of a/R and S/R , as well as the crack initiation angle, have the major effects on the T -stress value. Acknowledgements The authors express their sincere gratitude to the Unique Engineering testing laboratory for granting permission to understand procedure of 3 point bending test on SCB specimen.