Issue 70

D. Kosov et alii, Frattura ed Integrità Strutturale, 70 (2024) 133-156; DOI: 10.3221/IGF-ESIS.70.08

(a)

(c)

(e)

(b) (f) Figure 17: Experimental crack paths (a,c,e) and predicted fracture patterns (b,d,f) for pure mode I (a,b) and initial pure shear (c-f). (d)

(a) (b) Figure 18: Load-displacement curves for (a) pure mode I ( α =90 ˚ ) and pure mode II ( α =0 ˚ ) and (b) mixed mode problems. The loading-displacement evolution regarding the phase-field models according to Eq.9 and Eq.12 are shown in Fig. 18 at three different fracture status. It can be clearly observed that the loading-displacement relation is a function of mode mixity showing higher peak loads for initial pure shear mode II (  = 0 ˚ ) by employing of Eq.(9) compared to the pure mode I tension condition (  = 90 ˚ ). In addition, the slope angle of the curves in the first deformation section before reaching the peak load is also different, with a smaller value during shear (Fig.18a) for branching cracks. It is obvious that these states correspond to elastic modulus under tension and pure shear. Noteworthy is the different behavior of the curves during branching and kinking of cracks, the trajectories of which relate to mixed mode fracture. It can be seen in Fig.18b that the profiles of the load–displacement curves regarding such mode mixity also show differences. An abrupt failure is observed for both cases at the loading direction  = 0 ˚ , nevertheless, the specimen with branching dominant damage mechanism according to Eq.(9) yields a smaller value of peak load with respect to kinking crack path behavior in CTS specimen describing by Eq.(12). Comparing these simulation results to Shlyannikov and Fedotova experimental data both the predicted crack paths and the profiles of the loading–displacement relations show thorough agreement [25].

149