Fracture Analysis of Some Ceramics Under Mixed Mode Loading

Abstract

Mixed mode fracture resistance was analyzed for some previously tested ceramics using a three‐parameter fracture criterion called the generalized maximum tangential stress (GMTS) criterion. For using this fracture criterion, the size of a critical distance from the crack tip was required. Therefore, an analytical model was suggested for determining the size of critical distance in terms of mode I fracture toughness and the tensile strength of ceramics. For some ceramics with reported grain size, the size of critical distance was found to be approximately 100 times the average grain size. The experimental results obtained from the cracked Brazilian disk specimen and reported in the literature for sialon, mullite, SiC, glass, sintered carbide, porcelain, zirconia, and alumina could be estimated very well when the GMTS fracture criterion was used.

Aging effect on combined mode fracture resistance of bitumen

“…Furthermore, there are some theoretical models for evaluating the size of this region that present reasonably good estimations for the size of r c in terms of the fracture toughness and tensile strength of material . According to the literature, the size of this region may vary from a few micrometres (for metals or brittle polymers) to a few centimetres (for quasibrittle materials such as rocks) . Because of lack of sufficient data in the literature for estimating the critical size of bitumen, r c values of typical brittle polymers (typically in the range of 0.1 to 0.5 mm) was assumed for the tested binders.…”

“…[77][78][79] According to the literature, the size of this region may vary from a few micrometres (for metals or brittle polymers) to a few centimetres (for quasibrittle materials such as rocks). [80][81][82][83][84] Because of lack of sufficient data in the literature for estimating the critical size of bitumen, r c values of typical brittle polymers (typically in the range of 0.1 to 0.5 mm) was assumed for the tested binders. Based on the general mechanical and physical properties of the bituminous materials, it is expected that the size of r c might be increased for them by decreasing the temperature and increasing the aging level because of increasing the probability of nucleation and coalescence of larger numbers of microcracks ahead of the crack tip at such environmental conditions.…”

Discrete Lattice Model of Quasi-Brittle Fracture in Porous Graphite

“…According to Aliha and Ayatollahi [32], Awaji et al [33] and Claussen et al [34], the size of the fracture process zone scales with the squared ration of the fracture toughness and tensile strength. However, Ayatollahi and Aliha [35] have pointed out that the size is related to the average grain size alone. The modelling of the entire macro-crack tip region with microstructure-informed lattice will require a significant computational effort.…”

Experimental analysis of mixed mode crack propagation in brittle rocks: The effect of non-singular terms

“…(9), the FPZ length or r c should be known. There are several formulations in the literature for calculating the FPZ length [27][28][29][30][31]. In this paper, two formulas are considered: the conventional equation proposed by Schmidt [31] and a modified equation where the term A 3 is included in the Schmidt's model.…”