PSI - Issue 28

1146 Yifan Li et al. / Procedia Structural Integrity 28 (2020) 1140–1147 Author name / Structural Integrity Procedia 00 (2019) 000 – 000 7 Fig. 7 shows contour plots of von Mises stress for a specimen with relative crack length 2 a /W = 0.6 and D/W = 0.4 for four different mode mixities, i.e. pure mode I, pure mode II, = 20° and 40° . As expected, the von Mises stress contour is symmetric relative to the crack plane when the specimen under pure mode I loading. However, with the increase of the orientation angle , the von Mises stress contours become asymmetric with respect to the crack plane.

Fig. 7. The plots of von Mises stress profile near crack tip (when D/W=0.4, 2 a /W=0.6).

5. Conclusion A new fracture test configuration called Holed-Cracked Square Plate (HCSP) has been proposed for mixed mode I/II experiments on brittle and quasi-brittle materials. This specimen can achieve a full range mode mixities in fracture from pure mode I to pure mode II by changing the crack orientation angle. The specimen is simple to manufacture and only needs conventional tensile testing machines with simple loading configurations. Numerical studies have shown that the mode II geometry factor Y II increases as the orientation angle increases, but the mode I geometry factor Y I has the opposite tendency. The orientation angle II for pure mode II fracture increases by increasing the relative crack length 2 a /W at a constant ratio D/W, while the II decreases when the hole diameter to plate length ratio D/W enhances in a fixed crack length ratio 2 a /W. This specimen can be considered as a suitable substitute for the Brazilian Disk specimen and can be used to study the mechanical properties of brittle and quasi-brittle materials together with circular shaped samples. References ABAQUS, 2017. analysis of the user’s manual. Version 2017. Dassault Systèmes. Akbardoost, J., Ghadirian, H. R., Sangsefidi, M., 2017. Calculation of the crack tip parameters in the holed ‐ cracked flattened Brazilian disk (HCFBD) specimens under wide range of mixed mode I/II loading. Fatigue & Fracture of Engineering Materials & Structures 40(9), 1416 1427. Aliha, M. R. M., Ayatollahi, M. R., 2012. Analysis of fracture initiation angle in some cracked ceramics using the generalized maximum tangential stress criterion. International Journal of Solids and Structures 49(13), 1877-1883. Aliha, M. R. M., Ayatollahi, M. R., Smith, D. J., Pavier, M. J., 2010. Geometry and size effects on fracture trajectory in a limestone rock under mixed mode loading. Engineering Fracture Mechanics 77(11), 2200-2212. Aliha, M. R. M., Bahmani, A, 2017. Rock fracture toughness study under mixed mode I/III loading. Rock Mechanics and Rock Engineering 50(7), 1739-1751. Aliha, M. R. M., Bahmani, A., Akhondi, S., 2015. Numerical analysis of a new mixed mode I/III fracture test specimen. Engineering Fracture Mechanics 134, 95-110.