Experimental and Numerical Studies of Effect of Notch Width on Mode-I Fracture Toughness in Thick-walled Cylindrical Specimens

There are three notch displacement modes including the Mode I or opening mode where the notch displacement is perpendicular to the notch front, Mode II or shear mode where notch dimensions are displaced in the notch plane and the Mode III or tear mode where the notch dimensions are displaced in the notch plane parallel to the notch front. Some application areas of rock fracture mechanics can be listed as hydraulic fracturing, rock blasting, rock cutting, mechanized drilling, rock slope stability and comminution in mineral processing. The aim of the present study was to examine the effect parameter of width on the mode ICritical Stress Intensity Factor (Critical SIF) using a thick-walled hollow cylindrical marly specimen and the oil well environment was simulated in the laboratory. The marly specimens were prepared from the Bangestan formation in southern and southwestern Iran. To perform the tests, two artificial symmetrical notches with certain dimensions were created in specimens with an outer diameter (OD) of 73 mm, an inner diameter (ID) of 25 mm and a height of 150 mm. A triaxial stress was applied on the specimen and the pressure required for the propagation of the artificial notches was measured. Three tests were conducted to investigate the effect of notch width on the mode I Critical SIF. Two finite element software including ABAQUS 6.12 and ANSYS 14 were used for calculating I Critical SIF.  Excel and SPSS softwares were used for investigating the effect of notch width on the mode I Critical SIF. By conducting three tests, it was concluded that with an increase of 50 percent of the notch width, mode I Critical SIF decreases 20 percent. Meanwhile, it was found that the mode I Critical SIF linearly decreased with an increase in the notch width.