13th International Conference on Fracture June 16–21, 2013, Beijing, China Theoretical Analysis of Effects of Confining Pressure on the Stress Intensity Factors for Cracked Brazilian Disk Jigang Xu1, Shiming Dong1*, Zhenlin Wang1 1College of Architecture and Environment, Sichuan University, Chengdu 610065, China * Corresponding author: smdong@scu.edu.cn Abstract: In order to investigate effects of confining pressure on the stress intensity factors for a cracked Brazilian disk, the closed-form expressions of the stress intensity factors were obtained by using the weight function method in fracture mechanics for the cracked Brazilian disk loaded by the confining pressure, and then the explicit expressions of the stress intensity factors were achieved under both the confining pressure and diametrical forces loading condition. Based on the formulas of the stress intensity factors, effects of confining pressure on stress intensity factors of the cracked Brazilian disk was analyzed. The analyzed results show that the confining pressure has no effects on the mode II stress intensity factor, however, mode I stress intensity factors decrease with the increasing confining pressure. In addition, effects of confining pressure on the loading condition of pure mode II crack were also investigated. The analyzed results show that the critical loading angle for pure mode II crack decreases gradually to 0 degree with the increasing confining pressure. Key Words: cracked Brazilian disk, stress intensity factor, confining pressure, critical loading angle 1. Introduction Fracture toughness is an important parameter to describe the mechanical behavior of brittle materials and fracture toughness test is one of the main tasks of the fracture mechanics. How to accurately test fracture toughness of brittle materials has been studied by many researchers. It is very important to select a Suitable specimen for performing fracture toughness tests. The cracked Brazilian disk has been widely used for fracture toughness test of brittle materials as its closed-form solutions of the stress intensity factors can be achieved [1,2 ], and it can be easily achieved pure mode I, pure mode II and mixed-mode (I-II). Liu et al.[3] used the cracked Brazilian disk to measure the fracture toughness of fiber-reinforced composite material. Dong et al.[4,5] conducted the Brazilian disk test to investigate the static and dynamic fracture mechanical properties of PMMA. Nasseri et al.[6] conducted the Brazilian disk test to study the anisotropy of granite fracture toughness. However, most of the fracture toughness tests were conducted in a situation without confining pressure by now. This is not consistent with the actual working condition of some materials. As we know, many practical engineering structure materials serve in situation with confining pressure, such as underground rocks, structures in the deep water and so on. However, the material mechanical properties under the action of confining pressure are different from the properties under without confining pressure [7]. In order to investigate effects of confining pressure on the fracture toughness of brittle materials, many researchers have performed the fracture toughness experiments under the confining pressure loading conditions. But there were some unsolved problems in their experimental principle. For example, Al-Shayea et al.[8] have studied the effects of confining pressure on fracture toughness of a limestone rock using straight notched Brazilian disk specimens and hydraulic fracturing technique. They calculated rock mode I and mode II stress intensity factors by using the approximation formulas proposed by Atkinson et al.[1] and the variation of fracture toughness was found to be linearly
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